Stratigraphic Position Research Articles

Non-Ceramic Site of Shamanka 8 on the Southern Coast of Baikal Lake

Purpose. The southern coast of lake Baikal is a territory known in Siberian archaeology for its Kitoi cemeteries. Besides burials of the Shaman capes there are some Neolithic and Bronze age complexes at Circum–Baikal railway. In 2012 it the first non-ceramic site was discovered in South Baikal, which was named Shamanka 8. This paper presents the assemblage of this complex and discusses its chronological and cultural features.Results. The Shamanka 8 site is located on the top of the third hill of the Shaman cape. The cultural layer lies under the Holocene Optimum sediments. The site stratigraphic structure is characterized by compression. There is no bone fragments and ceramic. For lithic knapping, mainly local raw material (quartz) were used. The quartz assemblage has such features as poor formal standardization, high degree of flake fragmentation, cores with the orientation of fracture plane relative to the longitudinal axis, bipolar reduction. All of these specifics are explained by uneven fracture characteristics and bad workability of quartz, as well as its breakage patterns. Some artifacts, including single non-quartz tool, suggest that there may be a connection between the Shamanka 8 site and the industries of the Final Paleolithic sites in the Northern Baikal region and the Irkutsk region. Quartz small knife (?), carinated end-scraper and tubular core have analogies in the 2nd cultural layer of the Kurla II site, dated by 13.5 uncal kya. Similarly dated quartz components of Nirikan I and flint tool-kit of Verkholenskaya Gora I include other cultural link types.Conclusion. The similarity in the morphology of some tools with Final Paleolithic counterparts and stratigraphic position of finds allow us to assume the Final Sartan age of the Shamanka 8 site and dates it to the Bølling – Allerød warming. However, in the absence of direct radiocarbon dating, an Early Holocene/Early Neolithic attribution of the site is also possible. Further studies may help resolve this issue.

Stratigraphy, sedimentology, and paleoclimatic proxies of the Upper Jurassic Morrison Formation of central Montana: Geology of the Intermountain West

Since the discovery of dinosaurs in the late 19th century, the Upper Jurassic Morrison Formation has received considerable scholarly attention. However, the formation in central Montana needed to be sufficiently investigated. Recent dinosaur excavations from exposed Morrison strata on the southern flank of Spindletop dome near the town of Grass Range, Montana, prompted a review of the formation’s geology, paleobotany, and paleoclimate. A review of historical stratigraphic measurements of the formation in Montana reveals a considerable variance in measured thicknesses. Stratigraphic measurements and regional log data indicate that the formation averages 71 m thick across central Montana. A new regional isopach map of the formation from well-log data illustrates a broad distributive fluvial system that migrated from the southwest toward the northeast. The formation is divided into two informal facies in the study area: lower and upper depositional facies. The lower depositional beds represent the mud-rich distal-most distributive fluvial facies that overlies the stranded muddy tidal flat of the Swift Formation. An increased sandstone:mudstone ratio and small isolated fluvial channel and crevasse splay beds indicate that the upper depositional beds represent the slow progression of the distributive fluvial system. However, a review of the regional field stratigraphy and well-log data did not provide a regional correlatable facies change to warrant subdividing the formation into members.The stratigraphic positions and climatic interpretations for lithologic, faunal, and floral paleoclimatic proxies are specified. The compilation of climate proxy data from central Montana demonstrates that the climate in this region was wetter than in southern parts of the Morrison foreland basin. The climatic proxies signify that the environmental conditions were variable during the Late Jurassic in central Montana, displaying changing temperatures with mesic and xeric intervals of unknown duration.

