Depositional Paleoenvironment Research Articles

Geology, Palynomorphs Distribution, Stratigraphy and Depositional Environments of Lewumeji and Idogun Wells, Eastern Dahomey Basin Southwestern, Nigeria

Selected composited samples from Lewumeji (0-111m) and Idogun (0- 54m) wells, from Abeokuta Group, Eastern Dahomey Basin, Nigeria, were subjected to detailed lithologic and palynological studies. The studies aimed at determining the lithological sequence, relative age, palynological zone and paleoenvironments of deposition. The core samples were subjected to lithological description and palynological analysis using standard procedure in order to determine palynomorphs contents such as pollen, spore and dinoflagellates. The lithologies from both wells consist of reddish to brown clay, reddish to brown colour, rounded to sub rounded sandstone, dark grey shale denoting possibly fluvial, brackish, lagoonal and marine environments. A total of 31 well preserved low to moderate diverse palynomorphs were recovered from the studied area. The palynomorphs frequency percentage distribution shows that both wells have a higher ratio of land-derived pollen and spores to the marine dinoflagellates; (75%, 25% and 61%, 39%) for Lewumeji and Idogun wells respectively. The microfloral assemblages include abundant Cyathidites sp., Cyathidites minor, Tubistephanocolpites cylindricus, Proteacidites sp., Trilete spore, Foveotriletes margaritae, Monocolpites marginatus, Monoporites annulatus, Pteris sp, Distaverrusporites simplex and Laevigatosporites sp. The dinoflagellates recovered were characterized by the likes of Leiosphaeridia sp., Senegalinium sp., Oligosphaeridinium sp., Paleocytodinium sp., Cerodinium sp. and Subtilisphaera sp. The wells fall within Cyathidites Minor zone, characterized by the diagnostic occurrence of Cyathidites minor, Cyathidites sp. and Monocolpites marginatus dated Upper Maastrichtian to early Paleocene. Paleoenvironmental interpretations based on the abundance of freshwater swamps pollen and Spores, diagnostic dinoflagellates cyst and the Palynomorphs Marine Index (PMI) are suggestive of environmental settings that vary from continental to brackish water and shallow marine.

Assessment of Thermal Maturity, Source Rock Potential and Paleodepositional Environment of the Paleogene Lignites in Barsingsar, Bikaner–Nagaur Basin, Western Rajasthan, India

Investigations on the Paleogene lignites were carried out through geochemical, mineralogical and petrographic analyses to assess their paleodepositional environment, source rock potential and thermal maturity. The samples were collected from the Barsingsar lignite mines in the Bikaner–Nagaur Basin, Western Rajasthan, India. Huminite reflectance assigns these samples as lignite (low-rank coal). Barsingsar lignites are dominated by the huminite maceral group, while inertinites and liptinites occur in subordinated amount. The mineral matter is dominated by carbonates, pyrite and argillaceous (in descending order). Gelification index, tissue preservation index, groundwater index and vegetation index indicate the prevalence of a dry forest swamp having ombrotrophic to mesotrophic conditions in the paleomire. Rock–Eval pyrolysis indicates high hydrogen index relative to oxygen index and excellent hydrocarbon potential. The Barsingsar lignites are characterized by mixed type III and type II kerogens, which are thermally immature. Several minerals like quartz, coesite, siderite, aragonite and rutile minerals have been identified by XRD analysis, whereas selected trace elements primarily Sr, Zr, Cu, Pb, Zn, Cr, V, Ni, Rb and Co were also detected. Fourier-transform infrared spectroscopy pattern shows the dominance of clay minerals and the presence of aromatic, aliphatic and some oxygen functional groups in these lignites.

Oil-source correlation in the West Esh El Mellaha, southwestern margin of the Gulf of Suez rift, Egypt

