Institute of Paleobiology

Fjords are among the most efficient marine environments for trapping sediments and organic carbon (OC). They represent an important part of the global carbon cycle. Yet, quantitative data on OC burial rates are scarce in the Southern Hemisphere. Here, we present 210 Pb-derived sediment accumulation rates (SAR), OC burial rates, and sediment properties from 10 sediment cores collected in the fjords of South Georgia, the largest sub-Antarctic island: Antarctic Bay, Fortuna Bay, Stromness Bay, and Cumberland Bay. SARs range from 2.1 ± 0.4 to 14.9 ± 2.8 mm/yr, total organic carbon (TOC) from 0.28% to 2.1%, and modern OC burial rates from 17.4 ± 1.2 to 64.6 ± 12.1 gOC/m 2 /yr, placing them towards the upper range of values reported globally. High rates reflect large sediment supply from steep, glacierised catchments, intense precipitation, and relatively high primary productivity. A strong relationship between SAR and OC burial rate indicates sediment delivery as the primary control, with the highest modern OC burial rate at a glacier-proximal site combining the highest SAR and lowest TOC. Tidewater glacier-fed fjords show higher SAR and OC burial rates than river-dominated systems. However, the maximum recorded burial rate (95.9 ± 8.3 gOC/m 2 /yr) occurred in King Edward Cove during the early 20th century, driven by the whaling industry, while the modern value (55.5 ± 4.8) is about half. These results suggest that OC burial in tidewater glacier-dominated fjords may increase in the short term under warming due to enhanced meltwater discharge, but decline in the longer term as retreat transforms fjords into river-dominated systems.

Abstract Colombellinidae is an extinct family of marine gastropods occurring in carbonate facies from the Middle Jurassic to the lowermost Upper Cretaceous, primarily in Europe and rarely in Asia. Members of the family are characterized by thick, oval shells with a narrow aperture bearing anterior and posterior canals, a thickened peristome and a denticulate outer lip. Colombellinids share several shell characters with representatives of Cypraeoidea, including a narrow, elongated aperture, but unlike cypraeids, their shells are not convolute. Based on a comprehensive revision of all described species, the taxonomy of Colombellinidae is clarified, and the family is restricted to only two genera: Colombellina d’Orbigny, 1842, and Zittelia Gemmellaro, 1869. One new species, Colombellina crassigranulata sp. nov., from the Upper Jurassic of Bulgaria, and one new genus, Wadeina gen. nov., from the Upper Cretaceous (Campanian) of Tennessee, USA – with a type species previously included in Colombellinidae but here assigned to the family Personidae (Tonnoidea) – are described. The distribution of the family and associated facies indicates a preference for shallow marine carbonate environments, while their low abundance may indicate a carnivorous mode of life. A comparison of Colombellinidae with Tonnoidea, Cypraeoidea and Purpurinidae sheds a new light on the phylogenetic relationships of these groups and supports the interpretation of Colombellinidae as a stem or sister group of Cypraeoidea. This study contributes to a refined systematics of Jurassic–Cretaceous gastropods and provides new evidence for the early diversification of higher caenogastropods.

We provide a reassessment of the hypothesis of ammonite survival across the Cretaceous–Paleogene (Maastrichtian–Danian) boundary, based on new data from the lower Danian Cerithium Limestone Member at Stevns Klint, eastern Denmark. The occurrence of this unit in disjunct basins between eroded crests of uppermost Maastrichtian bryozoan mounds prompts a reconsideration of ammonite redeposition as an alternative to the survival hypothesis. We describe new ammonite specimens from the Cerithium Limestone, representing the genera Hoploscaphites, Baculites and Fresvillia. In order to elucidate the nature of these fossils, we study their local depositional settings, based on detailed, chiefly taphonomic and sedimentological (microfacies) observations. Results for the main part of the Cerithium Limestone point to the autochthonous nature of the enclosed ammonites, which implies that they are Danian survivors. Only a single individual from the lowermost part of the Cerithium Limestone is considered a reworked Maastrichtian fossil. In summary, our results confirm ammonite survival into the Danian for the bulk of the Cerithium Limestone fauna, stimulating questions for further research of what actually killed the last ammonites that lived on Earth.

