1. 145 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Late Eocene to Early Miocene Biostragraphy and Palaeoenvironments in the Beta Field of the Northern- Central Niger Delta, Nigeria Alex Etukokwu Ugochukwu a* , Isaac Odigi Minapuye b , Soronnadi-Ononiwu Geoffrey Chijioke c a,b,c Department of Geology, University of Port Harcourt Corresponding b Email: minapuyeodigi@gmail.com, c Email: chijiokesoronnadi@gmail.com Abstract Lithological, palynomorphs and foramininifera studies have been carried on samples from one (1) oil well in the Northern-Central depobelts of the Niger Delta. Fifty six (56) ditch cutting well samples composited at 30ft interval between 3960ft and 9060ft in MT-well Northern Niger Delta. Twenty-two 22 genera of foraminifera comprising mainly benthonic species were identified. Foraminifera and associated palynomorphs recovered from these sandy and shaly sediments permitted the dating, paleoenvironmental and paleoecological interpretation of the analyzed section. The well penetrated the shale and sandstone formations of the Agbada Formation. The studied section was assigned a Late Eocene to Early Miocene age with boundary between Oligocene and Early Miocene marked at 4470ft based on the occurrence of Cicatricosisporites drogensis while boundary between Late Eocene and Oligocene is marked at 7500ft based on the top occurrence Doualaidites laevigatus observed at that depth. Extremely poor recovery of planktonic foraminifera is evident while benthonic foraminifera, shell fragments and ostracods are well represented from 6090-8100ft with increasing faunal abundance and diversity with depth. The Late Eocene corresponds to the F5700 and P400 zones, characterized by the occurrence of Nonionella magnalingua and Cinctipoperioporites mulleri respectively while the Oligocene and early Miocene corresponds to the P500 and P600 zones of the Niger Delta Cenozoic chronostratigraphic chart [29]. The shell fragments indicate a shelf environment and palaeobathymetry is delineated within 0-30m water depth within the inner neritic delta front environment. The depositional settings were found to be similar to the present day Niger Delta, although palaeocology and paleoclimatic conditions were somewhat differ in Eocene to Miocene times of the Cenozoic Niger Delta. Keywords: Biostratigraphy; Paleoenvironment; Paleoecology; Paleoclimate; On-shore Niger Delta. ------------------------------------------------------------------------ * Corresponding author American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 146 1. Introduction Reference [14] described the Niger Delta as the largest on the continental margin of the Gulf of Guinea, covering an area extent of about 300,000 km² and has a sediment thickness of over 10km in the basin centre [13]. According to [29], three principal subsurface lithostratigraphic units are identifiable within the clastic sequences of the Tertiary Niger Delta: Benin, Agbada and Akata Formations respectively. The Akata Formation the oldest comprises of marine black shales and occasional turbiditic and channel fill sands and siltstone interbeds. Overlying the basal Akata is the paralic Agbada Formation characterized by an alternation of sandstone and shale sequences. The youngest, the Benin Formation consists predominantly of massive coarse sands and gravels. The silty shale of Akata Formation and the sandy shale of Agbada Formation are very fossiliferous. The startigraphic framework of the delta is based on pollen and foraminifera biostratigraphy and dated transgressive marker shales [24]. Depobelts otherwise known as sedimentation cycles are common in the Niger Delta. These cycles prograde over the oceanic crust into the Gulf of Guinea [30]. The total delta sequence is marked by a series of belts which reflect the depocentres succeeding each other in time and space by southward progradation. Each depobelt is bounded by major structure-building faults. Regionally, the Niger Delta is further subdivided into five depobelts [10] namely, Northern Delta, Great Ughelli, Central swamp, Coastal swamp and Off-shore (Fig.1). The study area falls within the Northern Delta which is the oldest of the Depobelts. Figure 1: Location map of Beta Field in the Niger Delta Though considerable data has been generated from many of the drilled wells in Niger Delta and information published is mainly on sedimentology; there is however, few published works on biostratigraphy of the Tertiary Niger Delta. Some of these include [24,31,23]. Paleoenvironmental studies in the Niger Delta are few [3,4;31,4;22,1,6] and they are all based on the use of lithologic data. Reference [22] used both lithologic American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 147 palynologic data in the reconstruction of paleoenvironment. Therefore, this paper undertakes a lithofacies, palynological and foraminiferal analysis of samples from MT -well in the Beta field of the Niger Delta; with a view to identify the P- and F -zones; to determine age, reconstruct the depositional environments, paleocology and paleoclimatic setting. 