There are several source rock units in the Gulf of Suez graben, but the Upper Cretaceous–Miocene sequence has probably produced most of the commercial hydrocarbons in this petroleum province. One hundred and nine shale, marl and marly shale samples collected from five wells in the West Esh El Mellaha Concession and surrounding area were studied by petrographic and organic geochemical methods to determine organic facies, depositional paleoenvironment, and thermal maturity. We also investigated the molecular and stable carbon isotopic compositions of nine oil samples to establish genetic relationships with the source rock samples.Pyrolysis data for samples from the Cenomanian–Santonian Matulla, Paleocene Esna, Eocene Thebes, Oligo-Miocene Nukhul and Lower–Middle Miocene Rudeis formations contain hydrogen-poor terrigenous Type-III to II/III kerogen. However, the Campanian–Maastrichtian Brown Limestone samples contain Type-II and Type-II/III kerogens indicating very good to excellent generation potential. The acyclic isoprenoids and normal alkane distributions and biomarkers in the source rock extracts indicate derivation from bacteria and algae, with varying contributions from land plants, deposited under suboxic to anoxic conditions in normal marine to higher salinity waters.The oil samples have high sulfur content and low to moderately high API gravity, typical of mature oils from pre-rift marine carbonate or calcareous shale lithofacies. Hierarchical cluster analysis (HCA) of 18 source-related biomarker ratios revealed four genetic families of oil samples. The two South Malak-1 oils (Family-4) are substantially different from the Rabeh E−8 and Rabeh E−10 (Family-1), Rabeh-1 and Hurghada-1 (Family-2) and Abu Marwa-1 and Wadi El Sahl-1 (Family-3) oil families, which are more closely related. Principal component analysis (PCA) and HCA based on the 18 ratios for the total data from extracts and oils indicate three groups. The South Malak-1 oils seem to be most closely related to the two Brown Limestone extracts. Group-1 oils appear to represent mixtures with one end member consisting of the South Malak-1 oils and the Brown Limestone source rock, but the other end member is not in the dataset.

Depositional Environment and facies analysis of Useni- 1, Niger Delta Basin, using well logs, core data

This study was carried out integrating well logs and core to build reservoir model for the Useni-1 oil field. Core data and well logs were used to evaluate the petrophysical characteristics of the reservoirs. The paleodepositional environment was deduce from the wells and cores data. The depositional facies model showed highly permeable channels where the wells where positioned. The environments identified that the fluvial channel facies with highly permeable zones constituted the reservoirs. Four reservoirs were mapped at depth range of 8000ft to 8400ft with thicknesses varying from 20ft to 400ft. Petrophysical results showed that porosity of the reservoirs varied from 12% to 28 %; permeability from 145.70 md to 454.70md; water saturation from 21.65% to 54.50% and hydrocarbon saturation from 45.50% to 78.50 %. Core data and the gamma ray log trends with right boxcar trend indicate fluvial point bar and tidal channel fills in the lower delta plain setting. By-passed hydrocarbons were identified in low resistivity pay sands D1, D2 at depth of 7800 – 78100ft in the field.

High-resolution molecular stratigraphy of Oligocene\u2013Miocene sequence of Tumaco-1-ST-P well, Tumaco forearc Basin, Colombia

In the present work, high-resolution molecular stratigraphy technique has been applied to the rock samples from Tumaco-1-ST-P well to investigate vertical variations of the deposited organic matter (O.M.) based on screening parameter and high-resolution biomarkers in both saturate and aromatic fractions in order to establish its origin, organic facies, depositional paleoenvironment, thermal maturity, biodegradation processes and to evaluate the exploratory potential in this frontier forearc basin. The O.M. is immature with a high concentration of biolipids (early diagenesis) and with poor to fair generation potential originated from a type II/III or III kerogen. Original total organic carbon (TOCo) and original hydrocarbon index (HIo) values for each formation and lithology are determined to evaluate the hydrocarbons potential in the basin. n-alkanes, isoprenoids, and tricyclic terpanes suggest an algal/bacterial and terrestrial input deposited on a marine-deltaic shale under oxic to suboxic conditions. The O.M. was deposited on siliciclastic rocks in a marine-continental (transitional) environment, although carbonate rocks were also deposited in the bottom of the column (late Oligocene). The molecular stratigraphic interpretation allows to conclude that organic facies and lithology in Tumaco-1-ST-P are characterized in Cascajal and Tangareal del Mira Fms. (1000–5000 ft) by a marine-deltaic paleoenvironment with an important terrestrial contribution and varying between deltaic plain and prodelta during the late Miocene. At the top of Tumaco Fm (5000–9000 ft) in the late to medium Miocene, the depositional environment was like the marine delta of the Tangareal del Mira Fm, changing to a marine platform environment at 8000 to 10,000 ft depth in the middle to early Miocene. Toward the bottom of the column (10,000–12,000 ft), Tumaco Fm was deposited in the late Oligocene under a marine shelf environment. In the present paper, we propose a modeling approach, based on the evolution of the thermal maturity through the stratigraphic column, that at 17,000 feet depth could exist rocks with O.M. in the hydrocarbon generation window for Tumaco Basin, Colombia.