A new Liassophlebiidae (Odonata: Heterophlebioidea) from strata close to the Triassic-Jurassic boundary in Somerset, UK

ABSTRACT Liassophlebiidae is an extinct family of damsel-dragonflies found in Upper Triassic and Lower Jurassic strata of Europe, Asia and Antarctica. Whilst Liassophlebiidae is well represented by Lower Jurassic fossils, their lowest occurrence in the Upper Triassic has hitherto only been suggested by three fragmentary specimens. These were originally ascribed to two species: Liassophlebia withersi and Liassophlebia batheri, but the latter is now considered nomen dubium. Here we describe a fourth, better preserved specimen that is likely to be Rhaetian (Late Triassic) in age. The specimen, BRSMG Cg3101 a+b, was collected from Bowdens Quarry, Somerset, UK, from the lower part of the White Lias Formation. The specimen comprises an incomplete forewing attributed to Liassophlebia due to: the small number of antenodals, antesubnodals and crossveins between RP and MA based RP3/4 in the base of RP2 opposite the subnodus; a straight and elongate secondary longitudinal vein in the postdiscoidal area; numerous cells and secondary veins in radial and median areas. The specimen is likely to represent a new species and provides stronger evidence than the previous three specimens of the presence of Liassophlebiidae during the late Rhaetian. Its stratigraphical position suggests that Liassophlebiidae arose in the immediate aftermath of the Triassic-Jurassic mass extinction.

On the early development of Huastecs (Gulf of Mexico) revealed by the Earth's magnetic field recorded in domestic hearths

AbstractA detailed magnetic mineralogy and archaeomagnetic study was carried out on recently discovered domestic hearths and burned floors at the Chak Pet archaeological settlement (Tamaulipas, Mexico). The study aimed to obtain reliable absolute chronological constraints on the early development of Huastecs during the Formative period. Oriented hand samples corresponded to four domestic hearths and one burned floor. Continuous thermomagnetic curves revealed mostly irreversible behavior, while titanomagnetites, titanomaghemites, and goethites are assumed to carry the remanent magnetization. In total, 87 specimens were subjected to stepwise demagnetization of natural remanent magnetization using an alternating field procedure. Characteristic remanent magnetization directions were obtained for 29 samples of two hearths and one burned floor. No single, technically acceptable paleointensity determination was obtained. The new archaeomagnetic age intervals for Chak Pet allow locating the origin of this settlement at the Gulf of Mexico within the Middle Formative (900–600 BCE) continuing until the Late Formative period (350–100 BCE). New archaeomagnetic ages are in accordance with the diagnostic pottery analysis. Dated archaeological elements are associated with both ceramic types and different sets of burials, providing a reliable tool to calibrate their chronological and stratigraphic positions.

Tracing the origin of Lago Mare biota: Ostracods and mollusks from the late Neogene of the Slavonian mountains in the southern Pannonian Basin (NE Croatia)

Lake Pannon was a huge central European, long-lived endorheic lake occupying the Pannonian Basin System during the late Neogene. The benthic fauna of this originally sparsely populated brackish lake went through a spectacular adaptive radiation leading to a great number of autochthonous species. Although largely endemic, some of these species are excellent stratigraphic markers of the Lago Mare interval in the Mediterranean Basin. This situation apparently reflects a short-termed unidirectional migration-wave in the latest Miocene. The latter interval marks the final phase of a major environmental perturbation followed by a massive evaporite deposition termed the Messinian Salinity Crisis. The Section Bozara, located in the southern Pannonian Basin at the southern slopes of Mt. Papuk, bears a well-preserved benthic fauna representative of Lake Pannon. It is embedded into a 25-m-thick succession of alternating mud and sand packages. We detected therein 25 ostracod and 18 mollusk taxa enabling, along with a sedimentary facies analysis, an integrated evaluation of the depositional setting, biostratigraphic position, and paleogeographic distribution pattern. Accordingly, the depositional environment shows a shallowing upward trend from deep-water sublittoral and distal prodelta settings to deltaic high-energy littoral conditions. The biostratigraphic markers, such as the bivalve Rhombocongeria rhomboidea (Hörnes, 1867) and the ostracod Caspiocypris pontica (Sokač, 1972), constrained its stratigraphic position to the Portaferrian interval (8.0–4.5 Ma). Of 16 ostracod taxa determined at the species level, 10 are shared with the Eastern Paratethys, whereas only 3 are present in the Mediterranean Lago Mare deposits as well. In contrast, among 12 corresponding mollusk taxa, only 4 are known from the Eastern Paratethys, all being absent in the Lago Mare interval. Such a paleobiogeographic pattern suggests that the time window of the outflow event from Lake Pannon into the Eastern Paratethys was not synchronous with, but must have preceded, the hypothetic Eastern Paratethys drainage event generating the Lago Mare depositional conditions in the Mediterranean Basin.

