hara into a verdant landscape dotted with lakes, rivers, 
and vegetation ranging from wooded steppe to savanna 
(Petit-Maire & Riser, 1981; Petit-Maire & Riser, 1983). 
Pollen analyses have revealed the presence of tropical 
and Sahelian taxa, indicating increased biodiversity. In 
addition, speleothem records confirm the persistence of 
humid conditions during the Late Pleistocene and early 
Holocene (Ritchie et al., 1985; Salzmann & Waller, 
1998; Lézine & Casanova, 1989; Cheddadi et al., 2009; 
Ait Brahim et al., 2023; Helmens, 2014; Lézine et al., 
2023; Paine et al., 2024). However, as summer insola-
tion gradually declined, the African monsoon retreated 
southward, leading to progressive aridification and the re
-establishment of desert conditions across the Sahara 
(Nicole Petit-Maire et al., 1983; Salzmann & Waller, 
1998). This process of desertification is well document-
ed during the mid-Holocene, particularly through lacus-
trine records such as those from Lake Yoa in Chad, 
which reveal a continuous and gradual drying trend over 
the past 6.000 years (Kröpelin et al., 2008). An abrupt 
increase in Saharan dust deposition in the Atlantic 
around 5.000 cal BP further supports this shift 
(DeMenocal et al., 2000). Marine sediment records also 
confirm this trend, as shown by the studies of Lézine et 
al. (2005), Weldeab et al. (2005), and Haslett & Smart 
(2006). 

Despite these climatic evidence, research on the 
evolution of fluvial systems in North Africa remains lim-
ited. Yet, alluvial archives represent valuable indirect 
indicators of paleohydrological dynamics during the Late 

Available online http://amq.aiqua.it 
ISSN (print): 2279-7327, ISSN (online): 2279-7335 
 
 

Alpine and Mediterranean Quaternary, 38 (2), 2025, 85-109 https://doi.org/10.26382/AMQ.2025.05 

1. INTRODUCTION 
 

The glacial periods of the Late Quaternary, particu-
larly Marine Isotope Stages (MIS) 5b and 3, as well as 
the Holocene interglacial, reflect the complex processes 
underlying Earth’s climatic variability (Siddall et al., 
2006; Romero et al., 2011; Bereiter et al., 2012). These 
periods are characterized by alternating wet and dry 
phases, which continue to be the focus of extensive 
research aimed at understanding the origins and driving 
mechanisms of these climatic shifts (Foley et al., 2003; 
Castañeda et al., 2009; Specht et al., 2024; Zaky et al., 
2024). During the early Holocene, substantial evidence 
indicates significantly increased moisture levels across 
the Sahara Desert in North Africa (Petit-Maire & Riser, 
1981; Petit-Maire & Riser, 1983; Pachur et al., 1987; 
Petit-Maire, 1989; Pachur & Hoelzmann, 1991; Depreux 
et al., 2021; Petit-Maire, 2021; Cheddadi et al., 2021). 
Geomorphological, lacustrine, and paleoecological rec-
ords consistently show that the region was markedly 
wetter than today and extensively vegetated throughout 
the early to mid-Holocene. This multi-millennial phase of 
enhanced humidity is commonly referred to as the 
“African Humid Period” or the “Green Sahara” (Street-
Perrott et al., 1993; Kröpelin et al., 2008; Lézine et al., 
2011; Limondin-Lozouet et al., 2013; Burrough & Thom-
as, 2013; Campbell et al., 2017; Depreux et al., 2022; 
Lghamour et al., 2024). Furthermore, the northward 
expansion of the African monsoon brought abundant 
rainfall to areas that are now arid, transforming the Sa-

HIGH-RESOLUTION MORPHO-SEDIMENTARY AND PALEOENVIRONMENTAL EVOLUTION 
OF WADI AKKA (DRÂA BASIN, MOROCCO) 
FROM LATE PLEISTOCENE TO HOLOCENE 

 
Fatima Saadi 1,2, Larbi Boudad 1, Mailys Richard 3,4, Jean-François Berger 2 

 
1 Geosciences, Water, Environment Laboratory, Earth Sciences Dep., Faculty of Sciences, Mohammed V University in Rabat, Morocco. 

2 CNRS, UMR 5600 EVS-IRG, University of Lyon, France. 
3 Archéosciences Bordeaux, UMR 6034 CNRS-Bordeaux Montaigne University, Pessac, France. 

4 Department of Early Prehistory and Quaternary Ecology, University of Tübingen, Tübingen, Germany. 
 

Corresponding author: Fatima Saadi <fatima_saadi@um5.ac.ma> 
 

ABSTRACT: The fluvial evolution of southern Morocco during the Late Quaternary, particularly in non-Mediterranean basins such as the 
Wadi Akka, a tributary of the Drâa, remains poorly documented. This study presents the first chronostratigraphic framework for the Wadi 
Akka formations, based on a high-resolution reconstruction of fluvial dynamics and paleoenvironmental changes since the end of the last 
interglacial period. The analysis follows a multiproxy approach, combining geomorphological, sedimentological, and geochemical data, and 
is supported by 13 radiocarbon and four optically stimulated luminescence (OSL) ages. Nine main stratigraphic units reveal alternating 
phases of aggradation, pedosedimentary stability, and incision, associated with climatic fluctuations from Marine Isotope Stage (MIS) 5b 
(~82 ka) to the late Holocene. During MIS 3 (~40 ka cal BP), a low-energy hydromorphic environment prevailed, marked by fine sedimenta-
tion and soil development under relatively humid conditions. The early African Humid Period (11.400-9.700 cal BP) is characterized by 
fluvio-lacustrine settings, peat layers, and tufa deposits, indicating stable, wet environments. Conversely, arid phases are marked by signifi-
cant incision and sedimentary hiatuses, particularly between 9.500-8.500 and after 6.000 cal BP. Alluviation phases are also dated to 
around 7.200 and 656-579 cal BP. The presence of tuf deposits and travertine dams indicates peaks in humidity, especially during the 
beginning of Little Ice Age. Finally, comparison with other regional archives has allowed for the reconstruction of Upper Pleistocene and 
Holocene paleoenvironmental conditions at both regional and supra-regional scales, highlighting the correspondence between phases 
recorded in the Akka Plain and broader climatic events in the region. 
 
Keywords: Fluvial geomorphology, multi-proxy analysis, MIS 5b and MIS 3, Holocene, Akka Plain, Drâa Valley. 



   

 

Pleistocene and Holocene. Unlike slope or colluvial 
deposits, which reflect more localized processes, fluvial 
records integrate environmental changes across entire 
watersheds, offering a broader and more comprehen-
sive perspective on past hydrological variability (Faust 
et al., 2004; Zielhofer & Faust, 2008; Zielhofer et al., 
2008). 

This transitional period is crucial for understanding 
the profound landscape transformations and the multiple 
forcing mechanisms that have driven the ongoing aridifi-
cation of North Africa. However, the current state of 
research highlights significant gaps, as many regions 
still lack chronological frameworks or pedo-sedimentary 
archives documenting paleoenvironmental, climatic, and 
anthropogenic events during the Late Quaternary. In 
southern Morocco, the Akka Wadi is a major right-bank 
tributary of the Drâa River in its lower basin, which 
spans approximately 66 km² and extends into the north-
western Sahara Desert. The history of studies on this 
sector of Africa has received little attention from geo-

morphologists and Quaternary scientists. Notably, the 
Akka Plain has never been investigated in the context of 
Holocene paleoenvironmental reconstructions. This area 
of south-eastern Morocco lacks of absolute chronologi-
cal data, despite a few earlier contributions (Weisrock et 
al., 1991; Wengler et al., 2002; Mathieu et al., 2004; 
Weisrock et al., 2006, 2008). As a result, there remains 
a significant gap in morpho-pedosedimentary and pale-
oenvironmental documentation of climatic and anthropo-
genic changes during the recent Quaternary (Mathieu et 
al., 2004). In contrast, only a handful of recent studies 
have focused on marine sequences off Cape Ghir in 
southern Morocco (Baqloul et al., 2021; Tadoumant et 
al., 2022). Meanwhile, the Mediterranean watersheds of 
northern Morocco, such as the Moulouya River and its 
tributaries, as well as the Kert River, have been the fo-
cus of extensive geomorphological and paleoenviron-
mental research. (Lefèvre, 1985; El Amrani et al., 2008; 
Zielhofer et al., 2010; Ibouhouten et al., 2010; Bartz et 
al., 2018; Depreux et al, 2021, 2022), resulting in a ro-

 
 

86 

 
 

Saadi F. et al. 

Fig. 1 - Geographical location of the study area: a) Satellite image of Morocco showing the Akka sub-basin (outlined in white) within the 
Drâa basin (outlined in black line). (Source: Terra Color imagery, Esri, 2009), b) Topographical map of the Akka watershed highlighting the 
study area. (Source: Shuttle Radar Topography Mission (SRTM)), c) Geological and geomorphological map of the Akka plain with the 
study area indicated by a red rectangle. The legend below corresponds to maps (c) and (d), d) Locations of the profiles and stratigraphic 
sections studied along the eastern and western banks of the wadi.  

 



   

 

 bust and near-continuous Holocene chronostratigraphic 
framework for that region.  

The main objectives of this study are as follows; a) 
to carry out a comprehensive geomorphological analysis 
of alluvial formations across several sectors of the Akka 
Basin, b) to refine the chronostratigraphic framework of 
recent Quaternary alluvial deposits through the examina-
tion of multiple transects and the application of absolute 
dating methods, including radiocarbon (¹⁴C) and optically 
stimulated luminescence (OSL), c) to perform detailed 
physico-chemical and sedimentological analyses on 
samples collected from selected profiles, with the aim of 
developing a diachronic model reconstructing the hydro-
geomorphological and paleoenvironmental evolution of 
the region, d) to investigate the climatic and anthropo-
genic drivers of the observed paleoenvironmental 
changes in the Akka sequence by comparing our results 
with published paleoclimatic and paleoenvironmental 
data at the regional scale, encompassing the north-
western Sahara and broader North Africa. 

 
2. STUDY AREA 
 

The Akka Wadi is a major right-bank tributary of the 
Drâa River (Fig. 1a), situated in the pre-Saharan zone of 
the Western Anti-Atlas in southern Morocco. It drains a 
sub-basin covering approximately 2.190 km² along a 
course of about 100 km (Fig. 1b). Due to its geograph-
ical position, the Tata-Akka region experiences a conti-
nental Saharan hyper-arid climate. Annual precipitation 
is low, averaging around 100 mm (Monographie 2015 - 
Agence du Bassin Hydraulique Drâa), primarily occur-
ring as intense thunderstorms. Prolonged dry spells of 4 
to 5 months without rainfall are common. Temperatures 
exhibit considerable daily and seasonal variability, rang-
ing from minima of around 12 °C in winter to highest 
values reaching 49 °C in summer.  

 
3. MATERIALS AND METHODS 
 
3.1. Geomorphological and Chronostratigraphic 
Context 

The identification of the studied terraces is based 
on a geomorphological survey combining the analysis of 
Google Earth satellite images and field observations. 
Satellite images allowed the identification of the best-
preserved Holocene alluvial terraces, while field cam-
paigns validated these observations by identifying the 
most intact construction sections, exposed by the recent 
natural incision of watercourses. Four field campaigns 
were thus conducted in the Akka region, southern Mo-
rocco, in May 2022, April 2023, November 2023, and 
January 2024. 

The geomorphological map of the Akka area (Fig. 
1c) illustrates the geological and morphological frame-
work of the study site. The upstream watershed is domi-
nated by rugged mountainous terrain reaching approxi-
mately 1100 m in altitude, characterized by steep slopes 
composed of ancient Ordovician rocks, notably the Bani 

 
 

87 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 

- - - - -                 >>>>> 
 
Fig. 2 - a) Panoramic photograph of the left bank outcrop of 
Akka Wadi; b) Stratigraphic section of the left bank showing the 
location of the three studied stratigraphic profiles (1, 2, and 3), 
c) Panoramic photograph of the right bank outcrop of Akka Wa-
di; d) Stratigraphic section of the right bank with the location of 
the studied profiles (4a and 4b), 



   

 

sandstones. Downstream, the landscape extends into 
low alluvial desert plains, rich in pebbles, up to the con-
fluence of the Wadi Akka with the Drâa River (Fig. 1b). 

The oldest terraces, T1 and T2 (Fig. 1c), consist of 
gravel formations attributed to the Middle to Upper 
Pleistocene, as indicated by the geological map of the 
Western Anti-Atlas and the Drâa Plains (Akka-
Tafagount-Tata) (Choubert & Ennadifi, 1970). These 
two terraces were not investigated in the field due to the 
absence of precise chronological constraints but are 
included here for contextual purposes. The most recent 
terrace, T3, where the studied outcrops are located, is 
composed of fluviolacustrine deposits and more or less 
bedded floodplain silts, very locally interrupted by gravel 
layers with a thickness of 5 to 6 meters. These sedi-
ments, mainly greenish silts and occasional tufa depos-
its, are attributed to the Holocene (Choubert & Ennadifi, 
1970). Below the T3 terrace lies the Ant/T3 terrace (Fig. 
1c,d), which is topographically lower and corresponds to 
anthrosol deposits linked to the establishment of the 
Akka oasis, a topic that will be addressed in more detail 
later. 

Two stratigraphic sections were studied on the 
recent T3 terrace. The first section, (Figs. 2a and 2b), 
located on the left bank of the Akka wadi (29°
22'50.66"N/8°15'51.25"W), includes three profiles 

(profiles 1, 2, and 3) arranged from north to south. The 
second section, located on the right bank (29°
22'47.40"N/ 8°15'57.39"W), contains a fourth profile 
(profile 4). These profiles were selected based on the 
clear continuity of the sedimentary layers, which is es-
sential for accurate stratigraphic interpretation. The 
lithostratigraphic analysis of the four profiles led to the 
identification of 19 sedimentary grouped in 9 main units.  

The identification of sedimentary units is primarily 
based on lithological descriptions carried out in the field, 
including outcrop sketches, as well as the analysis of 
structures, texture, and color of the units. Due to local 
topographic configurations, successive interbedding of 
alluvial layers, oblique intersections of old palaeochan-
nels, observable truncations, and longitudinal facies 
variations, it is often necessary to study several comple-
mentary sedimentary logs at the same site. This ap-
proach makes it possible to best reconstruct the alluvial 
archive, to capture its initial geometry by developing a 
local master core that is representative of all the hydro-
geomorphological and sedimentary events recorded in 
the stratigraphic sequence. 

Figure 3 shows a lithostratigraphic correlation of 
the various units and sub-units from the studied profiles 
on both sides of the Akka wadi. The four profiles reveal 
eight broadly comparable pedosedimentary phases on 

 
 

88 

Fig. 3 - Correlation of the four dated stratigraphic sequences. (The crossed-out dates indicate a chronostratigraphic inconsistency). 

 
 

Saadi F. et al. 



   

 

blocks was extracted and prepared for luminescence 
analyses. The external part of the blocks, which was 
exposed to light during sampling, was kept for dose rate 
measurements. 

