Foraminiferal Biofacies Research Articles

Paleoenvironmental characterisation of the Campos Basin slope (SE Brazil) in front of Cape São Tomé based on benthic foraminiferal biofacies succession since MIS 5

The distribution of benthic foraminifera and the assemblage dynamics were analysed on piston core GL-54 to understand the changes in paleoecology since Marine Isotopic Stage 5 (MIS 5). The core was drilled on the upper slope of the Campos Basin on the Rio de Janeiro (Brazil) coast. Benthic foraminifera biofacies, ecological indices, lithological facies, biostratigraphy, and isotopic analyses were undertaken to characterise the paleoenvironment in front of Cape of São Tomé. Two distinct biofacies were identified in the GL-54 sedimentary record since the Last Interglacial Period (MIS 5). These two biofacies point to seasonal organic matter and a well-oxygenated environment, however, Biofacies 2 can be differentiated from Biofacies 1 by the presence of significant bottom water currents. Biofacies 2 has the same species as Biofacies 1, except for Miliolinella subrotunda. Benthic foraminiferal species and biofacies from GL-54 were compared to the ones present in the upper portion of the GL-39 piston core, which was drilled from the middle slope of the same basin. Species such as Globocassidulina crassa, Islandiella norcrossi, Alabaminella weddellensis, Bolivina paula, M. subrotunda, Bulimina aculeata, Globocassidulina subglobosa, Rotorbinella lepida, and Uvigerina peregrina were found in both piston cores. The biofacies of both piston cores were correlated, pointing to similarities between the upper slope and the middle slope in the Campos Basin since MIS 5. In general, the upper and middle slopes of the Campos Basin are characterised as a well-oxygenated environment with variation in the deposition of organic matter. In addition to these environmental factors, there is evidence for a strong bottom current in MIS 2 at both sites, probably due to the displacement of Brazil Current and Intermediate Western Boundary Current.

Pliocene–Pleistocene warm-water incursions and water mass changes on the Ross Sea continental shelf (Antarctica) based on foraminifera from IODP Expedition 374

Abstract. International Ocean Discovery Program (IODP) Expedition 374 sailed to the Ross Sea in 2018 to reconstruct paleoenvironments, track the history of key water masses, and assess model simulations that show warm-water incursions from the Southern Ocean led to the loss of marine-based Antarctic ice sheets during past interglacials. IODP Site U1523 (water depth 828 m) is located at the continental shelf break, northeast of Pennell Bank on the southeastern flank of Iselin Bank, where it lies beneath the Antarctic Slope Current (ASC). This site is sensitive to warm-water incursions from the Ross Sea Gyre and modified Circumpolar Deep Water (mCDW) today and during times of past warming climate. Multiple incursions of subpolar or temperate planktic foraminifera taxa occurred at Site U1523 after 3.8 Ma and prior to ∼ 1.82 Ma. Many of these warm-water taxa incursions likely represent interglacials of the latest Early Pliocene and Early Pleistocene, including Marine Isotope Stage (MIS) Gi7 to Gi3 (∼ 3.72–3.65 Ma), and Early Pleistocene MIS 91 or 90 (∼ 2.34–2.32 Ma) and MIS 77–67 (∼ 2.03–1.83 Ma) and suggest warmer-than-present conditions and less ice cover in the Ross Sea. However, a moderately resolved age model based on four key events prohibits us from precisely correlating with Marine Isotope Stages established by the LR04 Stack; therefore, these correlations are best estimates. Diatom-rich intervals during the latest Pliocene at Site U1523 include evidence of anomalously warm conditions based on the presence of subtropical and temperate planktic foraminiferal species in what likely correlates with interglacial MIS G17 (∼ 2.95 Ma), and a second interval that likely correlates with MIS KM3 (∼ 3.16 Ma) of the mid-Piacenzian Warm Period. Collectively, these multiple incursions of warmer-water planktic foraminifera provide evidence for polar amplification during super-interglacials of the Pliocene and Early Pleistocene. Higher abundances of planktic and benthic foraminifera during the Mid- to Late Pleistocene associated with interglacials of the MIS 37–31 interval (∼ 1.23–1.07 Ma), MIS 25 (∼ 0.95 Ma), MIS 15 (∼ 0.60 Ma), and MIS 6–5e transition (∼ 0.133–0.126 Ma) also indicate a reduced ice shelf and relatively warm conditions, including multiple warmer interglacials during the Mid-Pleistocene Transition (MPT). A decrease in sedimentation rate after ∼ 1.78 Ma is followed by a major change in benthic foraminiferal biofacies marked by a decrease in Globocassidulina subglobosa and a decrease in mud (< 63 µm) after ∼ 1.5 Ma. Subsequent dominance of Trifarina earlandi biofacies beginning during MIS 15 (∼ 600 ka) indicate progressive strengthening of the Antarctic Slope Current along the shelf edge of the Ross Sea during the mid to Late Pleistocene. A sharp increase in foraminiferal fragmentation after the MPT (∼ 900 ka) and variable abundances of T. earlandi indicate higher productivity, a stronger but variable ASC during interglacials, and/or corrosive waters, suggesting changes in water masses entering (mCDW) and exiting (High Salinity Shelf Water or Dense Shelf Water) the Ross Sea since the MPT.