Holocene paleodepositional changes reflected in the sedimentary microbiome of the Black Sea.

Subsurface microbial communities are generally thought to be structured through in situ environmental conditions such as the availability of electron acceptors and donors and porosity, but recent studies suggest that the vertical distribution of a subset of subseafloor microbial taxa, which were present at the time of deposition, were selected by the paleodepositional environment. However, additional highly resolved temporal records of subsurface microbiomes and paired paleoenvironmental reconstructions are needed to justify this claim. Here, we performed a highly resolved shotgun metagenomics survey to study the taxonomic and functional diversity of the subsurface microbiome in Holocene sediments underlying the permanently stratified and anoxic Black Sea. Obligate aerobic bacteria made the largest contribution to the observed shifts in microbial communities associated with known Holocene climate stages and transitions. This suggests that the aerobic fraction of the subseafloor microbiome was seeded from the water column and did not undergo post-depositional selection. In contrast, obligate and facultative anaerobic bacteria showed the most significant response to the establishment of modern-day environmental conditions 5.2ka ago that led to a major shift in planktonic communities and in the type of sequestered organic matter available for microbial degradation. No significant shift in the subseafloor microbiome was observed as a result of environmental changes that occurred shortly after the marine reconnection, 9ka ago. This supports the general view that the marine reconnection was a gradual process. We conclude that a high-resolution analysis of downcore changes in the subseafloor microbiome can provide detailed insights into paleoenvironmental conditions and biogeochemical processes that occurred at the time of deposition.

Clay Mineralogical Characteristics of Sediments Deposited during the Late Quaternary in the Larsen Ice Shelf B Embayment, Antarctica

Variations in grain size, clay mineral composition, and stable isotopes (δ13C and δ15N) are closely linked to the sedimentary facies that reflect mineralogical and geochemical modification during the retreat and advance of the Larsen ice shelf. A whole round core of marine sediment (EAP13-GC17, 236 cm below the sea floor) was collected on the northwestern Larsen B embayment of the Antarctic Peninsula during a marine geological expedition (the ARA13 Cruise Expedition by the Korea Polar Research Institute, 2013). Four sedimentary facies (U1–U4) were clearly distinguishable: bioturbated sandy mud (open marine, U1), laminated sandy mud (sub–floating ice shelf, U2), sandy clay aggregates (deglacial, U3), and muddy diamictons (sub-glacial, U4), as well as interbedded silty. Clay minerals, including smectite, chlorite, illite, and kaolinite, were detected throughout the core. An increase in the clay mineral ratio of smectite/(illite + chlorite) was clearly observed in the open marine condition, which was strongly indicated by both a heavier isotopic composition of δ13C and δ15N (−24.4‰ and 4.3‰, respectively), and an abrupt increase in 10Be concentration (~30 times). An increase in the average values of the crystal packet thickness of illite (~1.5 times) in U1 also indicated sediments transported in open marine conditions. Based on the clay mineral composition in U1, the sediments are likely to have been transported from the Weddell Sea. The clay mineralogical assessments conducted in this region have significant implications for our understanding of paleodepositional environments.

Pebble Morphometric Study of the Ogwashi-Asaba Formation at Ubakala and Environs in Southeastern Nigeria

