Abstract This study examines the climatic controls on dolomite precipitation through a multiproxy investigation of a carbonate‐rich sediment core from Salinas Lake, a hypersaline playa in Alicante, south‐eastern Iberia. The ~120,000 year record captures depositional cycles and palaeoenvironmental changes driven by late Pleistocene to Holocene climate variability. Integrated analyses of sedimentology, lithology, geochemistry (elemental concentrations, total organic carbon, stable carbon and oxygen isotopes), scanning electron microscopy, microbial community characterisation and palynology reconstruct lake hydrology and its influence on carbonate mineralogy. The sediment succession is marked by alternating calcite‐ and dolomite‐rich intervals, with dolomite crystals displaying morphological evolution from spherical to rhombohedral forms with depth. Stable isotope signatures (δ13C: −6.5‰ to −2.4‰ VPDB; δ18O: −2.3‰ to +4.9‰ VPDB), alongside microbial structures such as extracellular polymeric substances (EPS) and internal crystal voids, suggest a biologically mediated precipitation mechanism. These mineralogical shifts closely correspond to rapid hydrological changes driven by Dansgaard–Oeschger climate oscillations, with dolomite formation favoured under arid, evaporative conditions that concentrate Mg and Ca ions and promote microbial mat development. Halophilic microbial communities, capable of catalysing carbonate precipitation, probably enhance dolomite nucleation and growth through EPS production and geochemical modulation. This work underscores the complex interplay between climate, hydrology, microbial activity and sedimentary mineral formation, providing new insights into the longstanding ‘dolomite problem’ within sedimentary environments.
Jing Lyu, Sofía Barragán-Montilla, Sofía Barragán-Montilla
et al.
The Late Miocene and Early Pliocene were characterized by widespread oxygen depletion in the Pacific and Indian Oceans, coinciding with the “Late Miocene–Early Pliocene Biogenic Bloom” (LMBB). In the Indian Ocean, this oxygen depletion has been linked to enhanced productivity in the northern basins, leading to Oxygen Minimum Zone (OMZ) expansion. A longstanding hypothesis proposes that the OMZ extended south of Broken Ridge (∼31°S). We test this hypothesis using benthic foraminiferal assemblages from ODP Site 752 (∼1086 m water depth) spanning the last 9 Myr. We apply a semi-quantitative reconstruction of bottom water oxygenation using the Enhanced Benthic Foraminiferal Oxygen Index (EBFOI), benchmarked against the present-day core-top assemblage. Our results indicate persistently oxic bottom water conditions (3.2–5.2 mL/L) throughout the study interval. Although significant faunal changes occur, particularly between 5.5 and 2.2 Ma, these do not align with LMBB timing. Instead, we interpret assemblage shifts as responses to the intensification of Tasman Leakage, which brought oxygen-rich intermediate waters into the southern Indian Ocean. Our results challenge previous interpretations of OMZ expansion to Broken Ridge and highlight the role of southward water mass sourcing in shaping intermediate-depth oxygenation. This study provides a new mechanistic framework and emphasizes the importance of integrating faunal, sedimentological, and geochemical data to reassess regional OMZ histories.
Christina G Warinner, Kristine Korzow Richter, M. Collins
Paleoproteomics, the study of ancient proteins, is a rapidly growing field at the intersection of molecular biology, paleontology, archaeology, paleoecology, and history. Paleoproteomics research leverages the longevity and diversity of proteins to explore fundamental questions about the past. While its origins predate the characterization of DNA, it was only with the advent of soft ionization mass spectrometry that the study of ancient proteins became truly feasible. Technological gains over the past 20 years have allowed increasing opportunities to better understand preservation, degradation, and recovery of the rich bioarchive of ancient proteins found in the archaeological and paleontological records. Growing from a handful of studies in the 1990s on individual highly abundant ancient proteins, paleoproteomics today is an expanding field with diverse applications ranging from the taxonomic identification of highly fragmented bones and shells and the phylogenetic resolution of extinct species to the exploration of past cuisines from dental calculus and pottery food crusts and the characterization of past diseases. More broadly, these studies have opened new doors in understanding past human–animal interactions, the reconstruction of past environments and environmental changes, the expansion of the hominin fossil record through large scale screening of nondiagnostic bone fragments, and the phylogenetic resolution of the vertebrate fossil record. Even with these advances, much of the ancient proteomic record still remains unexplored. Here we provide an overview of the history of the field, a summary of the major methods and applications currently in use, and a critical evaluation of current challenges. We conclude by looking to the future, for which innovative solutions and emerging technology will play an important role in enabling us to access the still unexplored “dark” proteome, allowing for a fuller understanding of the role ancient proteins can play in the interpretation of the past.
