Biostratigraphic Tool Research Articles

A palynological zonation for the Neogene of the Solimões/Amazon basin, northwestern Amazonia

ABSTRACT The tropical rainforests of northwestern Amazonia possess the highest plant diversity of any biome in the world. Understanding their origin, development, maintenance, and future in the face of ongoing global warming requires study of the plant fossil record and a predictive time framework. In this region, palynology is the best biostratigraphic tool because palynomorphs are the most abundant fossils. To construct a biostratigraphic zonation for the Neogene of the Solimões/Amazon basin in northwestern Amazonia, we analyzed palynological information from 25 sections, a total of 143,411 palynomorph grains from 622 samples. Using graphic correlation, we propose seven palynological zones that comprise the Miocene and a portion of the Pleistocene—the Pliocene is absent in the region. We then calibrated these zones against the geological timetable through correlation with a previous calibrated zonation and U/Pb geochronology.

Global correlation of the Guadalupian–Lopingian transition and associated events using a quantitative conodont-based biostratigraphic scheme

The Guadalupian–Lopingian boundary (GLB) interval contains global-scale changes in biota and environment. The establishment of a uniform time scale and a robust system of global correlation are critical in order to unravel the tempo of these events. Conodonts are key biostratigraphic tools; however, major discrepancies exist in conodont taxonomy and correlation in this interval. In this paper, we compile conodont data from 17 well-studied sections in South China, Japan, Oman and North America, comprising 206 occurrences and 100 species, based on previous publications and our own revisions, to test the reproducibility and correlation value of formerly established interval zones. The Unitary Association method (UAM), a quantitative stratigraphic method for the construction of biozones, is applied to construct a robust conodont biozonation for the GLB. Eleven unitary associations (UAs) and eight unitary association zones (UAZs) are recognized to establish biozones and the GLB was constrained within the UAZ5. According to the reproducibility of these UAZs, the correlation of the Lopingian is generally better than the Guadalupian. Apparent contradictions revealed by the UAZs suggest that biostratigraphic and/or taxonomic issues are present within the Clarkina liangshanensis, C. leveni, C. transcaucasica interval zones. The interval between UAZ4 and UAZ5 records the conodont turnover event from Jinogondolella to Clarkina in the paleoequatorial region. Our results suggest that the UAZs are more reliable for correlation. By contrast, some taxonomic and phylogenetic issues are present in the interval zones based on the conodont succession around the GLB. Although at a coarser stratigraphic resolution, removing all the contradictions enables UAZs to better correlate global sections compared with interval zones. The newly established UAZs indicate that the previously reported isotope excursions around the GLB in different regions may be temporally inconsistent.

Chitinozoan response to the ‘Kellwasser events’: population dynamics and morphological deformities across the Frasnian–Famennian mass extinction

AbstractFossil (zoo)plankton dynamics during Devonian ocean‐anoxic and extinction events can shed light on the palaeoceanographic and geochemical processes that shaped the middle Palaeozoic biosphere. However, datasets on (Upper) Devonian marine palynology, illustrating such dynamics, remain underexplored. The type section of the Sweetland Creek Shale in Iowa (USA) offers a detailed conodont zonation for the upper Frasnian and across the Frasnian–Famennian boundary, records the Upper and Lower Kellwasser events and has pristine preservation of organic material, making this an ideal section to study the effects of this catastrophic event on chitinozoan zooplankton populations. A total of 3998 specimens were recovered, imaged and classified into 12 distinct species, 10 of which were previously unknown. This study demonstrates the unrealized potential of chitinozoans as a regional biostratigraphic tool in the Upper Devonian. The Lower Kellwasser Event is characterized by a drop in chitinozoan abundance and the run up to the Upper Kellwasser Event marks a period of rapid species turnover rates. Interestingly, every assemblage in this interval is nearly monospecific. Patterns of changing spine morphologies in Fungochitina pilosa, Ramochitina sp. A and Saharochitina sp. A are herein explored as potential ecophenotypic expressions. We identify Angochitina monstrosa as a new disaster species. The discovery of two teratological chitinozoans specimens, in combination with the presence of the disaster species Angochitina monstrosa and deformation in contemporaneous conodonts, supports our previous discovery that marine teratology is a feature of many Palaeozoic extinction events, possibly triggered by the injection of hydrothermal brines into the ocean.

