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Stratigraphy, paleontology, and depositional setting of the Late Eocene (Priabonian) lower Pagat Member, Tanjung Formation, in the Asem Asem Basin, South Kalimantan, Indonesia
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Marine sedimentary rocks of the late Eocene Pagat Member of the Tanjung Formation in the Asem Asem Basin near Satui, Kalimantan, provide an important geological archive for understanding the paleontological evolution of southern Kalimantan (Indonesian Borneo) in the interval leading up the development of the Central Indo-Pacific marine biodiversity hotspot. In this paper, we describe amoderately diverse assemblage of marine invertebrates within a sedimentological and stratigraphical context. In the studied section, the Pagat Member of the Tanjung Formation records an interval of overall marine transgression and chronicles a transition from the marginal marine and continental siliciclastic succession in the underlying Tambak Member to the carbonate platform succession in the overlying Berai Formation. The lower part of the Pagat Member contains heterolithic interbedded siliciclastic sandstone and glauconitic shale, with thin bioclastic floatstone and bioclastic rudstone beds. This segues into a calcareous shale succession with common foraminiferal packstone/rudstone lenses interpreted as low-relief biostromes. A diverse trace fossil assemblage occurs primarily in a muddy/glauconitic sandstone, sandy mudstone, and bioclastic packstone/rudstone succession, constraining the depositional setting to a mid-ramp/mid to distal continental shelf setting below fair-weather wave base but above stormwave base. Each biostrome rests upon a storm-generated ravinement surface characterized by a low-diversity Glossifungites or Trypanites trace fossil assemblage. The erosional surfaces were colonized by organisms that preferred stable substrates, including larger benthic foraminifera, solitary corals, oysters, and serpulid annelid worms. The biostromes comprised islands of highmarine biodiversity on the mud-dominated Pagat coastline. Together, the biostromes analyzed in this study contained 13 genera of symbiont-bearing larger benthic foraminifera, ∼40 mollusk taxa, at least 5 brachyuran decapod genera, and 6 coral genera (Anthemiphyllia, Balanophyllia, Caryophyllia, Cycloseris, Trachyphyllia, and Trochocyathus), as well as a variety of bryozoans, serpulids, echinoids, and asterozoans. High foraminiferal and molluscan diversity, coupled with modest coral diversity, supports the hypothesis that the origin of the diverse tropical invertebrate faunas that characterize the modern Indo-Australian region may have occurred in the latest Eocene/earliest Oligocene.
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RBINS Staff Publications 2025 OA
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Depositional framework of the Sangkarewang and Sawahlunto Formations, Ombilin Basin, West Sumatra, Indonesia
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Analyses of rock samples collected during recent fieldwork in the Ombilin Basin of west-central Sumatra, Indonesia yielded pollen data that constrain the age and depositional setting of associated plant macrofossil and vertebrate fossil-bearing units in the Sangkarewang and Sawahlunto formations. Articulated fish and plant fossils were recovered from bedding plane surfaces of fissile, laminated shales in the Sangkarewang Formation that are interpreted to have been deposited in an actively-subsiding, deep, anoxic lake. The overlying Talawi Member of the Sawahlunto Formation records stratigraphy consistent with deposition in a segue to marginal lacustrine marsh and poorly-drained paleosol settings. Interbedded carbonate mudstone / wackestone and lignitic claystone units in the basal Talawi Member preserve scattered, disarticulated fossils of fish, reptiles, an amphibian, and one mammal tooth. These beds grade into a heterolithic succession of fine-grained clastic rock, with coal interbeds likely deposited in a coastal alluvial setting. Marine influences in this interval are indicated by the nature of physical sedimentary structures in several zones, the presence of trace fossils such as Diplocraterion, Cylindrichnus and Teichichnus, and the occurrence of foraminiferal linings, dinocysts and other palynomorphs indicative of mangrove and back-mangrove settings. Palynological analysis indicates that the most probable age of the Sawahlunto Formation ranges from the middle to late Eocene, with a possible extension from the middle Eocene to the early Oligocene.
