Palaeontological Data Research Articles

The Cretaceous of the Spanish Central System: A review of the lithostratigraphy, palaeontology and sequence stratigraphy, including new educational perspectives

The Southern Cretaceous of the Central System is formed by both terrigenous and carbonate rocks that have been affected by intense dolomitization. They are part of the sediments deposited on the western margin of the Iberian Basin during the Cenomanian–Maastrichtian, the depositional architecture of which has been reconstructed through a detailed sequence stratigraphical study and analysis of its fossil record. It is formed by three large transgressive-regressive cycles in which the carbonate platform moves towards the West, while the terrigenous facies of its base decreases and the overlying clay facies, with gypsum, increases. The integration of sedimentological and palaeontological data, and the identification of a set of parasequences has allowed the differentiation of thirteen depositional sequences. This research has been essential to carry out modern geological mapping and provide society with a model that improves the economic geology and geotechnical exploration of these areas. Furthermore, this scientific progress has also impacted on the interest of society towards the geosciences and, specially, palaeontology. This has widened the scope for new research fields related to scientific outreach for the community and learning opportunities at different educational levels.

A new labiduroid earwig from mid-Cretaceous Kachin amber (Dermaptera: Labiduroidea)

The earwig family Labiduridae occupies a putatively important position in the phylogeny of Dermaptera and is clearly of significant antiquity, with occurrences from the mid-Cretaceous and perhaps the Early Cretaceous. Nonetheless, palaeontological data on the family remains scant. Here we report a new genus and species of labidurids from mid-Cretaceous Kachin amber. Metaxylabis baii gen. et sp. nov. is described and figured, and its characters are compared with those of all other Mesozoic Labiduridae. The genus can be excluded from all of the current subfamilies of Labiduridae and is placed in its own subfamily, Metaxylabidinae subfam. nov. Remarks are given on the phylogenetic affinities of Mesozoic fossils and the need for more extensive sampling of palaeontological and genomic data.

Shallow-water whale-fall communities: Evidence from the middle–late Eocene basilosaurid whale bones, Wadi El-Hitan, Fayum, Egypt

The present study examines the basilosaurid whale bone specimens collected from the Sandouk El-Borneta section, Wadi El-Hitan (Valley of Whales), Fayum, Egypt. These specimens are embedded in highly fossiliferous calcareous sandstones of the middle Eocene Gehannam and the upper Eocene Birket Qarun formations. These whale bones display some post-mortem alterations, representing good signs of at least three distinct stages in what is called the whale fall. The co-occurrence of shark, ray, and crocodile fossil specimens with the examined whale bones may indicate the first mobile-scavenger stage. Borings of the siboglinid polychaete genus Osedax represent the most common worm type that deeply bioeroded the whale bones, contributing to their rapid degradation, and representing the enrichment-opportunist stage. These fossil traces of the bone-eating worm Osedax represent the first record in the Eocene Epoch regionally and inter-regionally, filling the gap between the Late Cretaceous and the Oligocene occurrences. Subsequently, the studied whale bones served as hard substrates for some calcareous tube-dwelling encrusting polychaetes, balanoid barnacles, sheet‐like cheilostome bryozoans, and scleractinian corals. Furthermore, a bioerosion structure produced by polychaete annelids was also observed. The presence of these sclerobionts assemblage confirms the well-developed final reef stage with prolonged exposure and colonisation of these whale bones prior to final burial. Based on the recorded post-mortem alterations, together with other sedimentological and palaeontological data, the studied whale bones were deposited in a shallow open marine bay to sheltered gulf environments, which were characterised by low depositional energy, low to moderate rate of sedimentation, and high surface water productivity.

Testing alternative tectonic models for the Permian-Pleistocene tectonic development of the Kyrenia Range, N Cyprus: Implications for E Mediterranean Tethyan palaeogeography

