Planktonic Foraminiferal Zones Research Articles

The Early Aptian Oceanic Anoxic event (OAE-1a) of the uppermost M'Cherga formation of northern Tunisia: Geochemical characterization and inferred petroleum potential

The Early Aptian organic-rich deep marine deposits of the upper Member of the M'Cherga Formation (Valanginian-Aptian) of northern Tunisia were studied based on a multidisciplinary approach including biostratigraphy, sedimentology and organic geochemistry. This study is based on the analysis of 128 samples collected from three sections (Oued Bazina, Djebba and Tel Ghozlene) selected from the salt dome zone (SDZ) and one section of Jebel Oust, situated westward of the Tunisian range. This work is supplemented by previous research undertaken on Oued Zarga and Jebel Ammar sections. Taxonomic analysis of previous and new data (ammonites and planktonic foraminifera) indicate that three informal lithological units rich in organic matter (U1, U2 and U3) are of Early Aptian age, covering both Blowiella blowi and Leupoldina cabri planktonic foraminiferal zones and indiscriminate Lowermost Aptian to the Deshayesites deshayesi – Dufrenoyia furcata ammonite Zones interval.The Rock-Eval analytical results indicate that the studied Early Aptian strata are relatively rich in total organic carbon (TOC) content with values reaching 4.6 % within the U3 (Leupoldina cabri biozone). The latter occurring in the different studied sections constitutes an important deepening phase related to a global sea-level rise testified by the development of well laminated platy limestones containing abundant ammonites and radiolaria. This unit (U3), covering Leupoldina cabri planktonic foraminiferal zone and Deshayesites deshayesi to Dufrenoyia furcata ammonite Zones interval records the Oceanic Anoxic Event -1a (OAE-1a).The palynofacies assemblages show that the organic matter is mainly represented by amorphous particles. The Tmax values ranging from 437 °C to 456 °C (Mean Tmax: 446 °C) and the measured vitrinite reflectance ranging from 0.79 to 1.03 %, indicate that most samples are early mature except for those of the Tel Ghozlene (TG) section which are within the peak oil-generation-window. Lateral facies and thickness variation, in addition to the organic matter distribution throughout the studied domains, strongly suggest the imprint of salt tectonics both on the sedimentological pattern and associated anoxia during the Aptian. Maturation of the organic-rich facies occurred during the Upper Cretaceous-Paleogene compressional phase and associated salt dome remobilization. Source rocks, developed in the Upper Member of the M'Cherga Formation, are attributed to the OAE1a Event and should be considered when reviewing the petroleum potential of conventional and unconventional resources in northern Tunisia.

Cretaceous planktonic foraminiferal biostratigraphy of the Umbria–Marche Basin (Central Italy)

Abstract The Umbria–Marche Basin of central Italy includes some of the most studied, continuous and well-exposed sequences of Cretaceous pelagic sediments known from the Tethyan Realm. A complete and well-preserved Cretaceous pelagic composite succession of this area is here presented. It has been constructed through the integration of the well-established magnetostratigraphy with the planktonic foraminiferal biostratigraphy based on previous and newly identified events from six key sections and one drill core. The recovery of planktonic foraminifera successfully disaggregated from the hard lithologies allows the identification and precise placement of several primary and secondary bioevents. In particular, the record of the identified bioevents counts 35 primary biohorizons, which allow the subdivision of the studied succession into 34 zones and 4 subzones. Following this study and previous findings on Cretaceous planktonic foraminifera, an updated planktonic foraminiferal zonation for the Cretaceous Period is proposed. This refined magnetobiostratigraphical framework, which in this study is integrated with the Cretaceous inoceramid, anoxic and carbon-isotope events recognized in the Umbria–Marche Basin, may provide an invaluable tool for improving Cretaceous correlations at low to middle latitudes, as well as palaeoenvironmental, palaeoclimatic and palaeoceanographical interpretations.