BILOZERSKA SERIES OF THE UKRAINIAN SHIELD: PROBLEMS OF STRATIGRAPHY AND CORRELATION

The article discusses the problematic issues of the geological structure of the Bilozersky synclinorium of the Ukrainian Shield, its stratigraphic structure, formation composition and absolute age of the rock associations that compose it. The interrelationships of interregional correlation of the Bilozerska and Kryvyi Rih series of the Ukrainian Shield are considered. Significant adjustments to the current stratigraphic scheme of the Bilozerska series are proposed. The necessity of abolishing the upper metasedimentary stratum (Pereverzevska Suite) and returning to the traditional twoshell structure of the Bilozerska series, which consists of a sub-iron-bearing essentially terrigenous and iron-bearing terrigenous-chemogenic ferruginous-siliceous suite, is noted. The author’s interpretation of the folded structure of the central zone of the Bilozerska structure is proposed, which allows to explain all the complexities of its stratigraphy in a consistent manner, to reconcile the stratigraphic position of the Teplivska Association of the Bilozersky synclinorium with the position of the Talc Horizon of the Kryvyi Rih series, and to show a complete correspondence in the general sequence of stratons between the sediments of the Bilozerska and Kryvyi Rih series. The complete lithologic, stratigraphic, and formational correlation of the Bilozerska series with the section of the Kryvyi Rih series within the Skelyuvatsko- Saksagan sedimentary cycle is shown by a set of features. It is recommended to unite the Kryvyi Rih and Bilozerska series into a single supra-regional and superserial taxon – the Kryvyi Rih-Bilozersky complex.

Life on the way out of Shuram Excursion: New locality of Ediacaran biota in the Ura Uplift of the southern Siberian Platform

The Ura Uplift section in the Patom Highlands area of Siberia is one of the most complete Neoproterozoic carbonate-siliciclastic succession with excellent chemostratigraphic records (δ13C and 87Sr/86Sr). Present study reveals the first finds of Ediacaran macrofossils within thick siliciclastic/carbonate succession of the Chencha and Zherba formations with well-established negative δ13C anomaly attributed to the Shuram Excursion in this section. The fossils are preserved in glauconitic and quartz sandstone horizons in shallow-marine tide-influenced nearshore environment and share many taphonomic and morphological features with the White Sea- and Nama-type biotas. On the one hand, stratigraphic position of some of fossils within the uppermost Shuram Excursion falls into the time interval ∼573–567 Ma and therefore is correlative to the Avalon-type fossil assemblage. On the other hand, the new fossil assemblage indicates to the earlier appearance of some Nama-type species, such as erniettomorphs, than it was thought. In addition, the new assemblage is characterised by low-diversity metazoan community dominated by microbial textures. It potentially supports the hypothesis that the Ediacaran shallow water fossil assemblages were significantly less species-rich than their deeper water counterparts. The discovery of the oldest macrofossils in South Siberia both opens a new window to understand their palaeoecology and taphonomy, and demonstrates that palaeontological potential of such a vast region has not entirely been realised.