DINOSTRAT version 2.1-GTS2020

Abstract. DINOSTRAT version 2.1-GTS2020 is now available (https://doi.org/10.5281/zenodo.10506652, Bijl et al., 2024b). This version updates DINOSTRAT to the Geologic Time Scale 2020, and new publications are added into the database. The resulting database now contains over 9450 entries from 209 sites. This update has not led to major and profound changes in the conclusions made previously. DINOSTRAT allows full presentation of the first and last stratigraphic occurrences of dinoflagellate cyst subfamilies and families, as well as the evolutionary turnover throughout geologic history, as a reliable representation of dinoflagellate evolution. Although the picture of dinoflagellate evolution from DINOSTRAT is broadly consistent with that in previous publications, with DINOSTRAT the underlying data are openly available, reproducible and up to date. This release of DINOSTRAT allows calibration of stratigraphic records to the Geologic Time Scale 2020 using dinoflagellate cysts as a biostratigraphic tool.

First record of Pridolian graptolites from South America: Biostratigraphic and paleogeographic remarks

Graptolites were planktonic organisms that constitute one of the essential biostratigraphic tools used in Paleozoic successions worldwide. Notably, Pridolian (upper Silurian) graptolites have been globally recognized in several geological units, but completely absent from South American sections until now. This study introduces the first Pridolian graptolite assemblage in this subcontinent. The Rinconada Formation, from the Eastern Precordillera of San Juan Province, Argentina, has an abundant fossil content that includes: graptolites, brachiopods, bivalves, trilobites, corals, plant remains, and microfossils. Two graptolite taxa have been identified and described, including Skalograptus parultimus (Jaeger) and cf. Enigmagraptus. Both genera are mentioned for the first time in South America. As a result, the S. parultimus Biozone is recorded from the upper outcropping levels of the Rinconada Formation at its eponymous section, indicating an early Pridolian age. This discovery represents the first mention of Pridolian graptolites for South America, and increases the knowledge about the graptolite content of the studied formation as well. In addition, the assemblage might represent the faunal recovery interval after the Kozlowskii-Lau Event, a globally recorded episode of biotic crisis. The co-occurrence of graptolites and plant remains within the same stratigraphic levels in the Rinconada Formation represents the first and oldest record in western Argentina. Finally, the age of the Rinconada Formation is reviewed, and a local, regional, and global correlation is proposed with several Pridolian sections around the globe.

Quantitative biostratigraphy of Upper Albian to Lower Cenomanian (Cretaceous) calcareous nannofossils of mid-latitude regions

Late Albian - early Cenomanian calcareous nannofossil assemblages from five mid-latitude localities (23-35 degrees) were analyzed using probabilistic and deterministic methods to produce comprehensive and quantitative biostratigraphic sequences that were compared to the widely used 'CC' and 'UC' calcareous nannofossil zonation schemes. This was done to examine their fidelity and general applicability for mid-latitude biostratigraphy and determine whether these quantitative methods can increase the resolution of said schemes. Four biozones spanning the upper Albian through middle Cenomanian were determined using unitary associations (UAs) and ranking and scaling (RASC) optimum sequence from which last appearance datum (LAD) of – Gartnerago stenostaurion, first appearance datum (FAD) – Lithraphidites eccentricus, and LAD – Staurolithites mutterlosei were determined to be reliable early Cenomanian markers at mid-latitudes, while the FAD and LAD of Calculites anfractus are unreliable bioevents and should not be used as a secondary marker for the Albian - Cenomanian boundary. In addition, we have revised the stratigraphic position of the FAD of L. eccentricus, which was previously assigned to the middle-Cenomanian. The proposed FAD was shortly after the Albian - Cenomanian boundary, before the FAD of Corollithion kennedyi. We conclude that UAs are more robust than RASC bioevents for this time sequence; however, both methods do not account for the asynchronicity of depositional and biotic chances. Despite these caveats, combining the results for both methods has proven to be a powerful quantitative biostratigraphic tool.