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RBINS Staff Publications 2025 OA
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3D models related to the publication: Morphological study of the anterior dentition in Raoellidae (Mammalia, Artiodactyla), new insight on their dietary habits
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The present 3D dataset contains 3D models of new material from the middle Eocene of the Upper Subathu Formation in the Kalakot area (India), documenting the anterior dentition of the raoellid Indohyus indirae. Raoellidae are closely related to stem cetaceans and bring crucial information to understand the earliest phase of land to water transition in Cetacea.
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RBINS Staff Publications 2025 OA
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India as a “Noah’s Ark” before Collision with Eurasia: Palaeoenvironment and Palaeobiogeography of the Continental Early Eocene Vertebrate Fauna of Gujarat
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For the past twenty years, an Indian-American-Belgian team carried out twelve seasons of collaborative fieldwork in search of vertebrates from the Cambay Formation in lignite mines of Gujarat, western India. Here is a summary of our main discoveries in the Vastan, Mangrol, and Tadkeshwar mines, including an updated overview of the whole vertebrate fauna. The fauna is around 54.5 million years old, representing tropical rainforest conditions in a coastal brackish palaeoenvironment. It includes the earliest modern mammals from the Indian subcontinent as well as endemic taxa. The most important result at the palaeobiogeographical level is the discovery of several vertebrate taxa of Gondwanan affinities, indicating that the early Eocene was a crucial period in India when Laurasian taxa with western European affinities co-existed with relict taxa from Gondwana before the actual collision of India and Eurasia. Terrestrial faunas could have dispersed to or from Europe when the Indian subcontinent came into contact, episodically, with different island blocks, such as the Kohistan-Ladakh island-arc system, along the northern margin of Neotethys Ocean.
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RBINS Staff Publications 2025 OA
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Bioerosional marks in the shells of two sea turtle taxa from the middle Eocene of Belgium
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This study analyses the diverse types of bioerosion marks on the shells of two sea turtle specimens from the Lutetian (middle Eocene) of Belgium. The objective is to understand the physical stressors affecting these organisms in ancient marine environments and to identify the potential factors responsible for these changes. The first specimen, the holotype of Eochelone brabantica, presents multiple erosive anomalies on its costal plates. The second individual, corresponding to Puppigerus camperi, exhibits different types of shell deviations, also of an erosive character. The combination of macroscopic and imaging techniques (i.e., CT scanning and 3D surface scanning) allow us the precise observation and identification of the different alterations. Comparative analyses suggest several external factors as potential causes of the anomalies of the two specimens (i.e., invertebrate feeding traces and trauma). This detailed examination provides specific insights into the types and causes of shell alterations in these Eocene turtles, offering a clearer understanding of their interactions in the marine ecosystem in which they lived.
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RBINS Staff Publications 2025 OA
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Morphological study of the anterior dentition in Raoellidae (Mammalia, Artiodactyla), new insight on their dietary habits
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Raoellidae are small artiodactyls from the Indian subcontinent closely related to stem cetaceans. They bring crucial information to understand the early phase of the land-to- water transition in Cetacea. If they are considered to be partly aquatic, the question of their dietary habits remains partly understood due to their “transitional” morphology. Raoellidae are largely documented by their cheek teeth and getting a better knowledge of their anterior dentition constitutes an additional proxy to discuss their feeding habits. In this work, we document the anterior dentition of Indohyus indirae from an unprecedented sample of in situ and isolated teeth from the locality of East Aiji-2 in the Kalakot area (Rajouri district, India). We propose identification criteria for upper and lower incisors and canines in raoellids. Based on CT scan data, virtual reconstruction of in situ dentition, and identification of the isolated incisors and canines, we reconstruct a composite anterior dentition of Indohyus supported by the correspondence of wear facets between upper and lower teeth. This constitutes the first attempt at reconstruction of the anterior dentition of a raoellid. We show that the upper incisors are caniniform and very similar morphologically, whereas the lower incisors are pointed but remain incisiform and quite different from one another. We also describe noticeable intraspecific variation, at the level of upper canines, suggesting a potential sexual dimorphism in this species. Upper and lower incisors are recurved, with the upper incisor row arranged on a widely opened arch. Taken altogether the anterior dentition forms a grasping device, allowing the animal to capture and secure food, a characteristic shared with stem cetaceans. This would mark the first step towards the carnivorous diet in these peculiar artiodactyls.