2. Location of study The Niger Delta is situated in southern Nigeria between latitudes 3° N and 6° N and longitude 5° E and 8° E [24]. It has area coverage of 75,000 sq km and is bounded to the northwest and west by the western African shield, which terminates at the Benin hinge line and to the east, by the Calabar hinge line (Fig. 1). The Anambra basin and Abakaliki anticlinorium mark its northern limit. To the south, it is bounded by the Gulf of Guinea. The MT well is in Beta field, located between Northern and Central Depobelt of the Niger Delta (Fig 1). It lies between latitude 5° and 6° north of the equator and longitude 6° and 7° E. 3. Regional geologic setting of the Niger Delta The Niger Delta occupies the ocean ward part of a larger and older tectonic feature, the Benue Trough. The initiation of the Benue trough and its sequential filling with marine sediments following the Cretaceous marine incursions provided the most important chain of (geologic) episodes that built-up the Niger Delta [26,27]. Other depocenters along the African Atlantic coast also contributed to the deltaic build-ups. In accordance with [33] the stratigraphic history of the Niger Delta Basin regarding tectonic events informs that the basin represents the third cycle in the evolution of the southern Nigerian sedimentary basins; (1) Benue-Abakiliki phase (Aptian- Santonian, (2) Anambra-Benin phase (Santonian- Early Eocene) (3) Niger Delta phase (Late Eocene-Recent). Based on the dominant environmental influence, the sedimentary sequence of the base consists in ascending order of three major lithostratigraphic and diachronous facies units [31], namely, prodelta facies (marine environment), delta front facies (transitional environment) and delta plain facies (continental environment). During the Tertiary, sediment supply was mainly from the north and east through the Niger, Benue and Cross Rivers. The Benue and Cross Rivers provided substantial amounts of volcanic detritus from the Cameroon volcanic zone beginning in the Miocene. The Niger Delta clastic wedge prograded into the Gulf of Guinea at a steadily increasing rate in response to the evolution of these drainage areas and continued basement subsidence. Regression rates increased in the Eocene, with an increasing volume of sediments accumulated since the Oligocene [31]. The Agbada and Akata Formations are Eocene to Recent in age, while the Benin Formation is Oligocene to Recent in age. Normal faults triggered by the movement of deep seated, overpressured, ductile, marine shale have deformed much of the Niger Delta clastic wedge [10]. Many of these faults formed during delta progradation and were syndepositional affecting sediment dispersal. In addition these fault growths were also accompanied by slope instability along the continental margin. Thus structural complexity in local areas reflects the density and style of faulting. Simple structures like crestal folds and flanks occur with the faults. Growth faults comprise antthetic faults and major structure-building faults (some [which bound the depobelts), steep, parallel crestal faults which cut the rollover structures. Growth fault-related structures are the dominant hydrocarbon traps in the Niger Delta (Fig. 2). 3.1 Niger Delta morphology American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 148 The morphology of Niger Delta changed from an early stage spanning the Paleocene to early Eocene to a later stage of delta development in Miocene time. The early coastlines were concave to the sea and the distributions of deposits were strongly influenced by basement topography [4]. Delta progradation occurred along two major axes, the first paralleled the Niger River, where sediment supply exceeded subsidence rate. The second, smaller than the first, became active during Eocene to early Oligocene basinward of the Cross River where shorelines advanced into the Olumbe-1 area [10]. Figure 2: Structural styles in the Niger Delta [29] In Late Miocene, the delta prograded far enough that shorelines between Warri and Port Harcourt became broadly concave into the basin. Accelerated loading by this rapid delta progradation mobilized underlying unstable shales. These shales for diapiric structures, deforming overlying strata [29]. 3.2 The Niger Delta depo-belts Deposits of the last depositional cycle have been divided into a series of six depobelts [10] also called depocenters or megasequences separated by major synsedimentary fault zones. These depobelts formed when paths of sediment supply were restricted by patterns of structural deformation, focusing sediment accumulation into restricted areas on the delta. Such depobelts changed position over time as local accommodation was filled and the locus of deposition shifted basin ward [10]. Deposition of the three formations occurred in each of the five offlapping siliciclastic sedimentation cycles that comprise the Niger Delta. These cycles (depobelts) are 30- 60 kilometers wide, prograde southwestward 250 kilometers over oceanic crust into the Gulf of Guinea [30], and are defined by synsedimentary faulting that occurred in response to variable rates of subsidence and sediment supply rates resulted in deposition of discrete depobelts when further crustal subsidence of the basin could no longer be accommodated, the focus of sediment deposition shifted seaward, forming a new depobelt American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 149 [10]. Each depobelt is a separate unit that corresponds to a break in regional dip