Three published alternative tectonic models of the Permian-Pleistocene development of the Kyrenia Range, N Cyprus are tested, supported by new field, geochemical and micropalaeontological evidence: 1. The Kyrenia Range represents the northern continental margin of the S Neotethys, close to its present relative position. The range initiated as a Permian-Cretaceous rift/passive margin, switching to a N-facing active margin during Late Cretaceous-Neogene; 2. The Range was located along the N African continental margin until the Neogene when northward subduction transferred it to the southern margin of the Eurasian plate; 3. The Range is a far-travelled allochthon that was emplaced to near its present position, probably during the Eocene.In the light of regional comparisons, especially with southern Turkey, the combined evidence mainly supports tectonic model 1. Sedimentary and palaeontological data show that the restored stratigraphy of the Kyrenia Range indicates Late Permian initial rifting and Early-Middle Triassic advanced rifting, followed by Jurassic-Early Cretaceous passive margin subsidence. Small exposures of ophiolite-related melange located between the Mesozoic carbonate platform and the overlying latest Cretaceous-Palaeogene deep-water volcanic-sedimentary succession include evidence of HP/LT metamorphism, pointing to Late Cretaceous subduction. MORB/boninites, diabase-gabbro and extensive harzburgitic serpentinite originated as a SSZ ophiolite, together with a possible high-grade metamorphic sole (garnet amphibolite) and an accretionary prism (E-MORB/OIB; metachert). Microfossil evidence indicates exhumation of the melange and the underlying platform prior to Late Maastrichtian. A mass-transport complex formed within a compression-related foredeep during the Middle Eocene. Associated southward thrusting and folding culminated in emergence and subaerial erosion, generating a major unconformity, that was followed by subaerial and then marine deltaic deposits (Late Eocene-Oligocene). Following major Late Miocene southward thrusting, uplift of the Kyrenia Range took place during the Pleistocene, related to collision of the leading edge of the North African plate (Eratosthenes Seamount) with the Eurasian (Anatolian) plate.

The biostratigraphy and palaeobiogeography of Cambrian and Ordovician acritarchs and chitinozoa from the Simeh-Kuh, NW Damghan City, the Alborz Mountains, northern Iran

A study in Simeh-Kuh, northern Iran, focuses on Ordovician strata, documenting acritarchs and chitinozoa, and has helped to understand ancient environments. The aim is chronostratigraphical calibration, using palaeontological data including brachiopods, trilobites, and graptolites. Ninety-three surface samples were collected and analysed, yielding a rich collection of 117 morphotypes, including 59 acritarch species and 58 chitinozoan species. Eight acritarch assemblage biozones (A–H) and 14 chitinozoan biozones (1–14) were established. Biozones A–F indicate Late Cambrian to Middle Ordovician ages in the Lashkarak Formation, while biozones G–H indicate the Late Ordovician in the Ghelli Formation. The Eremochitina brevis-Linochitina pissotensis biozones suggest late Floian to late Darriwilian ages, and the Belonechitina robusta-Armoricochitina nigerica biozones support a Late Ordovician age. These findings place the Alborz Mountains in the North Gondwana Domain during the Ordovician. Palynomorphs with a thermal alteration index of 4.0–4.5 indicate overmature organic matter in Lower Palaeozoic deposits, potentially linked to the Ordovician metamorphic event in the southern Caspian Sea. Additionally, four new species were identified: Cyathochitina sp. A, Tanuchitina hosseini-nezhadi sp. nov., Dactylofusa kazzazii sp. nov., and Inflatarium alborzensis sp. nov.

Bio-, Lithostratigraphic and Geochemical Markers of Global Events in the Upper Devonian of the South of Western Siberia and their Value for Inter-regional Correlations

Abstract —Upper Devonian carbonate reef complexes have been studied on the territory of the Kolyvan-Tom’ Folded Area in sections in the right bank of Tom’ River. Facies analysis of the exposed part of the reef complex indicates the predominance of fore-reef and continental margin depositional environments of a tectonically active margin. The identified conodont associations are represented by cosmopolitan representatives of the genera Ancyrodella, Ancyrolepis, Icriodus, Mehlina, Palmatolepis, Polygnathus and “Polylophodonta” suggesting a correlation with the punctata–jamieae, rhenana–linguiformis, triangularis and Lower crepida conodont zones. The largest conodont diversity occurs at the triangularis/crepida boundary. Biofacies analysis of ostracod distribution has led to identification of characteristic associations and their restriction to certain parts of the palaeobasin. Substage boundaries yielded ostracods with both smooth and ornamented shells. In the lower part of the substages, smooth forms predominate, whereas the middle and upper parts of the substages are characterised by forms with tuberculate and reticulated surface. Hollinella valentinae Beds were traced in the Upper Frasnian Solomino Formation, and Acratia granuliformis Beds were traced in the Lower Famennian Kosoy Utyos and lower Mitikha members. Isotope geochemistry of the Upper Devonian sections of the south of Western Siberia reveals Frasnian global events – the Middlesex/punctata and the Upper Kellwasser, their stratigraphic position confirmed by palaeontological data, as well as by the globally expressed negative carbon isotope anomaly. These boundaries are marked by changes in depositional regime reflecting sea-level eustatic fluctuations, which are complemented with faunal changes.