Holocene Foraminifera, Climate, and Decelerating Rise in Sea Level on the Mud Patch, Southern New England Continental Shelf

Abstract We examined Holocene benthic foraminiferal biofacies, % planktonic foraminifera, and lithofacies changes from New England mud patch cores and present a relative sea-level (RSL) record to evaluate evolution of these rapidly deposited (30–79 cm/kyr) muds. Sandy lower Holocene sections are dominated by Bulimina marginata. The mud patch developed from 11–9 ka as RSL rise slowed from 10 to 7 mm/yr; mud deposition began when the cores (69 to 91 m modern) were inundated below storm wave base. An Elphidium-B. marginata fauna developed at ca. 7–6 ka as RSL rise slowed from approximately 7 to 2 mm/yr. A Globobulimina fauna developed at 3 ka as RSL rise slowed to 1 mm/yr, reflecting lower O2 conditions. Single specimen δ18O analyses of Globobulimina show ∼1‰ variations over the past 3 kyr, reflecting a shelf bottom water seasonal cycle of 4–5°C, and a temperature minimum during the Little Ice Age with warming since.

Foraminiferal biofacies distribution in the outer channel of Chilika Lagoon, Odisha, India

Benthic foraminiferal assemblages are widely used as a proxy to monitor the coastal environment’s health. The current work involves the seasonal distribution of foraminifera in the outer channel sector of the Chilika Lagoon, Odisha during 2017–2018. The outer channel is marine as the sea mouth is nearby. Altogether 28 species of benthic foraminifera are identified, among which dominant are Ammonia spp. The other calcareous taxa are Elphidium spp, Quinqueloculina sp., Haynesina spp., Pararotalia sp., Hanzawaia sp., Nonionellina sp. and agglutinated forms such as Miliammina sp., Trochammina sp. and Textularina sp. are found in moderate abundance. Based on the pre-monsoon abundance, the cluster analyses show two distinct biofacies zones in the studied area. Total foraminiferal number (TFN) increases during pre-monsoon compared to post-monsoon months. A trend of decreasing abundance was observed in TFN, mainly calcareous taxa towards the inner part of the lagoon, that is, away from the sea mouth.

Identifying and Constraining Marsh-Type Transitions in Response to Increasing Erosion over the Past Century

