Southern Tethyan Research Articles

BIOSTRATIGRAPHY AND PROTEROGENESIS OF VERNEUILINA FAUNA FROM THE SOUTHERN TETHYS

The Campanian-Ypresian (C-Y) fauna in the Southern Tethys (ST) include rich small benthic foraminifera (SBF) reveals significant biostratigraphic changes during the C-Y transition. A progressive evolutionary trend within the Verneuilina lineage allowed to establish the Campanian V. iraqensis Total Range Zone (TRZ), and three successive zones in the Maastrichtian-Ypresian, namely: the Maastrichtian V. aegyptiaca Interval Range Zone (IRZ), the Paleocene V. laevigata IRZ, and the Ypresian V. luxorensis TRZ, which may correlate with the standard planktonic foraminifera zones: Globotruncana aegyptiaca IRZ to Acarinina pentacamerata PRZ, and span about 23 M.Y. (75-52 Ma). On the other hand, a minor difference in the test morphology and differences in the stratigraphic ranges of the members of the genus Verneuilina are recognized as being of decisive specific value. For that, the Proterogenesis Rule can be applied here on the Late C-Y six species of the genus Verneuilina, and these are: Verneuilina aegyptiaca and V. karreri, V. laevigata and V. luxorensis. Another two species are believed here as new: Verneuilina iraqensis and Verneuilina jordanica. The identified species were recorded from many localities in the ST (Tunisia, Egypt, Jordan, Iraq, Iran, United Arab Emirates, Qatar and Pakistan), and one of them are recorded in Spain, in the Northern Tethys (NT).

PERCULTALINA: A NEW LAGENID BENTHIC FORAMINIFERAL GENUS

Percultalina n. gen. is introduced here to include the Early Paleogene benthic Lagenid foraminiferids from Jordan and Egypt (Southern Tethys) that characterized by its large lenticular initial portion followed by two or more uniserial elongate erected or inclined inflated rounded chambers, ornamented surface by elevated sutures with a row of tubercles or nodes along the sutures, and spinose surface. This new genus has been previously assigned to different genera: Vaginulinopsis Reuss, or Percultazonaria Loeblich & Tappan, or Marginulinopsis Silvestri. Three Early Paleogene species of the new genus are described here from two countries in Jordan: Percultalina wadiarabensis (Futyan) with rectilinear uniserial portion of the test (the genotype of the new genus), and Egypt: Percultalina misrensis Anan (n. sp.), and P. sinaensis with inclined uniserial portion of the test. Moreover, varied and diverse genera of the Lagenid benthic foraminifera are attempted here to study the holotypes of seven diagnostic genera of this group: Lenticulina Lamarck, Cribrolenticulina Haman, Marginulinopsis Silvestri, Percultazonaria Anan, Leticuzonaria Anan, Lenticubella Anan and Percultalina Anan. The taxonomic revision of these seven genera will greatly aid paleontologists and biostratigraphers to helpfully understanding.

PALEONTOLOGY, PALEOENVIRONMENT AND PALEOGEOGRAPHY OF THE EARLY PALEOGENE PAKISTANIAN BENTHIC FORAMINIFERAL SPECIES OF HAQUE – SUBORDER TEXTULARIINA (AGGLUTINATED FORAMINIFERA)