Emended Sandbian (Ordovician) conodont biostratigraphy in Baltoscandia and a new species ofAmorphognathus

AbstractConodonts are an important biostratigraphic tool for many Phanerozoic stages. Along with graptolites, they define all global Ordovician Stage boundaries. Within the Upper Ordovician interval, a known species ofAmorphognathus tvaerensis(Bergström) is present in both Sandbian and Katian stratotype sections. Study of changes in the succession ofA. tvaerensisrevealed that elements in the upper part of its range differ morphologically quite distinctly from those in its lower part. Here, they are described as a new conodont species,A. viiraesp. nov. This new species is recognized in several Estonian and Swedish sections, with apparent occurrence also in Mójcza Quarry, Holy Cross Mountains, Poland and Black Knob Ridge, Oklahoma, USA. Detailed analysis of earlyAmorphognathuselements from Estonian and Swedish sections revealed the absence ofA. inaequalis(Rhodes) in both regions, although a conodont subzone based on this species was identified earlier by some authors. Both the absence ofA. inaequalis(Rhodes) and recognition of the new speciesA. viiraesp. nov. resulted in the revision of the conodont zonation, and a new version of it is proposed for the Sandbian Stage in the Atlantic Realm. The new zonation includes (from below)Pygodus anserinus,Baltoniodus variabilis,A. tvaerensis,B. gerdae,A. viiraeandB. alobatusConodont zones.

Frans Florschütz as founding father of pollen analysis in the Netherlands, and expansion of palynology into the tropics

Frans Florschütz (1887‒1965) developed pollen analysis in the Netherlands as a biostratigraphical tool on the interface between geology, palaeobotany, soil science and climate history. He was involved in agricultural practice and the building of large infrastructure. Florschütz established centres of pollen analysis at the universities in Wageningen (1924) and Utrecht (1928), was appointed professor in Leiden (1948) and after retirement founded a chair in pollen analysis in Nijmegen (1960). The botanical institute in Utrecht was Florschütz’ alma mater where he supervised students over two decades. Since 1947 Florschütz trained micropalaeontologists how to use fossil pollen as a biostratigraphical tool in oil industry. He inspired Jonker in Utrecht and Zagwijn in Leiden. Several of his students focused on tropical areas and used applied and academic pollen analysis to explore tropical ecosystems, such as Polak (1930s) and Muller (1950s) in southeast Asia, Van Zinderen Bakker (1950s) in southern Africa, Van der Hammen (1950s) in northern South America, Van Zeist and Bottema (1960s) in the Middle East. He stimulated Shell to be a pioneer in using pollen-based stratigraphy in oil exploration in the tropics. In the late 1940s and 1950s biostratigraphers Germeraad, Hopping, Kuyl, Muller and Waterbolk studied samples from the Caribbean, Nigeria and British Borneo in Shell’s Pollen Laboratories in Maracaibo (Venezuela) and in The Hague. In 1944 ‘pollen analysis’ was renamed ‘palynology’ for good reasons. Laboratory practice in applied research developed differently from academic palynology leading to a hybrid research field. Implications are briefly discussed.

Interpretation of Depositional Environment of Fusulinid Bearing Middle Permian Succession of Bolula and Khaja Ghar Formation, Bamian Zone, Central Afghanistan

The study area belongs to the north Afghanistan having complex tectonic setting, because of separation of the Afghanistan plate from Pangea in Early Permian and its subsequent northward journey and collision with Eurasian plate. The rock exposed in the area belongs to Paleozoic, Mesozoic to Quaternary with Proterozoic basement. Particularly the Permian succession of Afghanistan is rich in fusulinids (larger foraminifera), is age diagnostic, provides strong biostratigraphic tool for the Permian deposits, and has paleobiogeographic applications. The Bamian zone of north Afghanistan has good exposure to Middle Permian and is designated as Bolula and Khaja Ghar Formation is undertaken in this study. The Bolula Formation overlies the greenschist and basalts, composed mainly of carbonate rocks (Dolostone and limestone), having massive limestone, with some quartz and secondary calcite vein in the succession. The intermittent siliciclastic wedges within the carbonate succession are identified as input within the platform with tectonic pulses in the hinterland. Bolula and Khaja Ghar succession is divided into 8 lithofacies ( Facies A to H) and 6 carbonate Facies viz. Sparry calcites limestone, Micritic limestone, Fossiliferous limestones (Biomicrite), Peloidal limestone (Fecal pellets), Interlaminated micritic and sparite limestone, and sandy limestone (micritic). The Bolula and Khaja Ghar Formation in the Bamian area have deposited in a shallow marine shelf environment because of predominance of carbonate rocks and presence of shallow-water marine fossils including fusulinids, small benthic foraminifera, algae, bivalve, brachiopods fragments, corals and bryozoans, etc. In the Bamian zone the unconformity between Upper Carboniferous and Lower Permian; indicates extensive gap in sedimentation, traceable to many parts of Afghanistan as unconformity or tectonic contact is considered here as sequence boundary.