For luminescence dating analyses, each sample 
was sieved with water and the 100-140 µm fraction was 
chemically treated following published protocols (e.g. 
Tribolo et al., 2013) including HCl (10%) to dissolve the 
carbonates and H2O2 (30%) to degrade the organic 
matter. The quartz and feldspars were extracted using 
density separation with heavy liquid (heteropoly tung-
state of sodium). Three separations were conducted, 
the first one to extract heavy minerals (d=2.72 g/cm3), 
the second one to separate quartz and feldspars 
(d=2.62 g/cm3) and the third one to separate plagioclase 
and potassium feldspars (d=2.58 g/cm3). The quartz 
fraction was then treated using H2SiF6 (31%) over one 
week and rinsed with HCl (10%) to eliminate the possi-
ble remaining feldspars. 

For dose rate measurements, the external part of 
each block was dried in an oven and the difference be-
tween the wet and the dry weight was used to calculate 
the water content. Note that due to the warm conditions 
at the time of the sampling, the samples were almost 
dried and the measured water content may not reflect 
the average water content during burial time. The ages 
were thus calculated assuming a water content of 6%. 
This fraction was then sealed in a container that was 
analysed using a laboratory gamma-ray spectrometer 
equipped with a high-resolution, broad energy Ge 
(BEGe) detector to determine the U, Th, and K content 
in each sample and derive the beta dose rate. The gam-
ma dose rate was measured in situ using a portable 
gamma-ray spectrometer connected to a LaBr probe 
(Inspector 1000, Canberra) at the same location as the 
samples. The data were treated using the “threshold” 
technique (Mercier & Falguères, 2007). The cosmic 
dose rate was calculated taking into account the current 
depth of the samples following the equation in Prescott 
& Hutton (1988). 

 
b - Luminescence measurements 

Multi-grain (MG) analyses were first conducted on 
the quartz of the four samples (1 mm ø aliquots) using 
the protocol given in Tab. S1 with a TL/OSL Lexsyg 
Smart reader (Richter et al., 2015) and a Lexsyg Re-
search reader (Richter et al., 2013). The OSL signal 
was integrated using the first 1.5 seconds and the back-
ground subtracted using the last 20 seconds, and the 
signal was detected with a combination of UV filters 
(Schott BG-3, 3 mm in conjunction with a Delta 
BP365/50 EX). Dose recovery tests (DRT) were con-
ducted on MG quartz aliquots in order to assess the 
reliability of the protocol. The disks were bleached two 
minutes in a solar simulator (Hönle 500) and a given 
dose of 266 Gy (AKKA2-OSL1), 202 Gy (AKKA2-OSL2), 
and 91 Gy (AKKA2-OSL3) was applied before applying 
the single aliquot regeneration (SAR) protocol in Tab. 
S1. The preheat temperature was fixed at 240°C 
(AKKA2-OSL1, 2 and 3) and 260°C (AKKA2-OSL1 and 
3), and three aliquots were measured for each tempera-
ture. The DRT (recovered/given) values are, for AKKA2-
OSL 1, 0.76 ± 15% (240°C) and 0.75 ± 3% (260°C); for 
AKKA2-OSL 2, 0.95 ± 3% (240°C); for AKKA2-OSL3, 
0.94 ± 5% (240°C) and 0.95 ± 10% (260°C). However, 
considering that the OSL signal of AKKA2-OSL1 was 
close to saturation and that the DRT values were under 

both banks, along with significant morphological chang-
es in the alluvial plain, related to successive incision and 
refill events. While the two stratigraphic sections are 
easily accessible for sampling, the scarcity or absence 
of carbonized remains, especially throughout the coarse 
basal unit (U1) and the subsequent unit (U2), led us to 
complement radiocarbon dating with the luminescence 
dating method, as a complementary technique for the 
parts where radiocarbon dating material is not available. 
A detailed description each of these main units is provid-
ed in Section 4.2. 

 
3.2. Sedimentological and pedological analysis 

Sediment samples of approximately 200 g were 
systematically collected at regular intervals of 4 to 6 cm 
by recovering material in bulk (using a trowel or pick 
from the walls of the natural section, thereby destroying 
the sedimentary structure), based on the lithostratigraph-
ic variations observed in the field. A total of 259 samples 
were collected from the four sequences. according to the 
chronostratigraphic order of the master core created. 
These samples underwent a multiproxy analysis in the 
laboratory, following a systematic stratified approach, 
including geochemistry, sedimentology, and chronology. 

 
3.3. CHRONOLOGY 
 
3.3.1. Radiocarbon dating 

The chronology of the studied sequences is based 
on 13 AMS radiocarbon ages obtained from charcoal 
and organic matter (mineralized peat). Due to the scarci-
ty of carbonaceous material, more than 45 samples 
sieved through a 200-micron mesh (>50), followed by 
binocular examination at magnifications up to 50x in 
both natural and incident light to better identify carbon-
ized micro-debris. Despite using AMS, many carbonized 
micro-fragments had to be combined to reach the re-
quired 1 to 2 mg for dating. We sometimes had to group 
2 samples 6 cm apart, but always included in the same 
stratigraphic sub-unit. This methodological approach 
ensures that all collected material comes from the same 
stratigraphic unit. The obtained ages were then as-
sessed for chronostratigraphic consistency, and any 
date showing inconsistency was systematically excluded 
in order to ensure the robustness of the proposed chron-
ological framework. The AMS analyses were performed 
at the Poznań laboratories (Poland). Dates were cali-
brated using IntCal20 (Reimer et al., 2020) with Calib 8 
software. Radiocarbon dating results are presented in 
Table 1.  

 
3.3.2. Optically Stimulated Luminescence (OSL) and 
Post-Infrared Stimulated Luminescence (pIRIR) Da-
ting 

Four blocks were collected from the two studied 
sections for luminescence dating of sediments. On the 
left bank, sample AKKA2-OSL1 (profile 4) was taken at 
a depth of 225 cm, while AKKA2-OSL2 (profile 4) comes 
from a level at 380 cm. On the right bank, AKKA2-OSL3 
(profile 1) was collected at a depth of 250 cm, and AK-
KA2-OSL4 (profile 2) at 280 cm. 

 
a - Sample preparation 

The samples were prepared at the Archéosciences 
Bordeaux laboratory (Bordeaux Montaigne University, 
France), under subdued red light and controlled condi-
tions in order to prevent light exposure. The core of the 

 
 

89 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

the commonly accepted range for MG aliquots of 1 ± 
10%, the post-infrared infrared stimulated luminescence 
protocol at 290°C (pIRIR290, Thiel et al., 2011) was ap-
plied on K-feldspars (supplementary Tab. S2) using a 
TL/OSL Lexsyg Smart reader. The IRSL signal was 
detected with a combination of optical filters (Schott BG 
39-3 mm; AHF Brightline HC 414/46-3.5 mm). For the 
other samples, some of the quartz DRCs were saturated 
or close to saturation (OSL 2 and 3) and high overdis-
persion (OD) values were obtained (21%, 34% and 55% 
for AKKA2-OSL2, 3 and 4 respectively), probably due to 
differential bleaching (see details in the results section). 
Single grain (SG) OSL analyses were thus performed 
using the protocol displayed in Tab. S3 on a Risø OSL/
TL reader. A green laser was used to measure 1000 
grains and the signal was detected using Hoya U340 
filters. DRT tests were conducted on SG disks for AK-
KA2-OSL 2 (given dose = 147 Gy) and 3 (given dose = 
69 Gy) using the protocol in Tab. S3. The recovered/
given values are 0.99 ± 15% (AKKA2-OSL2) and 1.18 ± 
20% (AKKA2-OSL3). These ratios are included within 1 
± 20%, due to the intrinsic variations of the samples at 
the single grain scale. The equivalent doses obtained 
using both single and multi-grain measurements were 
selected using the following criteria: a recycling ratio 
limit of 10%; a recuperation <5% of the natural signal; a 
maximum test dose error of 10%; and a test dose signal 
>3 sigma above background. The MG pIRIR290 signal 
was integrated using the first 5 seconds and the back-
ground subtracted using the last 50 seconds. The SG 
OSL signal was integrated using the first 0.07 seconds 
and the background subtracted using the last 0.25 sec-
onds. The DRC were obtained using an exponential + 
linear function for the pIRIR290 measurements and an 
exponential function for the OSL measurements. 

 
3.3.3. Sedimentological and geochemical analyses  

The sedimentological and geochemical analyses 
presented in this study were conducted on the OMEAA 
platform of UMR 5600 - EVS (Environment, City, Socie-
ty) at the Université Lumière Lyon. 

 
a - Laser Granulometry  

Grain size analysis was carried out to measure the 
size of sediment particles and to assess the energy 
required for their transport. The method is based on 
measuring laser beam diffraction and the light intensity 
scattered by particles smaller than 2 mm. Measure-
ments were performed using a Fritsch Analysette 22 
laser granulometer. 

Prior to laser granulometry, the samples were 
chemically pretreated: several treatments with H₂O₂ to 
remove organic matter, and with HCl to dissolve car-
bonates, followed by deflocculation with KCl. After rins-
ing and centrifugation, the samples were dispersed in a 
sodium hexametaphosphate solution. This method ena-
bles the evaluation of flow energy by reconstructing 
transport hydrodynamics and provides a precise charac-
terization of clay (0.4-2 μm), silt (2-63 μm), and sand (63 
μm-2 mm) fractions, as well as variations in hydrological 
regimes over time. Data processing was performed 
using the Gradistat software (version 8), developed in 
Excel by Simon J. Blott and Kenneth Pye (Blott & Pye, 
2001). The D50 and D90 values were used to assess 
flow energy: D50 represents the median flow value, 
while D90 indicates the maximum flow energy 
(Passega, 1964; Bravard, 1983). Although D99 would 

more accurately represent the maximum competence of 
the current responsible for particle transport (Salvador, 
2016), the data curves did not allow reliable determina-
tion of D99 values, so D90 was preferred instead. 

 
b - Loss on Ignition (LOI) 

The loss on ignition (LOI) method was used to 
determine the organic matter (OM) and carbonate 
(CaCO₃) content of 259 samples. Samples were first 
dried at 106°C for 24 hours. Organic matter content was 
then measured by calcining the dried, ground samples 
at 550°C for 4 hours using a Nabertherm muffle fur-
nace,while carbonate content was determined by firing 
the samples at 950°C for 2 hours (Heiri et al., 2001). 

 
c - Volume Magnetic Susceptibility (MS) 

Magnetic susceptibility provides insights into the 
composition and origin of sediments, as well as the post-
depositional processes they may have undergone, par-
ticularly pedogenesis. This parameter is highly depend-
ent on the chemical and mineralogical composition of 
the sediments, notably the presence of minerals sensi-
tive to magnetic fields - especially iron-bearing phases 
such as ferrimagnetic minerals (iron oxides, hydroxides, 
and oxyhydroxides) (Dearing, 1999). 

At a local scale, magnetic susceptibility can also be 
influenced by various environmental and diagenetic 
processes, including redox conditions associated with 
fluctuations in the water table, pedogenic processes 
involving the alteration, mobilization, and concentration 
of iron compounds by microbial and bacterial activity, 
bioturbation, physico-chemical weathering (e.g., hydroly-
sis), secondary processes following erosion and 
transport, and even the impact of fire on soil surfaces 
(Mullins, 1977). 

Measurements were conducted on oven-dried and 
finely ground samples to minimize grain-size effects. 
Samples were placed in plastic cups and analyzed using 
a Bartington MS2E dual-frequency sensor operating at 
4.65 kHz, with a sensitivity range of 0.1 and a measure-
ment period of 15 seconds. Each sample was measured 
in triplicate, and the mean value was recorded following 
the protocol established by Dearing (1999). Results are 
expressed in SI units (10⁻⁸ m³/kg). 

 
d - Geochemical Analysis and Principal Component 
Analysis (PCA) 

X-ray fluorescence can be used to approximate the 
geochemical composition of sediment through the detec-
tion of a number of major and minor elements. To ana-
lyze the geochemical content of the three alluvial se-
quences studied, we used aportable Nikon XRF spec-
trometer. which can measure the quantities of forty ma-
jor and minor elements. Data quality in terms of data 
precision was analyzed by performing triplicate meas-
urements. Samples, previously dried and ground, were 
placed in cups covered with a film to minimize interfer-
ence from factors such as grain size, porosity, and mois-
ture content (Profe et al., 2016).  

The geochemical data were analyzed by establish-
ing correlation curves between stratigraphic logs and 
measured elemental concentrations to identify those 
showing significant variations. Only the elements Mn, Al, 
Fe, K, Rb, Ti, Si, Zr, Sr, S, Cr, Mg, and Ca were selected 
for their consistent detection above limits and meaning-
ful variability. Several geochemical ratios were used to 
evaluate flow energy and redox conditions. The Zr/Rb 

 
 

90 

 
 

Saadi F. et al. 



   

 

upstream of the site a common process in fluvial con-
texts. 

 
4.1.2. OSL and pIRIR290 dating 

The equivalent doses for the pIRIR290 multi-grain 
analyses of AKKA2-OSL1 were computed using the 
Central Age Model (CAM, Galbraith et al., 1999), giving 
an OD value of 9 ± 3%, Tab. 2. For the other three sam-
ples, the single grain measurements allowed the mini-
mum age model (MAM) in order to give more weight to 
the well-bleached grains and discard saturated grains. 
The OD value obtained on the SG measurement of AK-
KA2-OSL2 is similar to the one obtained on MG ali-
quots, of 21%. However, the OD values are higher for 
AKKA2-OSL3 and 4, of 52% and 61% respectively (Tab. 
2). The MAM allowed taking into account the youngest 
grains, i.e., providing a minimum age estimate for the 
layer. Ages are displayed in  Tab. 2 and range from 82. 
9 ± 5.5 ka (AKKA2-OSL1) to 8.5 ± 1.4 ka (OSL3). Note 
that the yield of accepted quartz grains is low, under 
3%. The statistics regarding the single grain selection 
criteria are available in supplementary material Table. 
S4. The dose rate data are presented in  Tab. 3. 

 
4.2. Landforms, Textures and Compositions: Multi-
Proxy analyses of the alluvial Sequences of Akka 

A detailed analysis of the four Akka Plain profiles - 
based on granulometric, structural, colorimetric, and 
pedological criteria (including bioturbation intensity, root 
traces, types and densities of secondary carbonates, 
and redox features) - identified nine major litho-
pedostratigraphic units, further divided into 19 sub-units. 
These units reflect the local hydrogeomorphological 
history, encompassing erosion, aggradation, and minor 
bed mobility.  