The present study is a part of the comprehensive works concerned with the complete record of the Paleogene small benthic foraminiferal content in the Ranikot and Laki Formations of the Nammal Gorge, Salt and Sor Ranges of Pakistan. The first part was concerned with the Miliolina and Lagenina foraminiferal assemblage of Haque from Pakistan, and followed by the second part which concerned with the Rotaliid assemblage of the same author of Pakistan. The third part is concerned with the Textulariid part and presented in this study. Twenty one Early Paleogene Pakistanian smaller Textulariid (Agglutinated) benthic foraminiferal species and subspecies from the Ranikot and Laki Formations of the Nammal Gorge, Salt and Sor Ranges of Pakistan have been studied and are systematically listed. This systematic description provides a list of modern synonyms, short remarks about morphological features, and some annotations about taxa with problematic generic status. These species are: Spiroplectinella ushbali, Gaudryina nitida, Siphogaudryina daviesi, S. elongata, S. nammalensis, Verneuilina laevigata, Tritaxia elongata, T. limbata, Dorothia nammalensis, Marssonella nammalensis, Bigenerina khirthari, B. metingensis, B. nodosa, Textularia crookshanki, T. haquei, T. punjabensis, Clavulinoides lakiensis, C. spatha, C. symmetrica, Valvulina n. nammalensis, V. nammalensis longa. Most of the recorded species are an endemic to Pakistan, except five species Siphogaudryina elongata, Tritaxia elongata, T. limbata, Textularia crookshanki and T. punjabensis are recorded in some Northern Tethys (France, Hungary) and Southern Tethys (India, Iran, UAE, Egypt, Algeria). The paleoenvironmental interpretations of the identified species in the study area of Pakistan were deposited in somewhat deep water and open-marine environments. The abundance of pelagic Pakistanian benthic foraminiferal assemblages indicate an open connection to the Tethys, which represents middle-outer neritic environment (100-200 m depth) and shows an affinity with the Atlantic-Tethyan Regions: “Midway Type Fauna “.

PALEONTOLOGY AND EVOLUTIONARY LINEAGES OF THE DIAGNOSTIC BENTHIC FORAMINIFERAL GENUS ORTHOKARSTENIA

This work is focused on the members of the Late Cretaceous-Early Paleogene (K-Pg) diagnostic benthic foraminiferal genus Orthokarstenia which is regionally important in paleontology and stratigraphic correlations. The large number of tests available and the rapid morphologic changes, offer an opportunity to study evolutionary changes in these foraminiferal taxa over a time span of about 25 m. y. (75-50 Ma). Six species of the genus Orthokarstenia are presented: O. applinae, O. eleganta, O. esnehensis, O. higazyi, O. nakkadyi and O. oveyi, which were recorded in eight localities in the Southern Tethys: Nigeria, Tunisia, Egypt (central and north Africa), Jordan, Saudi Arabia, UAE, Iran and Pakistan (southwest Asia). Evolutionary changes of them are indicated by such criteria, such as changes in the test-size, chambers arrangement, type of sutures, periphery or surface ornamentation. These changes help to define the major faunal change of the Campanian/Maastrichtian (C/M) boundary, K/Pg boundary, and can used in biostratigraphic subdivisions and correlations based on benthic foraminifera, beside planktic foraminiferal zonation.

LENTICUBELLA: A NEW TETHYAN LAGENID BENTHIC FORAMINIFERAL GENUS

Lenticubella n. gen. is introduced here to include the Paleocene benthic Lagenid Foraminiferids from some Tethyan localities (Poland and Egypt) that characterized by symmetrical planispirally enrolled hyaline calcareous test in the early stage, followed by later uniserial stage, moderately involute chambers, smooth surface, radiate aperture, with periphery keeled in some individuals. Some representatives of the new genus have been previously assigned to the genus Darbyella, or Lenticulina, or Robulus. The new genus has a compiled characters between its lenticular test (as the genus Lenticulina Lamarck (with its symmetrical planispirally enrolled test, and smooth surface), and also another genus Darbyella Howe and Wallace (which has planispiral-uniserial test with inclined positon on the uniserial part on the early planispiral direction). Two Paleocene species of the new genus are described from Poland in the Northern Tethys (L. irregularis and L. polonica), and another two species from Egypt in the Southern Tethys (L. kurkurensis and L. misrensis). The Polonian species have flush or slightly depressed sutures, while the Egyptian species have raised sutures, mainly in the planispiral stage, but slightly depressed sutures in the uniserial stage.