Diverse vase-shaped microfossils within a Cryogenian glacial setting in the Urucum Formation (Brazil)

Vase-shaped microfossils (VSMs) attributed to testate amoebae occur globally in diverse assemblages in Tonian rocks. These microfossils have thus been considered a potential biostratigraphic tool, especially for the interval between 789 and 729 Ma. Here we report a diverse and well-preserved in situ VSM assemblage, including several taxa previously considered as Tonian, within glacially influenced deposits for which sedimentological data support a Cryogenian age. However, the more robust recent multi-proxy correlation proposed by Freitas et al. (2021) indicates a Marinoan age for the studied succession. Detrital zircon data provide a maximum depositional weighted mean age of 749 ± 3 Ma for the VSM-bearing, organic-rich, fine-grained deposits within the Marinoan sequence in the Urucum Formation. Nine taxa are described from the fine-grained deposits in the upper Urucum Formation, Jacadigo Group, Brazil: Cycliocyrillium simplex, Bonniea dacruchares, Bonniea pytinaia, Bombycion micron, Limeta lageniformis, Palaeoarcella athanata, Trigonocyrillium horodyskii, Pakupaku kabin and cf. Taruma rata. The discovery of well-preserved in situ VSMs attributable to specific Tonian taxa within a Cryogenian succession challenges previous thinking that these organisms disappeared from marine ecosystems at the end of the Tonian.

Dextral to sinistral coiling switch in planktic foraminifer Morozovella during the Early Eocene Climatic Optimum

Coiling direction is a basic characteristic of trochospiral planktic foraminifera. Modifications in the coiling direction within ancient planktic foraminiferal populations may reflect important changes in evolution or environment, yet they remain scarcely discussed. Here we investigate fluctuations in the coiling direction within Morozovella assemblages from sections that span the interval of peak Cenozoic warmth, the Early Eocene Climatic Optimum (EECO; ~53–49 million years ago, Ma), at Atlantic Ocean Drilling Program (ODP) sites 1051, 1258 and 1263. The surface-dwelling genus Morozovella is of particular interest because it dominated tropical-subtropical early Paleogene assemblages then suffered an abrupt and permanent decline in abundance and taxonomic diversity at the start of the EECO. At all ODP sites, morozovellids display a dominant dextral coiling preference during the interval preceding the EECO. However, all the Morozovella species at all sites modify their coiling from preferentially dextral to sinistral coiling within the EECO, <200 kyr after the K/X event (~52.8 Ma), providing a new biostratigraphic tool for correlation. We also document that before the major shift in morozovellid coiling, transient excursions to higher abundances of sinistral tests occurred in conjunction with negative carbon isotope excursions. Significantly, carbon isotope data reveal that sinistral morphotypes belonging to the same morphospecies typically have lower δ 13 C values. The dominance of sinistral morphotypes, at the expense of dextral forms within the EECO, coupled with the lower δ 13 C signatures of the former, suggests that the sinistral forms were less dependent on their photosymbiotic partnerships and thus able to adapt more readily to paleoceanographic change at the EECO. The observed sinistral and dextral coiling of morozovellids can be a genetically heritable characteristic that lies within cryptic speciation across multiple morphologically defined species. Alternatively the coiling changes were exclusively ecophenotypic responses whereby different species were able to preferentially adopt sinistral coiling in reaction to the changed conditions in the mixed-layer during the EECO. Previous interpretations of coiling flips in planktic foraminifera in the early Eocene, especially including morozovellids, have favoured a genetic explanation rather than an ecological response. Our present data cannot validate or disprove this idea, but should stimulate renewed thought on the matter. • Coiling data on Morozovella species are presented from three widely separated Atlantic Ocean Drilling Program sites. • Morozovella switch from dextral to sinistral coiling direction across the Early Eocene Climatic Optimum. • Changes in coiling direction occurred in multiple morphologically distinct species. • Carbon isotopes indicate dextral and sinistral morphotypes differ in their ecology. • Sinistral morphotypes were less dependent on photosymbiosis and thus able to adapt more readily to paleoceanographic change.