Integrated biostratigraphy (orbitolinids, calcareous nannofossils, and palynomorphs) of the Lower Cretaceous Sarcheshmeh Formation, western Koppeh-Dagh Basin, NE Iran

An integrated biostratigraphy using orbitolinids, calcareous nannofossils, and dinoflagellate cysts was conducted on the Lower Cretaceous Sarcheshmeh Formation in two stratigraphic sections from the western Koppeh-Dagh Basin (NE Iran). The analyzed successions consist mainly of deep-marine shales and marlstones with intercalations of thin-bedded orbitolinid-bearing limestones. These strata yielded common to abundant and fairly well to well-preserved calcareous nannofossil assemblages. The aforementioned assemblages led to the identification of parts of the NC6 and NC7a biozones that can be correlated with parts of the CC7a and CC7b zones. The organic-walled dinoflagellate cysts also show well-preserved and relatively diverse assemblages in the studied sections that corresponded to the Odontochitina operculata Zone. Additionally, within the limestone intercalations of the Sarcheshmeh Formation, two index species of orbitolinids, Praeorbitolina cormyi Schroeder, and P. wienandsi Schroeder, were recorded, indicating the presence of the Praeorbitolina cormyi Zone. According to the literature, these recognized biozones are compatible with the ammonite zones of Deshayesites forbesi, Deshayesites deshayesi, and Dufrenoyia furcata, as well as the Globigerinelloides blowi and Leupoldina cabri planktonic foraminiferal zones. By the compilation of all acquired data, an age of late early Aptian (late Bedoulian) is deduced for the Sarcheshmeh Formation in the studied sections.

Biostratigraphical and paleoenvironmental studies of some Miocene‒Pliocene successions in Northwestern Nile Delta, Egypt

ABSTRACT Cuttings and logs from four boreholes in the Mediterranean Sea, offshore the northwestern side of the Nile Delta, Egypt (30°00’–30°24’ N, 31°18’–31°30’ E), were examined lithostratigraphically, biostratigraphically and paleoenvironmentally. Five planktonic foraminiferal zones were determined assigning the studied boreholes to be late Miocene-Early Pliocene in age. These zones are Globorotalia mediteraneaneana Zone Sphaeroidinellopsis seminulina Zone, Globorotalia margaritae margaritae Zone, Globorotalia puncticulata Zone and Globorotalia inflate. Studying benthonic foraminifera indicated a general shallowing upward trend in all boreholes and tracking the distribution of the foraminiferal assemblages by counting the total number of foraminifera and planktic/benthic ratios provide a history of the progression of deltaic facies with secondary cycles of sea-level change.

Paleoenvironment, sequence stratigraphy, and sea level change in the upper Maastrichtian–Danian boundary interval in Gabal Aras, east Qena, Nile Valley, Egypt

The Cretaceous–Paleogene (K–Pg) boundary interval at Gabal Aras, Qena region (part of the southern Tethyan margin) was investigated in detail for calcareous nannofossil and foraminiferal (planktonic and benthonic) assemblages to characterize the surface and bottom sea water conditions. The K–Pg boundary is marked by a minor hiatus expressed by the absence of the lowermost Danian P0 and Pα planktonic foraminiferal zones. Benthonic foraminifera assemblages indicate moderately oxygenated bottom sea waters associated with oligo-mesotrophic conditions during early late Maastrichtian, and mesotrophic conditions during the latest Maastrichtian. The benthonic foraminiferal assemblage reflects a decrease in the food supply in the bottom sea water during the early Danian, while well-oxygenated and oligotrophic conditions dominated during late Danian. The late Maastrichtian surface water witnessed a general cooling trend that was interrupted by a warming episode that could correspond to the Late Maastrichtian Warming Event (LMWE). Acme of Thoracosphaera associated with increased abundance of Neobiscutum romeinii were observed within the upper part of NP1 Zone indicating stressful surface water conditions. The increase of the epifaunal foraminiferal taxa and the occurrence of Cruciplacolithus primus throughout NP2 and NP3 zones reflect a progressive return to normal marine conditions. In the framework of sequence stratigraphy, two third-order depositional sequences covering the K–Pg boundary interval were identified, interpreted, and correlated. The obtained sea-level curve was evaluated to assess whether it was controlled by the eustatic sea-level changes, regional tectonics, or both these factors.