Genetic structure of southern populations of Hydrochoerus hydrochaeris (Rodentia: Caviidae)

Abstract The capybara (Hydrochoerus hydrochaeris) is a large semi-aquatic rodent with a broad distribution across South America. Although it is a relatively common and well-known species, there are few studies on its evolutionary history. Consequently, we decided to investigate the genetic diversity, population structure, and demographic history of capybaras, including new populations from its southern distribution range, by using a 226 bp fragment of the mitochondrial D-loop region. We found 16 haplotypes and populations, with moderate levels of haplotype and nucleotide diversity. In addition, the genetic structure analyses suggested high genetic divergence among populations, mainly among Pampean and Chacoan populations. We also found a consistent phylogeographical pattern with the distribution of main rivers. In agreement with palaeontological data, we propose two colonization pathways towards the south driven by main basins: Paraná–Paraguay and Uruguay–Atlantic.

Late Cretaceous (Cenomanian-Turonian) temperature evolution and biotic response in the Adriatic Carbonate Platform region of Friuli, northeast Italy

Climate modelling and palaeotemperature reconstructions derived from several proxies (TEX86, δ18O) suggest that the Late Cretaceous was one of the warmest intervals in Earth history. The greenhouse climate reached its acme near the Cenomanian-Turonian boundary (CTB) interval with sea surface temperatures over 35 °C in low and mid- palaeolatitudes, coinciding with the highest sea level stands of the Phanerozoic. Following this warming phase, a general cooling trend punctuated by short-term hot snaps characterized the rest of the Cretaceous. Palaeotemperature and palaeoenvironmental changes are well documented in deep-water carbonate deposits based on variations in geochemical proxies and distribution patterns of macro- and microfauna. However, such climatic and environmental fluctuations severely impacted carbonate platforms, sedimentary environments that are particularly sensitive to external perturbations. Palaeontological data show major changes within the main carbonate platform producers (rudists and benthic foraminifera) during the early Late Cretaceous. Both groups experienced major taxonomic turnovers at the CTB, followed by a further re-radiation in the middle/late Turonian. The lack of detailed palaeoclimatic reconstructions in shallow water carbonate succession hampers the possibility to investigate a possible causal relationship between temperature changes and faunal evolution. In this paper, we report integrated geochemical, sedimentological, and palaeontological data from the Adriatic Carbonate Platform (Friuli, north-east Italy). Benthic foraminifera biostratigraphy and isotope stratigraphy (δ13C and 87Sr/86Sr) were used to precisely constrain the stratigraphy of the late Cenomanian-middle Turonian interval. δ18O analysis on both well-preserved rudist shells and bulk rock samples enabled the construction of high-resolution palaeotemperature curves. The resulting temperature trends are comparable with those from the deep-water record across the late Cenomanian-Turonian interval. The warmest phase was in the Early Turonian with sea surface palaeotemperatures as high as 41–45 °C recorded in rudist shells. Data show temperature fluctuation from the late Cenomanian to the Early Turonian with a magnitude >7 °C. Benthic foraminifera and rudist evolution responded to these palaeotemperature fluctuations, and their decline in the late Cenomanian and full recovery in the Turonian suggest a strong link with temperature changes.

Upper Triassic (middle Norian) conodont biostratigraphy succession from Qamdo, eastern Tibet