Pebble morphometric study was carried out for the Ogwashi-Asaba Formation so as to understand its paleodepositional environment. The three axes; the long (l), the intermediate (i) and the short (s) were measured for the two sets of one hundred and forty (140) and one hundred and fifty (150) pebbles collected from two outcrops of the Ogwashi-Asaba Formation. Pebble form indices such as Maximum Projection Sphericity (MPSI), coefficient of flatness (FR %), elongation ratio (ER) and oblate-prolate (OP) index were computed from these measurements. Roundness was estimated using Sames image sets. The mean values of the pebble form indices ranges from 49.78 to 52.02 for coefficient of flatness (FR %). 0.71 to 0.73 for sphericity, 2.60 t0 3.53 for oblate-prolate index, and 0.66 to 0.69 for elongation ratio. The calculated indices are suggestive of fluvial sedimentation for the Ogwashi-Asaba Formation. Bivariate plots of coefficient of flatness (FR %) versus maximum projection sphericity index (MPSI) and plots of sphericity (MPSI) versus oblate-prolate index (OP) are also indicative of fluvial origin. Scatter plots of roundness versus elongation ratio shows that 100% of the pebbles are in a littoral field. Plots of bivariate parameters such as simple skewness versus simple standard deviation, and second moment skewness versus second moment standard deviation suggests the Ogwashi-Asaba Formation as a product of the fluvial depositional processes. Keywords: Niger Delta Basin, Ogwashi-Asaba Formation, Pebble morphometry, Pebble Form indices. DOI : 10.7176/JNSR/9-6-06 Publication date :March 31 st 2019

An Assay on Alkyl Aromatic Hydrocarbons: Unexpected Group-Type Separation of Diaromatic Hydrocarbons in Cretaceous Crude Oils from Brazilian Marginal Basin

Numerous aromatic biomarkers such as aromatic carotenoids and aryl isoprenoids have been reported in Brazilian Cretaceous oils. The n-alkyl aromatics such as n-alkyl benzenes (ϕ-Cn), toluenes (ϕT-Cn), xylenes, and mesitylenes have also been detected in geological samples and can be valuable tools in geochemical and environmental investigations. In this work, comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC–TOFMS) and GC–tandem MS (GC–MS/MS) were applied to identify the alkyl aromatic series in two crude oils from the Sergipe-Alagoas Basin, Brazil. Geochemical characteristics indicate a different depositional paleoenvironment for each sample, marine and lacustrine end-members. Aromatic compounds were identified using full mass spectrum information, diagnostic ions (i.e., m/z 92 for alkylbenzenes and m/z 106 for alkyltoluenes), selected reaction monitoring transitions, and coinjection with an authentic C21 n-pentadecylbenzene standard. The Sergipe-Alagoas o...

Shoreface facies model of Cretaceous Jessu Formation, Yola Sub-basin, Northern Benue Trough, northeast Nigeria: New insights from facies analysis and molecular geochemistry

The Yola Sub-basin in the Northern Benue Trough is a frontier exploration basin in northeastern Nigeria and to date, there is no subsurface data available. The oldest sedimentary unit in the Yola Sub-basin is the Bima Formation, followed by Yolde, Dukul, Jessu, Sekuliye, Numanha and Lamja Formations, ranging in age from Berremian-Aptian-Albian to Santonian. The sediments of Jessu Formation were studied based on facies analysis (lithofacies and palynofacies) and geochemistry (biomarker distribution) with an objective of analysing and interpreting the source input/origin, paleodepositional conditions, paleodepositional environment and to reconstruct depositional and facis model for the studied successions. The study revealed that the sediments were deposited in a distal oxic-suboxic to relatively anoxic shelf (shallow marine) environment with both aquatic,-marine and terrestrially derived source inputs. Depositional framework indicate a progradational wave and storm-dominated shoreface-offshore facies succession, displaying a coarsening upward trend. This represent a regressive shoreface-offshore depositional system, consistent with earlier interpretations that the Cretaceous sediments of Jessu Formation were deposited during a brief regressive phase in the Northern Benue Trough.

Geochemical characteristics of the Upper Cretaceous to Lower Eocene sedimentary rocks from the Pieniny Klippen Belt (Western Carpathians, Slovakia): implications for tectonic setting, paleoenvironment and paleoclimate

This paper presents geochemical data on sedimentary rocks from the Upper Cretaceous to Lower Eocene formations of the Pieniny Klippen Belt (Western Carpathians, Slovakia). On the basis of geochemical analyses of 15 samples, the plate tectonic setting of sediment accumulation and paleodepositional environment were reconstructed, which may help to understand a part of evolution of this orographically remarkable zone. Four main rock groups were identified within the samples studied: fine- to medium-grained sandstones, siltstones or claystones, pebbly/sandy mudstones and shales. In the Al2O3*5-SiO2-CaO*2 ternary diagram, they displayed developed sand and mud flat characteristics with light rich clay content. According to high-silica and lowsilica multi-dimensional diagrams, the investigated rocks might have originated from a continental collision tectonic setting. The Zr/Rb values (0.76–6.47) mirrored a fluctuation of hydro energy during deposition of the sediments studied. Paleoclimate indexes, such as the C-value (0.03–0.49) and Sr/Cu (3.25–202.27), revealed arid to semiarid climatic conditions during deposition of the studied sediments. In addition, the chemical data were used to constrain paleoredox conditions of the depositional environment, which proved that these sediments had been deposited mainly beneath the oxic water column with relatively low paleoproductivity, as evidenced by P/Ti with an average of 0.13 and Ba/Al with an average of 34.30.