Biostratigraphy of larger foraminifera from the Middle Eocene Jahrum-Pabdeh formations (Zagros region, SW Iran) and their correlation with the planktonic foraminiferal zones

Eocene larger benthic foraminifera including orthophragmines, nummulitids and alveolinids from the Jahrum and Pabdeh formations in the Zagros region are presented. The studied 20-m-thick stratigraphic interval contains, Asterocyclina Gumbel 1870, Nemkovella Less 1987, Orbitoclypeus Silvestri 1907, Discocyclina Gumbel 1870, Nummulites Lamarck 1801, Assilina d'Orbigny 1826 and Alveolina d'Orbigny 1826. This larger benthic foraminiferal assemblage testifies for the shallow benthic zones (SBZs) 15 to 17, which ranges from the middle Lutetian up to the early Bartonian. Further micropaleontological analysis made on intercalated planktonic-rich levels helps calibrate the larger foraminifera biostratigraphy, demonstrating a correlation with the E11 biozone. This confirms that the chronostratigraphic calibration of the SBZs made by previous authors for the peri-Mediterranean area can, through the middle Lutetian to the early Bartonian, be applicable in the Middle East as well.

Biostratigraphic study of the Paleocene succession at south Wadi Qena, Egypt

This biostratigraphic study of the Paleocene sedimentary sequence at three localities in Qena region, Egypt provides a detailed assessment of the lithological features and planktonic and benthic foraminiferal taxa in order to re-assess the age of the lithologic units, identify possible unconformities, and infer the paleobathymetry and depositional environments. From south to north, these localities are Gebel Serai, Gebel Aras, and Gebel Abu Had where the Dakhla Formation (Danian–Selandian), Tarawan Formation (Selandian–Thanetian), and Esna Formation (Thanetian) are exposed. Biostratigraphic analyses suggest the occurrence of 53 foramineferal species constituting eight planktonic foraminiferal Zones. These are in stratigraphic order: Parvularugoglobigerina eugubina, Parasubbotina pseudobulloides, Praemurica trinidadensis, and Praemurica uncinata biozones (Danian age), Morozovella angulate and Igorina pusilla pusilla biozones (Selandian age), Gloanomalina pseudomenardii Zone (Selandian-Thanetian age), and Igorina laevigata Zone (Thanetian age). In the Middle part of the Dakhla Formation, a bed of marl and shale rich in organic matter approximately ∼1.2 m thick is present, and is rich in both planktonic and benthic foraminiferal species. This unit determines the datum of the last appearance of Pr. uncinata and the boundary between the Danian and Selandian. The Selandian-Thanetian deposits are characterized by planktonic and benthic foraminiferal species of outer neritic environment, whereas the Danian deposits comprise outer neritic planktonic and benthic foraminiferal genera, probably as a result of sea level changes during Danian/Selandian. The contact between the Tarawan and Esna formations coincides with the first appearance datum of Morozovella velascoensis and the last appearance datum of Gl. pseudomenardii. This suggests that the Planktonic 4c is absent in the study area and the Tarawan/Esna contact is paraconformable. The quantitative analysis of the foraminiferal contents in the different formations indicates the high value of planktonic/benthic ratio and low value of agglutinated/calcareous ratio in the middle of the Dakhla Formation and the contact between Tarawan and Esna formations. Thus, by using both lithostratigraphy and biostratigraphy to infer the lateral relationships between facies associations and paleontological changes, and interpreting the depositional environments in terms of relative changes in sea level, this study has added new knowledge about the geologic history of the study area during the Paleocene.

Electro-sequence analysis and natural resources potential of a transitional environment in central swamp depobelt, Niger delta, Nigeria

