Stratigraphic Research Articles

Time, space and synoptic topography: how to read outcrops as a granular record of Earth history

Siliciclastic strata commonly preserve chronostratigraphic surfaces that record the ancient interface of sediment and water/air, in the form of true substrates on bedding planes and sampled topography in stratigraphic profiles. Such surfaces are commonly a reflection of sedimentary stasis, a sedimentation state where neither deposition or erosion was occurring. Sedimentary stasis may be instantaneous, temporary or prolonged, and may also be considered to occur when the constituent grains of a substrate remain in motion as the surface active layer, when the elevation of the lithic surface does not change. The preservation of patches of synoptic topography requires only that sedimentation states of deposition, erosion and stasis fluctuate, but is more common in lower energy parts of a depositional environment. Certain sedimentary features associated with true substrates and sampled topography can, through modern analogy, be used to determine the likely duration of sedimentary stasis. Here we use original case studies to show how the duration of this stasis can be variable depending on facies and stratal age, but that at outcrop scale it is always a very short interval relative to the longevity of a depositional environment. With examples from several siliciclastic facies and geological periods, we show that stratigraphic time preserved at outcrop scale can be very short, indicating that the total stratigraphic record is built brick by brick of many lower hierarchy snapshots. This understanding shifts perspectives on the stratigraphic record as an archive, with implications for the meaning of sedimentary signatures at outcrop and the construction of narratives to understand Earth history.

Classification Framework for Assessing Anthropogenic Sedimentary Facies

As the mass of human-made materials now surpasses that of Earth’s total dry biomass, there is a critical need for sedimentologists to account for anthropogenic materials when analyzing depositional environments. To address this, a classification scheme is presented that extends traditional sedimentological models to encompass the diversity of modern sediments and their complex dynamics. Through relying on established sedimentological principles, the framework incorporates bed-scale, grain-scale, and sedimentary structure descriptors, as well as a methodology for describing the composition of a deposit and flexible nomenclature. It is designed to be integrative and adaptable, permitting the incorporation of additional descriptions as necessary, and is applicable across depositional settings that are dominated by either natural or anthropogenic processes. The scheme offers a practical, systematic approach to categorize and analyze the textures and structures of anthropogenic sediments, facilitating the reconstruction of modern and geologically recent environments. This unifying starting point enables more detailed predictions of material behavior and their environmental impacts, with implications for recycling, reuse, and management strategies. Furthermore, standardized nomenclature will enhance the capacity for data comparability across field sites, facilitating further understanding of our environment. Applications of this classification scheme include many interdisciplinary possibilities, overlapping with archeology, environmental monitoring, and engineering. By adopting this classification, sedimentologists can forge a deeper understanding of the stratigraphic record of the Anthropocene, contribute to developing more comprehensive strategies to manage Earth’s changing landscapes, and better understand our future geological record.

Integrating paleoparasitological, paleogenetic, and archaeological data to understand the paleoecological scenario of pre-Columbian archaeological site Gruta do Gentio II, Brazil.

Paleoparasitology and paleogenetics is the study parasites in ancient remains from latrines, mummified individuals, and coprolites, that is fossilized or desiccated feces. Paleoparasitological studies in Brazil began with analyses of coprolites from the Gruta do Gentio II (GGII) archaeological site, the oldest site related to the Una ceramist tradition (12,000 to 410 BP), Brazil. The GGII archaeological site contained numerous human burials, lithics, and cultural artifacts such as basketry, ceremonial ornaments, and unique pottery of the Una tradition. Coprolites of GGII were submitted to paleoparasitological, and paleogenetic analyses for parasite identification and coprolite origin. In addition, the archaeological characterization of the GGII site was integrated into paleo analyses for proposing a paleoecological scenario. Five taxa of parasites, including Ancylostomidae, Echinostoma sp., Spirometra sp., and Trichostrongylus sp., and three different morphotypes of Capillariidae were recognized in multiple coprolites that were distributed heterogeneously in several stratigraphical layers. The origin of coprolites was genetically defined as five species of mammals, humans, felines as Panthera onca and Leopardus pardalis, and marsupials as Didelphis albiventris and Philander opossum. This is the first study in Brazil that identified both, parasites and species of animals in Pleistocene/Holocene producers of coprolites with geographical and temporal information. The integration of paleoparasitology, paleogenetics, and archaeology is essential to propose paleoecological scenarios from the past of Brazil.