An integrated high-resolution image log, sequence stratigraphy and palynofacies analysis to reconstruct the Albian – Cenomanian basin depositional setting and cyclicity: Insights from the southern Tethys

Borehole image logs are used to overcome the lack of core samples and other conventional open-hole logs in many subsurface reservoirs around the world, significantly reducing the likelihood of petroleum resource exploration. These image logs can provide high-resolution data to visualize sedimentary structures, facies types, lithofacies, geomechanical characteristics, and depositional trends. Sedimentologists recognize the Bahariya Formation of the North-Western Desert of Egypt as the typical coastal -shallow marine depositional model that emphasizes a typical heterogeneous sandstone reservoir with many obstacles in production profile. One of the most significant issues related to the heterogeneous Bahariya reservoir that confronts hydrocarbon producers is the loss of productive target zones due to spatial facies changes. This research aims to overcome the exploration and development challenges of the complex and heterogeneous sandstone reservoir of the Albian – Cenomanian Bahariya Formation that lies in the Abu Gharadig Basin, Southern Tyths, Egypt. In this work, we used integrated image logging in conjunction with palynofacies, core samples, and sequence stratigraphy to provide high resolution information that can aid in better resource exploitation. Furthermore, we utilized the integrated work in the definition of the high-resolution para-sequences, sequences boundaries, lithofacies characteristics and paleocurrent analysis of each facies association. The interpretation of coastal shallow marine facies from four BHI-logs was established and calibrated with two core sets in order to define the best hydrocarbon reservoir intervals and focus on improving the development plan of the study area. Our findings show that the Bahariya Formation is characterized by eleven facies associations which have been interpreted based on the integrating of the twenty-seven electrofacies extracted from the FMI images, wireline logs, and core photographs. The identified facies associations were classified into five depositional sequences and their boundaries were determined using dipmeter patterns and extracted lithofacies from BHI. The LST and MFS deposits in both the fourth and fifth depositional cycles, respectively, whereas the HST deposits are found only in the third depositional cycle. According to our findings, the development of the shoreface sandy facies of cycles three and five represents the maximum rate of sea-level rise, as well as the development of the offshore sand bar system, which represents high-quality sandstone reservoirs. This case study demonstrates how image logs can be used to better understand the spatial distribution and geometries of sandstone bodies in the Bahariya Formation. Furthermore, it provides a reference imaging fingerprint of high-resolution coastal shallow marine, high-frequency sequences analysis, sedimentary structures, and extracted electrofacies analogues that can be used in the basin and elsewhere.

South Tethyan passive margin paleoslope orientation inferred from soft-sediment deformation and fault kinematic analysis: a case study from the Cretaceous of Borj Cedria area, Tunisia

The Cretaceous outcrops of Borj Cedria-Bou Kournine area belongs to the NE-trending Atlas system of northern Tunisia. This area exposes sub-meridian folds associated with numerous N- to NW-trending major fault systems. This study together with previous surveys reveals that this N-trending folding is believed to be related to the inversion of the Jurassic and Early Cretaceous pre-existing fault zones and generated in response to the late compressive deformations. In addition, the study area provides evidence of soft-sediment deformations by good exposures of Cretaceous-aged slump sheets. Slump folds are usually associated with several meso-scale syn-sedimentary normal faulting together with frequent reworked blocs and occasional conglomeratic horizons. All these features indicate sedimentation on irregular seafloor topography. The aim of the present study is to investigate slump folds by applying techniques to reconstruct the contemporaneous slope gradient which has triggered soft-sediment deformations. Moreover, the brittle deformation is quantified using fault kinematic analysis together with the analysis of lithostratigraphic correlation and syn-sedimentary structures. Considerable thickness variations of Cretaceous deposits are interpreted as controlled by normal faulting activities. Likewise, fault kinematic analysis typifies a regional pure extension that trends NNW during Barremain, NNE during Albian, and probably NW during Cenomanian time. Based on slump folds analysis, the inferred sub-marine paleoslope is believed to have a northward dipping during Barremian and a NNE-dipping during Albian time. On the light of the over-mentioned interpretations, it is believed that Cretaceous sedimentation of the study area is highly controlled by major syn-depositional normal faults associated with intra basin growth faulting. These fault systems seem to be related to the Southern Tethyan expansion of the rifted continental passive margin.