Sequence stratigraphy and Electrosequence of the Don-Field Central Swamp depobelt of the Niger Delta Basin, was carried out using well logs, biostratigraphic and core data. The aim of this study is to re-characterise and revalidate the reservoirs within the study area and provide an optimum framework for predicting reservoir character, development and reservoir quality distribution. Detailed petrophysical evaluation reveals proficient hydrocarbon reservoir units with variable parameters (i.e. porosity, permeability and shale volume) that can accommodate productive hydrocarbon reserve. Core data analyses revealed heavy minerals like pyrites and glauconites that can be of economic interest. The gamma wireline signatures of the wells show reservoir units that are predominantly blocky in shape indicative of fluvial channels. Fluvial channels are typically associated with coastal and/or marginal marine environments. More so, the aforementioned observations were validated using palaeoenvironmental interpretation of strata penetrated by Well-1, Well-2, and Well-3 via the sidewall core analyses. Sequence stratigraphic surfaces such as maximum flooding surfaces (MFS) and sequence boundary (SB) were observed to show good correlation with palynological and foraminiferal zones. The stacking patterns (i.e. progradation, retrogradation and aggradation) encountered gave acumen into systems tracts (i.e. lowstand system tract (LST), transgressıve system tract (TST) and highstand system tract (HST) interpretation. These system tracts constitute a depositional sequence set of middle—late Miocene age bounded chronologically by MFS of 9.5 Ma, 12.8 Ma, 15.0 Ma, 15.9 Ma and SB of 12.1 Ma, 13.1 Ma, 15.5 Ma, 15.9 Ma. The SB and MFS were delineated based on Shell Petroleum Development Company (SPDC) biozonation scheme: F-zone and P-zone were within P820-P680 and F9500-F9600/F9700 as contained in the biofacies interpreted data of index fossils (Globorotalia foshi S.I; Globorotalia praefohsi; Globorotalia peripheroacuta; Orbulina spp; Praeorbulina sicana; Paragloborotalia mayeri; Neogloboquadrina acostaensis) which corresponded to the alphanumeric code N8–N16 planktonic foraminiferal zones of Blow.

Planktonic Foraminiferal Biostratigraphy of the Upper Cretaceous of the Central European Basin

Planktonic foraminifera are one of the most stratigraphically important groups of organisms for the Cretaceous system. However, standard foraminiferal zonations based mostly on species from the Tethyan bioprovince are hardly applicable in temperate regions where warm-water taxa are scarce or lacking. We propose a foraminiferal zonation based on foraminiferal events recognized in the northern Foraminiferal Transitional Bioprovince, which likely has a high correlation potential at least at a regional scale. Fifteen planktonic foraminiferal zones are distinguished from the upper Albian up to the uppermost Maastrichtian strata in extra-Carpathian Poland and western Ukraine. From the bottom to the top, Thalmanninella appenninica, Th. globotruncanoides, Th. reicheli, Rotalipora cushmani, Whiteinella archaeocretacea, Helvetoglobotruncana helvetica, Marginotruncana coronata, M. sinuosa, Pseudotextularia nuttalli, Globotruncana linneiana, G. arca, Contusotruncana plummerae, Rugoglobigerina pennyi, Globotruncanella petaloidea and Guembelitria cretacea. These zones are calibrated by macrofaunal zonations.

Pseudoreticulate-Subreticulate-Reticulate Nummulites and their possible evolution in the middle Eocene-lower Oligocene succession of Surat-Bharuch, Gujarat India