The lithostratigraphic and chronological results are 
detailed in section 4.2.1, and the sedimentological and 
physico-chemical analyses in section 4.2.2. ‘’Multi-proxy 
analyses and types of pedosedimentary environments’’. 
 

ratio serves as an indicator of flooding and coarser 
(sandy) alluvial deposits in a fluvial context (Rothwell & 
Croudace, 2015; Jones et al., 2012; Wang et al., 2011). 
The Fe/Mn ratio help in assessing the redox conditions 
of the alluvial plain (Rothwell & Croudace, 2015), while 
the Ca/Mg ratio indicates biochemical calcite precipita-
tion related to low environmental hydrodynamics 
(Lauterbach et al., 2011). The Si/Al ratio is used to iden-
tify the origin of windblown or sediment dust (Klasen et 
al., 2015; Zech et al., 2008; Profe et al., 2016) and is 
correlated with other proxies influenced by grain size 
(Liang et al., 2013). Lastly, the Rb/Sr ratio serves as an 
indicator of soil weathering and/or erosion of developed 
soils (Jones et al., 2012; Rothwell & Croudace, 2015; 
Profe et al., 2016).  

To synthesize geochemical data signal, a Principal 
Component Analysis (PCA) was conducted. Only the 
eleven most relevant elements - Rb, Fe, Ti, K, Al, Mg, 
Si, Zr, S, Mn, and Ca - were included in the PCA, based 
on their environmental interpretability and local strati-
graphic relevance. The analysis was performed in R 
using the FactoMineR, package. No standardization was 
applied, as all variables were expressed in comparable 
intensity units derived from the XRF measurements. The 
PCA was based on a correlation matrix (default in Fac-
toMineR), and no missing values were present in the 
selected dataset. 

 
4. RESULTS AND INTERPRETATIONS 
 
4.1. Chronological Results  
 
4.1.1. Radiocarbon Dating  

Radiocarbon dating provided a total of 13 ages on 
organic material (charcoal and organic matter). Of these, 
six dates were excluded because they were inconsistent 
with the chronostratigraphic framework established in 
the field. These discrepancies appear to be mainly due 
to contamination by older material, likely reintroduced as 
a result of repeated phases of erosion and alluviation 

 

 
 

91 

Tab. 1 - Chronological data of samples from the Wadi Akka: conventional radiocarbon ages and calibrated ages. 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

BP (11.227-11.736 cal BP). 
 
Unit 4 (U4): This formation appears at the base of 
profile 2 (Fig. 5a). It begins with the deposition of a mas-
sive clayey silt layer with a pale brown hue (10YR 6/3, 
pale brown), measuring 50-70 cm in thickness. This 
basal unit is dated by radiocarbon ¹⁴C to approximately 
10.520 cal BP (10.097-10.690 cal BP). Overlying this 
layer is a thicker deposit of brownish clayey silts (U4b) 
(10YR 5/6, yellowish brown), characterized by interca-
lated centimeter-scale layers of blackish, highly mineral-
ized peat. The peat is notably flaky and composed of 
strongly humified plant debris, arranged in indistinct 
micro-beds (Fig. 5c). 

Also present are cylindrical travertine tubes (4-5 
cm long, <1.5 cm in diameter) with calcified walls (Fig. 
5c), Melanopsis sp. shells, and a thin yellowish-orange 
oxidized lens. Morphologically, this unit represents the 
sedimentary infill of a broad alluvial channel - approxi-
mately 150 meters wide - exposed at the base of profile 
2 and extending beneath the modern alluvial plain (Fig. 
2a/b/3). The upper part of the unit has been dated to 
around 9.591 cal BP (9.025-10.187 cal BP).  

 
Unit 5 (U5) is identified in both the left and right 
bank deposits of the Akka Wadi (Fig. 3) and comprises 
four sub-units. Sub-unit U5a is a thin, 10 cm layer of 
heterometric gravels Gs1 (Gravel sheet) (Fig. 6a), locat-
ed above U4b. It is discontinuously preserved along the 

4.2.1. Litho-chronostratigraphy 
Unit 1 (U1): The basal formation (U1a) is found 
at the base of both outcrops on the left and right 
banks (Fig. 3). It consists of a conglomerate deposit 
made up of heterometric gravels (2-10 cm) set in a 
greyish sandy matrix (10YR 7/2, light gray), exhibit-
ing a compact texture. The thickness ranges from 
40 cm on the left bank to 70 cm on the right bank 
(Fig. 3). No samples were collected from this unit. 
Above this, Unit 1b (U1b) (Fig. 4a) consists of alter-
nating infill deposits within narrow or flared gravelly 
channels, which are shallow, along with lenses of 
heterometric gravels (Figs. 2c and 2d). This sedi-
mentary structure is particularly well-exposed on the 
right bank, where it displays a braided pattern, indi-
cating high lateral channel migration and significant 
instability of the floodplain, with a thickness of nearly 2 
meters (Fig. 2d). Overlying this is Unit 1c (U1c), a silty 
clay deposit (10YR 7/3, very pale brown) with a massive 
structure containing some secondary carbonate nodules. 
An OSL date obtained from this formation suggests an 
age of approximately 82.900 ± 5.500 years. 
 
Unit 2 (U2): This unit, observed only on the right 
bank of the wadi in profile 4 (Fig. 3), consists of a silt 
deposit approximately 1.50 m thick, (Fig.4a) with a 
greenish-gray color (10YR 7/2, light gray). The deposit 
exhibits a polyhedral structure and contains some shell 
fragments. OSL dating places this unit at approximately 
40.5 ± 2.4 ka (Tab. 2). 

 
Unit 3 (U3): This unit is clearly distinguishable in the 
outcrop by its greenish to light gray color (10YR 7/2, light 
gray), observed on the left bank of the Akka Wadi (Figs. 
2a, 2b, and 3). It appears at the base of profiles 1 and 3 
(Fig. 4b) and is characterized by a massive silty facies, 
50 to 70 cm thick, containing a few centimeter-sized 
lenses of heterometric gravels. Above this lies a massive 
deposit of silt to fine silty sand (U3b), associated with the 
presence of Melanopsis (probably of aff. cariosa type, 
according to Linnaeus (1789)). This unit (U3), which 
outcrops discontinuously on the left bank of the Akka 
Wadi (Figs. 2a, 2b), is preserved over a limited distance 
of approximately 250 meters to the south. This formation 
is dated by radiocarbon ¹⁴C to around around 11.428 cal 

 
 

92 

Tab. 2 - Multi-grain (MG) pIRIR290 ages obtained from K-feldspar of sample AKKA2-OSL1 and single-grain (SG) OSL ages obtained from 
quartz of samples AKKA2-OSL2, 3, and 4 (1σ uncertainties). For MG analyses, De values were measured on 1 mm diameter aliquots. For 
SG analyses, quartz grains were mounted on standard 150 μm hole disks, reporting accepted (n) and measured (N) grains with overdi-
spersion (OD). Alpha and beta dose rates were calculated from radioactive elements (U, Th, K) measured by gamma spectrometry (Tab. 
3), using conversion factors from Guérin et al. (2011) and alpha attenuation factors (0.14 for U, 0.17 for Th) from Brennan et al. (1991). 
Gamma dose rates were measured in situ (Tab. 3), and cosmic dose rates were estimated from burial depth (Prescott & Hutton, 1988). 
Feldspar ages were calculated using the Central Age Model (CAM, Galbraith et al., 1999) with beta absorption factors (0.098 for U, 0.139 
for Th, and 0.039 for K) as per Guérin et al. (2012) and an α-value of 0.08 ± 25%. The internal dose rate for the K-feldspars was calculated 
using a K-content assumed of 12 ± 1%. Quartz ages used the Minimum Age Model (MAM) with beta absorption factors (0.100 for U, 0.142 
for Th, and 0.041 for K) following Guérin et al. (2012) and an s-a value of 4.5 ± 20% 

 
Tab. 3 - U, Th and K contents of sediment samples analysed with a 
laboratory gamma-ray spectrometer equipped with a high-resolution, 
broad energy Ge (BEGe) detector and in-situ gamma dose rate meas-
ured using a portable gamma-ray spectrometer.  

 
 

Saadi F. et al. 



   

 

shell debris of Melanopsis sp. Numerous root traces are 
also visible, pointing to the development of local hydro-
hygrophilous vegetation. Overlying this, sub-unit U5c is 
a 20 to 60 cm thick layer of homogeneous fine sand of 
similar coloration (10YR 6/4), marking a transition in 
sedimentation dynamics and a clear increase in hydro-
dynamic energy. This intensification culminates in sub-
unit U5d, a deposit of heterometric gravels (Gs2) rang-
ing from 10 to 20 cm in thickness, which is consistently 
visible across the outcrop (Figs. 5a, 6a). This gravel 

right bank outcrop and marks a lithostratigraphic discon-
tinuity, as it erodes the upper part of the underlying fluvio
-palustrine deposits (U4b). This erosional contact indi-
cates a significant shift in sedimentary dynamics, prefig-
uring the processes that dominate the subsequent sub-
units. Sub-unit U5b is composed of massive clayey silts 
with a light beige color (10YR 6/4 - light yellowish 
brown), measuring between 40 cm thick on the right 
bank and up to 1 m on the left bank. This facies includes 
small tufa lenses forming calcified filaments, as well as 

 
 

93 

 

Fig. 4 - Field photographs of profiles 3 and 4: a) Sedimentary units of profile 4 on the right bank, showing sample locations and OSL and 
radiocarbon (¹⁴C) dates, b) Profile 3 on the left bank, which forms the base of profile 2, c) Gravelly unit U1a at the base of profile 4.  

Fig. 5 - Field photographs of profile 2 on the left bank: a) Overview of the sedimentary units composing profile 2, with sample locations and 
chronological sequence, b) Detailed view of units U8, U9a, and U9b, c) Close-up of unit U3b, highlighting travertine tubes, dark peat lay-
ers, and Melanopsis shell fragments.  

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

prises a tuffaceous sand layer with a yellowish-brown 
color (10YR 6/4) and a thickness of 70 cm. This deposit 
features large, heavily cemented travertine tubes (Fig. 
6b), associated with shell fragments. 

 
4.2.2. Multi-proxy analyses and discussion of sedi-
mentary environment types  

The cross-analysis of sedimentological and physi-
co-chemical data (Fig. 7) allows for the reconstruction of 
past environmental dynamics of the Akka plain. Based 
on the results obtained, three main types of pedosedi-
mentary environments (TPE) have been identified. Each 
of these environments is characterized by specific fea-
tures reflecting depositional conditions (grain size, hy-
drodynamic energy), the degree of pedogenetic altera-
tion, carbonate precipitation dynamics, organic matter 
accumulation, redox conditions, and sediment prove-
nance. These elements are summarized in Table 5. 

These parameters were assessed using a series of 
environmental proxies: Grain size indices (D50 and 
D90) indicate depositional energy; Magnetic susceptibil-
ity (MS) and the Rb/Sr ratio inform on the intensity of 
pedogenetic processes, sometimes associated with high 
concentrations of organic matter; Carbonate content 
(CaCO₃) and the Ca/Mg ratio reflect carbonate precipi-
tation conditions, organic matter (OM) content indicates 
biological productivity or the preservation of authigenic 
vegetation, the Fe/Mn ratio is used as a marker of redox 
conditions, finally, the Si/Al ratio serves as an indicator 
of detrital input and can also be interpreted as a proxy 
for aridity. 

 
TPE 1: Low-energy fluvio-palustrine environment 

This type of environment includes units U1b, U2, 
U3a, and U4b (Fig. 7). It is characterized by a high pro-
portion of fine particles (silt and clay), representing be-
tween 70% and 90% of the total grain size, with a clear 
dominance of silt. D50 and D90 values below 30 μm 
indicate very calm depositional conditions, typical of 
stable, shallow, or even semi-permanent settings such 
as wetlands or marshes. Magnetic susceptibility is low 
(5 to 10 × 10⁻⁸ m³·kg⁻¹), consistent with a low concen-

layer reflects a major increase in flow energy, likely as-
sociated with a significant incision phase of the wadi 
between profiles 4 and 3, as illustrated in Figure 3. 
 
Unit 6 (U6) is deposited above the gravelly phase 
(Gs2) (Fig. 3). It appears in Profiles 1 and 2 (Figs. 5a 
and 6a) and is characterized by a facies similar to Unit 
U5b, consisting of massive, tuffaceous clayey silts with a 
light brown color (10YR 6/4 pale brown). Its thickness 
ranges from 20 to 30 cm and contains a few Melanopsis 
shells. This formation is dated between 8.500 (U5d) and 
7.204 cal BP (U7a). 

 
Unit 7 (U7) starts with a massive deposit of silt 
(U7a), light yellowish-brown in color (10YR 6/4), clearly 
visible in Profiles 1 and 2, with a thickness ranging from 
20 to 50 cm. This layer contains a few roots, especially 
on the right bank in Profile 2 (Fig. 5a). Above it lies a 
thick layer of silty sand (U7b), varying from 30 cm to 1 m 
thick in Profile 2. This alluvial plain aggradation features 
a sometimes well-developed and cemented tufa layer, 
associated with a few Melanopsis shells. The formation 
is dated to 7.204 cal BP (6.992-7.420 cal BP). 

 
Unit 8 (U8) corresponds to a channel deposit com-
posed of massive silts that overlie Unit U7b (Profile 2) 
(Fig. 2b), with a thickness of about 50 cm. It extends 
over 85 meters, exclusively along the left bank in Profile 
1 (Fig. 2c/d). The unit is also marked by the presence of 
a few root traces. 

 
Unit 9 (U9) is subdivided into three sub-units, ob-
served in the upper parts of both outcrops on the left and 
right banks (Fig. 3), south of Profile 4. The first sub-unit, 
U9a, consists of a loose-textured silty sand deposit with 
a yellowish-brown color (10YR 5/4) and a thickness of 
60 cm (Fig. 5b). The next sub-unit, U9b, is a fine sand 
layer about 70 cm thick, perforated by numerous root 
traces. It is overlain by a thin 10 cm layer of heterometric 
gravels (Gs3), found only in Profile 1 (Fig. 3). This for-
mation is dated to 656 cal BP (506-904 cal BP). The 
final sub-unit, U9c, is observed only in Profile 1. It com-

 
 

94 

 

Fig. 6 - Field photos of profile 1: a) View of the sedimentary units forming profile 1 on the left bank to the north; b) Zoom on the tuffaceous 
alluvium deposit (U9c) with large travertine tubes; c) Stromatolithic travertine dam observed to the north of profile 1, deposited at the same 
level as unit U9c.  

 
 

Saadi F. et al. 



   

 

 

 
 

95 

Tab. 4 - Synthetic description of the lithostratigraphic facies and the deposits related to the sedimentary environments identified in the 
Akka sequences.  

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

 

 
 

96 

Fig. 7 - Correlation diagramms of the principal granulometric, magnetic, and geochemical properties from the four studied profiles, integrat-
ed to propose a reference cross-section of the Akka alluvial sequence. Colored bands highlight the distinctive characteristics of each sedi-
mentary unit. Geochemical ratios are expressed relative to the average values of each ratio. Black arrows atop the curves indicate sedi-
mentary discontinuities within the alluvial record. 

 
 

Saadi F. et al. 