o f the delta and is bounded landward by growth faults and seaward by large counter-regional faults or the growth fault of the next seaward belt [11,10]. Five major depobelts are generally recognized, each with its own sedimentation, deformation, and petroleum history. Reference [10] describe three depobelt provinces based on structure. The northern delta province, which overlies relatively shallow basement, has the oldest growth faults that are generally rotational, evenly spaced, and increases their steepness seaward. The central delta province has depobelts with well-defined structures such as successively deeper rollover crests that shift seaward for any given growth fault. Lastly, the distal delta province is the most structurally complex due to internal gravity tectonics on the modern continental slope. Classic integrated geological studies have shown that several different depobelts abound in the Niger Delta Basin. The depobelts consists of Northern Delta, Greater Ughelli Onshore, Central swamp, Coastal swamp, Shallow and Deep offshore. 3.3 Tectonic and structural setting of the Niger Delta Along the west coast of equatorial Africa, the tectonic framework (Fig. 3) of the continental margin along the West Coast of equatorial Africa is controlled by Cretaceous fracture zones expressed as trenches and ridges in the deep Atlantic. The fracture zone ridges subdivide the margin into individual basins, and, in Nigeria, form the boundary faults of the Cretaceous Benue-Abakaliki Trough, which cuts far into the West African shield. The trough represents a failed arm of a rift triple junction associated with the opening of the South Atlantic. In this region, rifting started in the Late Jurassic and persisted into the Middle Cretaceous (Lehner and De Ruiter, 1977). In the region of the Niger Delta, rifting diminished in the Late Cretaceous (Michele and his colleagues 1999). Figure 3: Tectonic framework of the Niger Delta American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 150 After rifting ceased, gravity tectonism became the primary deformational process. Shale mobility induced internal deformation and occurred in response to two processes [14]. First, shale diapers formed from loading of poorly compacted, over-pressured, prodelta and delta-slope clays (Akata Formation.) by the higher density delta-front sands (Agbada Formation). Second, slope instability occurred due to lack of lateral, basinward, support for the under-compacted delta-slope clays (Akata Formation). For any given depobelt, gravity tectonics were completed before deposition of the Benin Formation and are expressed in complex structures, including shale diapers, roll-over anticlines, collapsed growth fault crest, back-to-back features, and steeply dipping, closely spaced flank faults [11]. 3.4 Stratigraphy of the Niger Delta The sediments of the Cenozoic Niger Delta may reach a maximum thickness of 9000-12000 m, in the central part of the basin. A detailed description of the sedimentary facies units has been published by [29,32] and Weber and [29]. Based on dominant environmental influences, the units are, continental environment, transitional environment and marine environment, this research work shall adopt their description. The lithostratigraphic subdivision includes: (1) Benin Formation; (2) Agbada Formation; and (3) Akata Formation. Designated from the bottom, the Akata, Agbada and Benin formations respectively (Fig 4). Figure 4: Stratigraphic framework of the Niger Delta modified from [2] 4. Materials and Methods 4.1 Materials Ditch cuttings containing shaly and sandy samples were collected at 30ft intervals, from 1207m (3960ft) to 2761.4m (9060ft) in the Agbada Formation. Lithologic, palynological and foraminiferal analyses were carried out on the fifty six (56) ditch cutting samples recovered from MT-well. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 151 4.1.1 Lithologic Description Depth to depth sample description was carried on each sample using a hand lens and 2.0m concentration of HCL to check effervescence which consequently, indicates the presence or absence of carbonaceous materials. The studied sections of the MT-well ranged from 3990ft – 9060ft and sampled at 30ft intervals. The lithology is composed of shales and sandstones intercalations, with more shale at the base than at the top (Fig.5). The sands are predominantly white at the top, light brown in the middle section and dark brown towards the base of the section studied. The shales are dark grey in colour, fissile and mostly non-calcareous. The sandstones ranged in grain sizes from fine to medium grained but mostly medium grained, friable and non-calcareous. Details description of the section is presented in Fig. 5. The shale and sand intercalation suggests the parallic conditions of deposition. Figure 5: Lithologic description of MT Well American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 152 4.2 Foraminifera 4.2.1 Methods The foraminifera recovered in this study were obtained by the unpublished extraction technique for invertebrate microfossils at the Geological Laboratory of the University of Port Harcourt of Nigeria. This involved soaking crushed samples (I) in kerosene for one to two hours and (2) in hydrogen peroxide overnight and washing through a sieve (diameter 74µm) to remove unwanted mud. Thereafter, the samples were dried and picked for foraminifera. 