A biostratigraphically well constrained middle Eocene to lower Oligocene shelf succession (ca. 33 m) of the Amravati Formation in the Vagalkhod-Dinod area of Surat-Bharuch Districts, Gujarat, India contains Nummulites having varied septal filaments, among which complicated filaments show progressive changes in the succession. Complications by the intersection of filaments with spiral laminae/ridge, bifurcation of filaments at low angle and joining by transverse trabeculae, and bifurcation and re-joining of filaments at high and varied angles, and consecutive bifurcation and trifurcation of filaments allowed their categorization in different species. Successive appearances of pseudoreticulate filaments (Nummulites acutus, Nummulites broachensis and Nummulites longilocula), subreticulate filaments (Nummulites hormoensis and Nummulites ptukhiani) and reticulate filaments (Nummulites fabianii, Nummulites retiatus and Nummulites fichteli) reflect gradual complication with time, producing a bioseries that is also manifested by changes in canals and equatorial chambers. The eight species of Nummulites are differentiated and described within the pseudoreticulate subreticulate- reticulate group and based on their stratigraphic distribution, seven zones in ascending order namely, the Nummulites acutus Assemblage Zone, Nummulites broachensis Range Zone, SRG Barren zone, Nummulites hormoensis-Nummulites fabianii Interval Zone, Nummulites fabianii Range Zone, Nummulites fabianii-Nummulites retiatus Interval Zone and Nummulites fichteli Range Zone are recognized and described. The zones are tentatively correlated with the SB zones and their ages are assigned by planktonic foraminiferal zones. Complexity of septal filaments within the Nummulites of the succession began with the development of pseudoreticulation (by the intersection of radial filaments with spiral laminae) during the late Lutetian; afterward during the early Bartonian Stage bifurcation develops in a septal filament along with occasional joining by transverse trabeculae; subreticulation remained restricted to the late Bartonian,while reticulation appeared at the beginning of the Priabonian to flourish during the Priabonian to mid Rupelian.The bioseries by septal filaments shows three evolutionary trends in these species: 1) evolution of N. acutus to N. fichteli through N. broachensis-N. hormoensis-N. ptukhiani-N. fabianii; besides acquiring complication of septal filaments this trend shows a general increase in the size of the proloculus, an increase of the size of the B-form, increasing complication in canals, and lowering the height of equatorial chambers concomitant with the increase of length; 2) evolution of N. acutus to N. broachensis to N. longilocula; this trend is restricted to the pseudoreticulate group; discerning changes involve connecting adjacent septal filaments by transverse trabeculae and spiral laminae, and development of rudimentary mesh of septal filaments, complication in canals and slit-like long equatorial chambers; 3). evolution of N. hormoensis to N. retiatus; changes involve in the development of reticulation from subreticulate septal filaments, decrease in the height of chambers, complication in canals, and development of laminae and mesh as grooves. Nummulites acutus is ancestral to all the discussed species. The evolution of Nummulites leading to complicated septal filaments is known during the corresponding span in the Mediterranean region, East African region, and a few locations in western European and southeast Asian regions, but the trends of evolution as studied in the Amravati Formation differs in the distinct developments of pseudoreticulate lineage, N. ptukhiani as an intermediate evolutionary form between N. hormoensis and N. fabianii, and in the development of complex subreticulation from a simple one. The studied succession is the only one of its kind in the Indian region to have successive development of pseudoreticulate-subreticulate-reticulate Nummulites across the Lutetian/Bartonian, Bartonian/Priabonian and Priabonian/Rupelian boundaries.

Middle Eocene echinoids from the western Eucla Basin, Western Australia

– The oldest carbonate sediments in the western Eucla Basin in south-western Australia are a series of cool-water bryozoan-dominated bioclastic grainstones, packstones and marls that represent deposition during the Tortachilla Transgression during the Bartonian (middle Eocene) planktonic foraminiferal zones 14–15.

The K-Pg boundary section at Nasiłów, Poland: stratigraphic reassessment based on foraminifers, dinoflagellate cysts and palaeomagnetism

The Nasiłów section represents the uppermost part of the Middle Vistula River section, a classical Polish extra-Carpathian Cretaceous section, and gives access to the Cretaceous–Paleogene (K-Pg) boundary interval. Despite many papers that have been published so far, our newly collected data shed new light on the completeness of biostratigraphic and sedimentary records of the K-Pg at that site. The Nasiłów section encompasses the upper Maastrichtian regional XII and XIII foraminiferal assemblage zones and the lower Danian P0?-Pα standard planktonic foraminiferal zones. The K-Pg boundary is placed at the top of a phosphatic layer. The grey marly chalk unit, never before subjected to examination of biostratigraphically important taxa, displays blooms of guembelitrids pointing to the uppermost Maastrichtian (XIII foraminiferal assemblage Zone) as well as of planktonic and benthic foraminifers of a reduced test size. Such foraminiferal dwarfism is commonly observed near the end of the Cretaceous and interpreted as a response to the Deccan volcanism (possible 2nd phase) that caused climate changes and ocean acidification. The terminal Maastrichtian age of the marly chalk unit is additionally supported by an acme of the dinoflagellate cyst Palinodinium grallator , together with Tallasiphora pelagica and Disphaerogena carposphaeropsis . The “Greensand”, a distinct glauconite-quartz sand unit, contains exclusively terminal Maastrichtian planktonic foraminifers and dinoflagellate cyst assemblages. Individual specimens of Danian age are interpreted to be either an effect of contamination or were translocated down by burrowers into the Greensand. The lowermost portion of the Siwak (informal lithostratigraphic unit) demonstrates an early Danian age based on the co-occurrence of the common planktonic foraminifers Globoconusa daubjergensis, Guembelitria cretacea, Muricohedbergella monmouthensis, M. planispira, Planoheterohelix globulosa, Parvularuglobigerina extensa and P. alabamensis . The last occurrence of Palynodinium grallator and the first occurrences of Carptella cornuta and Senoniasphaera inornata , recorded directly above the phosphatic layer, support the same age assignment. The new palaeomagnetic data cannot prove remagnetization at the boundary interval, in contrast to previous research which gave support to a hiatus in the critical interval

