AMQ abs Giustini et al PALCOM 135-139 corr.pub Available online http://amq.aiqua.it ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, Vol. 31 (Quaternary: Past, Present, Future - AIQUA Conference, Florence, 13-14/06/2018), 135 - 139 AN INTRODUCTION TO THE EARLY HOLOCENE “EOLIAN” DEPOSITS OF GROTTA ROMANELLI, APULIA, SOUTHERN ITALY Francesca Giustini 1, Fabio Bona 4, Mauro Brilli 1, Jacopo Conti 2, Alessia D’Agostino 2, Giuseppe Lembo 3, Ilaria Mazzini 1, Beniamino Mecozzi 2, Brunella Muttillo 3, Raffaele Sardella 2 1 Istituto di Geologia Ambientale e Geoingegneria (IGAG), CNR, Roma, Italy 2 Dipartimento di Scienze della Terra, Università di Roma “Sapienza”, Roma, Italy 3 Dipartimento di Studi Umanistici, Sezione di Scienze Preistoriche e Antropologiche, Università degli Studi di Ferrara, Ferrara, Italy 4 Dipartimento di Scienze della Terra “A. Desio”, Università degli Studi di Milano, Milano, Italy Corresponding author: F. Giustini ABSTRACT: Due to its geographic position and geomorphological configuration, Grotta Romanelli acted as a sediment trap since at least MIS 5. The so-called ‘terre brune’ sequence is a deposit mainly of eolian origin bearing upper Palaeolithic artefacts and fossil re- mains of vertebrate fauna; it was deposited during the Glacial-Interglacial transition and the Holocene. Sedimentology and mineralogy of this deposit are investigated. The stratigraphic sequence provides a promising archive within which both human and climatic impacts can be studied. KEYWORDS: Grain size, mineralogy, Holocene, Grotta Romanelli, southern Italy 1. INTRODUCTION Eolian deposits have long been con- sidered a significant resource for the past environment reconstruction. Eolian activi- ty is, in fact, modulated/influenced by global climate changes (Porter, 1989) as documented, for example, in the Chinese Loess Plateau, i.e. one of the longest and most continuous palaeoclimatic records of the Quaternary interglacial-glacial cy- cles (Ding et al., 2005). In Italy, Quater- nary eolian deposits were described in different sites (Sevink & Kummer, 1984; Cremaschi, 1990; Narcisi, 2000; Giraudi et al., 2013; Boretto et al., 2017). Loess deposits in northern Italy and the Adriatic edge of central Italy were associated to periglacial environment, whereas in cen- tral and southern Italy their origin was attributed to dust coming from North Afri- ca, where arid conditions during MIS 4 and 2 and in the late Holocene may have enhanced the dust supply in southern Mediterranean sector (Giraudi, 1995; Narcisi, 2000). Eolian deposits accumulated in caves can provide archives of past climate and human-induced changes. These deposits are additionally a significant source of information about land-atmosphere transfer processes, atmospheric residence times, land-surface depositional processes (Evans & Soreghan, 2015). Grotta Romanelli, located on the Adriatic coast of southern Apulia (Italy), is considered a key site for the Mediterranean Quaternary for its archaeological and palaeontological content. The cave opens in Upper Cre- taceous limestone (Bosellini et al., 1999) at about 7.4 m above sea level, and is filled with thick deposits contain- ing rich fossil remains of vertebrate and a wide variety of artefacts (see Sardella et al., 2018 and references there- in). The stratigraphic sequence, as described by Blanc (1920, 1928), schematically consists (from the top to the bottom) of: (i) an upper complex, called ‘terre brune’ (‘levels A-E’), bearing upper Palaeolithic artefacts and vertebrate fauna including Pinguinus impennis (= Alca impennis in Blanc, 1927); (ii) a thin stalagmitic layer (called ‘level F’), dated at 40,000± 3250 years (Fornaca- Rinaldi & Radmilli, 1968); (iii) a deposit called ‘terre ros- se’ (‘level G’); (iv) a thick stalagmitic layer (‘level H’); (v) a bone breccia (‘level I’), and (vi) a beach deposit (‘level K’) Fig. 1 - Geological sketch of the coastal area of Grotta Romanelli bay (Sardella et al., 2018). https://doi.org/10.26382/AIQUA.2018.AIQUAconference referred to the Tyrrhenian Stage (MIS 5). The ‘terre brune’ and ‘terre rosse’ deposits are con- sidered mainly of eolian origin (Blanc, 1920, 1928; Blanc & Cortesi, 1941); according to radi- ocarbon dates, the ‘terre brune’ sequence ap- pears to span from about 9.5 to 12 ka (Alessio et al., 1965; Bella et al., 1958; Vogel & Water- bolk, 1963). In this study we provide the first results of the sedimentological and mineralogical charac- terization of the ‘terre brune’ deposit, which may represent a record of the Holocene climate in southern Italy and provide a promising archive within which both human and climatic impacts can be studied. 