Ophiolite Association in the Rhodope Massif as indicator of the paleogeographical setting

All ophiolite associations mark epochs of active tectonic movements, which lead to significant petrological processes and modification of the relief of the Earth’s crust. Here we present a geological-petrographical characterization of one ophiolitic associations composed of: a) serpentinites; b) amphibolites-metamorphosed volcanic rocks and tuffs; c) metagabbros and metagabbrodiabases, placed among the Proterozoic metamorphic complex in the Rhodope Massif of Bulgaria on the Balkan Peninsula, South-Eastern Europе. The goal is to clarify the paleogeographical and geological setting during its creation. The methods of lithostratigraphic profiling and correlations on the database of geological field mapping were used, supplemented by microscopic, geochemical and isotopic studies of numerous rock samples. The summarized results confirm a certain stratigraphic level of the Ophiolite Association among the metamorphic complex and a complicated and protracted heterogenetic development, which is typical for the ophiolite associations created in eras of closing oceans, opposite movement of tectonic plates, subduction-obduction environment with appearance of autochthonous Neoproterozoic magmatism. Obducted fragments of serpentinites mark an old erosional continental surface, subsequently covered by transgressively deposited pelitic-carbonate sediments. The general conclusion of our study confirms the concept that the metamorphic complex of the Rhodope Massif represents a unified stratigraphic system consisting of two petrographic groups of different ages, with which we oppose the idea of a trust construction, launched by a group of geologists.

New information on Bonapartenykus (Alvarezsauridae: Theropoda) from the Allen Formation (middle Campanian-lower Maastrichtian) of Río Negro Province, Patagonia, Argentina clarifies the Patagonykinae body plan.

Alvarezsauria is a group of morphologically distinctive, medium- to small-sized later-diverging coelurosaurian theropod dinosaurs, whose record ranges from the Late Jurassic to the Late Cretaceous. This clade had a widespread distribution in Laurasia in what is now Europe, Asia, and North America, although there are also several Cretaceous taxa from Gondwana in what is now Argentina that all belong to the family Alvarezsauridae. Although alvarezsaurid taxonomic diversity and anatomical knowledge has expanded over the last decade, alvarezsaurid internal phylogenetic relationships remain highly debated. In this contribution, we describe new alvarezsaurid material and review previously reported alvarezsaurid specimens from the middle Campanian-lower Maastrichtian Allen Formation discovered at the Salitral Ojo de Agua locality in Río Negro province, Patagonia, Argentina. Although these specimens were collected at different times without precise original provenance information, here we gathered X-ray diffraction data of the associated sediments that now suggests that all of these specimens come from the same site and stratigraphic level as the holotype of the alvarezsaurid Bonapartenykus ultimus. Based on this new provenance information and the morphological similarity of the considered specimens, here we tentatively refer them to the genus Bonapartenykus. These newly referred specimens add to the record of this genus and shed light on the body plan of the alvarezsaurid clade Patagonykinae by permitting a more complete reconstruction of the neck, pectoral girdle, hindlimb, and tail.

Spatial distribution of fine-grained floodplain deposits and anthropogenic materials based on official borehole data in the floodplain of Leipzig, Germany.