Evolution of the Maastrichtian–Paleocene sedimentary basin in the Safaga-Quseir region, Red Sea Coast, Egypt

Integrated field, litho- and bio-stratigraphic analyses were carried out on three Maastrichtian–Paleocene successions exposed at the Gabal Wasif, Wadi Syatin and Gabal Hamadat sections, in the Safaga-Quseir region, Red Sea Coast, Egypt. Two formations are recognized; the Dakhla Fm. and the overlying Tarawan Fm. High resolution planktonic foraminiferal investigations resulted in the identification of eleven planktonic foraminiferal zones that represent four hiatuses caused by three syn-sedimentary tectonic events (I, II and III). These events are related to the onset of the Syrian Arc Orogeny. Tectonic Events I and II coincide with the Cretaceous/Paleogene (K/Pg) and Danian/Selandian (D/S) boundaries, respectively, while Tectonic Event III occurred at the end of the Paleocene (latest Paleocene). Five paleo-relief profiles demonstrate the relative magnitudes of these tectonic events and their impact on the evolution of the sedimentary basin. Tectonic Event I had a regional effect and is seen in two sedimentary basins that are separated by a submarine paleohigh identified in the W. Syatin section. Tectonic Event II reached a maximum in magnitude toward the north in the Safaga area, forming a paleohigh in the G. Wasif and W. Syatin sections, while the G. Hamadat section represents the depocenter. Tectonic Event III had a limited impact toward the north in the Safaga area, where it formed a paleohigh at G. Wasif.

Upper Campanian-lower Maastrichtian integrated carbon isotope stratigraphy and calcareous microplankton biostratigraphy of North-central Tunisia

A comprehensive stratigraphic framework is presented for the upper Campanian-lower Maastrichtian succession of the Elles section in North-central Tunisia. This has been done by applying an integrated approach including calcareous nannofossil and planktonic foraminiferal biostratigraphy in conjunction with carbon isotope stratigraphy. The studied interval spans from the Uniplanarius sissinghii (CC21) to Reinhardtites levis (CC24) calcareous nannofossil zones and their coeval planktonic foraminiferal zones from the Contusotruncana plummerae Zone to Planoglobulina acervulinoides Zone. Seven positive and negative δ13C events have been recognized and considered for high-resolution global correlation. Isochroneity and diachroneity of the microplankton bioevents regarding the carbon isotope stratigraphy were assessed. Some discrepancies were reported, and some of them denote actual diachronism. However, the impact of the different taxonomic concepts and/or environmental issues cannot be totally excluded. The Campanian/Maastrichtian boundary has been precisely positioned within the lowermost part of the El Haria Formation at the base of the δ13C event CMBc (72.15 ± 0.05 Ma). This level projects directly below the first occurrence of the planktonic foraminifer Gublerina cuvillieri and about 9.4 m below the last occurrence of the nannofossil Uniplanarius trifidus.

Strontium isotopes and planktonic foraminiferal biostratigraphy of Eocene carbonate rocks from the Adıyaman–Malatya vicinity (southeast Turkey) and chronostratigraphic implications