4.3 Palynology 4.3.1 Methods Palynological residues were obtained by the standard techniques of digesting unwanted constituents of sedimentary rock samples in mineral acids. Samples were treated with 50% hydrochloric acid and 60% hydrofluoric acid to remove calcium carbonate and silicate materials respectively. Whereas a short oxidation with concentrated nitric acid was necessary to remove humus and humic acids which rendered sculptural features of palynomorphs unrecognizable, this stage was omitted for those samples studied for palynodebris to retain their natural colours. Zinc bromide with a specific gravity of 2.1 was used to concentrate palynomorphs and other organic residues which were subsequently sieved. Oxidized residues were sieved through 10 urn and 80 urn nylon meshes, but only 10µrn mesh was used for unoxidized residues. Transmitted light microscope work was carried out on the 10- 80 µm fraction for palynomorphs. The identification of the palynomorphs taxa were done with guided work of [12] and some published palynomorph mircophotographs. The distribution of the recovered palynomorphs is shown in Plates1-4. 5. Results and Discussion 5.1 Lithologic Descriptions The studied sections are composed of shales and sandstones intercalations, but having more shale at the base than at the top. The sands are predominantly white at the top of the section, light brown in the mid section and dark brown towards the base. The shales are dark grey in colour, fissile and mostly non-calcareous. The sandstones ranged in grain sizes from fine to medium grained but mostly medium grained, friable and non- calcareous. The sand to shale ratio is presented in Fig. 6. The shale and sand intercalation supported the parallic conditions of deposition. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 153 Figure 6: Sand to Shale Ratio 5.2 Biostratigraphy Biostratigraphic analysis of MT-well involved lithologic sample descriptions, micropaleontologic sample preparations, taxonomic descriptions, analyses and interpretations of trends. The aspect of micropaleontologic sample preparations and analyses involved generation of data for both foraminiferal and palynomorph studies. The statistical counts generated for the occurrence of both palynomorphs and foraminifera are presented in Table1. The photomicrographs of key taxa are presented (Plates 1-4). Biostratigraphy frame work for the studied American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 154 section is summarized and presented in Table 4. The sections have been subdivided into P and F zones approach of [11,17]. Table 1: Occurrence of Foraminifera and Palynmorphs Depth Interval (ft) PALY FORAM TOTAL PALY % FORAM % 3960 – 3990 4 4 100 0 4050 – 4080 5 5 100 0 4080 – 4110 13 13 100 0 4110 – 4140 6 6 100 0 4200 – 4230 5 5 100 0 4290 – 4320 8 8 100 0 4320 – 4350 17 17 100 0 4410 – 4440 15 15 100 0 4440 – 4470 44 1 45 98 2 4470 – 4500 30 30 100 0 4800 – 4830 9 9 100 0 4830 – 4860 6 6 100 0 4860 – 4890 26 26 100 0 5730 – 5760 117 117 100 0 5820 – 5850 12 12 100 0 5880 – 5910 20 20 100 0 5910 – 5940 26 26 100 0 5940 – 5970 16 16 100 0 5970 – 6000 249 5 254 98 2 6000 – 6030 21 21 100 0 6030 – 6060 67 67 100 0 6060 – 6090 32 3 35 91 9 6330 – 6360 17 1 18 94 6 6360 – 6390 24 24 100 0 6600 – 6630 60 1 61 98 2 7020 – 7050 29 29 100 0 7050 – 7080 86 31 117 74 26 7110 – 7140 5 2 7 71 29 7320 – 7350 15 15 100 0 7380 – 7410 41 41 100 0 7470 – 7500 307 307 100 0 7560 – 7590 73 11 84 87 13 7920 – 7950 14 1 15 93 7 7950 – 7980 46 1 47 98 2 8010 – 8040 65 65 100 0 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 155 8040 – 8070 196 16 212 92 8 8070 – 8100 253 14 267 95 5 8100 – 8130 43 1 44 98 2 8130 – 8160 221 6 227 97 3 8160 – 8190 127 28 155 81 19 8220 – 8250 115 8 123 93 7 8250 – 8280 115 53 168 68 32 8280 – 8310 164 10 174 94 6 8310 – 8340 78 78 100 0 8340 – 8370 125 63 188 66 34 8370 – 8400 183 45 228 80 20 8430 – 8460 146 74 220 66 34 8460 – 8490 111 33 144 77 23 8490 – 8520 11 5 16 69 31 8520 – 8550 109 8 117 93 7 8550 – 8580 87 43 130 67 33 8580 – 8610 130 1 131 99 1 8760 – 8790 60 60 100 0 8940 – 8970 106 106 100 0 9000 – 9030 29 1 30 97 3 9030 – 9060 31 1 32 97 3 The results from the foraminifera analysis was poor and only benthonic foraminifera were recovered which is an indication of a shallow marine depositional environment. The absence of planktonic foraminifera in the analyzed samples made it difficult to assign ages of the sections encountered with foraminifera but rather with palynomorphs. The total recoveries of foraminifera and dinoflagellate (marine indicators) are presented in Table 2; and marine Index data is presented in Table 3. The organic constituents observed in the studied samples have been grouped according to the classification proposed by [36]. A summary of this classification is proposed in Fig. 7 (modified from [33]. Table 2: Cumulative percentage distributions of fauna and flora Data D ep th I n te rv al ( ft ) % P o ll en % S p o re % D in o fl ag el la te % F u n g al s p o re % F o ra m t es t li n in g % A lg ae % D ia to m % A cr it ar ch T o ta l % 3960 – 3990 75% 25% 4050 – 4080 100% 4080 – 4110 61% 8% 15% 8% 8% 100% American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 