REPRESENTATIVES OF SOME DIAGNOSTIC AGGLUTINATED FORAMINIFERAL GENERA OF THE SUBCLASS MONOTHALAMANA (BATHYSIPHON, ORBULINELLOIDES, REPMANINA, MILIAMMINA, AGGLUTINELLA, DENTOSTOMENIA, AMMOMASSILINA, PSAMMOLINGULINA) IN THE TETHYS

The present study deals with the paleontology, stratigraphy, paleogeography and paleoenvironment of the sixteen representatives of the Paleogene agglutinated benthic foraminifer Monothalamana of eight genera: Bathysiphon Sars, Orbulinelloides Saidova, Repmanina Suleymanov, Miliammina Heron-Allen & Earland, Agglutinella El-Nakhal, Dentostomina Cushman, Ammomassilina Cushman, Psammolingulina Silvestri. One species Orbulinelloides kaminskii is believed here to be new. As a whole these faunae are rarely described in the micropaleontological literatures, that’s why this study is detected. The recorded species are distributed on both sides of the Northern Tethys (Hungary, France), Southern Tethys (Egypt, UAE, Pakistan), Pacific and Atlantic Ocean. It seems that the changes in paleoceanographic conditions should accentuate the benthic faunal changes. Some of the recorded species are mostly confined to that mention localities in the Atlantic and Pacific Ocean, Northern and Southern Tethys, and it was recorded by a few authors. The deeper water species have smooth tests, while the shallow water specimens are coarser grained. The number differences of the recorded species between the different localities in the Tethys may be due to one or more parameters: the deficiency of available literatures, differences in ecological or environmental conditions (depth, salinity, water temperature, dissolved oxygen, nutrient, land barrier) and not homogeneity in the generic or species concept according to different authors.

Updated geochemical insights on the Weissert and Faraoni events in the southern Tethyan margin (northern Tunisia)

Updated geochemical insights on the Weissert and Faraoni events in the southern Tethyan margin (northern Tunisia)

Contribution of foraminifers in biostratigraphy and paleoecology interpretations of the basal Eocene from the phosphatic Sra Ouertaine basin, in the southern Tethys(Tunisia)

Micropaleontological, sedimentological and statistical studies were carried out on the late Paleocene-early Eocene succession of Sra Ouertaine and Dyr El Kef in Northern open phosphatic Basin of Tunisia. Based on the abundance and stratigraphic distribution of planktic foraminiferal species, five planktic zones have been recognized from the base to the top of the phosphatic layers. The El Acarinina sibaiyaensis Zone, the E2 Pseudohastigerina wilcoxensis Zone, the E3 Morozovella marginodentata Zone, the E4 Morozovella formosa Zones and the E5 Morozovella subbotinae Zone. The placement of Paleocene-Eocene boundary (PETM) is just below the base of the phosphatic interval. The ETM-2 event may be detectable in the analyzed biotic record of Sra Ouertaine.Based on benthic assemblages, abundances, cluster and multivariate statistical analyses, two biofacies were recognized for each section. The recognized ecozones are typical of warm and shallow water inner neritic setting (dominance of epifaunal fauna Anomalinoides, Dentalina and Cibicidoides associated with Frondicularia phosphatica, Trochamminoides globigeriniformis and Eponides elevatus). The paleoenvironment is eutrophic (presence of several bolivinitids and verneuilinids). For the Dyr El Kef section and P5 and E2 of Sra Ouertaine section, our records indicate that paleoenvironment is influenced by coastal upwelling without oxygen-deficiency, the paleodepth is estimated to be around 50 m. The paleoecosystem is diversified and balanced with a general tendency to stressed condition. While the upper part of Sra Ouertaine section is more eutrophic, influenced by coastal upwelling with oxygen-deficiency, the paleodepth is estimated to be less than 50 m and the ecosystem is unsettled.