Stony corals are long-lived, calcifying cnidarians that can be preserved within archaeological strata, offering insights into past seawater conditions, anthropogenic influences, and harbor dynamics. This study analyzes sub-fossil Cladocora sp. colonies from ancient Akko, Israel, dated to the Hellenistic period (~335–94 BCE), alongside modern Cladocora caespitosa from Haifa Bay, Israel. We employed micromorphology, stable isotope analysis, and DNA sequencing to assess species identity, colony growth form, and environmental conditions experienced by the corals. Comparisons suggest that Hellenistic Akko corals grew in high-light, cooler-water, high-energy environments, potentially with exposure to terrestrial waste. The exceptional preservation of these colonies indicates rapid burial, possibly linked to ancient harbor activities or extreme sedimentation. Our results demonstrate the utility of scleractinian corals as valuable paleoenvironmental archives, capable of integrating both biological and geochemical proxies to reconstruct past marine conditions. By linking archaeological and ecological records, this multidisciplinary approach provides a comprehensive understanding of historical coastal dynamics, including ancient harbor use, climate variability, and anthropogenic impacts.

<strong class="journal-contentHeaderColor">Abstract.</strong> Earth&rsquo;s climate history serves as a natural laboratory for testing the effect of warm climates on the biosphere. The Cretaceous period featured a prolonged greenhouse climate characterized by higher-than-modern atmospheric CO₂ concentrations and mostly ice-free poles. In such a climate, shallow seas in low latitudes probably became very hot, especially during the summers. At the same time, life seems to have thrived there in reef-like ecosystems built by rudists, an extinct group of bivalve molluscs. To test the seasonal temperature variability in this greenhouse period, and whether temperature extremes exceed the maximum tolerable temperatures of modern marine molluscs, we discuss a detailed sclerochronological (incrementally sampled) dataset of seasonal scale variability in shell chemistry from fossil rudist (<em>Torreites sanchezi</em> and <em>Vaccinites vesiculosus</em>) and oyster (<em>Oscillopha figari</em>) shells from the late Campanian (75-million-year-old) low latitude (3&deg; S paleolatitude) Saiwan site in present-day Oman. We combine trace element data and microscopy to screen fossil shells for diagenesis, before sampling well-preserved sections of a <em>Torreites sanchezi</em> rudist specimen for clumped isotope analysis. Based on this specimen alone, we identify a strong seasonal variability in temperature of 19.2 &plusmn; 3.8 &deg;C to 44.2 &plusmn; 4.0 &deg;C in the seawater at the Saiwan site. The oxygen isotopic composition of the seawater (&delta;¹⁸O_sw) varied from -4.62 &plusmn; 0.86 &permil; VSMOW in winter to +0.86 &plusmn; 1.6 &permil; VSMOW in summer. We use this information in combination with age modelling to infer temperature seasonality from incrementally sampled oxygen isotope profiles sourced from the literature, sampling multiple shells and species in the assemblage. We find that, on average, the Saiwan seawater experienced strong seasonal fluctuations in monthly temperature (18.7 &plusmn; 3.8 to 42.6 &plusmn; 4.0 &deg;C seasonal range) and water isotopic composition (-4.33 &plusmn; 0.86 to 0.59 &plusmn; 1.03 &permil; VSMOW). The latter would strongly bias the interpretation of stable oxygen isotopes in shell carbonate without independent control on either temperature or seawater composition. Combining our seasonal temperature estimates with shell chronologies based on seasonal cyclicity in stable isotope records and daily variability in trace element data, we show that <em>T. sanchezi</em> rudists record temperatures during the hottest periods of the year as well as during the winters, which were characterized by cooler temperatures and enhanced influx of freshwater. Both <em>O. figari</em> and <em>V. vesiculosus</em> plausibly stopped growing during these seasonal extremes. This study aims to demonstrate how high-resolution geochemical records through fossil mollusc shells can shed light on the variability in past warm ecosystems and open the discussion about the limits of life in the shallow marine realm during greenhouse climates. Future work should apply the clumped isotope paleothermometer on incrementally sampled bio-archives to explore the upper-temperature limits experienced by calcifiers in different environments throughout geological history.