This data set includes the spatial model of the thickness and distribution of fine-grained floodplain deposits in the Leipzig floodplain area. The data set originates from borehole records provided by the Saxon State Office for Environment, Agriculture, and Geology [1]. The data processing involved the categorization of the stratigraphic descriptions of the borehole logs. For that, a methodology was implemented to categorize those into 6 broader classifications (sand, gravel, clay, anthropogenic sediments, fine-grained/organic sediments and others) with 33 sub-categories. Subsequently, the stratigraphic layers were analysed to determine the depth and thickness of the fine-grained floodplain deposits, as well as the distribution of anthropogenic material. The data set was filtered, with the condition that each borehole log has at least one clayey layer and a gravel layer of at least 0.7 m thickness and, later, interpolated to present a complete spatial model for the research area. The final data set is based on 3,414 data points (data collection covers the period: 1852 to 2018) within the Leipzig floodplain and offers significant resource for future interdisciplinary research into the natural and anthropogenic history of the Leipzig's floodplains, offering valuable information for more detailed analyses and more precise modelling of fine-grained floodplain deposit distribution in the Leipzig floodplain area.

Thickness of the stratigraphic record of Britain: How the fidelity of geological and fossil data is unrelated to rock quantity

Thickness of the stratigraphic record of Britain: How the fidelity of geological and fossil data is unrelated to rock quantity

GEOSEISMIC CHARACTERISTICS, HYDROCARBON POTENTIAL AND RESOURCES OF THE NORTH KARA SEDIMENTARY BASIN

This study presents a geological model of the North Kara sedimentary basin, which was developed based on the integrated interpretation of seismic and geological data on islands and Siberian continental margin, and provides seismostratigraphic and structural-tectonic characterization of the basin. The results of the study indicate that the sedimentary cover of much of the basin is composed of Paleozoic sediments of Cambrian to Permian age, reaching 13–14 km in thickness in depression zones. The thickness of Mesozoic sediments over much of the basin is < 1 km; in the northwest, where the North Kara basin borders the Barents Sea basin, the thickness of Mesozoic sediments increases to 5–6 km, and the sedimentary cover comprises Paleozoic, Triassic, Jurassic and Cretaceous geoseismic sequences. In terms of its hydrocarbon potential, the North Kara sedimentary basin is regarded as part of the potential oil and gas-bearing area of the same name, having a good hydrocarbon potential based on seismic stratigraphic and structural-tectonic considerations. A number of large depressions and uplifts recognized in the structural geometries of different stratigraphic levels can be associated with petroleum generation and accumulation zones; a number of anticlinal, structural-tectonic, structural-stratigraphic traps that are distinguished in different sedimentary complexes ranging in age from Cambrian to Jurassic can be considered as promising exploration targets. The proposed quantitative assessment shows that the most probable initial in-place hydrocarbon resources of the North Kara sedimentary basin are equal to about 10.7 billion tons of hydrocarbon equivalent.

BITUMOIDS IN CAMBRIAN DEPOSITS OF THE CIS-YENISEI SUB-BASIN: FORMATION CONDITIONS, DIAGNOSTIC CRITE

The history of development of the Cis-Yenisei sedimentary sub-basin, the presence of several stratigraphic levels in the section of organic-rich Cambrian rocks, and high level of catagenetic transformations (i.e. high maturity level) of the organic matter suggest intensive hydrocarbon generation processes in these deposits in the geological past. The migration processes are shown to be responsible for high variability of bitumoids (chloroform-extractable part of organic matter), both in terms of their content and group/hydrocarbon composition. This is evidenced by three variety of bitumoids (allochthonous, autochthonous, and sedentary autochthonous) defined according to the Uspenskii-Vassoevich regularity. In order to attain more precise differentiation between these bitumoids, we propose here their classification by group and hydrocarbon composition, into seven classes. Allochthonous bitumoids (class VII) are described as hydrocarbon-dominated and migration-prone accounts for about 30% of the total amount of bitumoids, another (mixed) group (6%) is made up by autochthonous-allochthones bitumoids (classes V, VI), while the last group includes autochthonous and sedentary autochthonous bitumoids, with their composition dominated by asphaltenes and resins. Results of the molecular analysis of the composition of bitumoids generally attest to the genetic unity of autochthonous and allochthonous bitumoids. For allochthonous bitumoids, however, there is a wider range of values for molecular indicators, which evidence the influence of migration processes on their composition.