Marsh environments, characterized by their flora and fauna, change laterally in response to shoreline erosion, water levels and inundation, and anthropogenic activities. The Grand Bay coastal system (USA) has undergone multiple large-scale geomorphic and hydrologic changes resulting in altered sediment supply, depositional patterns, and degraded barrier islands, leaving wetland salt marshes vulnerable to increased wave activity. Two shore-perpendicular transect sites, one along a low-activity shoreline and the other in a high activity area of the same bay-marsh complex, were sampled to investigate how the marshes within 50 m of the modern shoreline have responded to different levels of increased wave activity over the past century. Surface sediments graded finer and more organic with increased distance from the shoreline while cores generally exhibited a coarsening upwards grain-size trend; all cores contained multiple large sedimentological shifts. 210Pb-based mass accumulation rates over the last two decades were greater than the long-term (centurial) average at each site with the fastest accumulation rates of 7.81 ± 1.58 and 7.79 ± 1.63 kg/m2/year at the sites nearest the shoreline. A shoreline change analysis of three time-slices (1848–2017, 1957–2017, 2016–2017) shows increased erosion at both sites since 1848 with modern rates of −0.95 and −0.88 m/year. Downcore sedimentology, mass accumulation rates, and shoreline change rates paired with foraminiferal biofacies and identification of local estuarine indicator species, Paratrochammina simplissima, aided in identifying paleo marsh types, their relative proximity to the shoreline, and sediment provenance. The high-energy marsh site transitioned from middle marsh to low marsh in the 1960s, and the low-energy marsh site transitioned later, at the end of the twentieth and early twenty-first century, due to its more protected location. Marsh type transition corresponds chronologically with the coarsening upwards grain-size trend observed and the degradation of Grand Batture Island; since its submergence, signatures of multiple storm event have been preserved downcore.

Stratigraphic and Paleoenvironmental Studies on the Lower Eocene Succession at El-Guss Abu Said Plateau, Farafra Oasis, Western Desert, Egypt

Abstract The Lower Eocene Succession at El-Guss Abu Said Plateau was examined to determine the paleoenvironments and nature of deposition based upon benthic foraminiferal biofacies. Lithostratigraphically, this succession consists of the Esna Formation (shale) at the base, the Nusf Formation (well-bedded marl with occasional limestone ledges), and the Farafra Formation (limestone) at the top. The Esna Formation is an outer shelf-upper bathyal facies rich in planktonic and deeper-dwelling smaller benthic foraminifera. The Nusf Formation and the Farafra Formation are rich in Nummulites and Alveolinids, indicating a carbonate platform facies. Three benthic foraminiferal biofacies, combined with the lithology of the rock units, indicate progressive shoaling, likely associated with tectonic uplift that occurred during the early Eocene in the El-Guss Abu-Said area.

An approach to using foraminifera in sequence stratigraphic analysis of Wadi Qena, Central Eastern Desert, Egypt

In Egypt, Wadi Qena Middle Eastern Desert, Paleogene successions exposed at Hawashiya and Abu Had sections from north to south were measured and comprehensively investigated for their foraminiferal content. The Dakhla, Tarawan, and Esna formations make up the investigated sections. The studied successions are subdivided into six biozones; they are five zones of the Late Paleocene (Igorina albeari subzone (P3b), G. Globanomalina pseudomenardii/P. Parasubbotina variospira subzone (P4a), Acarinina subsphaerica subzone (P4b), A. soldadoensis/G. pseudomenardii subzone (P4c), Morozovella velascoensis zone (P5), and one zone of the Early Eocene (P. Pseudohastigerina wilcoxensis/M. velascoensis zone (E2). The paleoenvironmental interpretations and interpretation of sea level changes over the study area during the Paleocene-Eocene time interval have been carried out based on the lithostratigraphy, biostratigraphy, paleoecologic parameters (total foraminiferal number (TFN), diversity indices of foraminifera, life strategies of planktonic foraminifera, planktonic/benthonic (P/B) foraminiferal ratio, agglutinated/calcareous benthonic foraminiferal ratios, benthonic foraminiferal biofacies and total organic carbon (TOC), and calcium carbonate CaCo3%). Five sequences are identified in the studied Lower Paleogene successions in the Wadi Qena area. Four depositional sequences are determined in the Paleocene, and one in the Lower Eocene. A comprehensive description of these depositional sequences and their boundaries is provided. The findings of the current study are calibrated with sequence stratigraphy of the world sea-level variations.

Facies Analysis and Paleoenvironmental Reconstruction of Well X, Onshore Niger Delta, Nigeria