   

 

ic susceptibility (MS) ranges from 5 to 15 × 10⁻⁸ m³·kg⁻¹, 
indicating a moderate presence of magnetic minerals. 
The Rb/Sr ratio is variable. Carbonate contents (CaCO₃) 
are moderate to high (50-70%), with high Ca/Mg ratios, 
suggesting carbonate precipitation partially linked to 
biogenic processes or calcium-rich groundwater inputs. 
Organic matter (OM) is moderately abundant, generally 
between 10% and 30%. Redox conditions are variable, 
with occasional Fe/Mn peaks, indicating a frequently 
water-saturated environment with possible fluctuations. 
The Si/Al ratio is generally low, indicating limited detrital 
input. However, some units (notably U5b, U6a, U7a, 
and U8) show peaks in the Si/Al ratio, indicating chang-
es in sediment sources after 9.700 cal BP, reflecting an 
increase in fluvial detital or aeolian influence. Altogether, 
these indicators reflect a calm and humid floodplain 
environment with fine sediment deposits, moderate to 
advanced pedogenesis, and carbonate precipitation. 
This type of setting corresponds to sub-humid to humid 
climatic conditions, with shallow groundwater tables and 
diffuse runoff and floods events. 

It is characteristic of low-energy floodplains, where 
water is present temporarily or semi-permanently, favor-
ing the deposition of fine and relatively stable sedi-
ments. These environments are often associated with 
channel margins, overflow areas, or wetlands fed by 
groundwater or diffuse surface flow. 

 
TPE 3: Dynamic high-energy alluvial environment 

This environment includes units U1a, U5a, U5c, 
U5d, U7, U9a, and U9b (Fig. 7). The grain size is 

tration of magnetic allogenic minerals, often linked to 
organic or carbonate-rich environments. The Rb/Sr ratio 
is generally high, indicating significant pedogenetic alter-
ation, possibly due to leaching processes or in-situ soil 
formation. Carbonate contents (CaCO₃) are high (50-
65%), as are Ca/Mg ratios, suggesting carbonate precip-
itation under calm conditions, favored by bicarbonate-
rich groundwater inputs. These deposits may be associ-
ated with the formation of carbonate tufas, particularly in 
the presence of dense vegetation and good water reten-
tion. Organic matter is abundant (20-50%), reflecting 
either local high biological productivity or/and good 
preservation under hydromorphic conditions. The Fe/Mn 
ratio shows medium to high values, indicating alterna-
tions between oxidizing and reducing conditions, com-
mon in periodically saturated environments. Lastly, the 
Si/Al ratio is generally low, suggesting limited detrital 
input and supporting the hypothesis of a closed environ-
ment with minimal allochthonous influence. 

Overall, these features indicate a low-energy fluvio-
palustrine environment, with high biological production, 
carbonate precipitation, organic soil development, and 
frequent hydromorphic conditions - typically associated 
with wetter climatic phases or/and high groundwater 
levels. 

 
TPE 2: Low-energy (carbonate-rich) floodplain 

This environment includes units U3b, U4a, U6, and 
U9c (Fig. 7). The grain size distribution is dominated by 
silty fractions (60-80%), with D50 values below 50 μm, 
indicating low to moderate depositional energy. Magnet-

 
 

97 

 

Tab. 5 - Comparative summary of Pedosedimentary Environment Types (TPE).  

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

correlation with units U1b, U2, and U4b. Iron, a terri-
genous element frequently used as a redox indicator 
(Rothwell & Croudace, 2015), reflects variations in the 
oxidation conditions of the environment but also is in-
volved in pedogenesis processes, while rubidium, gen-
erally associated with fine clay deposits, indicates detri-
tal input in a low-energy context, potentially linked to 
pedogenetic or soil erosion processes. In the lower part, 
zirconium (Zr) and silica (Si) are enriched in the samples 
from units U9a, U9b, and U5c. These elements, con-
tained in resistant minerals to physical and mechanical 
processes such as zircon, reflect high-energy deposits 
and suggest a predominantly aeolian and/or torrential 
river inputs. 

Overall, this analysis allows for the distinction of 
three main sedimentary poles: carbonate deposits with 
redox conditions represented by units U1b, U2, and 
U4b; alluvial detrital inputs mainly grouping units U7b 
and U8; and finally, coarse deposits with a dominant 
aeolian origin characterizing units U9a, U9b, and U5c. 

 
5. SYNTHESIS AND DISCUSSION 

 
In this section, we discuss the morphosedimentary 

and paleoenvironmental evolution of the Akka Plain. Our 
analysis draws on the geochemical composition and 
sedimentary dynamics of the formations, alongside the 
concurrent development of the alluvial plain’s geomor-
phological setting and the chronological framework of 
the deposits. By correlating these proxies, we recon-
struct the local geomorphological and paleoenvironmen-
tal history of the plain from the Late Pleistocene (MIS 
5b) to the present (Fig. 9). These results are compared 
with similar reconstructions from alluvial archives across 
North Africa, as well as with recently published paleoen-
vironmental and paleoclimatic data at local, regional, 
and supraregional scales throughout the eastern Sahara 
and North Africa (Fig. 10). Our approach involves corre-
lating evolutionary histories reconstructed in other re-
gions to validate and strengthen our local findings, 
thereby situating them within the broader context of 
paleoenvironmental dynamics. 

 
5.1. MIS 5b (ca. 82.9 ± 5.5 ka): Fluvial Aggradation 
and Hydroclimatic Instabilities 

During Phase 1, dated to approximately 82.9 ± 5.5 
ka, the Akka plain records a marked phase of aggrada-
tion, characterized by sediment accumulation reaching 
up to 4.5 meters in thickness. The sedimentary se-
quence displays a fining-upward trend: coarse sedi-
ments at the base gradually give way to finer materials, 
interspersed with gravelly layers in the upper section. 
These deposits are associated with narrow and shallow 
channels, where massive, heterometric gravel unit are 
observed - typical of a braided river system. This type of 
fluvial dynamic is generally seen in deep valleys sub-
jected to highly variable hydrological regimes or in re-
sponse to exceptional rainfall events (Lghamour et al., 
2024) Paine et al., (2024).  

The silty matrix binding the gravel elements sug-
gests deposition during waning flood stages. It also 
indicates the probable presence of permanent ponds 
during low-flow periods. These features reflect strong 
alluvial activity driven by unstable hydroclimatic condi-
tions, likely linked to the end of the last interglacial peri-
od (Marine Isotope Stage 5), a phase still poorly docu-
mented in the fluvial archives of southern Morocco and 

coarse, dominated by sand (70-80%) and sometimes 
gravel, indicating high hydrodynamic energy and strong-
er connectivity with upstream areas. Grain size indices 
are high (D50 > 100 μm, D90 > 220 μm), and the Zr/Rb 
ratio is also significant, confirming rapid and energetic 
fluvial transport. Magnetic susceptibility varies (10 to 50 
× 10⁻⁸ m³·kg⁻¹), with high values in certain units (e.g., 
U5a, U9b), indicating a stronger contribution of detrital 
magnetic minerals. The Rb/Sr ratio is low, reflecting 
limited mineral alteration due to rapid deposition and 
minimal pedogenetic development. Carbonate contents 
(CaCO₃) are moderate (40-50%), with low Ca/Mg ratios, 
indicating a context where carbonate precipitation is not 
favored due to the high-energy depositional dynamics. 
Organic matter content is very low (2-15%), reflecting a 
very detrital environment unfavorable for its accumula-
tion and frequently subject to remobilization. The Fe/Mn 
ratio is highly variable, suggesting possible alternations 
between oxidizing and reducing phases.  

Finally, the Si/Al ratio is high, confirming a substan-
tial input of coarse detrital material of aeolian or torren-
tial origin. 

Overall, this type of environment reflects an active, 
high-energy alluvial setting dominated by coarse inputs, 
minimal soil development, poor organic matter preserva-
tion, and indicative of episodic flood phases, aeolian 
redeposition of alluvial deposits associated to drier cli-
matic conditions. 

 
4.3. Principal Component Analysis (PCA) 

In order to gain a better understanding and simplify 
the analysis of the geochemical dataset obtained from X
-ray fluorescence (XRF), we conducted a Principal Com-
ponent Analysis (PCA). For a clearer representation of 
the results, only the most representative units from each 
profile were selected, thus forming the core geochemical 
dataset (Fig. 11 in supplementary material) 

Figure 8 shows the PCA biplot, where two axes are 
represented. Axis Dim1 explains 32% of the total vari-
ance, and axis Dim2 accounts for 20.7%, giving a cumu-
lative total of 52.7% of the overall inertia. The colored 
dots represent the samples, coded according to depth, 
with a gradient ranging from blue at the base of the se-
quence to orange at the top. The black arrows represent 
the geochemical variables, with their direction indicating 
correlation with the axes, and their length reflecting the 
strength of that correlation. The samples cluster into 
units (U1b, U2, U4b, U7b, U8, U9, and U5c), highlighting 
their relationships with certain elemental variables. 

The first dimension (Dim1), which explains 32% of 
the total variance, contrasts two groups. On the left side, 
there is a positive correlation between calcium (Ca), 
sulfur (S), and manganese (Mn) with the samples from 
units U1b and U2. Calcium and sulfur reflect carbonate 
and evaporite deposits. Their joint enrichment suggests 
carbonate deposits associated with hydrological fluctua-
tions of the water table. On the opposite side, to the 
right, titanium (Ti), potassium (K), aluminum (Al), and 
magnesium (Mg) show a positive correlation with the 
samples from units U7b and U8. Titanium, of continental 
origin, is mainly linked to coarse detrital inputs, while 
potassium and aluminum, associated with clay minerals, 
reflect finer sediment inputs. This elemental grouping 
characterizes an alluvial minerogenic detrital dynamic. 

The second dimension (Dim2), which accounts for 
20.7% of the variance, separates two trends. In the up-
per part, iron (Fe) and rubidium (Rb) show a positive 

 
 

98 

 
 

Saadi F. et al. 



   

 

silty unit U2. This unit, about 1 meter thick, is character-
ized by predominantly fine deposits (over 80% silt), indi-
cating a stable sedimentary environment influenced by 
low-energy hydrological dynamics. The greenish-grey 
color (10YR 7/2), the massive polyhedral structure of 
the deposit, and a high organic matter content (over 
30%) confirm the presence of active hydromorphic pe-
dogenetic processes associated with a high, quasi-
permanent fluvial aquifer, during sedimentation. These 
features point to a prolonged period of soil exposure, 
consistent with a phase of relative landscape stability. 

The sedimentological characteristics, confirmed by 
associated grain-size and geochemical analyses, sug-
gest a low-energy depositional environment with limited 
aridity, supporting the hypothesis of a more humid cli-
mate during this period. 

Available paleoenvironmental and paleoclimatic 
data on MIS 3 in Morocco, although limited, reinforce 
these observations. In the southern part of the country, 
geomorphological analyses of the fluvial systems of the 
wadi Tamadroust and Wadi Noun reveal the accumula-
tion of lacustrine deposits dating between 50 and 30 ka 
BP. These findings indicate low-energy fluvial activity 
during MIS 3, in a relatively humid climatic context 
(Weisrock et al., 2006). At the regional scale, alluvial 
archives from the Falémé Valley in Senegal also docu-
ment a high load of fine sediments and progressive 
aggradation of the riverbed during MIS 3 and 2 (Rasse 

Northern Africa. 
This interpretation is supported by data from the 

Wintimdouine cave stalagmite, located about 200 km 
west of Akka and 30 km north of Agadir (Ait Brahim et 
al., 2017; Ait Brahim et al., 2023). Isotopic analysis of 
this karst archive reveals a period of high rainfall be-
tween 84 and 77 ka BP, during the Late Pleistocene, 
reflecting intensified precipitation and regional runoff. 
The variability of δ¹³C and δ¹⁸O, with more negative val-
ues around 80 ka and more positive values near 73 ka, 
suggests that both proxies respond to the same orbital-
scale climatic forcing (Ait Brahim et al., 2023).  

Meanwhile, records from Dim Cave in southern 
Turkey show a peak in detrital input during the MIS 5a-
MIS 4 transition (81-70 ka), associated with increased 
erosion, surface weathering, and progressive mineralog-
ical changes (Paine et al., 2024). These developments 
indicate a decline in regional moisture availability, fol-
lowed by a pronounced aridity peak after 74 ka, corre-
sponding to a rapid transition to intense cold and dry 
conditions observed across the Northern Hemisphere's 
paleoclimatic archives. 

 
5.2. MIS 3 (ca. 60-30 ka): Evidence of fluvial dynam-
ics and relationship to humid/arid fluctuations. 

Around 40.500 ± 2.400 years ago, during Marine 
Isotope Stage 3 (MIS 3), the Akka plain experienced a 
new phase of aggradation (Fig. 9), represented by the 

 

 
 

99 

Fig. 8 - Results of the Principal Component Analysis (PCA) performed on the Akka geochemical dataset. Colored areas associated with 
clusters of projected samples emphasize the hydro-sedimentary and environmental contexts corresponding to each correlation group.  

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

north, in Morocco particularly in the sedimentary records 
of the Noun, Assaka, and Kert rivers, as well as in the 
Moulouya Basin, where indicators of hydrological reacti-
vation and hydromorphy appear between 11.500 and 
10.800 cal BP (Ouammou, 1993; Boudad et al., 2003; 
Mathieu et al., 2004; Zielhofer et al., 2008). Despite the 
limited dating of alluvial archives in some areas of 
southern Morocco, such as thocse from the Wadi Noun 
(Weisrock et al., 1991), and the scarcity of data from 
Saharan fluvial systems in this region, the deposits from 
the Akka plain represent the first clear and well-dated 
evidence of hydrological dynamics associated with the 
African Humid Period (AHP) in southern Morocco. 

 
5.4. Early Holocene / African Humid Period 11.5-8 ka 
BP 

This phase, dated between 10.520 and 9.591 cal 
BP, begins with a marked incision of about 1.5 m, cut-
ting into the previous phase as well as the underlying 
Pleistocene formations (Fig. 9). It is followed by a fine 
alluvial aggradation reaching a thickness of 2 m, repre-
sented by unit U4. This phase is part of the Early Holo-
cene dynamics, characterized by a progressive intensifi-

et al., 2020) (Fig. 10). These observations are further 
supported by the work of Preusser et al. (2002), who 
reported an absence of aeolian remobilization in the 
Wahiba Sands region of Oman (Eastern Arabia) be-
tween 64 and 22 ka BP, indicating a prolonged humid 
phase between 58 and 32 ka BP. 

 
5.3. Late Pleistocene / Younger Dryas (15-11.5 ka): 
fluvial reactivation and early signs of the African 
Humid Period 

This phase (Fig. 9), dated between 11.428 and 
10.520 cal BP, begins with a clear incision of the riv-
erbed on the left bank, followed by fine alluvial aggrada-
tion forming unit U3, with a thickness ranging from 1.5 to 
2 meters. This sequence reflects fluctuating hydrological 
dynamics: at its base, the deposits indicate a low-energy 
fluvio-palustrine environment, which gradually transitions 
to conditions still dominated by low energy but intermit-
tently disrupted by brief, more powerful hydrological 
events, as evidenced by the localized presence of 
coarse sand layers interpreted as the result of sudden 
flood events. 