2. MATERIALS AND METHODS During September 2016 the stratigraphic section SS1, located in the western sector of the cave, was selected as the representative profile for a multidisciplinary study of ‘terre brune’ deposit. The SS1, about 2.80 m thick, was cleaned, documented and sampled at a resolution of ca. 3 cm (Fig. 2). Ninety-six sam- ples were collected for sedimentological and mineralogical analyses. Grain sizes were determined using a CI- LAS 1064L laser diffraction particle size analyz- er (range from 0.04 to 500 μm). The grain size fractions are according to the classification of Wentworth (1922). Mineralogy was determined using a Philips PW1840 diffractometer (CuKa/Ni: 40 KV and 20 mA) on bulk sediment and on clay fraction of selected samples. Identification of the mineral phases was determined with XPowder12 free- ware software. The calcium carbonate content (CaCO3 %) was measured gas-volumetrically, by addition of HCl in a Dietrich-Frühling calcimeter. Carbon (δ13C) and oxygen (δ18O) isotopes were determined on calcium carbonate contained in sediment sieved to < 20 μm, which reacted with 100% phosphoric acid at 70°C using a Thermo GasBench device connect- ed to a Delta Plus mass spectrometer. Results are ex- pressed in delta per mill versus VPDB standard. 3. RESULTS Field observation of the section revealed the pres- ence of cross-laminations and large-scale ripples of variable thickness (1 - 10 cm). These structures are made of dark brown, cracked clayey-silt sediment, or silty sand with dull yellowish color. Layers of detrital limestone, generally rich in palaeontological and archae- ological remains, are also present. Laboratory analyses confirmed that the grain size distribution is generally bimodal, with elevated percent- ages in clay (from 27 to 59%, mean 47%) and silt (from 26 to 54%, mean 44%) grain size fractions; in several samples the sand fractions are also detected. Variations in these proxies along the sedimentary sequence are shown in Fig. 3. The grain size records show three inter- vals (55 - 75 cm, 90 - 130 cm and 195 - 230 cm) with lower percentage of clay fraction (Fig. 3a) that is coun- terbalanced by the content of the sand fractions (>63 μm, Fig. 3c-e). X-ray diffraction shows that samples are mainly composed by quartz and minor amounts of calcite, pla- gioclase, feldspar. Oriented XRD of the finest fraction of selected samples revealed the presence of clay miner- als of the illite and kaolinite groups. The intensity of the main peak of quartz was used for a further stratigraphic record (Fig. 3f). It shows that when sediments are en- riched in clay fraction they are depleted in quartz and vice versa, because the fine fraction contains higher amounts of clay minerals. Carbonate contents vary from 0 to ca. 12% (Fig. 3g); of note is that the samples in which carbonate was not detected still contain small amounts of carbonate that are below the detection limit of the method. The interval between 90 and 190 cm comprises the largest amount of calcite particles; this part of the sequence is also particularly rich in palaeontological and archaeolog- ical remains. Calcite contained in the grain size fraction <20 μm has oxygen isotope composition between -15.52‰ and 136 Giustini F. et al. Fig. 2 - Picture of stratigraphic section SS1. 137 -0.55‰ vs. VPDB. The δ18O record is shown in Fig. 3h; the upper (top - 70 cm) and the lower (200 - 280 cm) parts of the curve show several abrupt shifts towards very low isotopic values, up to -15.52‰ and -12.14‰, respectively. Between 90 and 190 cm the record ap- proximately shows uniform isotopic compositions with an average of -3.65‰; this value would indicate that the carbonate fraction at this level has mainly the contribu- tion of the isotopic signal of the marine carbonates, then it has in prevalence detrital nature. 4. DISCUSSION AND CONCLUSION The ‘terre brune’ deposit was mainly considered of eolian origin, due to the mineralogical composition and morphology of quartz grains (Blanc, 1920, 1928; Blanc & Cortesi, 1941). Our data are in accordance with the mineralogical and sedimentological composition pre- sented in the previous studies about Grotta Romanelli, and with studies from other Italian sites where eolian deposits were identified (Narcisi, 2000; 2001; Giraudi et al., 2013). Available chronology of the ‘terre brune’ (Alessio et al., 1965; Bella et al., 1958; Vogel & Waterbolk, 1963) temporally constraints the deposit to the beginning of Holocene, although the lowermost portion has never been dated. Preliminary results of new radiocarbon da- ting consistently indicate that the investigated section was formed between the late Last Glacial and the early Holocene (Calcagnile et al., 2018), when different cli- mates occurred in the Mediterranean basin. Various proxy data suggested dry and cold climate condition during the Late Glacial, enhanced meteoric precipitation during the transition from the Late Glacial to the Holo- cene, a general climate amelioration and wetter condi- tions during early Holocene, and a change toward the present-day dry regime at 6-5 ka BP (Allen et al., 1999; Sadori & Narcisi, 2001; Bar-Matthews et al., 2003; Zan- chetta et al., 2007; Martrat et al., 2014). The sedimentological and geochemical records of