Cenozoic sediments are spread across southeast and eastern Anatolia, including the Adıyaman–Malatya regions of southeast Turkey. This study presents the first detailed petrographic, micropaleontologic, and strontium isotope analyses of the Eocene marl, clayey limestone, and limestone units that outcrop unconformably above the Mesozoic Meydan and İspendere ophiolitic rocks in the Adıyaman and Malatya regions, respectively. These carbonate rocks contain abundant planktonic foraminifera, including Turborotalia frontosa, Subbotina senni, Subbotina eocaena, Acarinina bullbrooki, Guembelitrioides nuttalli, Globigerinatheka subconglobata, and G. curryi, and benthic taxa (Nummulites, Discocyclina, and Chapmanina).Two planktonic foraminiferal zones were defined: the Turborotalia frontosa zone representing the Early–Middle Eocene (Ypresian–Lutetian/Bartonian), and the Turborotalia possagnoensis zone representing the Middle Eocene (Lutetian–Bartonian). Strontium isotope ratios (87Sr/86Sr) calculated for four samples ranged between 0.707663 and 0.707784, indicating an age of 45.1–51.9 million years (Ypresian–Lutetian/Bartonian). The presence of echinoid thorns in the units indicates a shallow marine environment where carbonates developed on the seaward side of a reef. For the first time in the study region and southeast Anatolia, this study has revealed the stratigraphic position of the Nummulitic limestone of the Kırkgeçit Formation unconformably overlying the ophiolites. Therefore, based on strontium isotope analyses and planktonic foraminiferal micropaleontology, the Kırkgeçit Formation is estimated as Early–Middle Eocene (Ypresian–Lutetian/Bartonian) in age.

Evolution of the Paleocene–lower Eocene sedimentary basin in the Safaga–Quseir region, Eastern Desert, Egypt

Stratigraphy of three Paleocene–Eocene successions (Wasif, Syatin, and Hamadat) in the Safaga–Quseir region (Eastern Desert, Egypt) were achieved. These successions consist of four lithostratigraphic units: the Dakhla, Tarawan, Esna, and Thebes formations. Eight planktonic foraminiferal zones were identified, which led to detect two hiatuses caused by two syn-sedimentary tectonic events (I and II), related to the Syrian Arc Orogeny. These tectonic events were restricted to the northern part of the study area (Wasif), where they led to uplift of the sedimentary basin and forming two paleohighs. Tectonic Event I took placed at the end of the Paleocene, whereas the Tectonic Event II took placed at the Paleocene/Eocene (P/E) boundary. The southern portion of the study area has complete strata at the Syatin and Hamadat sections, and it represents the depocenter during these two events. In addition, the Dababiya Quarry Member, which marks the P/E boundary in Egypt, was well represented at the Syatin and the Hamadat sections.

Maastrichtian–Paleocene sequences at Dakhla-Abu Minqar District, Western Desert, Egypt: stratigraphical and paleoenvironmental framework

Integrated lithostratigraphic and biostratigraphic data of two well-exposed Maastrichtian–Paleocene successions, namely, the Owina and the Abu Minqar sections (Dakhla Oasis, Western Desert, Egypt), led to enhance the age resolution and shed lights on the paleoenvironmental conditions throughout the deposition of the investigated sequences. The integrated biostratigraphic data provide eight calcareous planktonic zones (five planktonic foraminifera, and three calcareous nannofossil zones) cover the studied interval. The paleoenvironmental setting of the Maastrichtian interval which represented by the lower Kharga Shale unit (Micula murus and Gansserina gansseri calcareous plankton zones) reveals shallow marine environmental conditions of inner neritic probably of marginal setting with high organic matter influx and low-oxygen level interrupted by some transgressive phases. While, shallower marine conditions associated with a sea-level drop mark the Cretaceous/Paleogene (K/Pg) boundary. The lowermost part of the Paleocene interval (NP3, NP4, P1b, P1c, and P2 calcareous plankton zones) which covered the lower part of the upper Kharga Shale unit is marked by middle-outer neritic depositional setting, well-oxygenated seawater, as well as a low organic matter influx coupled with relative sea-level rise. Above this level until reach the base of the Tarawan Formation, a major drop in the sea-level is observed. This interval is marked by absence of the calcareous planktonic taxa. Only agglutinated foraminiferal taxa are recorded during this interval. While the Tarawan Formation (P4b planktonic foraminiferal Zone) is marked by outer neritic depositional setting that represents a sea-level transgressive phase. According to the field observations and the presence/absence of the calcareous planktonic zonal marker species; two tectonic events are detected. The tectonic event I took place at the K/Pg boundary and resulted in a significant hiatus at the studied area. Tectonic event II is observed at the contact between the Dakhla and the Tarawan formations across the Danian–Selandian transition. It is evidenced by the existence of an erosive (irregular) surface at the basal part of the Tarawan Formation. These events could be attributed to the echo of the Syrian Arc tectonism which interrupted the global sea-level curve throughout the Maastrichtian–Paleocene time.