156 4110 – 4140 33% 17% 33% 17% 100% 4200 – 4230 20% 20% 40% 20% 100% 4290 – 4320 38% 50% 12% 100% 4320 – 4350 12% 64% 6% 6% 6% 6% 100% 4410 – 4440 7% 53% 33% 7% 100% 4440 – 4470 91% 7% 2% 100% 4470 – 4500 7% 66% 13% 7% 7% 100% 4800 – 4830 11% 45% 22% 11% 11% 100% 4830 – 4860 17% 66% 17% 100% 4860 – 4890 34% 54% 8% 4% 100% 5730 – 5760 36% 46% 17% 1% 100% 5820 – 5850 75% 17% 8% 100% 5880 – 5910 65% 5% 15% 10% 5% 100% 5910 – 5940 8% 73% 15% 4% 100% 5940 – 5970 6% 31% 63% 100% 5970 – 6000 5% 93% 2% 100% 6000 – 6030 5% 75% 10% 10% 100% 6030 – 6060 8% 73% 8% 3% 4% 4% 100% 6060 – 6090 13% 59% 22% 6% 100% 6330 – 6360 12% 76% 12% 100% 6360 – 6390 8% 63% 13% 4% 4% 8% 100% 6600 – 6630 11% 75% 7% 3% 2% 2% 100% 7020 – 7050 21% 66% 7% 3% 3% 100% 7050 – 7080 13% 48% 23% 2% 2% 12% 100% 7110 – 7140 60% 20% 20% 100% 7320 – 7350 47% 40% 13% 200% 7380 – 7410 18% 69% 13% 100% 7470 – 7500 33% 65% 1% 1% 100% 7560 – 7590 22% 45% 9% 1% 1% 22% 100% 7920 – 7950 50% 50% 100% 7950 – 7980 11% 59% 24% 4% 2% 100% 8010 – 8040 31% 55% 14% 100% 8040 – 8070 23% 70% 6% 1% 100% 8070 – 8100 19% 68% 9% 1% 1% 1% 1% 100% 8100 – 8130 28% 47% 23% 2% 100% 8130 – 8160 8% 88% 3% 1% 100% 8160 – 8190 16% 73% 9% 2% 100% 8220 – 8250 33% 49% 18% 100% 8250 – 8280 24% 41% 35% 100% American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 157 8280 – 8310 16% 56% 26% 1% 1% 100% 8310 – 8340 18% 53% 27% 1% 1% 100% 8340 – 8370 17% 69% 14% 100% 8370 – 8400 10% 83% 4% 1% 1% 1% 100% 8430 – 8460 45% 44% 10% 1% 100% 8460 – 8490 38% 50% 5% 7% 100% 8490 – 8520 100% 100% 8520 – 8550 34% 45% 18% 3% 100% 8550 – 8580 11% 64% 24% 1% 100% 8580 – 8610 11% 83% 6% 100% 8760 – 8790 22% 63% 13% 2% 100% 8940 – 8970 22% 70% 7% 1% 100% 9000 – 9030 28% 38% 31% 3% 100% 9030 – 9060 46% 36% 16% 2% 100% Table 3: Marine Index Data Depth Interval (ft) CONTINENTAL INDICATOR MARINE INDICATORS Pollen Spore Total % Dinoflagell ate Foraminifera test lining Total % 3960 – 3990 3 3 100 0 4050 – 4080 5 5 100 0 4080 – 4110 8 8 80 1 1 2 20 4110 – 4140 2 1 3 60 2 2 40 4200 – 4230 1 1 2 50 2 2 50 4290 – 4320 3 4 7 88 1 1 12 4320 – 4350 2 11 13 87 1 1 2 13 4410 – 4440 1 8 9 64 5 5 36 4440 – 4470 40 40 91 3 1 4 9 4470 – 4500 2 20 22 85 4 4 15 4800 – 4830 1 4 5 71 2 2 29 4830 – 4860 1 4 5 100 0 4860 – 4890 9 14 23 92 2 2 8 5730 – 5760 42 53 95 83 20 20 17 5820 – 5850 9 9 75 2 1 3 15 5880 – 5910 13 13 81 1 2 3 19 5910 – 5940 2 19 21 81 4 1 5 19 5940 – 5970 1 5 6 38 10 10 62 5970 – 6000 13 231 244 96 5 5 10 4 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 158 6000 – 6030 1 16 17 89 2 2 11 6030 – 6060 5 49 54 87 5 3 8 13 6060 – 6090 4 19 23 66 7 5 12 34 6330 – 6360 2 13 15 94 1 1 6 6360 – 6390 2 15 17 85 3 3 15 6600 – 6630 7 45 52 90 4 2 6 10 7020 – 7050 6 19 25 93 2 2 7 7050 – 7080 11 42 53 50 20 33 53 50 7110 – 7140 3 3 50 1 2 3 50 7320 – 7350 7 6 13 87 2 2 13 7380 – 7410 7 27 34 87 5 5 13 7470 – 7500 102 201 303 99 3 3 1 7560 – 7590 16 33 49 74 6 11 17 26 7920 – 7950 7 7 14 93 1 1 7 7950 – 7980 5 27 32 73 11 1 12 27 8010 – 8040 20 36 56 86 9 9 14 8040 – 8070 46 138 184 87 11 17 28 13 8070 – 8100 48 175 223 85 24 15 39 15 8100 – 8130 12 20 32 74 10 1 11 26 8130 – 8160 10 115 125 93 4 6 10 7 8160 – 8190 20 92 112 74 12 28 40 26 8220 – 8250 38 56 94 76 21 8 29 24 8250 – 8280 28 47 75 45 40 53 93 55 8280 – 8310 26 93 119 69 43 11 54 31 8310 – 8340 14 41 55 72 21 21 28 8340 – 8370 21 86 107 57 18 63 81 43 8370 – 8400 19 153 172 76 7 46 53 24 8430 – 8460 66 63 129 59 15 74 89 41 8460 – 8490 42 56 98 72 5 33 38 28 8490 – 8520 11 11 69 5 5 31 8520 – 8550 37 49 86 74 19 11 30 26 8550 – 8580 10 56 66 51 20 44 64 49 8580 – 8610 14 102 116 93 8 1 9 7 8760 – 8790 13 37 50 86 8 8 14 8940 – 8970 23 74 97 92 8 8 8 9000 – 9030 8 11 19 66 9 1 10 34 9030 – 9060 14 11 25 81 5 1 6 19 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 159 Table 4: Summary of Palyno/ Foram Stratigraphic Succession in MT-Well (3990 – 9060ft) Interval (ft) P-Zone F-Zone Age Events Palynology Foraminifera 3990 – 4470 ? P600 ? Early Miocene Top Occurrence of Cicatricosisporites dorogensis at 4470ft BARREN 4470 - 7500 P500 Oligocene Top occurrence of Doualaidites laevigatus at 7500ft BARREN 7500 – 9060 P400 F5700 Late Eocene Occurrence of Cinctiperiporites mulleri within this interval Occurrence of Nonionella magnalingua at 8370ft 5.2.1 Palynomaceral group (PM) It comprises all fragments derived from higher plant debris and is subdivided to their degree of oxidation: PM1, PM2, PM3 and PM4. Figure 7: Origin and classification of particulate organic matter as used in this study (modified from [33]. PM1- Orange to dark brown, translucent, partially oxidized. PM2- Orange to dark brown fragments exhibiting cell-structures, moderately oxidized. When degraded, PM1 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 160 and PM2 are distinguished by the suffix B (PM1/2-B). PM3- Yellow to orange fragments exhibiting cell-structures. PM4- Black opaque fragments highly oxidized. It is also considered as the most stable palynomaceral and can be transported far out to a marine environment before being degraded [11][33]. PM4 is subdivided into two fractions: equidimensional PM4 and blade-shaped or tabular PM4 (PM4-T). 5.2.2 Sporomorphs This term includes pollen and spores. Because of their scarcity in the studied samples they are grouped together in this paper. Dinoflagellates cysts (Dinocysts) Dinocysts are the main representatives of the organic microplankton. All species encountered here are strictly marine. 