Abstract The Molybdenum isotopic composition (δ98/95Mo) of arc lavas is highly variable. While source processes play an important role in controlling the δ98/95Mo of arc magmas, the impact of differentiation on this variability remains poorly understood. In this study, we assess and deconvolute the effects of source and crustal processes on the δ98/95Mo of lavas and enclaves with adakitic compositions from Solander volcano, located above the incipient Puysegur subduction zone. These rocks show extreme δ98/95Mo variation (−0.35‰ to +0.79‰). The most mafic samples have light δ98/95Mo (−0.35‰ to −0.29‰) and low Mo/Ce ratios (0.006–0.007) consistent with published models invoking the addition of altered oceanic crust melts to their mantle source. However, the range of δ98/95Mo in the rest of the sample set is unlikely to result from source processes. Covariations of δ98/95Mo and Mo contents with MgO concentrations indicate that the δ98/95Mo and Mo content variability was generated during differentiation. Similar Sr‐Nd isotope compositions of all Solander lavas exclude a significant role for crustal assimilation. Mineral fractionation alone cannot reproduce the observed systematics without invoking unreasonable δ98/95Mo for the fractionated phases. Instead, we suggest that Mo mobility and associated isotopic fractionation during supercritical fluid exsolution and unmixing, followed by brine assimilation and magma mixing, are the first order controls on δ98/95Mo and Mo concentration variation in the Solander adakitic magmas. Thus, the role of magmatic fluids on the δ98/95Mo of intermediate‐silicic arc rocks can be significant, at least in adakitic systems, and needs to be considered prior to a source assessment.
Abstract Neck elongation has appeared independently in several tetrapod groups, including giraffes and sauropod dinosaurs on land, birds and pterosaurs in the air, and sauropterygians (plesiosaurs and relatives) in the oceans. Long necks arose in Early Triassic sauropterygians, but the nature and rate of that elongation has not been documented. Here, we report a new species of pachypleurosaurid sauropterygian, Chusaurus xiangensis gen. et sp. nov., based on two new specimens from the Early Triassic Nanzhang-Yuan’an Fauna in the South China Block. The new species shows key features of its Middle Triassic relatives, but has a relatively short neck, measuring 0.48 of the trunk length, compared to > 0.8 from the Middle Triassic onwards. Comparative phylogenetic analysis shows that neck elongation occurred rapidly in all Triassic eosauropterygian lineages, probably driven by feeding pressure in a time of rapid re-establishment of new kinds of marine ecosystems.
Of the most important characteristics of the Ranikothalia genus, as large benthic foraminifera, are the existence of ornamentation in the external part of the shell especially around the central umbilicus knob, marginal mesh channels (MMC) in the marginal chord, trabeculate system with channels, V-shape plate in the floor of chambers and accumulation of septum that differentiated this genus from Nummulites genus and placing it in the Palaeonummulitinae sub-family. The Ilerdian transgression near the P5 Zone (Pelagic P5) is a stratal key surface for the determination of the Paleocene-Eocene boundary in the neritic deposits. Ranikothalia nuttalli as an index species is used for recognition of the Paleocene–Eocene boundary in the Neo-Tethys shallow water successions. This species, in the Padagi section, resembling the Pakistan Indus Basin, accompanied with Miscellanea miscella, Discocyclina sp., Discocyclina sp., Assilina sp. that indicated SBZ5/6 and suggested lower Ilerdian (earliest Eocene) age.
Keywords: Ranikothalia , Ilerdian, systematic, Sistan Suture Zone
Introduction
Large benthic foraminifera, such as Fusulinidae, Oritoididae, Alveolinidae, Rotaliidae and Nummulitidae, are important fossil and extant forms that with respect to systematic and biostratigraphic widespread, are studied and some biozonation schemes based on them are suggested. Nummulitidae (such as Ranikothalia) are a group of large benthic foraminiferas developed in the Paleocene and Eocene of the Tethys basin. Larger benthic foraminiferas biozonation is represented by Serra-Kiel et al. (1998) which based on these group of foraminifera Paleocene and Eocene series are divided into 20 shallow benthic zones (SBZ1–SBZ20). The Paleocene–Eocene boundary is considered between SBZ4–SBZ5 (Scheibner & Speijer 2009).