The Late Triassic is a critical period that witnessed major biological and environmental events. The geographic range and taxonomic diversity of conodonts were significantly changed during the Late Triassic, with the geographic range contracting prior to complete extinction of the group near the end of the Triassic. In the present study, we recognize for the first time a continuous middle Norian (Upper Triassic) conodont succession from the Qamdo (Changdu) area, eastern Tibet (Xizang), which was part of the North Qiangtang and Qamdo-Simao Block (NQ-QSB) located in the northeastern Tethys Ocean during the Late Triassic. Four conodont zones are established from the middle Norian (Alaunian) of the Chaiwei section in Qamdo, and in ascending order these are: the Epigondolella spiculata Zone, the Orchardella elongata Zone, the Mockina postera Zone, and the E. serrulata Zone; the neighboring Tuoba section also records these four zones, in addition to the upper lower Norian (upper Lacian) Ancyrogondolella uniformis Zone. All of these zones (except for the M. postera Zone) have been recognized for the first time in eastern Tibet. The Lacian-Alaunian boundary is tentatively placed at the level of sample CW-3 at the Chaiwei section and at the level of sample TBL-36 at the Tuoba section by the first occurrence (FO) of E. spiculata in each section. The position of the Alaunian-Sevatian boundary (ASB) is uncertain since the conodont assemblage from the top of the Bolila Formation at the study sections lacks age-diagnostic elements. The conodonts recovered from the Qamdo area have not only dated the Bolila Formation but also refined the conodont biostratigraphic zonation of the Alaunian in the study area. This allows improved correlation between the faunas of Qamdo and their counterparts elsewhere in Tibet and Europe, although the conodont zonations from these regions display lower precision than those established from North America. The Alaunian conodont faunas at Chaiwei and Tuoba appear to be dominated by juvenile specimens; this often appears to be the case in the Alaunian of the Tethyan Realm, but seems not occur in North America. This may suggest that the conodonts living in these two realms may have inhabited different ecological environments. The faunal turnover around the Lacian-Alaunian transition, with the evolution of Epigondolella, Orchardella, and Mockina from Ancyrogondolella, can be recognized in both study sections, although it is more remarkable in the Tuoba section. Although the lack of previous detailed studies of Norian conodont biostratigraphy from Tibet hampers correlation in this region and beyond, this study demonstrates the possibility of establishing high-resolution conodont biostratigraphic successions from Tibet in the future, since the conodont faunas recognized from Tibet and adjacent areas (e.g., Baoshan) suggest that relatively complete Norian strata exist in these regions. Overall, this study also provides new data to improve our understanding of conodont evolution during the Alaunian, and is significant in providing palaeontological data for studying the palaeogeographic evolution of eastern Tethyan ocean basins in the Late Triassic.

How did submarine volcanic eruptions interact with organic matter to favour hydrocarbon generation in the Bohai Bay Basin, China?

ABSTRACT Based on the geological and geochemical analysis of volcanic rock and their surrounding rocks, combined with palaeontological data and hydrocarbon generation thermal simulation experiments, the mechanism of the impact of volcanic eruptions on the formation of organic matter and hydrocarbon generation in the Dongying Depression is investigated. According to the results, underwater volcanic eruptions play a significant role in promoting biological eruptions and water stratification by introducing heat, minerals, and metal elements. The formation of the basalt source rock symbiotic association went through three evolutionary stages, which were underwater eruption, late eruption, and normal sedimentation. These stages have influenced the generation of hydrocarbons from organic matter in the following ways: (1) The organic acid released from the source rock dissolves the adjacent basalt, and the transitional metal elements in the basalt become activated and enter the source rock, which catalyses the hydrocarbon generation from the source rock. (2) Alteration of olivine in basalt releases hydrogen, improving hydrocarbon generation efficiency of source rock. (3) The existence of a large number of carbonates improves the hydrocarbon generation rate and efficiency of source rocks and reduces the hydrocarbon generation threshold of source rocks.

Erratum to: The Neotectonics and Geological Structure of the Sevan Intermountain Basin (Armenia): New Structural and Palaeontologic Data

Erratum to: The Neotectonics and Geological Structure of the Sevan Intermountain Basin (Armenia): New Structural and Palaeontologic Data

Paleobiogeography of Lower-Middle Devonian Conulariids from southwest Gondwana

The bioregionalization of the Devonian fauna in southwest Gondwana has been extensively studied, focusing on the occurrences of brachiopods and trilobites, however, little attention has been given to Conulariids. The main goal of this paper is to propose a bioregionalization for the Conulariids (Conularia albertensis, C. quichua, C. sp., Paraconularia africana, P. ulrichana, and Reticulaconularia baini) from the Lower-Middle Devonian in southwest Gondwana. After a clustering analysis and diversity tests we have identified two distinct bioregions for Conulariids: the Amazon and southwest Gondwana, in the Amazon region the diversity is low, and can be attributed to scarcity of palaeontological data on the area. On the other hand, in the southwest Gondwana bioregion, diversity ranges from moderate to relatively high, which helps define a second-order bioregion, the Andeo-South Africa and Interior Gondwana. The first includes areas where diversity has higher values bordering southwest Gondwana (Bolivian Chaco-Peru, Zorritas-NOA-South Bolivia, South Africa and Malvinas areas). Further, in the Interior Gondwana bioregion are the Parnaíba (Parnaíba Basin), Alto Garças (north and northwest of Paraná Basin), Paraná (south of Paraná Basin, Uruguay and Paraguay) areas, where the diversity is slightly lower when compared to the Andeo-South Africa bioregion.