Valanginian cold/warm climatic oscillation and synsedimentary tectonic interaction for drowning the carbonate platform of Southern Tethys (Sicily)

Valanginian is a deeply investigated time interval due to the climatic, environmental and oceanographic changes that characterised it, globally recorded in sedimentary successions.During the Valanginian, an oscillation between warm and cold climatic phases is generally accepted as causing change in sedimentation, especially along the carbonate platform successions. In this context the so-called “Weissert event” occurred.The analysed stratigraphic interval consists of a Valanginian–Hauterivian package of two black metallic crusts (hardgrounds) and condensed pelagites, interbedded in the Lower Cretaceous carbonate shallow-water succession outcropping in the Palermo Mountains (NW Sicily). Integrating facies, structural, mineralogical and geochemical analysis, including analysis of δ13C and δ18O isotope records, the interaction between synsedimentary tectonics and climatic changes, as causing palaeoenvironmental and palaeoceanographic changes in the Lower Cretaceous Panormide carbonate platform, has been envisaged.A regional extensional tectonic event in the Southern Tethyan margin was detected at the Berriasian/Valanginian boundary, as responsible for the tectonic fragmentation of the Mesozoic Panormide carbonate platform in various fault-blocks. Locally, tectonic subsidence caused drowning of some of the fault-blocks. Before the recovery of the benthic carbonate factory in the Barremian, condensed pelagites and mineralised (Fe–Mn) crusts developed during the alternation of warm and cold climatic pulses.The positive–negative excursions of the Valanginian–Hauterivian δ13C pattern of the Colombrina section provide solid evidence for the chronostratigraphic assignment of the study interval to the drowning of many carbonate platforms that preludes the onset of the “Weissert event”. In detail, the drastic negative shift of δ13C in the late early Valanginian mineralised crust reveals massive release of isotopically light carbon to the atmosphere/hydrosphere reservoirs from a possible excess of volcanogenic CO2 or methane release from clathrate dissociation. Combining sedimentological data with the increase of the δ18O isotope records, two cold climate pulses are envisaged. The first one is assigned to the Berriasian/Valanginian boundary and led to the formation of the lower mineralised crust. The second and more evident positive shift of δ18O is assigned to the earliest late Valanginian, during the sedimentation of the laminated pelagites deposited immediately after the upper mineralisation event. These cold events that are comparable with the coeval cooling pulses recorded at a global scale highlight icehouse interludes during the Lower Cretaceous greenhouse mode.

PALEONTOLOGY, PALEOENVIRONMENT AND PALEOGEOGRAPHY OF THE EARLY PALEOGENE PAKISTANIAN BENTHIC FORAMINIFERAL SPECIES OF HAQUE - SUBORDER ROTALIINA

Eighty-five Early Paleogene Pakistanian smaller Rotaliid benthic foraminiferal species belong to thirty-nine genera from the Ranikot, Nammal and Laki Formations of the Nammal Gorge, Salt and Sor Ranges of Pakistan have been studied. The modern taxonomic consideration and systematic description of the species is based on the diagnostic morphology, list of synonyms, short remarks about morphological features, and annotations about taxa with problematic generic status. Most of the recorded species are, so far, an endemic to Pakistan, except 19 species of them were recorded in other localities in the Southern Tethys (India, Qatar, United Arab Emirates, Saudi Arabia, Egypt, Nigeria) and also in Northern Tethys (France, Spain, Slovenia). The high abundance of pelagic Pakistanian foraminiferal assemblage indicate open connection to the Tethys, which represents middle-outer neritic environment (100-200 m depth) and shows an affinity with Midway-Type Fauna ‘MTF’.