Ranikothalia nuttalli as an index species is used for recognition of the Paleocene–Eocene boundary in the Neo-Tethys shallow water successions. This species, in the Padagi section, resembles the Pakistan Indus Basin, accompanied with Miscellanea miscella, Discocyclina sp., Discocyclina sp., Assilina sp. that indicated SBZ5/6 and suggested the lower Ilerdian (earliest Eocene) age.
The purpose of this study is to identify and introduce the Ranikothalia nuttali species and investigate its expansion in the adjacent sedimentary basin in the Neo-Tethys Ocean.
Material & Method
To do research and biostratigraphic investigations of the Paleocene–Eocene deposits in the Sefid-Abeh basin, the Padagi section, ten rock samples are collected that 60 thin sections prepared from them. The systematic determination of Ranikothalia, in the level of genus and species, is done by using binocular microscope, and then based on identified Ranikothalia nutalli, the age of the Padagi section is suggested.
Discussion of Results & Conclusions
Studies of different genera of Nummulitidae in the thin sections and isolated forms led to the identification of different species of Ranikothalia especially Ranikothalia nutalli accompanied by other large benthic foraminiferas suggested the late Paleocene–early Eocene age for the Padagi section in the Sefid-Abeh basin.
Ranikothalia nutalli as a specific species for identification of the Paleocene–Eocene boundary in the Neo-Tethys shallow water succession is suggested. This specific species, in the Padagi section, is seen with Miscellanea miscella and the different species of Assilina and Discocyclina, such as the Indus basin, that show SBZ 5/6 and the earliest Eocene (lower Ilerdian) age.
The most important characteristics of Ranikothalia genus, as large benthic foraminifera, are the existence of ornamentation in the external part of the shell especially around the central umbilicus knob, marginal mesh channels (MMC) in the marginal chord, trabeculate system with channels, V-shape plate in the floor of chambers and accumulation of septum that differentiated this genus from Nummulites genus and placing it in the Palaeonummulitinae sub-family. The Ilerdian transgression in near the P5 Zone (Pelagic P5) is a stratal key surface for the determination of the Paleocene–Eocene boundary in the neritic deposits. Ranikothalia nuttalli as an index species is used for recognition of the Paleocene–Eocene boundary in the Neo-Tethys shallow water successions.
With regards to affinity and similarity of larger benthic foraminifera assemblages (widespread of Ranikothalia and Miscellanea) in the Sefid-Abeh basin (Padagi section) with Indus basin (in Pakistan and India) we can concluded that palaeobiogeographically, the mentioned basin is related to the eastern Neotethys.
The morphology of the pectoral girdle, the skeletal structure connecting the wing to the body, is a key determinant of flight capability, but in some respects is poorly known among stem birds. Here, the pectoral girdles of the Early Cretaceous birds Sapeornis and Piscivorenantiornis are reconstructed for the first time based on computed tomography and three-dimensional visualization, revealing key morphological details that are important for our understanding of early-flight evolution. Sapeornis exhibits a double articulation system (widely present in non-enantiornithine pennaraptoran theropods including crown birds), which involves, alongside the main scapula-coracoid joint, a small subsidiary joint, though variation exists with respect to the shape and size of the main and subsidiary articular contacts in non-enantiornithine pennaraptorans. This double articulation system contrasts with Piscivorenantiornis in which a spatially restricted scapula-coracoid joint is formed by a single set of opposing articular surfaces, a feature also present in other members of Enantiornithines, a major clade of stem birds known only from the Cretaceous. The unique single articulation system may reflect correspondingly unique flight behavior in enantiornithine birds, but this hypothesis requires further investigation from a functional perspective. Our renderings indicate that both Sapeornis and Piscivorenantiornis had a partially closed triosseal canal (a passage for muscle tendon that plays a key role in raising the wing), and our study suggests that this type of triosseal canal occurred in all known non-euornithine birds except Archaeopteryx, representing a transitional stage in flight apparatus evolution before the appearance of a fully closed bony triosseal canal as in modern birds. Our study reveals additional lineage-specific variations in pectoral girdle anatomy, as well as significant modification of the pectoral girdle along the line to crown birds. These modifications produced diverse pectoral girdle morphologies among Mesozoic birds, which allowed a commensurate range of capability levels and styles to emerge during the early evolution of flight.