Biofacies and lithofacies analysis of one hundred and ninety-two (192) ditch cutting rock samples from well x, onshore Niger Delta was carried out for the purpose of the paleoenvironmental reconstruction of the rock succession. The objectives were to identify the lithofacies units and species of foraminifera and to use both quantitave and qualitative foraminiferal assemblage to recognise the benthonic foraminiferal biofacies and integrate both results for delineation of paleobathymetric and paleoenvironmental settings of sediments penetrated by well x interval studied. The rock samples were prepared through wet-sieve analysis with 63µm mesh sieve size, and subsequently through dry-sieve analysis with 250µm and 500µm mesh sieve sizes. The prepared rock samples were analyzed to generate data for sedimentological grain-size analysis and foraminifera biofacies assemblages. The grain-size analysis provided lithofacies associations, sand/shale ratio and sorting/gradational profile for the studied intervals of well-x while the micropaleontological analysis identified a total of ninety-three (93) well preserved foraminiferal species from which three (3) biofacies associations were delineated. The biofacies include: Ammonia beccarii, Ammonia beccarii/Bolivina scalprata miocenica, and Haplophragmoides compressa/ Valvulina flexilis biofacies indicating Shallow Inner Neritic, Inner- Middle Neritic, and Outer Neritic – Upper Bathyal paleoenvironment respectively. The result of the sand/shale ratio and lithofacies associations indicated penetration into the Agbada Formation of the Niger delta and deposition within shallow to deep marine paleoenvironmental settings, predominantly as channels, intercalated with overbank and distal bar/bay deposits. Synthesis of the biofacies and lithofacies indicated stratigraphic development between coastal deltaic and upper bathyal paleowater depths.

Biostratigraphy and sequence stratigraphy of the deep offshore Niger Delta and implications for future hydrocarbon exploration in the Paleogene sequences

The Niger Delta Deep Offshore Basin has been the latest frontier within the Niger Delta for hydrocarbon exploration and production activities. Until the onset of drilling activities in the early 1990s, little was known about the biostratigraphy of this frontier setting. Thus, uncertainties existed in the ages ascribed to the various stratigraphic sequences. Presently, several wells have been drilled in the deep offshore Niger Delta and three-pronged biostratigraphic data and some sequence stratigraphic interpretations have become available. We have integrated biostratigraphic data comprising palynological, foraminiferal, and calcareous nannoplankton zonation and biofacies, wireline log information, and regional-3D seismic data, with simple basic sequence stratigraphic analysis for a detailed well correlation, regional mapping of hydrocarbon-bearing intervals, and evaluation of the thicknesses of promising stratigraphic intervals. Results indicate a significant effect on not only the earlier conceptualized age of the deepest prospective reservoirs, but also the ages of possible source rocks in the Paleogene of the Niger Delta offshore sequence. Our findings will help in the realistic assumptions of source rock characterization, charge modeling/prediction, and the stratigraphic thicknesses of the offshore sequences and their reservoirs. We examine the specific derivable age interpretations from the integration of at least six wells, biostratigraphic data with seismic, and the implications of these interpretations for hydrocarbon prospectivity of the Paleogene sequences. Furthermore, we document the biostratigraphy work done in the area, in all the structural belts where drilling has occurred including the deepest well drilled in the deep offshore Niger Delta, Bosi-006. The results of this study have a critical impact on the current regional geologic understanding of the deep offshore Niger Delta.

Albian to Turonian agglutinated foraminiferal assemblages of the Lower Saxony Cretaceous sub-basins – implications for sequence stratigraphy and paleoenvironmental interpretation

Abstract. Albian to Turonian carbonate deposits at three different locations of the Lower Saxony Cretaceous and thereby of the European mid-Cretaceous epeiric shelf sea were investigated for their fossil agglutinated foraminiferal fauna. In this study, 71 samples from two quarries and three drill cores were treated with formic acid, which enabled the study of agglutinated foraminiferal assemblages even in highly lithified limestones. In total, 114 species were determined and classified as belonging to nine morphogroups. In general, four agglutinated foraminiferal assemblages are distinguished: (1) an uppermost Albian–lowermost Cenomanian assemblage from the Wunstorf drill cores, with the dominant taxa Bathysiphon spp., Nothia spp., Psammosphaera fusca, Reophax subfusiformis, Bulbobaculites problematicus, Tritaxia tricarinata, Flourensina intermedia, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (2) a Cenomanian assemblage from the Baddeckenstedt quarry and Wunstorf drill cores, with Ammolagena clavata, Tritaxia tricarinata, Vialovella frankei, Arenobulimina truncata, and Voloshinoides advenus; (3) an assemblage related to the Cenomanian–Turonian Boundary Event in Wunstorf and Söhlde dominated by Bulbobaculites problematicus; and (4) a Turonian assemblage in the Wunstorf and Söhlde sections with high numbers of Ammolagena contorta, Repmanina charoides, Bulbobaculites problematicus, Gerochammina stanislawi, and Spiroplectammina navarroana. The latest Albian–earliest Cenomanian assemblage consists of tubular, globular, and elongate foraminiferal morphogroups which are typical for the low- to mid-latitude slope biofacies. All other assemblages are composed of elongate foraminiferal morphogroups with additionally globular forms in the proximal settings of Baddeckenstedt and Söhlde or flattened planispiral and streptospiral forms in more distal settings of Wunstorf. For these assemblages, a new agglutinated foraminiferal biofacies named “mid-latitude shelf biofacies” is proposed herein. Changes in the relative abundance of different morphogroups can often be referred to single features of depositional sequences. Furthermore, classical macro-bioevents, which are often depositional-related, of the Lower Saxony Cretaceous seem to have a micro-bioevent or acme equivalent of the agglutinated foraminiferal fauna.