EXAMINING ENVIRONMENTAL IMPACT THROUGH GEOLOGICAL INTERACTIONS AND EARTH'S LAYERS

Understanding the impact of geological processes on the environment is very important in comprehending Earth's evolving ecosystem and predicting future ecological challenges. This paper reviews how interactions between different Earth layers-the crust and mantle, affect ecological dynamics. Geological interactions, including tectonic shifts, mineral formation, and stratigraphic layering, were analysed; from this analysis, their effects on natural landscapes, resource distribution, and ecosystem balance were unravelled. The study also extends further to anthropogenic implications, showing how human activity coupled with these geological forces drives climate, biodiversity, and resource sustainability. Such analysis of this earth layer and geological interaction would thus provide a comprehensive view of the environmental impacts while offering substantial input toward sustainable environmental management and policy planning. These results reiterate the necessity for geological multi-disciplinarity and the use of ecological sciences while trying to solve some fundamental environmental issues that will guarantee a safe future because of an Earth system that is undergoing ever-increasing rates of change.

Upper Devonian сalcareous algae of the Northern part of the Lviv Paleozoic Trough (systematic composition, facial timing and stratigraphic significance)

As a result of the study of core material in the volume of 211 thin sections from five boreholes of the Northern part of the Lviv Paleozoic Trough, a complex of fossil green, red, and charophyte algae was revealed, which consists of 20 species of 13 genera of green, red, and charophyte algae, among which five species of five genera are identified for the first time for the Devonian deposits of the Lviv Paleozoic Trough. The carbonate deposits belong to the Frasnian and Famennian stages and are represented mainly by sandstones, argillites, siltstones, limestones, dolomites, marls, and white chalk. Carbonate deposits are represented mainly by pelitomorphic wackestones, packstones, wackestone-packstones, grainstones, grainstone-packstones, micrite, bioclastic wackestones, and microbioclastic pelitomorphic wackestones. Limestones often have a pelitomorphic texture, enriched with sand material or dolomitized. The algae are confined primarily to pelitomorphic wackestones of the Waulsortian type, which indicates the intermediate facies of the shelf margins, which were formed by the open circulation of sea waters. To a lesser extent, algae occur in packstones, grainstones, wack-packstones, and are found predominantly along the remains of foraminifera, crinoids, bryozoans, ostracods, and sponge spicules. It is revealed that the algal assemblage of the Famennian stage is depleted and represented mainly by the green tubular algae of the families Palaeoberesellaceae Mamet et Roux and Dasycladaceae Kützing. Higher up the section, a few charophyte algae of the genus Planoumbella Platonov are found. The assemblage of the Famennian stage is significantly enriched, both numerous and systematic. Numerous charophyte and red algae appear, especially in the upper part of the section, which corresponds to the stratigraphic level of the zone C1ta of Donbass. These deposits were considered for a long time to be Tournaisian until at the All-Union Congress in 1986 the Devonian-Carboniferous boundary at the base of the Gattendorfia (Acutimoceras) goniatite zone and the Siphonodella sulcata conodont zone was drawn, which represents the top of the C1ta zone of Donbass. At this level, the richest and most varied algae assemblage is revealed. Above this level, representatives of the genus Parachaetetes Deninger and charophyte algae are not found. The prevalence of the green siphoncladal algae in the Frasnian association indicates a calm hydrodynamic regime below the level of the tide, as well as the depth of the basin, which does not exceed 3-5 m, slight fluctuation in the depth of the sea basin, good illumination, and warm water. The significant distribution of charophyte algae in the Famennian time indicates a decrease in salinity in the paleobasin due to the flow of fresh water from the Kovel uplift.