An Aspect of Palyno Stratigraphy of “XM” Field Located in Semliki Basin South Western Uganda

“XM” field, a clastic sedimentary domain within the Albertine Graben, southwestern Uganda, was studied using palynological data, complemented with wire-line well logs, to determine the stratigraphy, age, and depositional setting. Field wide correlation was attempted using additional geological and stratigraphical data from the larger Albertine Graben. The study involved the use of geological computing tools such as Petrel and Strata Bug softwares which allowed for the graphic plots of palynoflora, identification of marker species, species abundances, species first and last occurrences and the geological correlation of the two wells. The palynological marker species identified include; Podocarpus spp., Tournefortia spp., Praedapollis flexibilis, Peregrinipollis nigericus, Gramineae spp., Laevigatosporites spp. and Verrucatosporites usmensis. This association of species indicates Early Pliocene to Holocene age. These species were further used in delineating the Early Pliocene age of well T2 into TZ1a and TZ1b. The TZ1a subzone is marked by index species of Laevigatosporites spp., the quantitative top occurrence of Sapotaceae spp. and Verrucatosporites usmensis. TZ1b is marked by the presence of index species of Laevigatosporites spp. and top occurrence of Sapotaceae spp. Further, the study revealed five informal palynological biozonation of the well T3 into; TZI, TZII, TZIII, TZIV and TZV all ranging in age from Early Pliocene to Holocene and defined based on top occurrences, downhole increases and decreases of some of the stratigraphical important species recorded in the well as follows: TZI is marked by the top occurrence of index specie Gramineae spp. TZII by the presence of index specie of Peregrinipollis nigericus and top occurrence of Praedapollis flexibilis. TZIII is defined by top occurrence of Tournefortia spp. and the downhole decrease in Podocarpus spp. TZIV is defined by the top downhole increase in Podocarpus spp. and TZV by the base downhole decrease in Podocarpus spp. In arriving at these interpretations, data and publications from other basins such as the Niger Delta in West Africa and the Muglad and Burundi Basins in Central and East Africa were used as analogues. The age of the drilled wells ranged from Early Pliocene to Holocene while the paleo environment of deposition was determined to be mostly continental ranging from fluvial to lacustrine settings.

Palynofacies analysis of Ida-4 well, Niger Delta Basin, Nigeria

Palynofacies analyses of the strata penetrated by Ida-4 wells were carried out with the aim of studying the stratigraphic sequence penetrated by the well in order to establish palynostratigraphic zones, relative age and the paleoenvironment of deposition. Fifty ditch cutting samples within the interval of 2179–3523 m were analyzed. The acid methods of sample preparation for palynofacies analyses were followed. The result of the analyses yielded low to abundant occurrences of pollen and spores with an abundance of small, medium and large sizes of palynomacerals 1 and 2, few occurrences of palynomacerals 3 and 4. The lithology consists of the alternation of shale and sandstone units with few intercalations of argillaceous sandstone units, indicating that the studied interval belongs to the Agbada Formation. The studied intervals were dated to the middle Miocene to late Miocene, based on the recovered age diagnostic marker species such as Zonocostatites ramonae, Multiareolites formosus, Verrutricolporites rotundiporus, Crassoretitriletes vanraadshoveni and Racemonocolpites hians. Two interval range palynostratigraphic zones: Multiareolites formosus – Zonocostatites ramonae, Verrutricolporites rotundiporus – Crassoretitriletes vanraadshoveni and a taxon range zone: Ainipollinite verus zone were proposed. Paleoenvironmental interpretation was based on the palynofacies association and the lithology which revealed that the stratigraphic interval studied was deposited in the Coastal-deltaic (marginal marine) environments.