Cenomanian oyster communities from a tide-dominated epeiric ramp in the southern Tethys: A sediment-fauna relationship

The Cenomanian shallow marine succession in the Southern Galala Plateau of Egypt contains rich benthic fauna and preserves enormous information on how paleo-communities respond to fluctuating environmental conditions. Based on rock and fossil data, the Galala Formation was interpreted to be the result of deposition on a tide-dominated homoclinal ramp. Three main facies associations representing three depositional environments (intertidal, shallow subtidal, and deep subtidal) were recognized. Three distinct macroinvertebrate associations corresponding to these environments and dominated mainly by oysters were quantitatively identified. They show a gradational vertical increase in diversity as well as in the infaunal and mobile species. This trend can be attributed to the Cenomanian sea-level rise, where harsh marginal marine environments in the middle Cenomanian became more stable toward the latest Cenomanian. Sea flooding may have eliminated barriers, enhanced water circulation, and stopped hyperpycnal flow and/or terrigenous flux. Consequently, oxic mesotrophic conditions may have prevailed and siliciclastic starvation may have concentrated fossil materials, and therefore, diversity increased. Based on the vertical and lateral changes of the facies stacking pattern, two main parasequence types were recognized, the first includes deep subtidal deposits changed upwards to shallow subtidal and the second includes shallow subtidal deposits that pass upward into intertidal. Moreover, two and one-half third-order mixed sequences were identified and correlated to their regional and global counterparts.

Latest Smithian (Early Triassic) ammonoid assemblages in Utah (western USA basin) and their implications for regional biostratigraphy, biogeography and placement of the Smithian/Spathian boundary

The late Smithian extinction represents a major event within the Early Triassic. This event generally corresponds to a succession of two, possibly three successively less diverse, cosmopolitan ammonoid assemblages, which when present, provide a robust biostratigraphic framework and precise correlations at different spatial scales. In the western USA basin, known occurrences of latest Smithian taxa are rare and until now, have only been documented from northeastern Nevada. Based on these restricted basinal occurrences, a regional zone representing the latest Smithian was postulated but not corroborated, as representative taxa had not yet been reported from outside Nevada. Here we document two new ammonoid assemblages from distant localities in northern Utah, overlying the late Smithian Anasibirites beds and characterized by the unambiguous co-occurrence of Xenoceltites subevolutus and Pseudosageceras augustum. The existence of a latest Smithian zone in the western USA basin is therefore validated, facilitating the identification of the Smithian/Spathian boundary and intra-basin correlation. This zone also correlates with the latest Smithian zone recognized from southern Tethyan basins. Additionally, these new data support other observed occurrences of Xenoceltites subevolutus throughout most of the late Smithian.

Unravelling the evolution of extraordinary long-range planktonic foraminifera species based on image processing analysis

The recent growing interest in Late Cretaceous biserial planktonic foraminifera (heterohelicids) has greatly enhanced their use as paleoceanographic and biostratigraphic markers. Pseudotextularia nuttalli, one of the most common cosmopolitan planktonic foraminifera, has an exceptionally long evolutionary range (Turonian-Maastrichtian). The image processing procedure we developed in this study enabled us to document changes in the growth pattern of Ps. nuttalli over time and between different oceanic provinces, and to identify possible speciation events within this lineage. The analysis was complemented by morphometric measurements of the penultimate chamber and test.The morphometric analyses do not indicate an early speciation event within this lineage, and thus, do not support splitting to Planoheterohelix praenuttalli (Turonian-Coniacian) and Pseudotextularia nuttalli (Coniacian-Maastrichtian). Our results indicate a gradual phyletic increase in mean test size from the Santonian through the Maastrichtian, along with increasing morphological diversification. This trend seems to coincide with the global cooling that culminated in the Late Cretaceous.Comparing between Ps. nuttalli from different oceanic provinces reveals that the Southern Tethys specimens are significantly less developed than their counterparts from the two tropical oceanic localities. This adaptive responsiveness suggests a negative correlation between test size and high productivity conditions in the upper water column.The case of Ps. nuttalli lineage exemplifies how extraordinary long-range species (>30 My) can evolutionarily change over time from “primitive” to “developed” forms, without showing a morphological gap. Such species may also show adaptive morphological diversification in response to different environments and, thus, are valuable for palaeoceanographic and paleoecologic reconstructions.