MORPHOLOGY AND PRESERVATION OF GAOJIASHANIA, AN ENIGMATIC TUBULAR FOSSIL FROM THE UPPER EDIACARAN DUNFEE MEMBER, DEEP SPRING FORMATION, NEVADA, USA

Abstract The upper Ediacaran stratigraphic record hosts fossil assemblages of Earth’s earliest communities of complex, macroscopic, multicellular life. Tubular fossils are a common and diverse, though frequently undercharacterized, component of many of these assemblages. Gaojiashania cyclus is an enigmatic tubular fossil and candidate index fossil found in upper Ediacaran strata globally and is best known from the Gaojiashan Lagerstätte of South China. Here we describe a recently discovered assemblage of Gaojiashania fossils from the Ediacaran Dunfee Member of the Deep Spring Formation of Nevada, USA. Both body and trace fossil affinities have been proposed for Gaojiashania; we present morphological and biostratinomic evidence for a body fossil affinity for the Dunfee specimens. Additionally, previous studies have highlighted that Ediacaran tubular fossils are characterized by a wide range of preservational modes, including association with pyrite, apatite, or clay minerals and preservation as carbonaceous compressions. Petrographic, SEM, and EDS data indicate that the Dunfee Gaojiashania specimens are preserved as ‘Ediacara-style’ external, internal and composite molds, in siltstone and sandstone with a clay mineral-rich matrix of both aluminosilicates and non-aluminous Mg- and Fe-rich silicate minerals that we interpret as authigenic clays. Authigenic clay-mediated fossilization of unmineralized tissues, including moldic preservation in heterolithic siliciclastic strata, as indicated by the Dunfee Gaojiashania, may be linked to the prevalence of both silica-rich and ferruginous seawater conditions prior to both the radiation of silica-biomineralizing organisms and the rise of ocean and atmospheric oxygen to modern levels. In this light, clay authigenesis may have played a critical role in facilitating multiple modes of Ediacaran and Cambrian exceptional fossilization, thus shaping the stratigraphic distribution of a range of Ediacara macrofossil taxa.

RECONSTRUCTION OF RAPHAEL SANTI’S PAINTING WORKSHOP FROM THE UMBRIAN-FLORENTINE PERIOD BASED ON THE AUTHORIAL REVERSE TECHNOLOGY

In the first stage of the research all the elements of painting technique and technology were developed, and painting materials as close as possible to those used by Raphael were prepared in order to obtain a research material compatible with the original material. Then, based on the technique and technology developed, an experimental image of the Madonna and Child was made as a test painting intended to simulate the complete structure of Raphael's original image. In the last stage, physicochemical tests of the experimental image were performed. Observation of the image in IR radiation, X-ray and stratigraphic examination of the image painting layers were performed. The infrared, X-ray and stratigraphic tests were compared with the analogous test results of three selected paintings by Raphael, which allowed interpretation of test results from the original works to a greater extent than before. In addition, experimental image research has highlighted the limitations of research into the stratigraphy of the painting layers, as well as instrumental studies that affect the current state of knowledge about Raphael Santi's painting workshop.

Postcranial Osteoderms of Late Permian Pareiasaurs from Eastern Europe – I. Chronology of Localities

To clarify the chronological sequence of East European localities of late Permian pareiasaurian osteoderms, a stratigraphic analysis of the osteoderm-bearing strata was carried out. Thirty localities have been dated with maximum accuracy, which characterize eight successive stratigraphic levels – the Vanyushonkian, Syominian and Kichugian beds of the Putyatinian Regional Stage (Upper Severodvinian), Chizhian and Rovdinian beds of the Bykovian Regional Stage (Lower Vyatkian), Aristovian and Gorokhovetsian beds of the Nefyodovian Regional Stage (Upper Vyatkian), and Lagernian beds of the Zhukovian Regional Stage (Upper Vyatkian).