Similar dynamics have been documented further 

 
 

100 

Fig. 9 - Model of the geomorphological and paleoenvironmental evolution of the Akka plain to since MIS 5b, Phases 5a, 5b and 7 present 
an imprecise chronology due to the lack of carbonaceous material within the sedimentary units. 

 
 

Saadi F. et al. 



   

 

in valley bottoms, the formation of organic-rich soils 
associated with hygro-hydrophilous vegetation, and the 
presence of weakly active alluvial channels. 

The localized presence of Melanopsis shells asso-
ciated with tubular tufa deposits (Fig. 5c) indicates slow 
and perennial flow in a freshwater environment saturat-
ed with calcium bicarbonate. This interpretation is sup-
ported by several geochemical indicators (Fig. 7) point-
ing to very low-energy conditions in a hydromorphic 
environment with high water stability. The observed 
oxidation deposit shows a subsequent partial drying of 

cation of regional humidity, corresponding to the first 
manifestations of the last African Humid Period (AHP). 

The sedimentological and geochemical characteris-
tics of this sequence indicate a low-energy fluvial sys-
tem, favorable to the development of stable marshy en-
vironments. The abundance of authigenic organic matter 
deposits (peat), the accumulation of carbonates (tufa), 
and the high silt content point to persistently humid cli-
matic conditions, under the effect of increased and more 
evenly distributed rainfall throughout the year. This hy-
drological context promoted the expansion of wetlands 

 
 

101 

Fig. 10 - Comparison of environmental and climatic records during the Late Pleistocene (MIS 5b) and the Holocene in North Africa. Chro-
nology is expressed in calibrated years before present (cal BP). Blue bands represent humid periods, while yellow bands indicate arid 
environmental phases. a) Paleoclimatic δ¹³C record from speleothems in Wintimdouine (Ait Brahim et al. 2023), b) Paleoclimatic δ¹⁸O 
record from speleothems in Wintimdouine (Ait Brahim et al., 2023), c) Mg/Ca ratio curve as a sea surface temperature (SST) proxy from 
planktonic foraminifera shells (Globigerinoides ruber) (Parker et al., 2016), d) Precipitation index for the western Mediterranean basin 
derived from speleothems from Chaara cave (Ait Brahim et al., 2019), e) Summer and winter insolation curves at 40°N (Berger & Loutre, 
1991), f) North Atlantic ice-rafted debris records showing both tuned and original datasets, with numbered Bond events chronology (Bond 
et al., 2001), g) Paleoenvironmental records from the Niayes peat bog, northern Senegal (Ndiaye et al., 2022), h) Climatic reconstructions 
from fossil diatoms in paleolakes in central Sahara, Chad (Yacoub et al., 2023), i) Paleoenvironmental records from the Charef River, 
northern Morocco (Depreux et al., 2022;  Depreux et al., 2021), j) Environmental records from the Takarkori River, southwestern Libya 
(Cremaschi et al., 2014), k) Environmental records from the Yami River, Sahara, western Africa (Lespez et al., 2011), l) Holocene pa-
leoenvironmental record from the middle Drâa basin (Saadi et al., 2024), m) Paleoenvironmental archives from the Akka plain (this study). 
Question marks in the Akka sequence highlight phases with chronological uncertainty.  

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

truncations and hiatuses, suggesting a transition to 
more arid conditions, accompanied by high fluvial ener-
gy. Three distinct phases are identified in the Akka plain 
during this period: phase 5, subdivided into three sub-
phases (5a, 5b, and 5c), as well as phases 6 and 7. 
These different phases illustrate a marked variability in 
fluvial dynamics and climatic conditions, typical of the 
Middle Holocene (Renssen et al., 2003; Roberts et al., 
2011; Fletcher et al., 2013; Berger et al., 2016) 

 
- Phase 5a: Fluvial incision and erosive dynamics 

The first sub-phase, corresponding to unit U5a, is 
marked by significant fluvial incision (Fig. 9), esti-
mated between 1 and 1.5 meters deep, cutting into 
the alluvium of the previous phase. Grain-size and 
geochemical analyses reveal a notable increase in 
flow energy, characterized by a high proportion of 
coarse fractions and elevated Zr/Rb and Si/Al ratios. 
These markers indicate an episode of intense ero-
sion, resulting in a negative sedimentary record 
(erosive truncation), probably linked to episodic allu-
vial discharges and significant aeolian input. This 
abrupt change reflects a substantial drop in the allu-
vial water table and hydrological instability in the 
Akka plain. This event could be associated with a 
regional arid phase that occurred around 9 300 cal 
BP, linked to the global Rapid Climate Change 
(RCC) event of that period. Similar dynamics have 
been observed in the Moulouya basin, where a 
nearly synchronous depositional hiatus has been 
identified (Depreux et al., 2022).  

 
- Phase 5b: Fluvial aggradation and return to humid 

conditions. 
The following sub-phase, corresponding to unit 

U5b, is marked by a resumption of fluvial aggradation 
within a more stable hydromorphic context. Flow condi-
tions became more regular, favoring a rise in the alluvial 
water table and sediment accumulation. Geochemical 
indicators reveal high organic matter content (up to 
30%), low carbonate concentration, predominance of 
fine particles, and a low Rb/Sr ratio, pointing to a tempo-
rary return to a humid, low-energy fluvial environment. 
 
- Phase 5c: Major erosive episode and return to arid 

conditions. 
The last sub-phase, dated by OSL between 9.500-

8.500 BP and corresponding to units U5c and U5d, rec-
ords a new episode of intense erosion, well preserved 
on both banks of the Wadi Akka. Grain-size and geo-
chemical data attest to this hydrological dynamic: a high 
proportion of coarse fractions (sands, gravels > 80%), 
elevated D50 and D90 values, and an accentuated Zr/
Rb ratio. These parameters reflect a powerful fluvial 
dynamic in a high-energy environment. Similarly, low 
Rb/Sr ratios suggest limited pedological alteration, while 
the low organic matter content indicates sedimentation 
dominated by detrital minerogenic inputs, with minimal 
biological contribution. These features are typical of 
more arid climatic conditions. 

This phase marks the transition between the Early 
and Middle Holocene and reflects a major change in 
sedimentary dynamics and paleoenvironmental condi-
tions. It remains poorly documented in most Maghrebian 
fluvial archives (Zielhofer et al., 2008; Depreux et al., 
2021).This regional sedimentary hiatus appears to result 
from major hydro-geomorphological disturbances affect-

the channel bed. 
At the regional scale, comparable sequences have 

been identified in the alluvial archives of the wadi Noun, 
characterized by fluvio-lacustrine deposits rich in organic 
matter, stagnant waters, and evidence of pedogenesis 
(Weisrock, 1980; Chennaoui et al., 2005; Weisrock et 
al., 2006). In the Moulouya basin, sedimentary and paly-
nological data reveal the presence of marshy environ-
ments and carbonate tufa formation between 10,800 and 
9 000 cal BP, associated with strong hydrological stabil-
ity (Depreux et al., 2021). These environments reflect 
prolonged humid conditions, confirmed by the identifica-
tion of several successive palynological biozones, the 
oldest indicating the presence of shallow lakes before 
10.600 cal BP, followed by a marked aridification epi-
sode around 5.000 cal BP (Limondin-Lozouet et al., 
2013). 

Beyond the Moroccan context, Early Holocene 
humid sequences are well documented at the North 
African scale. In the Niyes peat bogs, Senegal (Fig. 10), 
archives reveal a more wooded landscape, a high water 
table, and a strengthening of the monsoon around 9.500 
cal BP (Ndiaye et al., 2022). Data from Lake Chad also 
show a rise in lake level between 9.500 and 6.500 cal 
BP, characterized by low δ¹⁸O values and low conductiv-
ity, pointing to a positive water balance. In the Tadrart 
Acacus massif, southern Libya, the reactivation of 
springs is attested by travertine deposits dated to around 
9.500 cal BP (Fig. 10j), associated with a renewed activi-
ty of large Saharan hydrological systems (Cremaschi et 
al., 2010; Cremaschi & Zerboni, 2011). Further indica-
tions of the African Humid Period are found in Saharan 
paleo-lakes such as Hassi el Mejnah and Sebkha Mella-
la in Tunisia, which show an abrupt transition from arid 
to lacustrine conditions around 10.500 cal BP. These 
data collectively mark a hydrological optimum, particular-
ly in high-latitude regions (Fontes et al., 1985; Gasse et 
al., 1990; Gasse, 2002). 

These records reflect increased regional and supra
-regional humidity, driven by enhanced precipitation 
resulting from intensified summer insolation around 12 
ka cal BP (Berger & Loutre, 1991). This insolation peak 
caused a northward migration of the Intertropical Con-
vergence Zone (ITCZ), which shifted approximately 500 
to 800 km beyond its current position (Petit-Maire et al., 
1995; Gasse, 2000; Maley & Vernet, 2013). This shift 
facilitated the expansion of the West African monsoon 
domain, triggering significant climatic transformations 
across the region. The resulting increase in precipitation 
not only reactivated fluvial systems but also induced 
substantial changes in local ecosystems, promoting the 
development of wetter and more wooded landscapes 
(Kutzbach, 1981; DeMenocal & Tierney, 2012; Pausata 
et al., 2020). It is also noteworthy that the deserts of the 
Arabian Peninsula experienced a contemporaneous 
humid phase during the early to mid-Holocene, coincid-
ing with these African climatic shifts (Yan & Petit-Maire, 
1994; Lézine et al., 1998; Fleitmann et al., 2007). This 
synchronicity suggests that these climatic changes had 
a broad geographic reach, affecting not only the Sahara 
but also other arid regions at similar latitudes. 

 
5.5. Middle and Late Holocene (after 8 000 cal BP) 

The Middle and Late Holocene mark a notable 
change in the morpho-sedimentary, hydrodynamic, and 
paleoenvironmental dynamics of the Akka plain. This 
period is characterized by the appearance of numerous 

 
 

102 

 
 

Saadi F. et al. 



   

 

of detrital elements (Zr, Si) (fig. x), low organic matter 
concentration, and a notable decrease in carbonates. 
These indicators suggest a lowering of the water table. 
Furthermore, a significant increase in magnetic suscep-
tibility (MS), from 9 × 10⁻⁸ to 50 × 10⁻⁸ m³/kg, indicates a 
change in sediment provenance, probably linked to a 
modification in sediment supply sources. 

Phase 9, postdating 597 cal BP, is represented by 
unit U9c. It is expressed by a tufa formation containing 
travertine tubes, developed over alluvial deposits at 
higher elevation on the right bank of the Wadi Akka (Fig. 
6b). This phase is also marked by the development of a 
stromatolitic carbonate formation (Fig. 6c), indicating a 
prolonged period of water abundance and stagnation. 
This phase, probably dated to the last five centuries, 
may correspond to one of the humid periods of the Little 
Ice Age (LIA), well documented in Moroccan regional 
archives. For example, increased humidity is recorded 
around 150-300 cal BP in the Ifoulki stalagmite (Middle 
Atlas; Ait Brahim et al., 2017),and between 300-400 cal 
BP in the tufa deposits of Imouzzer Kandar (Azennoud 
et al., 2022). 

In North Africa, particularly in Saharan and pre-
Saharan regions, paleoenvironmental data for the Late 
Holocene remain scarce, especially in alluvial archives. 
A recent comprehensive study by Saadi et al. (2024) in 
the middle basin of the Wadi Drâa has begun to fill this 
gap by integrating paleoenvironmental, paleohydrologi-
cal, and archaeological archives. Their work provides an 
initial chronological framework for the main morphody-
namic and paleoenvironmental phases documented 
over the last 3.500 years (cal BP). 

Most of the environmental and climatic changes 
recorded in fluvial system archives have often been 
primarily attributed to human activities, with many stud-
ies emphasizing anthropogenic influences on geomor-
phological processes during the Late Holocene 
(Ramrath et al., 2000; Oldfield et al., 2003). However, 
the Holocene sedimentary archives of the Akka plain, 
located in a sub-Saharan region particularly sensitive to 
climatic fluctuations, indicate that the main environmen-
tal changes in this area are closely linked to major cli-
matic events. The chronological and sedimentary hia-
tuses observed during the second half of the Middle 
Holocene and throughout the Late Holocene in the Wadi 
Akka archives correspond to phases of sediment trunca-
tion and intense hydro-sedimentary instability in the 
floodplain. These episodes reflect a morphodynamic 
and hydrological context characterized by periods of 
severe erosion and substantial destruction of earlier 
sedimentary deposits. 

 
6. CONCLUSION  
 

The sedimentary archives of the Akka alluvial plain 
provide a valuable new reference for understanding the 
impacts of climate change on the continental Saharan 
environment of North Africa during the Late Pleistocene 
to Holocene. This study focuses particularly on MIS 5b, 
MIS 3, and the Early Holocene period associated with 
the African Humid Period (AHP). Employing a multidisci-
plinary approach - including geomorphological and sedi-
mentological field analyses, radiocarbon and OSL da-
ting, and geochemical investigations - four alluvial se-
quences from the Akka plain, a right-bank tributary of 
the Drâa River in southern Morocco, were examined. 
This research enabled the reconstruction of environ-

ing Moroccan fluvial systems, probably in response to 
two Rapid Climate Change (RCC) events that occurred 
around 8.200 and 7.600 cal BP in the Charef basin, a 
tributary of the lower Moulouya (Depreux et al., 2022) 

Phase 6, dated between 8.500 and 7.204 cal BP 
corresponds to sedimentary unit U6, and is character-
ized by a new phase of erosion (Fig. 9), followed by a 
thin alluvial aggradation (less than one meter). This se-
quence reflects a significant decrease in sedimentation 
rate, suggesting a reduction in fluvial dynamics, marking 
an environment of low fluvial activity. 

Phase 7 (U7 and U8) around 7.204 cal BP, begins 
with renewed aggradation in the alluvial plain (Fig. 9), 
with deposits thicknesses ranging from 1 to 1.5 meters. 
This period records an energy shift, marked by an in-
crease in coarse fractions and indices of aeolian contri-
butions. These observations suggest a return to arid 
conditions in the region, with an environment increasing-
ly influenced by wind action. 

At regional and continental scales, this phase coin-
cides with a period of progressive aridification, well doc-
umented in many paleoenvironmental archives. In partic-
ular, data from Lake Yoa, located in the heart of the 
central Sahara (Chad), reveal irregular declines in lake 
level beginning around 7.000 cal BP, reflecting a transi-
tion to more arid landscapes. These changes are gener-
ally attributed to modifications in North Atlantic atmos-
pheric dynamics, notably a weakening or reorganization 
of the Atlantic Meridional Overturning Circulation 
(AMOC). This phenomenon likely disrupted rainfall re-
gimes across North Africa, contributing to the progres-
sive drying of Sahelo-Saharan wetlands (Sylvestre et al., 
2024). 