Diversification of heterotrophic protists at the eve of Cambrian explosion

Molecular clocks suggest that at least some heterotrophic protists, such as foraminifera, testate amoebae and tintinnids, were present in ecosystems as far back as 1000 Ma. Vase-shaped microfossils of earlier testate amoebae from the supergroups Amoebozoa and Rhizaria occur globally in pre-Sturtian shallow marine deposits, and have thus been considered as a potential biostratigraphic tool, especially at a time span between 789 and 729 Ma. Organic-rich three-dimensional tests having flask-like shapes, constricted necks, distinct and often thickened collars of possible tintinnids affinity were recovered from 715 to 635 Ma carbonate deposits from the Tsagaan Oloom Formation, southwestern Mongolia. Phosphatic scaly structures of unknown affinity were reported from mid-Neoproterozoic (pre-Sturtian) strata of northwest Canada. Anyhow, the fossil records of heterotrophic protists aftermath the Cryogenian age are still shroud in mist. The three putative ciliate fossils, namely Eotintinnopsis, Wujiangella, and Yonyangella from the Neoproterozoic Doushantuo Formation in China were reassessed and likely to be taphonomically and diagenetically distorted and altered acritarchs. Here, we report a diverse assemblage of problematic from the terminal Ediacaran Gaojiashan biota in southern Shaanxi Province, China. Apart from the renowned vase-shaped Protolagena and Sicylagena, likely thought to be the earliest foraminifera, new findings include a hollow pear-shaped structure with long extending, a solid spindle-shaped structure with straight narrow central tube. Possible foraminifera from the Gaojiashan biota may throw welcome new light to the long obscured history of heterotrophic protists at the eve of the Cambrian explosion.

Discovery of a new Lower Cretaceous Wealden-type ostracod fauna from the Bouhedma Formation, Central Tunisian Atlas, North Africa

Micropalaeontological investigations of the Bouhedma Formation in the Jebel Majoura section from the southern Central Tunisian Atlas revealed four successive ostracod associations (in total 16 species of 13 genera) of higher palaeoenvironmental, and thus far limited biostratigraphic and palaeobiogeographic utility due to poor preservation. The most notable of these is a new upper Hauterivian?–Barremian non-marine Wealden-type ostracod assemblage of high diversity from the Lower Member of the Bouhedma Formation, the first one documented from the southern Central Tunisian Atlas, which consists of 9 species: Cypridea cyrtorostralis, Cypridea aff. tenuis, Cypridea aff. insulae, Cypridea sp., Theriosynoecum cf. fittoni, Vecticypris polita, Alicenula? leguminella, as well as Klieana sp. and Fabanella sp. The subsequent two ostracod assemblages from the Lower Member are characterized by the brackish species Rehacythereis? sp., Fabanella sp., Ilyocypris sp., and Schuleridea? sp. indicating transition to lagoonal environment. The subsequent ostracod assemblage from two levels of the Middle Member of the Bouhedma Formation is exclusively composed of the euryhaline marginal marine Paracypris sp., and the marine species Antepaijenborchella praealta, Protocythere cf. bedoulensis and Metacytheropteron aff. grosdidieri, reflecting a marine incursion event.The biostratigraphic utility, particularly that based on the non-marine fauna, is limited thus far but the results are consistent with an upper Hauterivian?–Barremian age previously assigned to the Bouhedma Formation from the southern Central Tunisian Atlas, facilitating its regional stratigraphic correlation with coeval series from the northern part of this palaeogeographic domain.The discovery of Tunisian Wealden-type non-marine ostracods from the southwestern margin of the Tethys (North Africa) sheds new light on the dispersal patterns and palaeobiogeography of these ostracods, their potential utility as biostratigraphic tool, as well as on the significance of the north Gondwanan continental basins and peri-Tethyan islands of the Central Tunisian Atlas for recording Early Cretaceous non-marine microfaunas and -floras.