Diagenesis of the Clay-Sulfate Stratigraphic Transition, Mount Sharp Group, Gale Crater, Mars.

The diversity and abundance of diagenetic textures observed in sedimentary rocks of the clay-sulfate transition recorded in the stratigraphic record of Gale crater are distinctive within the rover's traverse. This study catalogs all textures observed by the MAHLI instrument, including their abundances, morphologies, and cross-cutting relationships in order to suggest a paragenetic sequence in which multiple episodes of diagenetic fluid flow were required to form co-occurring color variations, pits, and nodules; secondary nodule populations; and two generations of Ca sulfate fracture-filling vein precipitation. Spatial heterogeneities in the abundance and diversity of these textures throughout the studied stratigraphic section loosely correlate with stratigraphic unit, suggesting that grain size and compaction controls on fluid pathways influenced their formation; these patterns are especially prevalent in the Pontours member, where primary stratigraphy is entirely overprinted by a nodular fabric, and the base of the stratigraphic section, where increased textural diversity may be influenced by the underlying less permeable clay-bearing rocks of the Glen Torridon region. Correlations between quantitative nodule abundance and subtle variations in measured bulk rock chemistry (especially MgO and SO3 enrichment) by the Alpha Particle X-Ray Spectrometer instrument suggest that an increase in Mg sulfate upsection is linked to precipitation of pore-filling diagenetic cement. Due to a lack of sedimentological evidence for widespread evaporite or near-surface crust formation of these Mg sulfates, we propose three alternative hypotheses for subsurface groundwater-related remobilization of pre-existing sulfates and reprecipitation at depth in pore spaces.

Hybrid turbidite-contourite system on the upper-slope continental margin of the offshore southern Tanzania

Cretaceous-Cenozoic hybrid turbidite-contourite (HTCs) systems on the upper-slope region of the northern Rovuma Basin, southern offshore Tanzania have been poorly studied. HTCs have been widely studied from several places due to their petroleum prospectivity, link to geohazards, and potential to help understand deep marine circulation processes and past climates. We have studied 3D seismic data into the northern Rovuma Basin to establish variation and orientation of seismic facies, architectural elements and geomorphologies (based on RMS amplitude maps) characterizing the Cretaceous-Cenozoic HTCs linked to channelized sediment transport and deposition. Two different migration patterns for channelized systems are recognized. They include Cretaceous-Middle Miocene and Middle Miocene-Holocene systems migrating toward SE and NW, respectively. Timing of change in migration trends coincides with change in traverse directions of major submarine channels that allowed sediment transportation by gravity flows. Trajectory of the submarine channels shifted from S-N to SW-NE and approximately W-E during the Middle Miocene, agreeing with the change in channel fills migration trends. The trajectory shift, for the revealed submarine channels was caused by tectonic activity linked to East African Rift System, so does the distribution and migration trends of the HTCs. The study area has hydrocarbon accumulations in the Oligo-Miocene sandstones containing HTCs characterized by a clearly defined depositional system with high RMS amplitudes. The Middle Miocene-Early Pliocene interval has a clear depositional configuration as well, but its low RMS amplitude indicates dominance of fine-grained HTCs with limited reservoir potential. The Late Pliocene-Holocene interval has very high RMS amplitude, but its chaotic configuration implies the presence of poorly sorted sedimentary fills having limited reservoir potential as well. This may be one of the reasons for hydrocarbon discoveries in the study area being limited within the Oligo-Miocene sandstones, and not the younger stratigraphic levels.