Benthic foraminifera distribution and sedimentary environmental evolution of a carbonate platform: A case study of the Guadalupian (middle Permian) in eastern Sichuan Basin

Benthic foraminifera are significant indicators of habitat changes and are useful for paleoenvironmental reconstruction. During the Permian period, the variation in species, individual sizes, and morphological characteristics of the different assemblages, such as the fusulinids, is a clue to paleoecological and paleoenvironmental interpretations. The eastern part of the Sichuan Basin, located near the equator in the middle Permian, Guadalupian period, was precipitated by thick beds of marine carbonate rocks with numerous benthic foraminifera. In this study, we record the species and calculate the frequency of benthic foraminifera from 445 thin sections of Guadalupian (Maokou Formation) marine carbonate rocks. Seven types of benthic foraminiferal biofacies are recognized and associated with five sedimentary microfacies in the Erya and Huilongchang sections, eastern Sichuan area. During the early Guadalupian period, small uniserial nodosariids and Endothyrida dominated the benthic foraminiferal assemblages; in the middle Guadalupian period, species of Miliolida, Ammodiscidae, and uniserial nodosariids were common; however, the species of Fusulinida, such as Schwagerina sp. and Verbeekina sp., were abundant in the late Guadalupian period. The associated sedimentary microfacies indicates a shallow open platform to marginal platform. In our study area, the early Guadalupian was deposited in an open platform to grain shoals. This was followed by gradual shallowing as the sedimentary environment shifted to marginal shallow shoals from the middle to late Guadalupian period until the paleoweathering abruptly terminated the deposition at the end of the Guadalupian period.

Late Paleocene-Early Eocene Foraminiferal Assemblage and Carbon Isotope Excursion Indicating Hyperthermal Events in Paleotropical Succession of Northwestern India

ABSTRACT This study focuses on marine sediments of the late Paleocene-early Eocene (∼55.5–49 Ma) interval from the Jaisalmer Basin of western India. It demarcates the Paleocene Eocene Thermal Maximum (PETM) using foraminiferal biostratigraphy and carbon isotope stratigraphy. A negative carbon isotope excursion of 4.5‰ delineates the PETM within the basin. We demarcate five foraminiferal biofacies using the detrended correspondence analysis. These reflect characteristics of ecology, bathymetry, relative age, and environment of deposition of the foraminifera. They record the response of foraminifera to the warmth of the PETM. Biofacies A was deposited within an inner neritic setting ∼55.5 Ma and includes benthic foraminifera Haplophragmoides spp., Ammobaculites spp., and Lenticulina spp. The presence of Pulsiphonina prima and Valvulineria scorbiculata in Biofacies B suggests an increase in runoff conditions in the basin. Fluctuating trophic conditions prevailed between ∼54–50 Ma. It is evidenced by alternating Biofacies C (endobenthic and chiloguembelinids of eutrophic conditions) and Biofacies D (epibenthic and acarininids of oligotrophic conditions). Biofacies E is dominated by deep-dwelling parasubbotinids, indicating an increase in bathymetry, possibly corresponding to the Early Eocene Climatic Optimum (∼49 Ma).