Following this phase, a long sedimentary hiatus is 
evident from geomorphological and especially geochron-
ological data of the Akka river archive. This hiatus, ex-
tending from about 7,204 to 656 cal BP, suggests a peri-
od of hydrodynamic instability in the Wadi Akka, marked 
by incision and truncation, probably caused by one or 
several successive arid episodes. Such interruptions are 
frequently observed in African fluvial deposits and are 
often attributed to a decline in fluvial activity at the end of 
the African Humid Period (AHP) (Lespez et al., 2011; 
Depreux et al., 2021). Meanwhile, Sahelian and Sudani-
an regions experienced increasing aridity between about 
5.000 and 3.000 cal BP (DeMenocal et al., 2000; Lézine 
et al., 2005; Gasse, 2000), leading to the southward shift 
of major vegetation zones toward their modern limits. 
This climatic drought phase also corresponds to the 
intensification of aeolian processes, particularly in the 
Inner Niger Delta and its surroundings (Makaske, 1998), 
which probably caused the erosion of the rare wetter 
fluvial records of the Late Holocene, identified elsewhere 
in the upstream basin of the Drâa (Saadi et al., 2024). In 
the Maghreb, this transition is reflected by increased 
episodes of torrential runoff and alluvial crises, indicating 
progressive regional aridification (Faust et al., 2004; 
Weisrock et al., 2006; Saadi et al., 2024). 

 
5.6. Late Holocene / Little Ice Age 

This interval marks a significant change in the sedi-
mentation regime, following a long sedimentary hiatus in 
the Akka plain archives. 

Phase 8, dated between 656 and 597 cal BP, is 
characterized by marked fluvial aggradation, reaching 
about 1 meter in thickness. This sequence reflects arid 
environmental conditions, evidenced by a high content 

 
 

103 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

for their very helpful comments and suggestions. We 
also thank the Poznań Radiocarbon Laboratory. We are 
grateful to the OMEAA platform (UMR 5600 EVS and 
5133 Archéorient, University of Lyon) for providing ac-
cess to the facilities necessary for sample processing, 
and to the IRG/EVS team for their financial support. We 
also extend our thanks to E. Rafins and M. Payet for 
preparing the luminescence (OSL) samples. 

 
REFERENCES 
 
Ait Brahim Y.A., Cheng H., Sifeddine A., Wassenburg 

J.A., Cruz F.W., Khodri M., Sha L., Pérez-Zanón 
N., Beraaouz E.H., Apaéstegui J. (2017) - 
Speleothem records decadal to multidecadal hy-
droclimate variations in southwestern Morocco 
during the last millennium. Earth and Planetary 
Science Letters, 476, 1-10. 

 Doi: 10.1016/j.epsl.2017.07.045  
Ait Brahim Y., Wassenburg J.A., Sha L., Cruz F.W., Dei-

ninger M., Sifeddine A., Bouchaou L., Spötl C., 
Edwards R.L., Cheng H. (2019) - North Atlantic ice
‐rafting, ocean and atmospheric circulation during 
the Holocene: Insights from Western Mediterra-
nean speleothems. Geophysical Research Letters, 
46(13), 7614-7623. 

 Doi: 10.1029/2019GL082405  
Ait Brahim Y.A., Sha L., Wassenburg J.A., Azennoud K., 

Cheng H., Cruz F.W., Bouchaou L. (2023) - The 
spatiotemporal extent of the Green Sahara during 
the last glacial period. Iscience, 26(7) 107018. 

 Doi: 10.1016/j.isci.2023.107018  
Aitken M.J. (1998) - An introduction to optical dating: 

The dating of Quaternary sediments by the use of 
photon-stimulated luminescence. Oxford, New 
York, Oxford University Press, pp. 267. 

 Doi: 10.1017/S0016756899551777  
Azennoud K., Baali A., Ait Brahim Y.A., Ahouach Y., Ha-

kam O. (2022) - Climate controls on tufa deposi-
tion over the last 5000 years: A case study from 
Northwest Africa. Palaeogeography, Palaeoclima-
tology, Palaeoecology, 586, 110767. 

 Doi: 10.1016/j.palaeo.2021.110767  
Baqloul A., Schefuß E., Kölling M., Dupont L., 

Groeneveld J., Zhao X., Reddad H., Bouchaou L., 
Bouimetarhan I. (2021) - Climate and land-use 
effects on hydrological and vegetation signals 
during the last three millennia: Evidence from sedi-
mentary leaf waxes in southwestern Morocco. The 
Holocene, 31(5), 699-708. 

 Doi: 10.1177/0959683620988053  
Bartz M., Rixhon G., Duval M., Arnold L. J., Demuro M., 

King G., Álvarez-Posada C., Parés J.M., Brückner 
H. (2018) - Une approche multi-méthodes origi-
nale: l’utilisation combinée de la résonance de 
spin électronique, de la luminescence et du paléo-
magnétisme pour reconstituer l’évolution quater-
naire de la basse Moulouya (NE du Maroc). 

Bereiter B., Lüthi D., Siegrist M., Schüpbach S., Stocker 
T.F., Fischer H. (2012) - Mode change of millennial 
CO2 variability during the last glacial cycle asso-
ciated with a bipolar marine carbon seesaw. 
Proceedings of the National Academy of Sciences, 
109(25), 9755-9760. 

 Doi: 10.1073/pnas.1204069109  
Berger A., Loutre M.-F. (1991) - Insolation values for the 

climate of the last 10 million years. Quaternary 

 
 

104 

 
 

Saadi F. et al. 

mental and morpho-hydrosedimentary conditions over 
five distinct phases, spanning more than 82,900 years, 
thereby providing new insights into the climatic and hy-
drological dynamics of the region.  

 

 Around 82.9 ka (MIS 5b), the Akka plain underwent a 
phase of high-energy braided fluvial activity, marked 
by coarse gravel deposition and significant lateral 
instability, under a humid climatic regime associated 
with the end of the last interglacial. 

 During MIS 3 (~40.5 ± 2.4 ka), fine-grained aggrada-
tion occurred under low-energy hydrological condi-
tions, supported by geochemical proxies (e.g., high 
Rb/Sr ratios, organic-rich horizons), reflecting en-
hanced soil development and relatively humid condi-
tions.40.5 ± 2.4 ka. 

 Between 11.428 and 10.260 cal BP, a phase of silty 
aggradation marks the early African Humid Period 
(AHP) in the wadi Akka alluvial records, indicating 
humid conditions with low hydrodynamic energy. 

 Between 10.260 and 9.500 cal BP, the persistence of 
humid and stable conditions is evidenced by tufa and 
peat accumulation, and the presence of aquatic fau-
na (e.g., Melanopsis), suggesting perennial freshwa-
ter environments and regional landscape stability. 
Between 9.500 to 8.500 cal BP, the system shifted 
toward a more dynamic regime, marked by torrential 
flows, coarse sediment input, and aeolian contribu-
tions, revealing a phase of increased climatic varia-
bility and sedimentary instability within the AHP. 

 A return to wetter conditions is suggested around 
7.204 cal BP, evidenced by silty aggradation and tufa 
facies, following a poorly documented but morphody-
namically active interval dominated by incision and 
erosion.The most recent period, between 656 and 
579 cal BP, signals a significant change in sedimen-
tation consistent with arid conditions. However, after 
597 cal BP, a wet phase is recorded, marked by large 
travertine tubes and stromatolithic travertine dams. 
This phase likely corresponds to the last humid epi-
sode of the Little Ice Age (LIA), also associated with 
paleosol formation in the middle Drâa Basin (Saadi et 
al., 2024). 

At Akka, the fluvial record predominantly preserves 
the most humid phases of the Late Pleistocene and 
Holocene, leading to an over-representation of wetter 
conditions in the sedimentary archive. In contrast, the 
Middle Holocene and much of the Late Holocene are 
characterized by incision and truncation events, often 
accompanied by gravel deposits resulting from highly 
erosive fluvial processes. These dynamics account for 
the frequent sedimentary hiatuses and discontinuities 
observed in the fluvial systems. Such periods appear to 
be linked to rapid climatic fluctuations and a general 
trend of aridification driven by orbital forcing. Neverthe-
less, this extended interval remains poorly constrained 
chronologically at Akka and will require substantial fu-
ture efforts in geochronology, particularly through OSL 
dating, contingent upon achieving sufficient bleaching of 
the alluvial deposits under study.  

 
ACKNOWLEDGMENTS 

This study was carried out as part of the PHC 
Toubkal/21/132 project (Campus France) 45924WJ, as 
well as the APPI-Lyon2 "Transmar" project. We would 
like to express our gratitude to the editor and reviewers 



   

 

requires Mediterranean winter rainfall. 
Proceedings of the National Academy of Sciences, 
118(23), e2024898118. 

 Doi: 10.1073/pnas.2024898118  
Chennaoui K., Nahid A., Argant J., Noçairi M., Malek F., 

Sahbi H. (2005) - Etude intégrée dʼun enregistre-
ment morphosédimentaire anthropique holocène: 
lʼescargotière de Tissouirine (Atlas atlantique, 
Maroc) - Revue de Paléobiologie, 24(2), 541-550. 

Choubert G., Ennadifi Y. (1970) - Carte géologique du 
flanc sud de l’Anti-Atlas Occidental et des Plaines 
du Dra: Akka-Tafagount-Tata. Service géologique 
du Maroc. 

Cremaschi M., Zerboni A. (2011) - Human communities 
in a drying landscape: Holocene climate change 
and cultural response in the central Sahara. Land-
scapes and Societies: Selected Cases, 67-89. 

 Doi: 10.1007/978-90-481-9413-1_5  
Cremaschi M., Zerboni A., Spötl C., Felletti F. (2010) - 

The calcareous tufa in the Tadrart Acacus Mt.(SW 
Fezzan, Libya): an early Holocene palaeoclimate 
archive in the central Sahara. Palaeogeography, 
Palaeoclimatology, Palaeoecology, 287(1-4), 81-
94. 

 Doi: 10.1016/j.palaeo.2010.01.019  
Cremaschi M., Zerboni A., Mercuri A.M., Olmi L., 

Biagetti S., Di Lernia S. (2014) - Takarkori rock 
shelter (SW Libya): an archive of Holocene climate 
and environmental changes in the central Sahara. 
Quaternary Science Reviews, 101, 36-60. 

 Doi: 10.1016/j.quascirev.2014.07.004  
Dearing J. (1999) - Magnetic susceptibility. Environ-

mental Magnetism: A Practical Guide, 35-62. 
DeMenocal P., Ortiz J., Guilderson T., Adkins J., 

Sarnthein M., Baker L., Yarusinsky M. (2000) - 
Abrupt onset and termination of the African Humid 
Period: rapid climate responses to gradual insola-
tion forcing. Quaternary Science Reviews, 19(1-5), 
347-361. 

DeMenocal P.B., Tierney J.E. (2012) - Green Sahara: 
African humid periods paced by Earth’s orbital 
changes. Nature Education Knowledge, 3(10), 12. 

Depreux B. (2021) - Dynamiques des systèmes fluviaux 
dans le bassin de la Moulouya (Maroc) à l’Holo-
cène: morphogenèse fluviale, changements clima-
tiques et occupations humaines. Montpellier 3. 

Depreux B., Lefèvre D., Berger J.-F., Segaoui F., 
Boudad L., El Harradji A., Degeai J.-P., Limondin-
Lozouet N. (2021) - Alluvial records of the African 
Humid Period from the NW African highlands 
(Moulouya basin, NE Morocco). Quaternary 
Science Reviews, 255, 106807. 

 Doi: 10.1016/j.quascirev.2021.106807  
Depreux B., Berger J.-F., Lefèvre D., Wackenheim Q., 

Andrieu-Ponel V., Vinai S., Degeai J.-P., El 
Harradji A., Boudad L., Sanz-Laliberté S. (2022) - 
First fluvial archive of the 8.2 and 7.6-7.3 ka 
events in North Africa (Charef River, High Pla-
teaus, NE Morocco). Scientific Reports, 12(1), 
7710. 

 Doi: 10.1038/s41598-022-11353-y  
El Amrani M., Macaire J.-J., Zarki H., Bréhéret J.-G., 

Fontugne M. (2008) - Contrasted morphosedimen-
tary activity of the lower Kert River (northeastern 
Morocco) during the Late Pleistocene and the 
Holocene. Possible impact of bioclimatic variations 
and human action. Comptes Rendus. Géoscience, 

Science Reviews, 10(4), 297-317. 
 Doi: 10.1016/0277-3791(91)90033-Q  
Berger J.-F., Delhon C., Magnin F., Bonte S., Peyric D., 

Thiebault S., Guilbert R., Beeching A. (2016) - A 
fluvial record of the mid-Holocene rapid climatic 
changes in the middle Rhone valley (Espeluche-
Lalo, France) and of their impact on Late Mesoli-
thic and Early Neolithic societies. Quaternary 
Science Reviews, 136, 66-84. 

 Doi: 10.1016/j.quascirev.2015.11.019  
Blott S.J., Pye K. (2001) - Gradistat: a grain size distribu-

tion and statistics package for the analysis of un-
consolidated sediments. Earth Surface Processes 
and Landforms, 26(11), 1237-1248. 

 Doi: 10.1002/esp.261  
Bond G., Kromer B., Beer J., Muscheler R., Evans M. 

N., Showers W., Hoffmann S., Lotti-Bond R., Haj-
das I., Bonani G. (2001) - Persistent solar in-
fluence on North Atlantic climate during the Holo-
cene. Science, 294(5549), 2130-2136. 

 Doi: 10.1126/science.1065680  
Boudad L., Kabiri L., Weisrock A., Wengler L., Fontugne 

M., El Maataoui M., Makayssi A., Vernet J.L. 
(2003) - Les formations fluviatiles du Pléistocène 
supérieur et de l’Holocène dans la "plaine" de Ta-
zoughmit (Oued Rheris, piémont sud-atlasique de 
Goulmina, Maroc). Quaternaire, 14(3), 139-154. 

 Doi: 10.3406/quate.2003.1738 
Bravard J.-P. (1983) - Les sédiments fins des plaines 

d’inondation dans la vallée du Haut-Rhône. Revue 
de Géographie Alpine, 71(4), 363-379. 

 Doi: 10.3406/rga.1983.2543  
Brennan B.J., Lyons R.G., Phillips S.W. (1991) - Atte-

nuation of alpha particle track dose for spherical 
grains. International Journal of Radiation Applica-
tions and Instrumentation. Part D. Nuclear Tracks 
and Radiation Measurements, 18(1-2), 249-253. 

 Doi: 10.1016/1359-0189(91)90119-3  
Burrough S.L., Thomas D.S.G. (2013) - Central southern 

Africa at the time of the African Humid Period: a 
new analysis of Holocene palaeoenvironmental 
and palaeoclimate data. Quaternary Science Re-
views, 80, 29-46. 

 Doi: 10.1016/j.quascirev.2013.08.001  
Campbell J.F.E., Fletcher W.J., Joannin S., Hughes P. 