Palynostratigraphy, Paleoclimate and Paleoenvironment of a Segment of GBO-04 Well, Onshore Western Niger Delta Basin, Nigeria

Palynological study of 50 ditch samples from a segment of GBO-04 well located onshore western Niger Delta Basin was carried out determine the age of the sediment and reconstruct the paleoclimate and paleodepositional environments. All the analyzed samples were composited at 60 ft. from stratigraphic depth interval of 3010 to 6030 ft. The lithology was made of shale and friable sandstone. Palynological slides were prepared following standard palynological preparation procedure involving sample maceration with hydrochloric (HCl) and hydrofluoric (HF) acids. The samples yielded well preserved, moderately diversified palynomorph assemblages comprising 72 taxa and belonging to pollen, spores, dinoflagellates, acritarch, algae and fungi spores. The stratigraphic distribution of floristic assemblage was highly variable. The assemblage was dominated by pollen and spores. The pollen included Monoporites annulatus, Brevicolporites guinetii, Sapotaceoidaepollenites spp., Psilatricolporites crassus, Psilatricolporites spp., Zonocostites ramonae, Retitricolporites irregularis, Monocolpites marginatus, Monocolpites spp., Pachydermites diederixi, Proxapertites cursus, Verrutricolporites spp., Ctenolophonidites spp., Arecipites exilimuratus, Arecipites cf. crassimuratus, Striatricolporites catatumbus, Canthiumidites spp., Chenopodiacaea spp., Clavainaperturites clavatus, Crototricolporites crotonoisculptus, Echiperiporites icacinoides, Echiperiporites spp. and Inaperturopollenites spp. The retrieved spores included Magnastriatites howardi, Acrostichum aureum, Laevigatosporites spp., Polypodiaceoisporites spp., Verrucatosporites spp., Crassoratitriletes vanraadshooveni and Verrucatosporites usmensis, Charred graminae curticle, Cyathidites spp. and Foveotriletes margaritae. The dinoflagellates included Achmosphaera spp., Andulusiella polymorpha, Batiacasphaera spp., Selenopemphix nephroides and Spiniferites spp. Leiosphaeridia spp. was the only acritarch recovered in the assemblage. The algae were Botryococcus braunii and Pediastrum spp. Fungi spores and hyphae and charred curticle constituted minor components of the assemblage. The stratigraphic interval was dated Early Miocene (Burgidalian-Langhian) based on the occurrence and distribution of Pachydmies diederixi, Praedopollis flexibilies, Crassoretitrilete vanraadshoodveni, Psilatricolporites crassus and Laevigasporites spp. The abundant occurrence of pollen and spores typical of low land rain forest in the assemblage indicated tropical paleoclimatic conditions. The distribution pattern of Monoporites annulatus (Poaceae) and Zonocostites ramonae (Rhizophora) suggested cyclical fluctuations of paleoclimate between wetter and drier phases. The sediments were laid down in lagoons, delta swamps and shallow marine nearshore paleoenvironments.

Palynological Study of OSE 1 Well in Offshore Niger Delta Basin: Implications for Age, Paleoclimate and Depositional Paleoenvironment