Paleoceanographic evolution of the Japan Sea during the Pleistocene – A benthic foraminiferal perspective

We reconstructed the paleoceanographic evolution of the Japan Sea over the Pleistocene using benthic foraminiferal and organic geochemical records from sediment cores recovered at IODP Site U1426, which was drilled at a water depth of 900 m on the Oki Ridge in the southern Japan Sea. The dominant benthic foraminiferal biofacies and the assemblage composition, total organic and inorganic carbon, coarse fraction percentages indicate a notable reduction in primary productivity between 2150 and 1700 ka, due to the restricted supply of nutrients from the northern Pacific Ocean through the northern connecting strait. The inflow of the Tsushima Warm Current via the southern strait began after 1700 ka and marked a major change in the productivity regime of the Japan Sea, as shown by the increased abundance of calcareous foraminifera and enhanced CaCO3 (%). A marked shift in productivity occurred during the Middle Pleistocene Transition, as indicated by the dominance of low-oxygen tolerant species, and a higher influx of total organic carbon (%). The onset of more extreme glaciation at ~490–470 ka coincident with the Mid-Brunhes Event was linked to marked changes in foraminiferal assemblage composition, reflecting major changes in sea-level, oxygen availability at the seafloor, and carbonate compensation depth during intense glacial-interglacial cycles. Productivity changes were also modulated by 23 kyr variability, related to precessional insolation forcing at low latitudes, and superimposed on the 41 and 100 kyr variability, linked to high-latitude climate fluctuations.

New insights into stratigraphy and paleoenvironment of the Upper Cretaceous–Eocene succession, Farafra Oasis, Western Desert, Egypt

Detailed field, litho-, bio-, sequence stratigraphy, and paleoenvironmental studies are carried out on the Aqabaat section, Farafra Oasis, Western Desert, Egypt. Lithostratigraphically, the Khoman Formation is here differentiated for the first time into three new distinctive members, which are easily detected at the field: the White Desert (at base), the Gunna (at middle), and the Aqabaat (at top). Biostratigraphically, six planktonic foraminiferal zones and subzones are here identified ranging in age from Maastrichtian to Ypresian. The foraminiferal indices, as well as the benthonic foraminiferal biofacies, indicated an outer neritic paleoenvironmental condition of the Maastrichtian rocks interrupted with shallowing of the relative sea-level at some intervals, especially at the upper parts. These shallowing settings are due to the impact of three syn-sedimentary tectonic events (I, II, and III), which are related to the Syrian Arc orogeny. The Tectonic Event I had a regional impact and led to form a positive structure in the sedimentary basin at the Cretaceous/Paleogene (K/Pg) boundary. The Tectonic Event II and III synchronized with the Danian/Selandian (D/S) and Paleocene/Eocene (P/E) boundaries, respectively. Four depositional sequences (SQ1–SQ4) are defined separated by four sequence boundaries (SB1–SB4) covering the Maastrichtian–Eocene sequence.

Foraminiferal analysis of AE-1 well, Agbada formation Onshore, Western Niger Delta Basin: Implication for biozonation and age dating

Foraminiferal and sedimentological analysis was carried out using ditch cutting samples from intervals 2700 ft. - 10,185 ft. in AE-1 well. The samples were composited at 60 ft. into ninety four (94) ditch cutting samples. The standard micropaleontological sample procedures to recover the foraminiferal biofacies assemblages was utilized, followed by analysis and interpretation of the obtained results. The sedimentological analysis reveals five lithofacies - sandstone, sandy shale, shaly sand, mudstone and sandy clay which constitute part of the Agbada Formation of the Niger Delta. The foraminiferal fauna recovered from the samples studied comprised of twenty four species grouped into nineteen genera from niniteen families and nineteen subfamilies. A few number of miscellaneous microfossils such as Ostracoda, Holothuroidea and Echinoderm remains were recovered. The total count of foraminiferal defined from this well is four hundred and nineteen (419). The planktic foraminiferal count was two hundred and forty two (242) (57.8 % of the total count) while the benthics foraminiferal count was one hundred and seventy seven (177) (42.2 % of the total count). Among the benthic forms, the calcareous consists of one hundred and forty nine forms (149) (33.4 % of the total benthic count) while the agglutinating benthic forms were thirty seven (37) (8.8 % of the total benthic count). One (1) planktic (Chiloguembelinacubensis) and three (3) benthic (Eponidesberthelotianus, Hanzawaiastratonii and Nonionellaauris) informal foraminiferal zones were established in the well. The age of the AE-1 well sediments has been interpreted to belong to Early Oligocene - Early Miocene in comparism with foraminiferal markers species whose stratigraphic ranges are well established in the Niger Delta and globally. This inferred the presence of the Rupelian - Burdigalian sediments in the Niger Delta.
 Keywords: Foraminiferal, Biozone, Age, Rupelian, Burdigalian.