Carboniferous macrofloral biostratigraphy: an overview

Abstract In the Carboniferous, terrestrial vegetation became widespread, diverse and abundant. The resulting fossil record has proved to be an effective biostratigraphic tool for intra- and interbasinal correlations. Besides palaeogeographical configurations, Carboniferous plant biostratigraphy is affected by a transition from greenhouse conditions during most of the Mississippian to an icehouse climate in the Pennsylvanian. The greenhouse Mississippian climate resulted in weak provincialism, with a cosmopolitan flora ranging from the tropics to middle latitudes. The global cooling around the Mississippian–Pennsylvanian boundary enhanced development of a latitudinal climatic zonation and related floral provincialism. These changes are expressed in the recognition of distinct realms or kingdoms, where the tropical Amerosinian Realm (or Euramerican and Cathaysian realms) is surrounded by the Angaran and Gondwanan realms occupying middle to high latitudes of the northern and southern hemispheres, respectively. Floristic endemism in the Pennsylvanian precludes development of a global macrofloral biostratigraphy. Instead, each realm or area has its own biostratigraphic scheme. Poorer and less diverse floras of the Gondwanan and Angaran realms resulted in the establishment of relatively low-resolution macrofloral biostratigraphic schemes. Higher-resolution macrofloral zonations exist only in the tropical Amerosinian Realm due to diverse and abundant floras dominated by free-sporing and early seed plants occupying extensive wetlands.

Diversity and biostratigraphy of the late Oligocene-late Miocene sand dollars (Echinoidea: Scutelliformes) of Argentina and Uruguay

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: “Iheringiella” sp. A is restricted to the late Oligocene, the genera Camachoaster and “Eoscutella” and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed “Monophoraster and Venericor Beds”. Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.

Middle to Late Paleocene larger benthic foraminifera from the Sirt Basin (Libya)

The Sirt Basin of Libya hosts significant hydrocarbon reservoirs in Paleocene shallow-marine carbonates (Upper Sabil Formation) with abundant larger benthic foraminifera. Benthic foraminifera proved to be an essential biostratigraphic tool for precise biostratigraphic dating of these carbonate platform/ramp deposits. A detailed systematic description of the Middle to Late Paleocene larger benthic foraminifera from the Sirt Basin is presented, which refines the biostratigraphic age of the Paleogene shallow-marine carbonates. Eight taxa are identified at a species level. Among them, Ranikothalia solimani is the most important taxon for the correlation of the Upper Sabil Formation. The taxa Miscellanea yvettae, Miscellanites primitivus, and Glomalveolina primaeva with co-occurrence of orthophragminid foraminifera constrain the age of the Upper Sabil Formation as Middle to Late Paleocene (Selandian-Early Thanetian).

Successive first downhole sporomorph-events: Applied biostratigraphic tool for fault delineation within Baharyia Formation, Abu Sennan area, Abu Gharadig Basin, Egypt

Two hundred and seventy four samples, covered the Bahariya sections encountered in 13 boreholes, drilled in three main fields of the General Petroleum Company concession, Abu Gharadig Basin, north Western Desert, were critically investigated for their palynomorphs content. A standard acid-based palynological processing technique is employed to extract the palynomorphs. Fair to moderate diversity and moderate to good preserved palynomorph assemblage has been recovered. This study yielded 107 species of spores, pollen grains and dinoflagellate cysts. Six remarkable successive first downhole appearance (FDA) sporomorph-events are defined and biostratigraphically utilized for dividing the Bahariya Formation and delineating the Bahariya/Kharita contact. The upper Bahriya unit includes the first Afropollis jardinus event dated latest early Cenomanian, while the middle Bahriya unit comprises the second Elatersporites klaszii event dated early Cenomanian. The lower Bahriya unit, dated early Cenomanian-late Albian, contains the third, fourth, and fifth Cretaceieporites densimurus, Trilobosporites laevigatus and Stellatopollis sp. events, respectively. The contact between Bahriya Formation and the upper part of the underlying Kharita Formation, dated early-middle Albian, is placed on Concavisimisporites punctatus event. The authors found the possibility of these six zones to be widely traced and provide potential bio-correlation tool for the Bahariya sections in Abu Gharadig Basin. According to the presence or absence of such six successive events and their average zonal thicknesses, the intra-formational disconformities and positions of the faults could be allocated with confidence. The remarkable thinning in the thickness of such zones could localize the position of disconformities caused by non deposition or erosion/faulting within the Bahariya sections. The aforementioned six events could be correlated and nicely matched with their equivalent six log-based cycles on the log responses. The authors encourage the Egyptian industrial geologists to follow the presented successive six sporomorph-events in the future palynological-steering exploration and production activities in the Bahariya rock unit and effectively utilize such events as intra- and inter-basinal dating tool and possible correlation control for the Bahariya sections across the northern basins of Egypt.