The Neotectonics and Geological Structure of the Sevan Intermountain Basin (Armenia): New Structural and Palaeontologic Data

The Neotectonics and Geological Structure of the Sevan Intermountain Basin (Armenia): New Structural and Palaeontologic Data

Can the intraspecific laws of variation be used as a predictive model for understanding species with insufficient data? The example of the early Heteroceratidae in their evolutionary context (heteromorph ammonites, Tethys upper Barremian)

The generalized ‘laws’ of intraspecific variability in ammonites are used as a predictive tool to define the limits of poorly known species of the early Heteroceratidae (Lazariniceras, heteromorph ammonites), based on the construction of the Heteroceras theoretical model of variation. The methodology is described and the model is confronted with the palaeontological data. The discussion of the results shows that the variability observed for Lazariniceras takes up most of the continuous variation of the theoretical model. To minimize bias, particular attention was paid to the strict stratigraphic control of the raw data (8 sections studied). Thus, and for the good application of the theoretical model, the stratigraphic canvas and the systematics of the groups studied were refined and discussed: (1) the abandonment of the Gerhardtia sartousiana Zone is proposed in favor of the new Camereiceras limentinum Zone; (2) Heteroceras astierianum, Heteroceras tardieui and Martelites bifurcatus are rehabilitated; and (3) Lazariniceras heterostylia sp. nov. and Lazariniceras lhaumeti sp. nov. are introduced while Lazariniceras astierianum is redefined. Once the theoretical model of the variation has been obtained, it was then possible to propose phylogenetic reconstruction hypotheses using the cladistic tool crossed with the stratigraphic data, used to study the evolutionary patterns and processes of the group. The results show that: (1) Lazariniceras is unambiguously a Heteroceratidae despite the absence of the early helical coiling; (2) Lazariniceras originates within the Toxancyloceras; (3) Ancyloceratidae is a paraphyletic taxon; (4) evolution of the studied group is expressed by changes in adult size, heterochronies and innovations.

‘A hard rain's a‐gonna fall’: torrential rain, flash floods and desert lakes in the Late Triassic Arden Sandstone of Central England

The Arden Sandstone Formation of central and western England is a thin but conspicuous arenaceous unit within the Late Triassic Mercia Mudstone Group. Sedimentological and palaeontological data point to lacustrine depositional conditions, in contrast to the red desert mudstones above and below which were deposited as continental dryland desert floodplains. The Arden Sandstone records deposits of the lake margins and may be the high stand lateral equivalent of the halite and gypsum deposits which formed in the lake centre. The Carnian age of the Arden Sandstone potentially links it to the Carnian Pluvial Episode, marking the coalescence, spread and freshening of the formerly saline desert lakes, and deposition of sandy, fluvial and lacustrine deposits, during the wetter climate that prevailed for at least a million years.

A Comment on: An Eocene army ant (2022) by Sosiak CE et al.

A Comment on: An Eocene army ant (2022) by Sosiak CE et al.

First record of tempestites from Quaternary lacustrine deposits in the Ağrı Basin (Eastern Anatolia, Türkiye): palaeoclimatological and palaeogeographic implications

Several event layers have been identified in lacustrine deposits in the AErI Basin of Anatolia (E Türkiye). Sedimentological and palaeontological data newly indicate a storm-induced origin for some of them. The sedimentary structures in three sections, a few tens of metres apart from each other laterally, such as hummocky cross-stratification, wave-generated cross-bedding, parallel bedding, erosional surfaces, and graded bedding, which are considered characteristic of tempestites, are clearly present. Additionally, fining-upwards units and biogenic escape structures located at different levels of these sections indicate a similar origin. The vertical variations in layer thickness, grain size, and sedimentary structures in these sedimentary sections indicate fluctuating hydrodynamic conditions during deposition, while lateral decrease in the size and wavelength of the structures reflects deepening. This interpretation of storm-induced deposition is compatible with regional palaeoclimatological and palaeogeographical data, and is supported by evidence of Quaternary storm-induced sedimentation in adjacent lacustrine basins in the region