Radiocarbon age-offset measurements reveal shifts in the transport mechanism and age of permafrost-derived organic carbon from Burial Lake, arctic Alaska from MIS 3 to present

The stability of arctic permafrost and the carbon it contains are currently threatened by a rapidly warming climate. Burial Lake, situated in northwestern arctic Alaska, is underlain by continuous permafrost and has a uniquely rich set of paleoclimate proxy data that comprise a 40-ka record of climate and environmental change extending well into Marine Isotope Stage (MIS) 3. Here, we examine the relationship between erosion, subsurface hydrology, and primary productivity from the Burial Lake sediments to improve our understanding of the links between climate, hydrology, sediment transport, and carbon mobility. The record is developed with radiocarbon (14C) age-offsets from two independent methods used to date the lake sediments: 1) 14C measurements on paired bulk sediment and plant macrofossils from the same stratigraphic layer of lake sediment and 2) ramped pyrolysis-oxidation (RPO) 14C analysis that separates fractions of organic carbon (OC) from a single bulk sediment sample based on thermochemical differences through continuous heating. As lakes capture and archive OC transported from the watershed, changes in the amount and relative age of permafrost-derived OC mobilized during past climatic variations can be documented by examining how age-offsets change over time. The Burial Lake sediment revealed higher age-offsets during the cold Last Glacial Maximum (LGM; ∼29-17 ka) than the comparatively warmer post-glacial (∼17 ka-present) and the MIS 3 interstadial (∼40-29 ka) periods. The relatively warm, wet climate of the post-glacial period promoted both terrestrial and aquatic productivity, resulting in increased OC deposition, and it likely favored transport via subsurface flow of dissolved OC (DOC) sourced from soils. This resulted in a greater flux of contemporary OC relative to ancient OC into the lake sediment, lowering the average age offset to ∼2 ka. In contrast, the low-productivity conditions of the LGM resulted in slow soil accumulation rates, leaving ancient OC in a shallower position in the soil profile and allowing it to be easily eroded in the form of particulate OC (POC). Although the amount of total OC deposited in the lakebed during the LGM is small relative to post-glacial deposition, the majority is ancient, which leads to a relatively high average age offset of ∼9 ka. Finally, climate and environmental conditions of the MIS 3 interstadial were intermediate between those of the post-glacial and the LGM. As with post-glacial sediments, a relatively large amount of OC is present; however, the vast majority of it is ancient (more similar to the LGM), and it produces an average age offset of ∼6 ka. The Burial Lake radiocarbon record demonstrates the complexities of the thaw and mobilization of permafrost OC in arctic Alaska, including the balance between production, transport, deposition, remobilization, and preservation. This record highlights the importance of considering factors that both enhance and inhibit erosion (i.e. vegetation cover, lake level, precipitation) and the mechanisms of OC transport (i.e. subsurface flow or erosion) in predictions of future permafrost response to changes in climate.

Characterization of Halimeda Bioherms of the Pre-Evaporitic Messinian of the Salento Peninsula (Southern Italy)

Calcareous green algae bioherms have recently gained significant attention in the scientific community, as they serve as valuable stratigraphic and paleoecological archives, comparable to the most studied coral reefs. Currently, the genus Halimeda, which is very abundant in tropical settings and common in temperate ones, contributes significantly to the production of sediments rich in CaCO3. This is due to a rapid calcification process that occurs in its peculiar internal structure. Halimeda bioherms represent a key case because of their non-continuous distribution in the stratigraphic record and in the Modern oceans. In fact, the presence of the green alga Halimeda is widely documented in present-day reefs throughout the entire tropical belt, although extensive bioherms are limited to areas such as the Indonesian K-Bank, the Caribbean, and particularly along the Australian Great Barrier Reef (GBR), where they reach remarkable extensions exceeding 6000 km2. Discontinuous distribution is also noted during the Miocene, with Halimeda bioherms reported only in three main localities within the Mediterranean basin, all dating to the pre-evaporitic Messinian. In this study, we present data obtained from detailed stratigraphic and sedimentological analyses of two small Halimeda bioherms (with a maximum thickness of 5 to 6 m), located in the southernmost portion of the Apulia Carbonate Platform (Salento Peninsula, Italy). Field observations, coupled with thin sections analysis show that despite these two sections being ascribed to different stratigraphic intervals, both record the same facies, with an alternation of shallowing-deepening cycles. While it is documented that different Halimeda species currently inhabiting carbonate systems respond variably to factors such as light, temperature, and salinity, the input of large quantities of nutrients via upwelling currents has recently become the most widely accepted hypothesis to support the occurrence of wide bioherms such as along the GBR. We infer that the occurrence of Salento Messinian Halimeda-rich facies could be related to upwelling of cool, nutrient-rich waters, possibly enhanced by the occurrence of internal waves (IWs). Such processes are well documented in the Salento Peninsula and in many areas of the Mediterranean throughout the Tortonian and likely still acting during the early Messinian.