The ammonites of the Les Ferres Aptian Basin (Lower Cretaceous, Southeast of France): the genus Toxoceratoides (Ancyloceratina, Helicancylidae)

Toxoceratoides (Ancyloceratina, Helicancylidae) is a lower Aptian (Lower Cretaceous) small heteromorph ammonoid mainly known by small samples of fragmentary specimens. In the present work, we study a sample of 145 specimens of this genus from the Deshayesites forbesi, Deshayesites deshayesi and Dufrenoyia furcata zones (lower Aptian) of the vicinity of the village of Les Ferres (southeastern France). The taxa recognized (in stratigraphic order) are: Toxoceratoides sp., Toxoceratoides royerianus (d’Orbigny, 1842) and Toxoceratoides rochi Casey, 1961. Their ontogenetic sequence is described; the intraspecific variability of Toxoceratoides rochi is considerable and it concerns adult size, coiling, duration of the ontogenetic stages and ornamentation. No sexual dimorphism is recognized. The main evolutionary pattern of the genus consists in the replacement of primitive ribs (here named ‘royerianus ribs’) by derived ribs (‘rochi ribs’) on the flexus and retroversum. The genus Toxoceratoides could be used as a biostratigraphic tool.

Two new species of &amp;lt;i&amp;gt;Mennerotodus&amp;lt;/i&amp;gt; Zhelezko, 1994 (Chondrichthyes: Lamniformes: Odontaspididae), from the Paleogene of the southeastern United States

Abstract. Mennerotodus Zhelezko, 1994, is an extinct lamniform shark known to occur in Paleogene strata of the Tethyan region of Asia and Europe. Although only a single species has been named, multiple subspecies have been erected and used as biostratigraphic tools in Asia. The genus has not been reported with confidence outside of the Tethyan region, but we have identified two new species of Mennerotodus from Paleogene deposits of the southeastern United States. Mennerotodus mackayi sp. nov. is described by teeth occurring in the lower Paleocene (Danian Stage) Pine Barren Member of the Clayton Formation of southern Alabama. A middle Eocene (Bartonian) species, Mennerotodus parmleyi sp. nov., is based on material occurring in the Clinchfield Formation in central Georgia. The early Paleocene record could indicate a North American origin for Mennerotodus relatively soon after the K–Pg event, with subsequent radiation to other parts of the world. The genus is likely more widely distributed than is currently known, but teeth can easily be overlooked due to their similarity to other taxa.

Anaerobic metabolism of Foraminifera thriving below the seafloor

Foraminifera are single-celled eukaryotes (protists) of large ecological importance, as well as environmental and paleoenvironmental indicators and biostratigraphic tools. In addition, they are capable of surviving in anoxic marine environments where they represent a major component of the benthic community. However, the cellular adaptations of Foraminifera to the anoxic environment remain poorly constrained. We sampled an oxic-anoxic transition zone in marine sediments from the Namibian shelf, where the genera Bolivina and Stainforthia dominated the Foraminifera community, and use metatranscriptomics to characterize Foraminifera metabolism across the different geochemical conditions. Relative Foraminifera gene expression in anoxic sediment increased an order of magnitude, which was confirmed in a 10-day incubation experiment where the development of anoxia coincided with a 20–40-fold increase in the relative abundance of Foraminifera protein encoding transcripts, attributed primarily to those involved in protein synthesis, intracellular protein trafficking, and modification of the cytoskeleton. This indicated that many Foraminifera were not only surviving but thriving, under the anoxic conditions. The anaerobic energy metabolism of these active Foraminifera was characterized by fermentation of sugars and amino acids, fumarate reduction, and potentially dissimilatory nitrate reduction. Moreover, the gene expression data indicate that under anoxia Foraminifera use the phosphogen creatine phosphate as an ATP store, allowing reserves of high-energy phosphate pool to be maintained for sudden demands of increased energy during anaerobic metabolism. This was co-expressed alongside genes involved in phagocytosis and clathrin-mediated endocytosis (CME). Foraminifera may use CME to utilize dissolved organic matter as a carbon and energy source, in addition to ingestion of prey cells via phagocytosis. These anaerobic metabolic mechanisms help to explain the ecological success of Foraminifera documented in the fossil record since the Cambrian period more than 500 million years ago.