Detecting Genuine Versus Pseudo-Absence in The Fossil Record: Applications of Occupancy Modelling For Conservation Palaeobiology

Palaeontological data provide a unique avenue to evaluate the impact of climatic, habitat and ecosystem change over longer temporal scales than typically examined in ecology and conservation, contributing critical data on extinction dynamics that can help contextualize the current biodiversity crisis. However, the fossil record is biased by a variety of factors. In particular, the issue of data absence causes a genuine concern when attempting to discern spatial patterns. Does the lack of a fossil occurrence indicate genuine absence or imperfect detection (i.e., pseudo-absence)? Failing to quantify, discern and mitigate both the main drivers and impacts of data absence will have major implications for any attempt to reconstruct past diversity dynamics, limiting the applicability of paleontological data for addressing questions pertaining to present-day biodiversity. Occupancy modelling, a technique commonly applied in the fields of ecology and conservation, provides a novel way to evaluate the impact of both spatial and temporal biases on the fossil record. By distinguishing between true (taxon genuinely absent) and false (taxon present, but not observed) absences, occupancy modelling produces independent and simultaneous probability estimates for both occupancy and detection. Here, we show how paleontological occurrences can be adapted for use alongside relevant modern and paleo covariate data in both single season models run using the R package ‘unmarked’ and dynamic occupancy models using a Bayesian framework. We additionally test the impact of varying spatial scale, as well as uneven numbers of repeated site visits, on model outcomes, and provide recommendations for conservation paleobiologists intending to run these models. Finally, we outline additional benefits of applying occupancy modelling within conservation paleobiology.

Ordovician strata of the Indian subcontinent

Abstract Ordovician rocks of the Indian Tethyan Himalaya contain a conspicuous angular unconformity between mostly marine Cambrian and overlying terrestrial Ordovician strata, which is a record of the Kurgiakh Orogeny. This tectonic event is traceable across the Tethyan Himalaya from Pakistan to Bhutan. The Pin Formation in the Spiti Valley provides a high-resolution account of the marine depositional history, palaeontology and isotope geochemistry of Late Ordovician events. The middle (Takche) member is late Katian and the upper Mikkim Member is lower Silurian (Llandovery), based on an ozarkodinid conodont fauna. The Pin Formation records the Boda event, the last warming interval prior to Hirnantian glaciation. The δ 13 C carb chemostratigraphic data allow precise global correlation, and recognition of the Paroveja positive excursion, the last major excursion of the Katian. The Mikkim Member records a ‘lower HICE’ (Hirnantian isotopic carbon excursion) of the Katian–Hirnantian boundary interval. Palaeontological data indicate that there are no known fossils diagnostic of any Ordovician ages older than the Katian Stage in India. Evidence of Ordovician sedimentary rocks in the Lesser Himalaya is intriguing, but presently equivocal. The widespread absence of pre-Katian strata on the Indian subcontinent is due to erosion associated with the Kurghiak orogeny and delayed onlap onto topographically high areas.

A new lithostratigraphic profile for Cretaceous to Paleogene successions in the West and Central African Rift System, Koum Basin, northern Cameroon

Six new formations (Gaba, Roumi, Poula, Mbissiri, Lende andKali) are proposed for Cretaceous to Paleogene sediments of the Koum Basin, northern Cameroon. The Koum Basin is one of numerous sedimentary basins lining the West and Central African Rift System and presents a complex evolutionary history involving extensional shearing and compressional events spanning the Cretaceous to Paleogene. Recent discoveries of hydrocarbons in associated basin such as Doba in Chad,motivated exploration of the Koum Basin. However, existing studies of the Koum Basin lack a viable lithostratigraphic framework, which is crucial for ongoing exploration efforts in this basin. The present study integrates lithologic, petrographic and palaeontologic data to map, stack and correlate several outcrop sections across the basin. Facies analysis suggests that deposition occurred in a fluvio-lacustrine palaeodeposional environment. The new units were described following the guidelines of the International Stratigraphic Guide. An updated geologicmap depicts the spatial distribution of the lithostratigraphic units that make up the Koum Basin. Palynomorphs, bivalves and dinosaur footprints are used to date the studied sections.