D., Rhanem M., Zielhofer C. (2017) - Environ-
mental drivers of Holocene forest development in 
the Middle Atlas, Morocco. Frontiers in Ecology 
and Evolution, 5, 113. 

 Doi: 10.3389/fevo.2017.00113 
Castañeda I.S., Mulitza S., Schefuß E., Lopes dos 

Santos R.A., Sinninghe Damsté J.S., Schouten S. 
(2009) - Wet phases in the Sahara/Sahel region 
and human migration patterns in North Africa. 
Proceedings of the National Academy of Sciences, 
106(48), 20159-20163. 

 Doi: 10.1073/pnas.0905771106  
Cheddadi R., Fady B., François L., Hajar L., Suc J., 

Huang K., Demarteau M., Vendramin G.G., Ortu E. 
(2009) - Putative glacial refugia of Cedrus atlantica 
deduced from Quaternary pollen records and mo-
dern genetic diversity. Journal of Biogeography, 36
(7), 1361-1371. 

 Doi: 10.1111/j.1365-2699.2008.02063.x  
Cheddadi R., Carré M., Nourelbait M., François L., 

Rhoujjati A., Manay R., Ochoa D., Schefuss E. 
(2021) - Early Holocene greening of the Sahara 

 
 

105 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

Quaternary Science: Published for the Quaternary 
Research Association, 21(3), 259-269. 

 Doi: 10.1002/jqs.970  
Heiri O., Lotter A.F., Lemcke G. (2001) - Loss on ignition 

as a method for estimating organic and carbonate 
content in sediments: reproducibility and compara-
bility of results. Journal of Paleolimnology, 25, 101-
110. 

 Doi: 10.1023/A:1008119611481  
Helmens K.F. (2014) - The Last Interglacial-Glacial cycle 

(MIS 5-2) re-examined based on long proxy re-
cords from central and northern Europe. Quater-
nary Science Reviews, 86, 115-143. 

 Doi: 10.1016/j.quascirev.2013.12.012  
Ibouhouten H., Zielhofer C., Mahjoubi R., Kamel S., 

Linstädter J., Mikdad A., Bussmann J., Werner P., 
Härtling J.W., Fenech K. (2010) - Archives allu-
viales holocènes et occupation humaine en Basse 
Moulouya (Maroc nord-oriental). Géomorphologie: 
Relief, Processus, Environnement, 16(1), 41-56. 

 Doi: 10.4000/geomorphologie.7812  
Jones A.F., Macklin M.G., Brewer P.A. (2012) - A geo-

chemical record of flooding on the upper River 
Severn, UK, during the last 3750 years. Geomor-
phology, 179, 89-105. 

 Doi: 10.1016/j.geomorph.2012.08.003  
Klasen N., Fischer P., Lehmkuhl F., Hilgers A. (2015) - 

Luminescence dating of loess deposits from the 
Remagen-Schwalbenberg site, Western Germany. 
Geochronometria, 42(1). 

 Doi: 10.13140/RG.2.2.29534.64328  
Kröpelin S., Verschuren D., Lézine A.-M., Eggermont H., 

Cocquyt C., Francus P., Cazet J.-P., Fagot M., 
Rumes B., Russell J. M. (2008) - Climate-driven 
ecosystem succession in the Sahara: the past 
6000 years. Science, 320(5877), 765-768. 

 Doi: 10.1126/science.1154913  
Kutzbach J.E. (1981) - Monsoon climate of the early 

Holocene: climate experiment with the earth’s 
orbital parameters for 9000 years ago. Science, 
214(4516), 59-61. 

 Doi: 10.1126/science.214.4516.59  
Lauterbach S., Brauer A., Andersen N., Danielopol D.L., 

Dulski P., Hüls M., Milecka K., Namiotko T., 
Obremska M., Von Grafenstein U. (2011) - Envi-
ronmental responses to Lateglacial climatic fluc-
tuations recorded in the sediments of pre-Alpine 
Lake Mondsee (northeastern Alps). Journal of 
Quaternary Science, 26(3), 253-267. 

 Doi: 10.1002/jqs.1448  
Lefèvre D. (1985) - Les formations plio-pléistocènes du 

bassin de Ksabi (Moyenne Moulouya, Maroc). 
Bordeaux 1. 

Lespez L., Le Drezen Y., Garnier A., Rasse M., Eichhorn 
B., Ozainne S., Ballouche A., Neumann K., 
Huysecom E. (2011) - High-resolution fluvial re-
cords of Holocene environmental changes in the 
Sahel: the Yamé River at Ounjougou (Mali, West 
Africa). Quaternary Science Reviews, 30(5-6), 737
-756. 

 Doi: 10.1016/j.quascirev.2010.12.021  
Lézine A.-M., Casanova J. (1989) - Pollen and hydrolo-

gical evidence for the interpretation of past cli-
mates in tropical West Africa during the Holocene. 
Quaternary Science Reviews, 8(1), 45-55. 

 Doi: 10.1016/0277-3791(89)90020-6  
Lézine A.-M., Saliege J.-F., Robert C., Wertz F., Inizan 

340(8), 533-542. 
 Doi: 10.1016/j.crte.2008.05.004  
Esri (2009) - "World Imagery", Accessed 2020-06-05. 
 www.arcgis.com/home/item.html?id=10df2279f968 

4e4a9f6a7f08febac2a9 
Faust D., Zielhofer C., Escudero R.B., del Olmo F.D. 

(2004) - High-resolution fluvial record of late Holo-
cene geomorphic change in northern Tunisia: cli-
matic or human impact? Quaternary Science Re-
views, 23(16-17), 1757-1775. 

 Doi: 10.1016/j.quascirev.2004.02.007  
Fleitmann D., Burns S.J., Mangini A., Mudelsee M., 

Kramers J., Villa I., Neff U., Al-Subbary A.A., 
Buettner A., Hippler D. (2007) - Holocene ITCZ 
and Indian monsoon dynamics recorded in stalag-
mites from Oman and Yemen (Socotra). Quaterna-
ry Science Reviews, 26(1-2), 170-188. 

 Doi: 10.1016/j.quascirev.2006.04.012 
Fletcher W.J., Debret M., Goñi M.F.S. (2013) - Mid-

Holocene emergence of a low-frequency millennial 
oscillation in western Mediterranean climate: Impli-
cations for past dynamics of the North Atlantic 
atmospheric westerlies. The Holocene, 23(2), 153-
166. 

 Doi: 10.1177/0959683612460783  
Foley J.A., Coe M.T., Scheffer M., Wang G. (2003) - 

Regime shifts in the Sahara and Sahel: interac-
tions between ecological and climatic systems in 
Northern Africa. Ecosystems, 6(6), 524-532. 

 Doi: 10.1007/s10021-002-0227-0  
Fontes J.C., Gasse F., Callot Y., Plaziat J.C., Carbonel 

P., Dupeuble P.A., Kaczmarska I. (1985) - Fresh-
water to marine-like environments from Holocene 
lakes in northern Sahara. Nature, 317(6038), 608-
610. 

 Doi: 10.1038/317608a0  
Galbraith R.F., Roberts R.G., Laslett G.M., Yoshida H., 

Olley J.M. (1999) - Optical dating of single and 
multiple grains of quartz from Jinmium rock shelter, 
northern Australia: Part I, experimental design and 
statistical models. Archaeometry, 41(2), 339-364. 

 Doi: 10.1111/j.1475-4754.1999.tb00987.x  
Gasse F. (2000) - Hydrological changes in the African 

tropics since the Last Glacial Maximum. Quaterna-
ry Science Reviews, 19(1-5), 189-211. 

 Doi: 10.1016/S0277-3791(99)00061-X  
Gasse F. (2002) - Diatom-inferred salinity and carbonate 

oxygen isotopes in Holocene waterbodies of the 
western Sahara and Sahel (Africa). Quaternary 
Science Reviews, 21(7), 737-767. 

 Doi: 10.1016/S0277-3791(01)00125-1  
Gasse F., Téhet R., Durand A., Gibert E., Fontes J.-C. 

(1990) - The arid-humid transition in the Sahara 
and the Sahel during the last deglaciation. Nature, 
346(6280), 141-146. 

 Doi: 10.1038/346141a0  
Guérin G., Mercier N., Adamiec G. (2011) - Dose-rate 

conversion factors: update. Ancient Tl, 29(1), 5-8. 
 Doi: 10.26034/la.atl.2011.443  
Guérin G., Mercier N., Nathan R., Adamiec G., Lefrais Y. 

(2012) - On the use of the infinite matrix assump-
tion and associated concepts: a critical review. 
Radiation Measurements, 47(9), 778-785. 

 Doi: 10.1016/j.radmeas.2012.04.004  
Haslett S.K., Smart C.W. (2006) - Late Quaternary up-

welling off tropical NW Africa: new micropalaeonto-
logical evidence from ODP Hole 658C. Journal of 

 
 

106 

 
 

Saadi F. et al. 



   

 

Mullins C.E. (1977) - Magnetic susceptibility of the soil 
and its significance in soil science-a review. Jour-
nal of Soil Science, 28(2), 223-246. 

 Doi: 10.1111/j.1365-2389.1977.tb02232.x  
Murray A.S., Wintle A.G. (2000) - Luminescence dating 

of quartz using an improved single-aliquot regene-
rative-dose protocol. Radiation Measurements, 32
(1), 57-73. 

 Doi: 10.1016/S1350-4487(99)00253-X  
Ndiaye A., Bentaleb I., Favier C., Fourel F., Sebag D., 

Fall M., Giresse P., Diouf B. (2022) - Reconstruc-
tion of the holocene climate and environmental 
changes of Niayes peat bog in northern coast of 
Senegal (NW Africa) based on stable isotopes and 
charcoals analysis. Quaternary Science Reviews, 
289, 107609. 

 Doi: 10.1016/j.quascirev.2022.107609  
Oldfield F., Asioli A., Accorsi C. A., Mercuri A.M., Juggins 

S., Langone L., Rolph T., Trincardi F., Wolff G., 
Gibbs Z. (2003) - A high resolution late Holocene 
palaeo environmental record from the central 
Adriatic Sea. Quaternary Science Reviews, 22(2-
4), 319-342. 

 Doi: 10.1016/S0277-3791(02)00088-4  
Ouammou A. (1993) - Evolution morphologique récente 

du bas plateau de Tiznit (Maroc). Nancy 2. 
Pachur H-J, Hoelzmann P. (1991) - Paleoclimatic impli-

cations of late Quaternary lacustrine sediments in 
western Nubia, Sudan. Quaternary Research, 36
(3), 257-276. 

 Doi: 10.1016/0033-5894(91)90002-M  
Pachur H-J, Röper H.-P., Kroepelin S., Goschin M. 

(1987) - Late Quaternary hydrography of the eas-
tern Sahara. 

Paine A.R., Baldini J.U.L., Ünal-Imer E., Wadsworth 
F.B., Iveson A.A., Humphreys M.C.S., Brown R.J., 
Müller W., Ottley C.J. (2024) - Abrupt climate 
change at the MIS 5/4 transition recorded in a 
speleothem from the Eastern Mediterranean. Qua-
ternary Science Reviews, 339, 108841. 

 Doi: 10.1016/j.quascirev.2024.108841  
Parker A.O., Schmidt M.W., Jobe Z.R., Slowey N.C. 

(2016) - A new perspective on West African hydro-
climate during the last deglaciation. Earth and 
Planetary Science Letters, 449, 79-88. 

 Doi: 10.1016/j.epsl.2016.05.038  
Passega R. (1964) - Grain size representation by CM 

patterns as a geologic tool. Journal of Sedimenta-
ry Research, 34(4), 830-847. 

 Doi: 10.1306/74D711A4-2B21-11D7-
8648000102C1865D  

Pausata F.S.R., Gaetani M., Messori G., Berg A., de 
Souza D. M., Sage R.F., DeMenocal P.B. (2020) - 
The greening of the Sahara: Past changes and 
future implications. One Earth, 2(3), 235-250. 

 Doi: 10.1016/j.oneear.2020.03.002  
Petit-Maire N. (1989) - Interglacial environments in pre-

sently hyperarid Sahara: palaeoclimatic implica-
tions. In Paleoclimatology and Paleometeorology: 
modern and past patterns of global atmospheric 
transport (637-661) - Springer. 

 Doi: 10.1007/978-94-009-0995-3_27  
Petit-Maire N. (2021) - Sahara: les grands changements 

climatiques naturels. Éditions Errance. 
Petit-Maire N., Riser J. (1981) - Holocene lake deposits 

and palaeoenvironments in central Sahara, nor-
theastern Mali. Palaeogeography, Palaeoclimato-

M.-L. (1998) - Holocene lakes from Ramlat as-
Sab’atayn (Yemen) illustrate the impact of mon-
soon activity in southern Arabia. Quaternary 
Research, 50(3), 290-299. 

 Doi: 10.1006/qres.1998.1996  
Lézine A.-M., Dupless, J.-C., Cazet J.-P. (2005) - West 

African monsoon variability during the last degla-
ciation and the Holocene: Evidence from fresh 
water algae, pollen and isotope data from core 
KW31, Gulf of Guinea. Palaeogeography, Palaeo-
climatology, Palaeoecology, 219(3-4), 225-237. 

 Doi: 10.1016/j.palaeo.2004.12.027  
Lézine A.-M., Hély C., Grenier C., Braconnot P., Krinner 

G. (2011) - Sahara and Sahel vulnerability to cli-
mate changes, lessons from Holocene hydrological 
data. Quaternary Science Reviews, 30(21-22), 
3001-3012. 

 Doi: 10.1016/j.quascirev.2011.07.006  
Lézine A.-M., Kageyama M., Bassinot F. (2023) - Data 

and models reveal humid environmental conditions 
during MIS 3 in two of the world’s largest deserts. 
Comptes Rendus. Géoscience, 355(S2), 229-246. 

 Doi: 10.5802/crgeos.240  
Lghamour M., Karrat L., Picotti V., Hajdas I., Haghipour 

N., Guidobaldi G., Heeb K.W., Gourari L. (2024) - 
Late Pleistocene to Holocene alluvial deposits of 
the Inaouène Valley and their paleoenvironmental 
significance (north Morocco). Quaternary Science 
Reviews, 344, 108941. 

 Doi: 10.1016/j.quascirev.2024.108941  
Liang L., Sun Y., Beets C.J., Prins M.A., Wu F., 

Vandenberghe J. (2013) - Impacts of grain size 
sorting and chemical weathering on the geoche-
mistry of Jingyuan loess in the northwestern 
Chinese Loess Plateau. Journal of Asian Earth 
Sciences, 69, 177-184. 

 Doi: 10.1016/j.jseaes.2012.12.015  
Limondin-Lozouet N., Haddoumi H., Lefèvre D., Ghamizi 

M., Aouraghe H., Salel T. (2013) - Holocene mol-
luscan succession from NE Morocco: Palaeoenvi-
ronmental reconstruction and biogeographical 
implications. Quaternary International, 302, 61-76. 