Palynological study of 45 ditch samples from sedimentary successions penetrated by OSE 1 well located offshore western Niger Delta Basin was undertaken to determine the age of the sediment and reconstruct the paleoclimate and depositional paleoenvironment. All the analyzed samples were composited at 30 ft from stratigraphic depth interval of 6330 to 9010 ft. The lithologic composition comprised mainly of brownish grey or light grey, fine-grained shales with a gypsiferous horizon near the bottom. Palynological slides were prepared following standard palynological preparation procedures of sample maceration with hydrochloric (HCl) and hydrofluoric (HF) acids. The samples yielded moderately well-preserved, low to high diversity palynomorph assemblages of 58 taxa comprising 29 pollen grains, 9 pteridophic spores, 17 dinoflagellates, one acritarch, one freshwater algae and a fungi spore. The stratigraphic distribution of microflora assemblages was highly variable. The assemblage abundance was dominated by pollen and spores. The retrieved pollen grains included Monoporites annulatus, Sapotaceoidaepollenites sp. Psilatricolporites crassus, Psilatricolporites sp., Zonocostites ramonae, Retitricolporites irregularis, Monocolpites marginatus, Monocolpites sp., Pachydermites diederixi, Proxapertites cursus, Verrutricolporites rotundiporus, Striatopollis catatumbus, Retistephanocolpites gracilis, Echiperiporites estalae, Echiperiporites sp. and Inaperturopollenites sp. The retrieved spores included Magnastriatites howardi, Acrostichum aureum, Laevigatosporites sp., Polypodiaceoisporites sp., Verrucatosporites sp., Crassoretitriletes vanraadshooveni and Stereisporites sp. The recorded dinoflagellates included Achomosphaera sp., Andalusiella sp., Polysphaeridium zoharyi, Selenopemphix nephroides and Spiniferites sp. Leiosphaeridia sp. was the only acritarch present in the assemblage. The freshwater algae was Botryococcus braunii. Fungi spore was present but not in significant amount. The stratigraphic interval was dated Early to Late Miocene (Burgidalian-Messinian) based on the occurrence and distribution of some stratigraphic fossil marker species including Magnatriatites howardi, Crassoretitriletes vanraadshooveni and Retistephanocolpites gracilis The abundant occurrence of pollen and spores typical of rain forest and freshwater swamp communities in the assemblage indicated tropical paleoclimatic conditions. The distribution pattern of Monoporites annulatus (Poaceae) and Zonocostites ramonae (Rhizophora) suggested seasonal fluctuations between dryer and wetter climatic conditions. The sediments were deposited in a wide range of environments including brackish lagoons, open salt water swamps, freahwater and nearshore to inner neritic settings.

Geochemistry of Maastrichtian Clastic Sedimentary Rocks from Western Flank of Anambra Basin, Nigeria: Implications for Provenance, Tectonic Setting, Paleoclimate and Depositional Paleoenvironment

The geochemistry, provenance, tectonic setting, paleoclimate and depositional paleoenvironment of Maastrichtian clastic sedimentary rocks from the western flank of Cretaceous-Tertiary intracratonic Anambra Basin, Nigeria have been studied through major and trace element geochemical analysis. Ten (10) representatives outcrop samples collected from two stratigraphic sections in the study area were analyzed chemically using Inductively Coupled Plasma Atomic Emission Spectroscopy, ICP-AES (Lithium Borate Fusion). The geochemical data shows that the sediments are enriched in major oxides including SiO2, Al2O3, Fe2O3 and TiO2 but depleted in other major element oxides. Also, the sandstones have higher concentrations in SiO2, CaO and Na2O compared to the associated mudrocks whereas the mudrocks are more enriched in Al2O3, Fe2O3, MgO, K2O, TiO2 and P2O5 compared to the sandstones. The mudrock samples have higher concentration of Ba, Ni, Sr, Y, Nb, Sc in comparison to sandstones. However, sandstone samples have higher concentration in Zr (1098.50 ppm) than the mudrocks (1038 ppm). The sandstones are classified as litharenites, sublitharenites, Fe-rich sandstones, while the mudrocks are labeled as shale and Fe-rich shale based on chemical composition. Analysis of the data shows a dominantly felsic igneous to intermediate igneous and quartzose sedimentary provenances of mixed granite and granodiorite composition as indicated by various discriminant plots. The inferred provenance is corroborated by the low concentrations of Cr, Ni and Sc in the samples and other proxies. On the basis of various tectonic setting discriminant function diagrams, the Maastrichtian sediments from the study area were deposited on passive margin tectonic setting that developed consequent to the breakup of Gwandana supercontinent but was later affected by tectonism in Santonian times. The alteration feldspars to smectite and kaolinite as depicted by the A-CN-K ternary diagram alongside the high values of chemical index of alteration (CIA, 87.38 - 98.09) and chemical index of weathering (CIW, 89.22 - 99.90) indicates paleogeographic setting characterized by warm and humid/tropical paleoclimatic condition where there was prevalence of intense chemical weathering. The low values of Sr/Ba ratio (0.31 - 0.70) suggest sediment deposition in continental to deltaic paleoenvironment.