Upper Cretaceous–lower Paleocene subsurface sequence, Farafra Oasis, Western Desert, Egypt: stratigraphical and paleoenvironmental inferences

This work presents details litho-, bio-, and sequence stratigraphy and paleoenvironmental studies on the Upper Cretaceous–lower Paleocene subsurface rocks of Sahl Baraka at Farafra Oasis, Western Desert, Egypt. Lithostratigraphically, two rock units were recognized: the Wadi Hennis (at the base) and the Khoman (at the top) formations. Ten planktonic foraminiferal zones were identified from the Khoman Formation covering the Campanian–Danian chronostratigraphic interval. Using the R-mode hierarchical cluster analyses, four benthonic foraminiferal biofacies (A, B, C, and D) were recognized. The data indicates that the sediments of the Khoman Formation were deposited in marine environments ranging from deep marine (outer neritic–upper bathyal setting) for the lower and middle parts to shallow marine one (middle–outer neritic setting) for the upper part. The Sahl Baraka area was located in a sedimentary basin subjected to three tectonic events during the Late Cretaceous–early Paleocene time which were related to the Syrian Arc Orogeny. These tectonic events interrupted the eustatic sea-level curve. The integrated data led to define three depositional sequences (sequence-1 to sequence-3) separated by three sequence boundaries (SB1–SB3) throughout the Late Cretaceous–early Paleocene time.

A 23000 year old record of paleoclimatic and environmental changes from the eastern Arabian Sea

Abstract Climate of the eastern Arabian Sea is highly influenced by both global climate and Indian monsoon. We produced multi-proxy records of benthic foraminiferal biofacies and stable isotope ratio (δ13C and δ18O), planktic foraminifera and total organic carbon (wt%) content of sediments from core SK291/GC11 in the upper continental shelf off Mangalore, off eastern Arabian Sea (EAS) to decipher paleoenvironmental and paleoclimatic changes during the past ~23,000 years. The monsoon was weak during the Last Glacial Maximum ~23,000–18,000 calibrated years before Present (cal yr BP) when sea level was lower. Globigerinoides ruber populations fluctuate from 30 to 60% in the studied interval with a maximum during ~6000–5000 cal yr BP and a minimum during 19,000–17,000 cal yr BP. The δ18O values of benthic foraminifer Ammonia gaimardii suggest pronounced cooling phases during ~23,000–18,000 cal yr BP, and a short-term cooling at ~6000 cal yr BP. Several intervals of high organic productivity and low oxygen conditions were identified based on benthic foraminiferal biofacies during 23,247–682 cal yr BP. Wind-induced surface mixing was intense during 3200–530 cal yr BP as evidenced by high Globigerina bulloides abundances. The core was affected by moderate chemical weathering and solar variability appears to have been an important forcing factor in shaping climate of the region.

Distribution of recent Foraminifera as depositional indicators in Yongle Atoll, Xisha Islands, South China Sea

Abstract The key to the utility of foraminifers as paleo-environmental indicators for coral reefs is the knowledge of modern assemblages in relation to environmental conditions. This study examined 44 surface-sediment samples from three small islands in Yongle Atoll, with the goal to investigate the relationship between foraminiferal distribution and environmental characterization. In samples, 192 foraminiferal species belonging to 74 genera were identified, among which the hyaline foraminifers totally dominated. Hierarchical Cluster Analysis resulted in the identification of three foraminiferal biofacies, representing different environmental settings and sedimentary regimes. (1) The Amphistegina (mainly Amphistegina lobifera) facies characterizes the upper fore-reef slope zone, which experiences strong wave action and currents from the open sea. (2) The Calcarina hispida–Neorotalia calcar facies represents the reef flat and lagoon slope zone, and patch reefs in the lagoon basin, which is the shallowest of all the biofacies, exposed to the strong solar radiation and strong hydrodynamic activity. (3) The Quinqueloculina crassa subcuneata–Elphidium advenum facies characterizes the lagoon basin, which is covered by fine sands and muds with abundant Halimeda fragments to water depths