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RBINS Staff Publications 2025 OA
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Early Delphinida (Cetacea, Odontoceti) from the Miocene of the southern North Sea Basin
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RBINS Staff Publications 2026
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Les Neuropterida du Jardin botanique Jean Massart (Région de Bruxelles-Capitale, Belgique) (Arthropoda: Insecta)
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RBINS Staff Publications 2026 OA
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First record of the leafhopper tribe Tharrini in Indochina with a new species of the genus Nisitra Walker, 1869 from Central Vietnam (Hemiptera, Cicadellidae, Coelidiinae)
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RBINS Staff Publications 2025
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Building a Lithotectonic Framework for Belgium
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Almost all geological subdisciplines depend, to varying extents, on regional geological knowledge. Stratigraphic terminology is typically well-defined, while other concepts rely on generally accepted definitions or hierarchical schemes, such as palaeontological, structural and magmatic terminologies. This is much less the case for the regional geological building blocks. Their nomenclature is usually composed of a reference to a geographical locality and a geological term. Examples from Belgium include the (Anglo-)Brabant Massif, Campine Basin, and Malmedy Graben. Despite wide recognition, such terms often lack precise definitions and may even present conflicting interpretations across different contexts and authors. Even when their meanings have drifted or become less precise, these terms continue to be utilized. Increased awareness has led to significant yet isolated initiatives aimed at improving the structure and definition of regional geological information [1-3], recently brought together through pan-European cooperation [4]. Lithotectonic unit appears to be the most effective concept for encompassing all geological features. A lithotectonic unit is characterized by its composition, structural elements, mutual relations, and/or geological history [5]. Following a geotemporal conceptual approach, lithotectonic units are defined and bounded by relative limits in time and space [6]. Lithotectonic limits are planar features corresponding to geological events which have formed and define these units. Examples of lithotectonic units include orogens, terranes, sedimentary basins, and grabens, while examples of lithotectonic limits include deformation fronts, faults, and unconformities. This approach facilitates the organization and formalization of relationships between units and limits through ontologies. The data model can be linked to established ontologies, such as the ICS Geological Time Scale Ontology [7], and allows future extensions, such as attribution to orogenic cycles [2]. The associated concepts can be linked to 2D and 3D visualizations, thereby adding an important layer of knowledge to geological maps and models. Primary objective of the newly established Lithotectonic Working Group, under the National Commission for Stratigraphy in Belgium, is to create a comprehensive lithotectonic framework, that systematically defines and describes the main geological units and limits of Belgium. This initiative aligns closely with emerging standards currently being developed and implemented at European level [4] and largely based on GeoSciML [8]. [1] Hintersberger et al. 2017, Jb Geol B-A 157:195-207. [2] Németh 2021, Miner Slovaca 2:81-90. [3] Le Bayon et al. 2022: https://doi.org/10.1051/bsgf/2022017. [4] GSEU 2022-2027: https://doi.org/10.3030/101075609. [5] INSPIRE 2015: https://inspire.ec.europa.eu/theme/ge. [6] Piessens et al. 2024: https://doi.org/10.31223/X5RT28. [7] Cox & Richard 2005: https://doi.org/10.1130/GES00022.1. [8] GeoSciML 2016: http://www.opengis.net/doc/geosciml/4.1.
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RBINS Staff Publications 2025