 Doi: 10.1016/j.quaint.2012.11.036  
Linnaeus C. (1789) - Systema Naturae per regna tria 

naturae, secundum classes, ordines, genera, 
species; cum characteribus, differentiis, synony-
mis, locis (Vol. 1). apud JB Delamolliere. 

Makaske B. (1998) - Anastomosing rivers: a review of 
their classification, origin and sedimentary pro-
ducts. Earth-Science Reviews, 53(3-4), 149-196. 

 Doi: 10.1016/S0012-8252(00)00038-6  
Maley J., Vernet R. (2013) - Peuples et évolution clima-

tique en Afrique nord-tropicale, de la fin du Néoli-
thique à l’aube de l’époque moderne. Afriques. 
Débats, Méthodes et Terrains d’histoire, 04. 

 Doi: 10.4000/afriques.1209  
Mathieu J., Weisrock A., Wengler L., Brochier J.E., Even 

G., Fontugne M., Mercier N., Ouammou A., 
Senegas F., Valladas H. (2004) - Holocene de-
posits in the lower section of the Assaka wadi, 
South Morocco: Preliminary results. Quaternaire, 
15(1-2), 207-218. 

Mercier N., Falguères C. (2007) - Field gamma dose-
rate measurement with a NaI (Tl) detector: re-
evaluation of the" threshold" technique. Ancient TL, 
25(1), 1-4. 

 Doi: 10.26034/la.atl.2007.400  

 
 

107 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

material research and dating application. Geochro-
nometria, 42(1), 202-209. 

 Doi: 10.1515/geochr-2015-0022  
Ritchie J.C., Eyles C.H., Haynes C.V. (1985) - Sediment 

and pollen evidence for an early to mid-Holocene 
humid period in the eastern Sahara. Nature, 314
(6009), 352-355. 

 Doi: 10.1038/314352a0  
Roberts N., Brayshaw D., Kuzucuoğlu C., Perez R., 

Sadori L. (2011) - The mid-Holocene climatic tran-
sition in the Mediterranean: Causes and conse-
quences. The Holocene, 21(1), 3-13. 

 Doi: 10.1177/0959683610388058  
Romero O.E., Leduc G., Vidal L., Fischer G. (2011) - 

Millennial variability and long‐term changes of the 
diatom production in the eastern equatorial Pacific 
during the last glacial cycle. Paleoceanography, 26
(2). 

 Doi: 10.1029/2010PA002099  
Rothwell R.G., Croudace I.W. (2015) - Twenty years of 

XRF core scanning marine sediments: What do 
geochemical proxies tell us? Micro-XRF Studies of 
Sediment Cores: Applications of a Non-Destructive 
Tool for the Environmental Sciences, 25-102. 

 Doi: 10.1007/978-94-017-9849-5_1  
Saadi F., Boudad L., Berger J.-F. (2024) - Late Holocene 

morphosedimentary and palaeoenvironmental 
study of the Middle Drâa river basin (southeastern 
Morocco). Quaternary International, 710, 29-48. 

 Doi: 10.1016/j.quaint.2024.09.003 
Salvador P.-G. (2016) - Caractérisation des remblaie-

ments sédimentaires de six paléochenaux de la 
plaine alluviale du Rhône par la méthode granulo-
métrique de Passega (Basses Terres, Ain, Isère). 
Bulletin de La Société Géographique de Liège, 67, 
107-124. 

 Doi: 10.25518/0770-7576.4492  
Salzmann U., Waller M. (1998) - The Holocene vege-

tational history of the Nigerian Sahel based on 
multiple pollen profiles. Review of Palaeobotany 
and Palynology, 100(1-2), 39-72. 

 Doi: 10.1016/S0034-6667(97)00053-5  
Siddall M., Stocker T. F., Blunier T., Spahni R., McManus 

J. F., Bard E. (2006) - Using a maximum simplicity 
paleoclimate model to simulate millennial variabili-
ty during the last four glacial periods. Quaternary 
Science Reviews, 25(23-24), 3185-3197. 

 Doi: 10.1016/j.quascirev.2005.12.014  
Specht N.F., Claussen M., Kleinen T. (2024) - Dynamic 

interaction between lakes, climate, and vegetation 
across northern Africa during the mid-Holocene. 
Climate of the Past, 20(7), 1595-1613. 

 Doi: 10.5194/cp-20-1595-2024  
Street-Perrott F.A., Hales P.E., Perrott R.A., Fontes J. 

C., Switsur V.R., Pearson A. (1993) - Late Quater-
nary palaeolimnology of a tropical marl lake: Wal-
lywash Great Pond, Jamaica. Journal of Paleolim-
nology, 9, 3-22. 

 Doi: 10.1007/BF00680032  
Sylvestre F., Melles M., Wennrich V., Dinies M., Chalié 

F., Swingedouw D., Dallmeyer A., Shi X., Claussen 
M., Jaeschke A. (2024) - Drought events during 
the African Humid Period suggest future drying of 
the Sahara. 

 Doi: 10.21203/rs.3.rs-5288623/v1  
Tadoumant S., Bouimetarhan I., Baqloul A., Hssaisoune 

M., Reddad H., Bouchaou L. (2022) - Modern pol-

logy, Palaeoecology, 35, 45-61. 
 Doi: 10.1016/0031-0182(81)90093-6  
Petit-Maire N., Riser J. (1983) - Sahara ou Sahel. Qua-

ternaire Récent Du Bassin de Taoudenni (Mali). 
Paris: Centre National de La Recherche Scienti-
fique, 473. 

Petit-Maire N., Riser J., Blanc-Vernet L., Fairbridge R.W. 
(1983) - Sahara ou Sahel?: quaternaire récent du 
Bassin de Taoudenni (Mali). C.N.R.S., Laboratoire 
de géologie du quaternaire, Marseille. 

Petit-Maire N., Sanlaville P., Yan Z. (1995) - Oscillations 
de la limite nord du domaine des moussons afri-
caine, indienne, et asiatique au cours du dernier 
cycle climatique. Bulletin de La Société Géolo-
gique de France, 166(2), 213-220. 

Prescott J.R., Hutton J.T. (1988) - Cosmic ray and gam-
ma ray dosimetry for TL and ESR. International 
Journal of Radiation Applications and Instrumenta-
tion. Part D. Nuclear Tracks and Radiation Mea-
surements, 14(1-2), 223-227. 

 Doi: 10.1016/1359-0189(88)90069-6  
Preusser F., Radies D., Matter A. (2002) - A 160.000-

year record of dune development and atmospheric 
circulation in Southern Arabia. Science, 296(5575), 
2018-2020. 

 Doi: 10.1126/science.1069875  
Profe J., Zolitschka B., Schirmer W., Frechen M., 

Ohlendorf C. (2016) - Geochemistry unravels MIS 
3/2 paleoenvironmental dynamics at the loess-
paleosol sequence Schwalbenberg II, Germany. 
Palaeogeography, Palaeoclimatology, Palaeoeco-
logy, 459, 537-551. 

 Doi: 10.1016/j.palaeo.2016.07.022  
Ramrath A., Sadori L., Negendank J.F.W. (2000) - Sedi-

ments from Lago di Mezzano, central Italy: a re-
cord of Lateglacial/Holocene climatic variations 
and anthropogenic impact. The Holocene, 10(1), 
87-95. 

 Doi: 10.1191/095968300669348734  
Rasse M., Lespez L., Lebrun B., Tribolo C., Chevrier B., 

Douze K., Garnier A., Davidoux S., Hadjas I., 
Ollier C. (2020) - Synthèse morpho-sédimentaire 
et occurences archéologiques dans la vallée de la 
Falémé (de 80 à 5 ka; Sénégal oriental): mise en 
évidence d’une permanence des occupations à la 
transition Pléistocène‑Holocène. Quaternaire. Re-
vue de l’Association Française Pour l’étude Du 
Quaternaire, 31/1, 71-88. 

 Doi: 10.4000/quaternaire.13181  
Reimer P.J., Austin W.E.N., Bard E., Bayliss A., 

Blackwell P.G., Ramsey C.B., Butzin M., Cheng H., 
Edwards R.L., Friedrich M. (2020) - The IntCal20 
Northern Hemisphere radiocarbon age calibration 
curve (0-55 cal kBP). Radiocarbon, 62(4), 725-
757. 

 Doi: 10.1017/RDC.2020.41  
Renssen H., Brovkin V., Fichefet T., Goosse H. (2003) - 

Holocene climate instability during the termination 
of the African Humid Period. Geophysical 
Research Letters, 30(4), 1177. 

 Doi: 10.1029/2002GL016636  
Richter D., Richter A., Dornich K. (2013) - Lexsyg - A 

new system for luminescence research. Geochro-
nometria, 40(4), 220-228. 

 Doi: 10.2478/s13386-013-0110-0  
Richter D., Richter A., Dornich K. (2015) - Lexsyg smart 

- A luminescence detection system for dosimetry, 

 
 

108 

 
 

Saadi F. et al. 



   

 

Wintle A.G., Murray A.S. (2006) - A review of quartz 
optically stimulated luminescence characteristics 
and their relevance in single-aliquot regeneration 
dating protocols. Radiation Measurements, 41(4), 
369-391. 

 Doi: 10.1016/j.radmeas.2005.11.001  
Yacoub A.N., Sylvestre F., Moussa A., Hoelzmann P., 

Alexandre A., Dinies M., Chalié F., Vallet-Coulomb 
C., Paillès C., Darius F. (2023) - The African Holo-
cene Humid Period in the Tibesti mountains 
(central Sahara, Chad): Climate reconstruction 
inferred from fossil diatoms and their oxygen iso-
tope composition. Quaternary Science Reviews, 
308, 108099.  

 Doi:10.1016/j.quascirev.2023.108099 
Yan Z., Petit-Maire N. (1994) - The last 140 ka in the 

Afro-Asian arid/semi-arid transitional zone. Pa-
laeogeography, Palaeoclimatology, Palaeoecology, 
110(3-4), 217-233. 

 Doi: 10.1016/0031-0182(94)90085-X  
Zaky A.S., de Azevedo A.Q., Vogel H., Jovane L., 

Hamdan M., Achyuthan H., Frontalini F., Szidat S., 
Anselmetti F.S. (2024) - Climate variability in nor-
thern Africa during the late Holocene: A multiproxy 
perspective from El-Beida Lake (Wadi El-Natrun, 
Egypt). Quaternary Science Reviews, 337, 
108801. 

 Doi: 10.1016/j.quascirev.2024.108801  
Zech M., Zech R., Zech W., Glaser B., Brodowski S., 

Amelung W. (2008) - Characterisation and palaeo-
climate of a loess-like permafrost palaeosol se-
quence in NE Siberia. Geoderma, 143(3-4), 281-
295. 

 Doi: 10.1016/j.geoderma.2007.11.012  
Zielhofer C., Faust D. (2008) - Mid-and Late Holocene 

fluvial chronology of Tunisia. Quaternary Science 
Reviews, 27(5-6), 580-588. 

 Doi: 10.1016/j.quascirev.2007.11.019  
Zielhofer C., Faust D., Linstädter J. (2008) - Late Pleis-

tocene and Holocene alluvial archives in the 
Southwestern Mediterranean: Changes in fluvial 
dynamics and past human response. Quaternary 
International, 181(1), 39-54. 

 Doi: 10.1016/j.quaint.2007.09.016  
Zielhofer C., Bussmann J., Ibouhouten H., Fenech K. 

(2010) - Flood frequencies reveal Holocene rapid 
climate changes (Lower Moulouya River, nor-
theastern Morocco). Journal of Quaternary 
Science, 25(5), 700-714. 

 Doi: 10.1002/jqs.1347  
 

len distribution and its relationship with environ-
mental gradient in southern Morocco. Review of 
Palaeobotany and Palynology, 298, 104595. 

 Doi: 10.1016/j.revpalbo.2021.104595  
Thiel C., Buylaert J.-P., Murray A., Terhorst B., Hofer I., 

Tsukamoto S., Frechen M. (2011) - Luminescence 
dating of the Stratzing loess profile (Austria)-
Testing the potential of an elevated temperature 
post-IR IRSL protocol. Quaternary International, 
234(1-2), 23-31. 

 Doi: 10.1016/j.quaint.2010.05.018  
Tribolo C., Mercier N., Douville E., Joron J.-L., Reyss J.-

L., Rufer D., Cantin N., Lefrais Y., Miller C.E., 
Porraz G. (2013) - OSL and TL dating of the 
Middle Stone Age sequence at Diepkloof Rock 
Shelter (South Africa): a clarification. Journal of 
Archaeological Science, 40(9), 3401-3411. 

 Doi: 10.1016/j.jas.2012.12.001  
Wang M., Zheng H., Xie X., Fan D., Yang S., Zhao Q., 

Wang K. (2011) - A 600-year flood history in the 
Yangtze River drainage: comparison between a 
subaqueous delta and historical records. Chinese 
Science Bulletin, 56, 188-195. 

 Doi: 10.1007/s11434-010-4212-2  
Weisrock A.L.E. (1980) - Géomorphologie et paléoenvi-

ronnements de l’Atlas atlantique (Maroc). Universi-
té de Lille III, Atelier national de reproduction des 
thèses. 

Weisrock A, Ouammou A., Hssaine A. (1991) - Erosion 
et sédimentation dans les oueds du Sud-Ouest 
marocain à l’Holocène. Géo Physio, 22-23, 95-
100. 

Weisrock A., Wahl L., Ouammou A., Chakir L. (2006) - 
Systèmes fluviaux du Sud-Ouest marocain et leur 
évolution depuis le Pléistocène supérieur. Géomor-
phologie: Relief, Processus, Environnement, 12(4), 
229-248. 

Weisrock A., Rousseau L., Reyss J.-L., Falguères C., 
Ghaleb B., Bahain J.-J., Beauchamp J., Boudad L., 
Mercier N., Mahieux G. (2008) - Travertins de la 
bordure nord du Sahara marocain: dispositifs mor-
phologiques, datations U/Th et indications paléocli-
matiques. Géomorphologie: Relief, Processus, 
Environnement, 14(3), 153-167. 

 Doi: 10.4000/geomorphologie.6793  
Weldeab S., Schneider R.R., Kölling M., Wefer G. (2005) 

- Holocene African droughts relate to eastern 
equatorial Atlantic cooling. Geology, 33(12), 981-
984. 

 Doi: 10.1130/G21874.1  
Wengler L., Weisrock A., Brochier J.-É., Brugal J.P., 

Fontugne M., Magnin F., Mathieu J., Mercier N., 
Ouammou A., Reyss J.-L. (2002) - Enregistrement 
fluviatile et paléoenvironnements au Pléistocène 
supérieur sur la bordure méridionale atlantique de 
l’Anti-Atlas (Oued Assaka, SO marocain). Quater-
naire, 13(3), 179-192. 

 Doi: 10.3406/quate.2002.1710  

 
 

109 

Ms. received: July 2, 2025  Revised: September 30, 2025 
Accepted: October 2, 2025  Available online: October 18, 2025 

 
 
High-resolution morpho-sedimentary and paleoenvironmental evolution of Wadi Akka  ... 



   

 

 

 
 

110