Evolution of the Paraíba do Sul Deltaic Complex (SE Brazil) based on benthic foraminiferal biofacies succession

Benthic foraminiferal assemblage distribution and paleoecology were analyzed in two previously studied well-cores (2-MU-1-RJ—ranging from 64.35 to 1.85 m; 2-BG-1-RJ—from 40.50 to 10.50 m) drilled in the central sector of Paraiba do Sul Deltaic Complex (PSDC), RJ, SE Brazil. The assemblages allowed to identify periods of higher and lower marine/continental influence in the study area and to infer events of marine ingressions or regressions during the late Pleistocene, associated with the penultimate marine transgression (123,000 years before the Present). Foraminifera were found in the upper part of both well-cores but they are more abundant in one of the studied well-core. Based on biofacies, the paleoenvironmental conditions and the complex dynamic estuarine evolution were analyzed. Seven foraminiferal biofacies associated with sea-level oscillations were determined throughout cluster analysis, as well as dominant and indicator species in the two well-cores. In the well-core (2-MU-1-RJ) with a higher abundance of foraminifera was identified the following environmental succession: (i) an inner shelf evolving to an estuarine environment; (ii) a return to marine shelf conditions; (iii) followed by the establishment of a lagoon system towards the well-core top. On the other well-core (2-BG-1-RJ), it can be observed the change of estuarine environment under the strong fluvial influence at the bottom of the studied interval; followed by an increase of marine influence from the middle toward the upper part of the well-core. The benthic foraminiferal absence in the samples at the top of the well-cores suggests an abrupt change from marine to the non-marine environment. The two well-cores were compared and the results contribute to the understanding of the estuarine complex dynamics of PSDC in late Pleistocene based on benthic foraminifera biofacies and their paleoecology in marine sediments of the upper portion of the well-cores. It recognized different environments due to the different location of the analyzed cores in the estuary and the neotectonic movements.

Quantitative Middle Eocene benthic foraminiferal biofacies from west-central Sinai, Egypt: Implications to paleobathymetry and sequence stratigraphy

Abstract The basinal depositional architecture, paleobathymetry and paleoproductivity assessment of west central Sinai (Egypt) lacks robust sequence stratigraphic framework inferred in conjunction with changes in benthic foraminiferal biofacies. Sinai is an economically important region for hydrocarbon exploration, hence understanding its depositional architecture is fundamental. For this, the planktic foraminifera biostratigraphy is done first to date the strata exposed at Wadi Nukhul, and then, the quantitative benthic foraminiferal biofacies are evaluated to infer changes in paleobathymetry and paleoproductivity. Five Eocene planktic biozones identified (E7b to E11), spanning 48.6 to 40.4 Ma are identified along with five 3rd order depositional sequences bounded by four sequence boundaries. Quantitative (Rotated factor analysis) benthic foraminiferal analysis revealed seven benthic foraminifera biofacies (A to F) suggesting a meso- to eutrophic, outer neritic, moderate to low oxygenated bottom waters, dominated largely by benthic foraminifera taxa, Bulimina, Uvigerina, Bolivina and Lenticulina. Exception to this trend is the presence of biofacies B (Discorbis ciperensis-Lenticulina cuvillieri) at the top of the Thebes Formation that reflects well‑oxygenated bottom waters straddling the middle to outer neritic depth boundary. The inferred relative sea level gradually decreases throughout the studied section (from bottom to top) and is consistent with a gradual global decline. Of interest is the possible identification of the Middle Eocene Climatic Optimum (~40.5–40 Ma), a global warming event that in the present study, encompasses the Uvigerina mediterranea-Spiroloculina esnaensis biofacies (Biofacies A) suggesting the presence of mesotrophic but moderately well‑oxygenated bottom waters at outer neritic depths. The base of the Thebes Formation is marked by the presence of an Oxygen Minimum Zone.