Paleoclimatic variability in the southern Tethys, Egypt: Insights from the mineralogy and geochemistry of Upper Cretaceous lacustrine organic-rich deposits

The effect of paleoclimate during global warming periods on Upper Cretaceous lacustrine deposits is not fully understood. In this study, comprehensive sedimentological, mineralogical, and geochemical data were used to unravel the past climatic changes and their influence on the accumulation of Campanian lacustrine organic-rich deposits in Egypt. Three sedimentary lithofacies associations are recorded within the uppermost part of the Quseir Formation. The laminated clay-rich mudstone lithofacies has the highest organic matter (TOC up to 1.2 wt.%). Sedimentological observations indicate that the bulk lithologic assemblage was originated in a shallow lacustrine setting. The studied samples consist of clay minerals, quartz, pyrite, carbonate, fluorapatite, and halite. The siliciclastic content reaches up to 78wt.%, whilst the carbonate content ranges from 3 to 22 wt.%. Compared to Post-Archean Australian shales (PAAS), the studied samples are significantly rich in Mg, Ca, P, Al, V, Ga, and Cr contents. The mudstone samples are characterized by high ratios (C-value, CIA, CIW, Mg/Ca, Fe/Mn, Ga/Rb) and low values (K2O/Al2O3), reflecting relatively warm and humid conditions during deposition of these sediments. The prevalence of smectite, as well as the sedimentary features, support that the lacustrine organic-rich mudstones are mainly deposited under warm seasonal climate (arid/humid). Additionally, the presence of dolomite and halite along with the Sr/Ba ratios (1.30–2.13), strongly suggest a saline water setting. The changes between aridity and humidity periods are probably the main reason for the significant variation in water chemistry, especially salinity. Therefore, the paleoclimatic variations largely controlled the depositional process during the formation of the Upper Cretaceous lacustrine organic-rich mudstones in the southern Tethys.

Impact of the late Cenomanian sea-level rise on the south Tethyan coastal ecosystem in the Middle East (Jordan, Egypt, and Tunisia): A quantitative eco-biostratigraphy approach

Sea-level rise can cause changes in coastal ecosystems. To understand the link between sea-level rise and the coastal ecosystems during the late Cenomanian of the southern Tethys, five exposed sections from three Middle East countries were quantitatively analyzed. The Unitary Association (UA) method allowed a two-fold increase in the resolution of zones compared to the Oppel method. Five UAs were obtained from analyses of both ammonite and benthic fauna. However, they were grouped into 3 UA Zones (UAZ) to enable basin-wide correlation. These zones were linked to one and half 3rd-order depositional cycles. During the Neolobites vibrayeanus/ Calycoceras guerangeri ammonite zone (95.5–94.4 Ma), high-energy shallow subtidal environments were formed by the transgression that followed the global sequence boundary ‘KCe 4’. They were dominated by stationary epifauna and suspension-feeders (mainly oyster bivalves). During highstand, a restricted lagoonal environment prevailed, where oyster bivalves, which have well-known adaptive strategies, were still dominant. No ammonites were recorded in this zone. Upward, the fauna has underwent a major shift, which documents the beginning of a new depositional sequence above a regional sequence boundary ‘KCe 5’ with a gradual increase of hemipelagic organic-rich sediments and planktic/nektic fauna in addition to infaunal deposit-feeders and mobile benthos, which have lived in a deeper subtidal environment (Vascoceras cauvini/Pseudospidoceras pseudonodosides ammonite zone; 94.4–93.8 Ma). This dramatic change in the character of the macrofauna at the Cenomanian/Turonian boundary (maximum flooding of KCe 5) can be attributed to the hydrodynamic changes associated with the eustatic sea-level rise. Therefore, the sea-level-based faunal changes can be integrated in sequence stratigraphic analyses. The geographic reproducibility of the UA mirrors the delay of the transgressive onlap in proximal sections, and thus, can be used to define transgressive and maximum flooding surfaces. This eco-biostratigraphic scheme can be implemented in reliable large-scale correlations.