Sedimentary record of oceanic plateau accretion: Revisiting the Eocene to Miocene stratigraphy of the northern Olympic Peninsula, Washington (USA)

Abstract Oceanic plateaus are common in modern oceanic basins and will ultimately collide with continental subduction zones. Despite the frequency of these events, complete sedimentary records of oceanic plateau collision and accretion have remained limited to only a few Cenozoic examples with excellent exposure and tectonic context. Our study focuses on building a stratigraphic record of plateau collision using the sedimentary strata deposited on the Siletzia oceanic plateau, which accreted to the Pacific Northwest at ca. 50 Ma. By combining previously published provenance and stratigraphic data with new lithofacies and geologic mapping, measured stratigraphic sections, conglomerate clast counts, and U-Pb zircon geochronology, we were able to divide the strata of the northern Olympic Peninsula in Washington, USA, into precollisional, syn-collisional, and postcollisional stages. Precollisional strata include early Eocene deep-marine hemipelagic to pelagic mudstones of the Aldwell Formation that were deposited directly on Siletzia basalts. These strata were deformed during collision and are separated from the overlying syn-collisional middle Eocene sandstone and conglomerate of the marine (?) Lyre Formation by an angular unconformity. Postcollisional strata were deposited by submarine fans and include interbedded sandstone and siltstone of the Hoko River and Makah formations. These units initially record the filling of isolated trench-slope basins by late Eocene time before eventual integration into an Oligocene regional forearc basin as the accreted Siletzia plateau began to subside. Our chronostratigraphy permits the correlation of basin strata across tectonic domains and provides more general insight into how forearc sedimentary systems evolve following the accretion of a young, buoyant oceanic plateau.

Pedogenic evidence sheds light on the post-Roman pedo-sedimentological and human history of Tarsus, the Roman capital of CE 60, Cilicia, Mersin, Türkiye

The ancient city of Tarsus is underlying a sediment of 400 cm where the contemporary Tarsus grew. The diffusely stratified layers of the deposited sediment from the Kydnos (Tarsus) river overlying the Roman Road excavation site located in the heart of the modern city. The sediment is laden with technogenic materials. The profile of the stratigraphic layers represents a Pedocomplex (PDC) and its horizons are the Pedomembers (PDMs). All the PDMs were described and sampled for physical, chemical, mineralogical, micromorphological, and thermoluminescense analyses seeking pedogenic evidences. The origin of PDC materials is a fluvial and/or lagoon environment (archaeologically predicted date, about 60 CE, and they are calcareous, high in available P and some are high in total phosphorus contents). They have been partially modified by human activity in a settlement area, thus bringing some historical evidence suggesting that the site was part of the growing city after its abandonment. Thin sections show a vigorous biological degradation of the organic residues in the PDMs along with occasional evidence of soil-forming processes. The preliminary conclusions were extracted from the results obtained through the newly formed hydroxyapatite (Hap) determined by micromorphology, therefore proposing the new suffix π for the WRB soil naming system. Primary, high temperature and clay minerals together with TL analyses of the layers, were conducted to reveal the provenance and weathering phases of the horizons. The seeds recovered from an inhabited layer helped to interpret the food and medicinal habits of the local society and the contemporary presence of the lagoon.