5.2.3 Foraminifera linings They are organic linings (tectin) of some foraminifera, and considered as a marine indicator. The palynomaceral group and sporomorphs constitute the allochthonous fraction (land derived), whereas Dinocysts and Foraminera linings represent the (relatively) autochthonous fraction (marine) of the organic residue. 5.3 Paleobathymetry The benthic foraminifera species found in studied section allowed the interpretation of the paleoenvironment to be marginal to shallow marine environment (Inner Nerritic). According to [3][4] this environment falls within 0- 50m water depth ( Fig.6). Figure 8: Depositional Environment and Bathymetric ranges used in Paleoenvironmental Interpretation Modified after [3,4,5] American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 161 5.4 Age of the section Age determination of the studied sections was basically characterized using palynomorphs. This was because the recoveries from foraminifera were very poor and only included benthonic foraminifera. The occurrence of the benthonic foraminifera started sparsely from 6060 – 6090ft and increased at 8070 – 8100ft from where biozonation (F-Zone). From the palynological analysis, the sediments were observed to be deposited during Late Eocene to ?Early Miocene times with the boundary between Oligocene and Early Miocene marked at 4470ft using the top occurrence of Cicatricosisporites dorogensis while that between Late Eocene and Oligocene was fixed at 7500ft using the top occurrence of Doualaidites laevigatus observed at that depth. Only the late part of Eocene was penetrated. Oligocene was not subdivided due to poor data and missing sections. 5.5 Paleoenvironmental interpretation Based on the palynomorphs and foraminifera recoveries, the paleoenvironment of deposition for the samples studied ranged between the shallow marine (the lower shale section of the study well) to marginal marine (littoral). The presence of benthonic foraminifera is also an indication of shallow marine paleoenvironment of deposition. The paleoenvironment of deposition interpretation was based on the palynomorph recoveries of the sample analyzed. The recoveries showed the presence mangrove swamp species, freshwater species, rain forest and savanna species (Table 6). However the mangrove swamp and freshwater species were dominant compared to the rain forest and savanna species. This suggests a paleoenvironment of mangrove swamp/fresh water environment. The presence of the rain forest and savannah species may have as a result of reworking by fluvial processes into the mangrove/freshwater environment. Based on palynology and foraminifera recoveries, the paleoenvironment of deposition for the samples studied ranged between the shallow marine i.e marginal marine (littoral). 5.6 Paleocology and Paleoclimatic Setting The palynomorphs recovered from the studied samples were classified into paleoecologic groups according to the vegetation zones of their extent parent plants or their nearest living relatives. The paleoecology groupings according to [18] were followed which was on the bases of nature, quantity and quality of recovered pollen and spores are dependent on their proximity to shore, ecology and eustacy. Fig. 9 is a schematic illustration of different environments with the extent and living plant relatives from where the pollens and spores where generated. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 162 Figure 9: Paleoecology based on extant parent plant proximity to shore after Poumot (1989) Four different environments (A – D) has been charaterized into paleoecology groupings based on the vegetation zones of the extant parent plants or their nearest living relatives. A. Upland flora which are dominated by conifers. Most modern conifers are arborescent (big trees with large branches (1 & 2)), and few shrub-like plants with multiple branched shoots, covered with spirally attached, elliptic leaves (3 & 4). B. Lowland flora with arborescent cycadophytes. These are plants with probably 1m high, large trunks and long leaves (5 – 11). C. Wetland areas dominated by hygrophytic plants such as sphenophytes, ferns and lycophytes. Sphenophytes include the dorsetails with short internodes which results in vertical, articulated stems with whorls of microphylls. the ferns are smaller, with fronds at least 15cm long attached to a more or less bulbous rhizome. The lycophytes include the herbaceous and subarborescent taxa (14 – 16). D. Coastal assemblage dominated by lycophytes and seed ferns. The seed ferns are probably an arborescent plant or at least a shrub with 0.05 – 1m long pinnate leaves. The leaf shape is variable in relation to their growing position on the trunk (17 – 19). About 111 different flora and fauna species were recovered from the sample preparations, these included: 47 pollen, 15 spores, 14 dinoflagelates, 2 fungal spores, 1 foraminifer test lining, 3 algae, 3 acritarch, 22 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 163 foraminifera and 4 miscellaneous marine species. The paleoecology identification was based on the sporomorph recoveries as continental species and foraminifera as marine