Taxonomy and paleobiogeography of the Maastrichtian cephalopods from the Abu Monqar-west Dakhla stretch, Western Desert, Egypt

ABSTRACT The Maastrichtian sedimentary succession in the Abu Monqar-west Dakhla stretch yields rare cephalopod content. Six cephalopods, including three nautiloids and three ammonoids, are described in detail and identified. Two new species of nautiloids are erected from the study area; these are Angulithes monqarensis nov. sp. and Anglonautilus hewaidyi nov. sp. The ammonoid Sphenodiscus lobatus (Tuomey) is firstly recorded from the Maastrichtian rocks of Egypt. Paleobiogeographically, Pachydiscus (P.) neubergicus has a wide geographic distribution within the Tethyan and Boreal realms. Sphenodiscus lobatus appeared earlier in the late Campanian of North America and then migrated through shallow environments to the Southern Tethys. The Anglonautilus appeared earlier in the Hauterivian age in the Northern Tethys and then migrated into Southern Tethys, Northern America, and Asia. The distribution of Baculites ovatus at the Southern Tethyan Province is chiefly controlled by the prevailed palaeoecological factors.

Facies-based model and basin architecture of the Eocene succession in Egypt (Eastern Desert and Sinai): an example for tectonically controlled sedimentation on the southern Tethyan margin

Integration of stratigraphy, spatial evolution, and syn-tectonism paved the way to propose a new depositional model for the Eocene rocks in the Eastern Desert and Sinai. Minia, Darat, Samalut, and Maghagha geological formations have been recognized. Eight sedimentary facies including tidal flat/lagoon complex, restricted inner lagoon, shoals, outer lagoon, back-bank, nummulite bank, fore-bank, and open marine have been identified. They were deposited in the shallow marine photic environment on a gently dipping platform ramp due to north of Egypt. Furthermore, this ramp shows three main faunal associations depending on water depth. The facies zones are arranged into a series of parallel NE-SW elongated subsiding sub-basins, separated by emerged and submerged swells rising from the bottom of the Eocene sea. Physically controlled sedimentary structures indicate a para-autochthonous to bio-concentration of the nummulite bodies. The spatio-temporal variations in the depositional environments and hiatuses in between and within the studied rock units indicate stratigraphic unrest. The Syrian Arc tectonism is the main trigger for such disturbance, which was rejuvenated and enlarged during the Late Cretaceous up to the Neogene in the eastern and southeastern Mediterranean domain.

Characters ofNummulites multiplicutiospiralisn. sp. from the Qarara Formation, Maghagha, Nile Valley, Egypt

AbstractNummulites multiplicutiospiralisn. sp. is described and illustrated for both generations from a claystone of Lutetian age in the Middle Eocene Qarara Formation, Maghagha, Nile valley, Egypt. Previously considered to beNummulites gizehensis, we describe this form as a new species based on diameter of the test and protoconch sizes, septal shape and granulations. The primary feature of this species is spiral multiplication, seen in spiral section. The species is also characterized morphologically by lenticular to flat tests with rounded periphery, wrinkled to broadly meandering septal filaments and few granules on the periphery in microspheric forms. The granules are spirally arranged on the septal filaments in megalospheric forms. Chambers are longer than high and the spire is irregular. The new taxon belongs to theNummulites partschiGroup, SubgroupN. gizehensis. Reflexive coiling in the spiral may develop through ontogeny as inN. rollandi, the species which was considered to be an index species in the southern Tethys (Boukhary et al., 1982 and Boukhary et al. 2010). The characters of the new species, as well as its retrogenesis and reflexive coiling, should be further studied in general inNummulitesspp., to understand the importance of such characters phylogenetically.