Explosive volcanoes eject large amounts of ashes in the form of fine-grained glass fragments (shards) during eruption. Depending on their size, degree of vesicularity and composition, pyroclastic glass shards have chemically reactive catalytic surfaces with high surface-to-volume ratios. They are able to adsorb organics, metals, and phosphates, as well as create microenvironments attractive for microbial growth. Pyroclastic material &amp;#8211; deposited in both aquatic and terrestrial environments &amp;#8211; was abundant on early Earth and some of the first habitats for life may have been glass-rich. Our new sedimentological, geomicrobiological and geochemical-petrological comparative studies (LAICPMS, EMPA, TEM, Raman) aim at evaluating the significance of volcanic glass shards as a substrate and source of nutrients for microbes and as a medium for preservation of biosignatures in the geological record.Here we show that modern (Holocene) and Paleoarchean volcanic glass shards deposited in aqueous settings (hyaloclasts) preserve evidence of alteration by microbial activity. For example, sub-recent (ca. 0.37 ka; Ka&amp;#378;mierczak &amp;amp; Kempe 2006) shards of island arc basalt composition (containing phenocrysts of the early crystallization process i.e., forsterite olivine, spinel, plagioclase-bytownite, pyroxene) are documented from the alkaline caldera lake Vai Lahi on Niuafo&amp;#8217;ou Island, Tonga (Kempe &amp;amp; Ka&amp;#378;mierczak 2012). Analyses by 3D Raman spectroscopy (depth profiling) reveal aragonite and calcite in the entire shard volume with associated carbonaceous matter, as well as spectra of anorthite and olivine.Most Niuafo&amp;#699;ou shards are coated with a laminated envelope of alternating aragonitic and silicate layers resembling oncoids cortex. Open vesicles and external faces of the shards host an organic matter and mineral assemblage texturally identical to that of the laminated envelope. Two types of alterations are identified in the Niuafo&amp;#8217;ou shards: i) pit-like etchings; and, ii) alveolar-spongy textures. Transmission electron microscopy reveals etch-like alterations (weathering or microbial activity?) on shard surfaces to a depth of ca. 2 &amp;#181;m. Elemental compositions of the altered layer point to a mixture of glass and the carbonate-silicate envelope.Niuafo&amp;#8217;ou shards were deposited in water of increased alkalinity that favored silica dissolution and carbonate precipitation. In turn, this leads to the growth of aragonite coatings as well as sizeable stromatolites in the lake. Such habitat is ideal for alkalophilic cyanobacteria that form biofilms and participate in the precipitation of mineral envelopes. Coated by carbonate-silicate, such glass shards can effectively preserve biosignatures even as far back as the Paleoarchean (

Ice rises and rumples are common features of the Antarctica ice sheet margin that appear where thick ice shelves are grounded to an underlying shallow submarine bank.&amp;#160; The ice rises buttress ice flow, partly controlling the extent of both grounded and floating ice. Here we reconstruct the unpinning of the Ross Ice Shelf (RIS) from Ross Bank, a broad, shallow submarine bank located approximately 100 km north of the current RIS calving front in the central Ross Sea.&amp;#160; The Ross Bank Ice Rise formed after the retreat of grounded ice from the adjacent deep-water Glomar Challenger and Pennell troughs following the Last Glacial Maximum.&amp;#160; High resolution seafloor bathymetry reveals small-scale, concentric backstepping moraines marking the progressive contraction of the edges of the ice rise toward the shallow bank crest.&amp;#160; Kasten and piston cores from the crest recovered clay-poor, winnowed glacimarine sediment rich in carbonate macrofossils, with radiocarbon ages indicating that the unpinning proceeded over several thousand years.&amp;#160; The long-lived pinning point eventually failed, with the RIS fully unpinning from the shallowest crest by 4160 &amp;#177; 20 14C year BP (uncorrected). This ultimately led to the shift of the RIS calving front to its current location.&amp;#160; Our reconstructions validate concerns that destabilizing ice rises could lead to significant reorganization of grounded and floating ice.

Primates are often considered to have a poor sense of smell. While all studies identify small olfactory bulbs (OB; the region of the brain responsible for processing scent) among haplorhines, whether or not strepsirrhines also possess small OBs is less clear, as is the evolutionary backdrop from which these patterns emerged. Here, we examine the relative size of the olfactory bulbs in cranial endocasts of living and fossil primates and their kin (Euarchontoglires [Primates, Dermoptera, Scandentia, Rodentia, Lagomorpha]), testing previous hypotheses. Regression analyses of OB volume and mass relative to endocranial volume (ECV) and body mass (BM), and ANOVAS of residuals, were performed on a dataset of 181 extant and 41 extinct species. Analyses show clear differences in the relative size of the OBs, with haplorhines possessing distinctly smaller OBs relative to all other clades. Pairwise tests indicate haplorhine OBs are significantly smaller than those of all other clades, including strepsirrhines; when the haplorhines are removed from analyses, strepsirrhines are significantly smaller than all other clades. This suggests that a reduction in OB size occurred at the crown primate node, a pattern also seen in ancestral state reconstruction (ASR) analyses. The ASR analyses suggest multiple iterations of olfactory bulb size decrease occurred in Haplorhini, reflecting large amounts of parallelism. These results likely differ from previous studies due to the inclusion of additional fossils and more appropriate outgroups based on up-to-date phylogenetic hypotheses.