Facies analysis and paleoenvironment of deposition of Cretaceous Jessu Formation, Yola Sub-basin, Northern Benue Trough, Nigeria

The Jessu Formation is one of the marine Cretaceous sediments in the Yola Sub-basin of the Northern Benue Trough, NE Nigeria. Lithofacies studies was carried out on the Jessu Formation exposed at Dukul and Cham streams outcrops, in order to identify facies, establish facies association and re-construct the paleodepositional environment. Ten (10) facies were identified on the bases of lithology, grain size, sedimentary structures and degree of bioturbation. These facies form four (4) facies associations, namely: the FA-1 (offshore marine), FA-2 (lower shoreface), FA-3 (middle shoreface) and FA-4 (upper shoreface). These facies associations form coarsening upward units from offshore marine to shoreface which suggests a shoreface deposit for the Jessu Formation. The coarsening upward facies succession indicated storm and wave influenced coastal system.

Regional paleodepositional environment of the Cretaceous in the Great Australian Bight – a support for frontier exploration

To reveal the development of the depositional environment in the Great Australian Bight, regional and high-resolution 3D-seismic interpretation and palynological evidence from well data was integrated with tectonic plate- and paleo topographical-reconstructions. Results from that work explain the drainage patterns and changes in the sedimentary evolution. A maximum transgression at the Cenomanian–Turonian boundary causes the deposition of the expected main source rock interval at the base of the Tiger mega-sequence. This is supported by Integrated Ocean Drilling Program wells (2017), asphalite strandings and dredge samples from the basin. A relative sea-level drop in the mid-Turonian initiates a forced regression and sand deposition in more distal parts of the basin. As a third mega-sequence the Hammerhead Formation progrades into the basin, depositing several thousand metres of deltaic sandstones and lagoonal shales. Our source to sink model based on our gross depositional environment maps could explain the presence of source rocks and reservoir intervals within this frontier exploration basin.

Upper Paleocene to lower Eocene microfacies, biostratigraphy, and paleoenvironmental reconstruction in the northern Farafra Oasis, Western Desert (Egypt)

Three Paleocene-Eocene (P-E) stratigraphic transect sections namely, from the north to south, Ain Maqfi, Farafra-Ain Dalla road, and El-Quess Abu Said in the northern Farafra Oasis,Western Desert (Egypt) are described and interpreted based upon field observations, microfacies analysis, chronostratigraphy and foraminiferal paleobathymetry, to detect the effect of the Syrian Arc Fold System (SAFS) on the lateral and vertical facies changes, various stratigraphic breaks and to reconstruct the depositional paleoenvironments. Lithostratigraphically, the P-E successions are composed of the upper part of the Dakhla Formation, Tarawan Chalk and Esna Shale Formation. Vertical and lateral facies changes are noted between tectonic paleo-highs and paleo-lows in the Farafra Oasis. Eight microfacies types are recognized. The larger benthic and planktonic foraminiferal zones are here used to correlate the shallow and deeper facies. Two larger benthic (SBZ4 and SBZ6), six planktonic foraminiferal (P4–E4) and one calcareous nannofossil (NP9b) biozones are identified. The recorded basal Eocene Dababiya Quarry Member (DQM) within the Esna Shale Formation in the central Farafra Oasis is represented by units 4 and 5 of the DQMat its GSSPwith a neritic facies types. Towards the northern part of the Farafra Oasis, the P-E interval occurs within the base of the Maqfi Limestone Member that contains the larger benthic foraminiferal SBZ6 Zone and is correlated with the DQM.Amajor sea-level fall near the upper part of P5 Zone, followed by a prominent sea-level risewith a minor hiatus across the P-E interval in the Farafra Oasis reflects the complex interplay between sea level changes and tectonic signatures. Two inferred paleoenvironments, namely inner neritic and mid-outer neritic shelf have been identified.

Soft-sediment deformation structures in gravelly fluvial deposits: A record of Cretaceous seismic activity in Patagonia?

Cretaceous sedimentary rocks corresponding to the Las Plumas Member of the Cerro Barcino Formation were deposited in the eastern margin of the Somuncurá - Cañadón Asfalto Basin. The analyzed succession records alluvial settings in a fault-proximal scenario and contains a 7 m thick stratigraphic interval bearing soft-sediment deformation structures which include: pebble load casts, pseudonodules, flame structures and contorted bedding. Deformed beds are bounded by undisturbed strata and these features can be traced along the 800 m of exposures. The sedimentological features such as size and shape of SSDS, clast fabric of gravels and depositional paleoenvironment added to the proximity to a fault zone support the interpretation of the described deformation features as formed by liquefaction and/or fluidization triggered by seismic shocks during syn-tectonic deposition.