Geologic age of the lower Josoji Formation, Shimane Peninsula, Southwest Honshu, Japan: Implications for an abrupt change to deep‐water during the earlier opening stage of the Japan Sea

AbstractThe lower part of the Josoji Formation, Shimane Peninsula, contains clues for figuring out changes in deep‐water characteristics during the opening of the Japan Sea. The foraminiferal assemblage includes early to middle Miocene biostratigraphic index taxa such as planktonic foraminiferalGloborotalia zealandicaandGloborotaloides suteri. The occurrence of these two species, together with the absence of praeorbulinids, suggests that the lower part of the Josoji Formation is assigned to the top of planktonic foraminiferal Zone N7/M4 (16.39 Ma). The benthic foraminiferal assemblage, which is characterized byCyclammina cancellataandMartinottiella communis, clearly suggests that the lower Josoji Formation was deposited at bathyal depths, and that it developed in association with the abrupt appearance of deep‐sea calcareous forms. Such bathyal taxa are the main constituents of theSpirosigmoilinella compressa–Globobulimina auriculataZone of the Josoji Formation and also of theGyrodina–GyroidinoidesZone at Ocean Drilling Program Site 797 in the Japan Sea. The base of these benthic foraminiferal zones can be correlated with the base of the nannofossilSphenolithus heteromorphusBase Zone (= CNM6/CN3); thus, its estimated age is 17.65 Ma. This biostratigraphic information suggests that the lower Josoji Formation was deposited from shortly before 17.65–16.39 Ma in upper limit age. Evidence that fresh to brackish and shallow‐water basins formed in the rifting interval of 20–18 Ma in the Japan Sea borderland suggests that the abrupt appearance of deep‐sea calcareous foraminifera occurred about 1 my earlier in this area than in other sedimentary basins and suggests that a significant paleoceanographic change occurred in the proto‐Japan Sea at 17.65 Ma.

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.

Palaeoecology and facies analysis of benthic communities in mid-Cretaceous successions in the Sinai platform, Egypt

Within the Aptian-Cenomanian formations of Sinai successions in Egypt, lateral and vertical changes occur in the numerous benthic communities. Microbenthos such as Orbitolina foraminifera and calcareous algae are widespread in the Aptian-Albian deposits in North Sinai, whereas oysters and gastropods are common in the Cenomanian siliciclastic deposits in South Sinai. In order to establish the biostratigraphy, 90 benthic and planktonic foraminifera species have been identified from the studied succession. Based on the stratigraphic distribution of the identified species the studied succession could be subdivided into three planktonic foraminiferal zones: Pseudothalmanninella ticinensis zone (Late Albian), Rotalipora cushmani zone (Middle-Late Cenomanian), and Whiteinella archaeocretacea zone (Late Cenomanian-Early Turonian). This work discusses the first record of the Albian dasycladalean alga Holosporella sugdeni (Elliott) from Sinai and reports on Montiella elitzae (Bakalova) from the Albian Risan Aneiza Formation. The occurrence of Orbitolina (Conicorbitolina) conica distinguished the Albian-Cenomanian boundary in the North Sinai sequences. The benthic communities of the studied successions indicated a faunal shift from an algal-orbitolinid foraminifera community around the Aptian-Early Albian to a rudist community during the Middle Albian and an oyster-gastropod community during the Cenomanian. This faunal shift coincided with the major sea transgression that covered North Sinai until the Middle Albian and reached South Sinai during the Cenomanian. The identified Cenomanian gastropods included Neoptyxis olisiponensis, Nerinea gemmifera, and Tylostoma bussoni. Many oyster species distinguished the Cenomanian deposits, such as Ceratostreon flabellatum, Rhynchostreon mermeti, Rhynchostreon suborbiculatum, and Costagyra olisiponensis. Identifying the benthic fauna and facies indicated a shallow inner to middle ramp environment. Stable carbon and oxygen isotope data from the Cenomanian oyster shells indicate an inner ramp environment. Comparing the carbon isotope values of the oysters with those previously recorded from the rudists may explain the different trophic levels of both groups.