the ‘terre brune’ sequence were used to reconstruct the environmental variations related to climate changes during the late Last Glacial and the early Holocene. Sediments of the lower part of the sequence (200- 280 cm), that may be correlated to ‘levels D-E’ of Blanc (1920) stratigraphy, are progressively enriched in medi- um sand and depleted in clay contents; also, the quartz content increases, whereas the carbonate content is low. As the coarsening of eolian input mainly depends on two factors, the wind speed and the distance from the source areas (Muhs, 2013), our data suggest that deposition of this part of the sequence occurred during a period of more intense wind transport. The source of this sediment could have been eolian dust from Sahara regions. Loess formed by quartz of Sahara origin, was identified in several Italian sites, e.g. the Lago di Vico and Lagaccione, maar lakes in central Italy (Narcisi, 2000; 2001; Narcisi & Anselmi, 1998), the island of Lampedusa (Giraudi, 2004), the high mountains of the central and southern Apennines (Frezzotti & Giraudi, 1990; Giraudi et al., 2013). This phase of deposition certainly took place before 12 ka BP. At that time it is likely that a coastal plain in front of Grotta Romanelli was still large and it may have also contributed to the Fig. 3 - (a) Percentage of clay (<4 μm), (b) percentage of silt (4-63 μm), (c) percentage of very fine sand (63-125 μm), (d) percentage of fine sand (125-250 μm), (e) percentage of medium sand (63-125 μm), (f) intensity of main quartz peak (cps), (g) carbonate content (CaCO3%), (e) δ 18O (‰ vs. VPDB) results plotted vs. depth for the stratigraphic section SS1 of ‘terre brune. Levels according to Blanc (1920) stratigraphy end published ages (*Alessio et al., 1965; §Bella et al., 1958; °Vogel & Waterbolk, 1963). Holocene eolian deposits of Grotta Romanelli (southern Italy) accretion of the ‘terre brune’; the coastal plain was eval- uated 20 km wide at the Last Glacial Maximum (22 ka BP), and characterized by different environments, from lagoon to wetland, possibly fringed by sand dunes (Cassoli et al., 1979). Palaeontological remains also indicate a terrestrial environment ranging from open semi-arid to an occasionally dried-out mud flat (Sardella et al., 2018). In the interval going from 70 to 200 cm, possibly corresponding to ‘level C’ of Blanc (1920) stratigraphy, the grain size distribution shows an increase of fine and very fine sands, whereas medium sand and clay de- crease. An average decrease of quartz intensity also corresponds to carbonate content rise (up to 12%). The observed pattern suggests a decreased capacity of eolian energy to transport coarse particles. At this stage it is also possible that the record data respond to a pro- gressive sea-level rise and a consequent reduction of the coastal plain which coincided with the main phase of deglaciation between ca. 11.5 ka BP (the end Younger Dryas) and ca. 8.2 ka BP (Lambert et al., 2014). In par- ticular the increase in carbonate content which is mainly of detrital origin, as isotopes would prove, may be con- sidered the effect of the decrease of the eolian transport and the reduction of quartz mass capacity to dilute other mineral phases. Considering that this part of the se- quence is particularly rich in palaeontological and ar- chaeological remains, it is possible to speculate that this detrital contribution could be additionally due to the hu- man occupation. The upper part of the sequence (70 cm - top) may correspond to the ‘level B’ of Blanc’s stratigraphy. The sediment contains a considerable amount of clay and silt, whereas the sand fractions are virtually absent. Quartz and carbonate content decrease. Overall, this pattern points to a dramatically decline in the energy of eolian depositional mechanism and to an almost com- plete drowning of the coastal plain which cannot provide further sediments to contribute to the eolian wedge ac- cretion. This is almost the last phase of sedimentation; the uppermost layer of the Banc’s stratigraphy, the ‘level A’, was not preserved, due to both natural erosion and several years of excavations and research (Sardella et al., 2018). The end of sedimentation in Grotta Romanelli oc- curred at about 6 ka BP, when 1) the coastal plain in front of Grotta Romanelli was greatly reduced and the sea level was about -7 m below the modern sea level (Lambeck et al., 2004); and 2) prevailing wind directions changed, probably in relation with the termination of the African Humid period (De Santis & Caldara 2015). ACKNOWLEDGEMENTS We thank “Soprintendenza archeologia belle arti e paesaggio per le province di Brindisi Lecce e Taran- to” (Superintend Dr. Maria Piccarreta and Dr. Laura Masiello) for the excavation permission. We thank N. Ciccarese, T. De Santis, Don Piero Frisullo and Red Coral (Castro) for their logistical support, L. Bellucci, D. A. Iurino, F. Strani and D. 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