species, the sporomorphs recovered were grouped into the following paleoecology groups based on their ecological affinities to the different envornments (A – D). The predominant paleoecology groups identified from the sporomorphs recovered included the mangrove swamp, the fresh water swamp, the rain forest and the savanna. The paleoecology of the studied section of MT- well ranged between inner neritic (foraminifera recoveries), to littoral (mangrove swamp - fresh water swamp). The fresh water swamp represents the wetland areas dominated by hygrophytic plants such as sphenophytes, ferns and lycophytes while the mangrove swamp represents the coastal assemblage dominated by lycophytes and seed ferns. Species of savanah sporomorphs ( Hinterland) recovered may be from terrestrial palynomorphs which become incorporated into marine sediments mainly due to fluvial transport which occur predominantly as silt-sized alluvial particles (Morley, 1995). The presence of Zonocostites ramonae – Rhizophora and dinoflagellates taxa such as Selenopemphix and spiniferites sp suggests a lagoonal to shallow marine environment [17,18]. Table 5: Palaecological groupings and climatic conditions for P pollen and spores Palaecological Groupings Miospores Climatic Indicators 1 Mangroove Swamp Forest Zonocostites ramonae, Spinizonocolpites echinatus, Psilatricolporites crassus, Psilatricolporites annuliporis, Verrucatosporites usmensis, Smooth monolete spore, Smooth trilete spore, Cicatricosisporites dorogensis Granulatisporites spp. WET 2 Fresh Water Swamp Retibrevitricolporites protrudens, Proteacidites spp, Pachydermites diederixi, Retistephanocolpites williamsi, Retibrevitricolporites ibadanensis WET 3 Rain Forest Verrucatosporites usmensis, Verrucatosporites tenellis Verrucatosporites farvus. WET 4 Savannah Striatricolpites catatumbus, Polyadopollenites vancampori, Retibrevitricolporites triangulates Retitricolporites irregularis. DRY American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 164 5.7 Summary and Conclusions The results generated from the micropaleontological analyses showed poor foraminifera recoveries. The sample is dominated by benthonic foraminifera,therefore cannot be used for age determination,but age was determined using diagnostic palynomorph markers. The ages ranged from Late Eocene to ?Early Miocene times with the boundary between Oligocene and Early Miocene marked at 4470ft using the top occurrence of Cicatricosisporites dorogensis while that between Late Eocene and Oligocene was fixed at 7500ft using the top occurrence of Doualaidites laevigatus observed at that depth. The preponderance of benthonic foraminifera is an indication of shallow marine deposition. This is also supported by high occurrence of terrestrially derived palynomorphs. The sand/shale ratio plot showed an intercalation of sand and shale which is interpreted to correspond to the Agbada Formation of the Niger Delta. The marine index plot also showed an indication of deposition within the continental environment more than the marine environment. The paleoecological groupings based on marker extant species indicated a dominant Mangrove swamp and Fresh water environments while rain forest and savanna species suggests a reworking of the few species into the mangrove swamp environment. Acknowledgements The authors thank the Cenozoic Niger Delta Working group of the Department of Geology, University of Port Harcourt for helpful discussion and improvement of the manuscript. The second author is the occupant to The O.B. Lulu Briggs Chair in Petroleum Geosciences Research Project. References [1] Adedukun, O.A (1981). Petrology, provenance and depositional environments of reservoir sandstones of Ossu-Izombe oilfield, Imo State, Nigeria. Journal of Petrol. Geology 4, 35-56. [2] Adeigbe O.C, Ola-Buarimo A.O, Moronhunkola A.O (2013). Palynological characterization of the tertiary offshore Emi- 1 well, Dahomey Basin, Southwestern Nigeria. International Journal of Scientific and Technological Research; 2:58-70. [3] Allen, J.R.L., (1965). Late Quaternary Niger Delta, and adjacent areas-sedimentary environments and lithofacies. American Association of Petroleum Geologists Bulletin, Vol.49, p. 547-600. [4] Allen, J.R.L. (1970). Sediments of the modern Niger Delta: A summary and review. In J.P Morgan (ed) Deltaic sedimentation, Modern and Ancient SEPM Spec. Publ. 15, 138-151. [5] Allen, P. & Allen, J.R., (1990). Basin analysis principles and applications, Blackwell science 451pp. [6] Amajor, L.C and Agbaire, D.W (1989). Depositional history of the reservoir sandstones Akpor and Apara oilfields, eastern Nigeria Delta. Journal Petrol. Geology. 12,453-464. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 165 [7] Avbovbo, A.A., (1978). Tertiary lithostratigraphy of Niger Delta. American Association of Petroleum Geologists Bulletin, vol. 62, p. 295-300. [8] Burke, K., (1972) Longshore drift, submarine canyons and submarine fans in development of Niger Delta: AAPG Bulletin, v. 56:1975-1983. [9] Davies, J.R. Mc Nestry, A. & Waters, R.A. (1991). Palaeoenvironments and Palynofacies of a pulsed transgression: the late Devonian and early Dinantian (Lower Carboniferous) rocks of southeast Wales – Geol. Magazine, 28, 4, 355-380. [10] Doust, H. & Omatsola, E. (1990). Niger Delta: In: Divergent/Passive Margin Basins, Edwards, J.D. and Santogrossi, P. (eds). American Association of Petroleum Geologists. Memoir 48, Tulsa Oklahoma: 201-238. [11] Evamy, B.P., J. Haremboure, P. Kamerling, W.A. Knaap, F.A. Molly and P.H. Rowlands, (1978). Hydrocarbon habitat of tertiary Niger Delta. American Association of Petroleum Geologists. Bulletin., 62:1-39. [12] Gereraad, J.H., C.A. Hopping and J. Muller, (1968) Palynology of tertiary sediments from tropical areas. Revised. Paleobotany Palynology., 6: 189-348. [13] Kaplan, A. Lasser C.U. & Norton, I.O. (1994). Tectonic map of the world. Panel 10: Tulsa, American Association of Petroleum Geologists. Bulletin vol 51, pp 761-779. [14] Kulke, H., (1995). Nigeria, In: H. Kulke (ed), Regional Petroleum Geology of the World. Part II: Africa, America, Australia and Antarctica pp 143-172, Berlin, gerbruder Borntraeger. [15] Lehner, P., and de Ruiter, P.A.C., (1977). Structural history of Atlantic Margin of Africa. American Association of Petroleum Geologists Bulletin, vol. 61, p. 961-981. [16] Michele, L.W.T., Ronald, R.C., and Michael, E.B., (1999). The Niger Delta Petroleum System. Niger Delta Province, Nigeria, Cameroon, and Equatorial Guinea, Africa. Open-file report 99-50-H. [17] Morley, R.J., (1995). Tertiary stratigraphic palynology in south East Asia: Current statue and new directions. Geol.Soc Malaysia, Bulletin. 1-36. [18] Muller. J., (1995). Palynology of Recent Orinoco delta and shelf sediments: Report of Orinoco shelf expedition. Micropaleontology 51 1-32. [19] Nwachukwu, J.I. and Chukwurah, P.I. (1986). Organic matter of Agbada Formation, Niger Delta, Nigeria: American Association of Petroleum Geologists Bulletin, Volume 70, pp 48-55. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 166 [20] Odigi, M., and Ofoegbu, C (1989). Distribution and Geology of non-metallic minerals in Nigeria. In: Groundwater and mineral Resources of Nigeria (Ed, C.O. Ofoegbu) Friedr View & Sohn. Earth Sci. vol.7 p 141-159. [21] Oloto, I.N., (2014). Biostratigraphy of the Upper Tertiary Western offshore Niger Delta, Nigeria. International Journal of Scientific & Technology Research. 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A review of the laboratory preparation of palynomorphs with a description of an effective non-acid technique. Revista Brasileira Paleontologia. 7 (1): 13-44. [29] Shell Petroleum Development Company SPDC (1980) Monograph of Nigerian pollen and spores. Nigeria. 80-148. [30] Shell Petroleum Development Company SPDC (2010) Chronostratigraphy Chart of the Niger Delta. [31] Short, K.C. and Stauble, J. (1967). Outline Geology of the Niger Delta. American Association of Petroleum Geologists Bulletin vol. 51, pp 761-779. [32] Stacher, P., (1995) Present understanding of the Niger Delta hydrocarbon habitat, In: Oti, M.N and G. Postman, (eds.). Geology of Deltas, p. 257-267. [33] Steffen, D and Gorin, G.E( 1993). Palynofacies of the Upper Tithonian- Berriansian deep-sea Carbonate in the Vocontian Trough ( SE France). Bull. Des Centres de Recherches Expl and Production. 17(1) 235-248. 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Plate 1 Explanation To Plate 1 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 168 Fig. 1: Textularia concava, T – Well, 4440 – 4470 ft. Figs. 2, 3, 4, 5 & 6: Haplophragmoides rugosa, T – Well, 5970 – 6000 ft. Fig. 7: Truncatulina ungeriana, T – Well, 6060 – 6090 ft. Fig. 8: Haplophragmoides rugosa, T – Well, 6060 – 6090 ft. Fig. 9: Cibicides corticatus, T – Well, 6060 – 6090 ft. Figs. 10 & 16: Ostracoda, T – Well, 7050 – 7080 ft. Fig. 11: Haplophragmoides wilbertirugosa, T – Well, 6600 – 6630 ft. Figs. 12 & 13: Ammobaculites exiguus, T – Well, 7560 – 7590 ft Fig. 14: Dissammina fallax, T – Well, 7050 – 7080 ft. Fig. 15: Shell fragment, T – Well, 6330 – 6360 ft. PLATE 2 Explanation To Plate 2 Figs. 1, 2, 3, 4 & 9: Trochammina inflata, T – Well, 8250 – 8280 ft. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 169 Fig. 5: Ammobaculites-exiguus, T – Well, 8250 – 8280 ft. Figs. 6 & 8: Haplophragmoides wilberti, T – Well, 8250 – 8280 ft. Fig. 7: Anomalina-ammonoides, T – Well, 8250 – 8280 ft. Figs. 10 & 12: Planorbulina larvata, T – Well, 8250 – 8280 ft. Figs. 11 & 13: Haplophragmoides wilbertirugosa, T – Well, 8250 – 8280 ft. Plate 3 EXPLANATION TO PLATE 3 Figs. 1, 2, 3 & 6: Elphidium simplex, T – Well, 8340 – 8370 ft. Fig. 4: Haplophragmoides wilberti, T – Well, 8340 – 8370 ft. Fig. 5: Nonionina umbilicatula, T – Well, 8340 – 8370 ft. Fig. 7: Nonionella magnalingua, T – Well, 8340 – 8370 ft. Fig. 8: Planorbulina larvata, T – Well, 8340 – 8370 ft. Fig. 9: Brizalina dilatata, T – Well, 8340 – 8370 ft. Fig. 10: Quinqueloculina costata, T – Well, 8340 – 8370 ft. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2019) Volume 62, No 1, pp 145-171 170 PLATE 4 EXPLANATION TO PLATE 4 Figs. 1, 3, 5 & 6: Planulina wuellerstorfi, T – Well, 8430 – 8460 ft. Fig. 2: Trochammininoides protues, T – Well, 8430 – 8460 ft. Fig. 4: Truncatulina ungeriana, T – Well, 8430 – 8460 ft. Fig. 7: Discorbis vencularis, T – Well, 8430 – 8460 ft. Figs. 8, 9 & 12: Haplophragmoides rugosa, T – Well, 8430 – 8460 ft. Figs. 11, 14 & 15: Dissammina fallax, T – Well, 8430 – 8460 ft. Fig. 13: Ostracoda, T – Well, 8430 – 8460 ft. Figs. 16 & 17: Gastropoda, T – Well, 8430 – 8460 ft.