The first dinosaurs in Iberia: a new dinosaur tracksite from the Sinemurian (Lower Jurassic) of Portugal

ABSTRACT Dinosaur fossils from the Lower Jurassic are very scarce in the Iberian Peninsula, which lacks a dinosaur track record. This study reports a new ichnosite from this age, at the Alvaiázere Municipality (Lusitanian Basin, Portugal) with several well-defined dinosaur and other archosaurs tracks. Seventeen tracks were identified at the top sedimentary surface of a fine-grained dolostone bed belonging to the Coimbra Formation (Sinemurian, Lower Jurassic). Therefore, the tracksite could have an age of ~196 to 194 Ma, based in the stratigraphic position of the tracksite in the Coimbra Formation succession. The ichnological comparison allows us to ascribe these tracks to Moyenisauropus and Batrachopus ichnogenera. The dinosaur tracks are assigned to the new ichnospecies Moyenisauropus lusitanicus isp. nov. The trackmaker could be a basal thyreophoran dinosaur related to Emausaurus or Scelidosaurus, and the presence of a manus-pes pair track set verifies that these tracks were made by a quadrupedal gait. The crocodylomorph trackmaker could be a teleosaurid. The analysed bioturbated fine-grained dolostone bed was deposited in very shallow subtidal to intertidal, carbonate lagoonal (?) environment. The evidence provided here indicates the presence of crocodylomorphs and thyreophoran dinosaurs in a tropical coastal wetland carbonate system developed during the Early Jurassic in the Lusitanian Basin (Atlantic western margin of Iberia).

A new isochron for stratigraphic correlation in the Permian Delaware Basin and beyond

Altered volcanic ash, preserved as bentonite clay within sedimentary depositional units, can facilitate regional stratigraphic correlation. While many bentonite ash beds have been documented in core extracted over decades of hydrocarbon exploration in the Delaware Basin, a particular ∼1 cm-thick bentonite has been identified at a distinct stratigraphic position, at a sedimentary facies transition from thin-bedded calciclastic turbidites to thick-bedded siliciclastic turbidites, in the compositionally-mixed upper Wolfcamp formation. A comparison of geochemical analyses of the ash from two cores and petrophysical correlations across eight wells was conducted to test the regional correlation of the ash. Despite diagenetic alteration since seafloor deposition ∼280 Ma, nearly identical geochemical trends between incompatible elemental subsets, including light and heavy rare earth elements, large ion lithophiles, and high field strength elements, suggest that these two ash deposits originated from the same volcanic center. Detailed sedimentologic analyses and lithostratigraphic correlations across three cores spaced tens of km apart confirm that the ash bed is bound by correlative quiescent deepwater strata. Based on the chemical composition, probable timing of deposition, and proximity, we speculate that the Las Delicias Arc produced this ash, and it was transported by wind and deposited as a hemipelagite into the Delaware Basin deep marine environment. This discovery implies the existence of the ash marker in other cores within Late Paleozoic western equatorial Pangea, e.g. in compositionally-mixed deep marine deposits of the Midland Basin and outcropping deposits around the Greater Permian Basin and beyond, which would facilitate regional chronostratigraphic correlation for a critical time in Earth's history.

Bioturbated strata in the Upper Cretaceous Aruma Formation, central Saudi Arabia: An analog for aquifers and hydrocarbon reservoirs with large burrows

The upper Cretaceous Aruma Formation in Central Saudi Arabia exhibits Thalassinoides-bearing strata resembling a bioturbated carbonate reservoir with large burrows. These burrows possess distinct stratigraphic characteristics. Certain intervals within the formation feature open or partially filled Thalassinoides, creating three-dimensional permeability pathways, while others contain Thalassinoides filled with low-permeability sediments. This comprehensive study investigates the paleoenvironment, ichnological features, bulk permeability influence, and stratigraphic variations of these bioturbated intervals. Incorporating field observations, laboratory analyses (including petrography, geochemical assessments, petrophysical measurements, and computed tomography scanning [CT]), we present the division of the studied interval into three biogenically influenced fluid flow media (BIFM 1–3). BIFM 1 comprises solution-enlarged open Thalassinoides (average shaft diameter: 5 cm) hosted within a mud-dominated matrix. BIFM 2 consists of Thalassinoides with mud-dominated infills (average shaft diameter: 3 cm) embedded in a dolomite matrix. BIFM 3 exhibits compacted open Thalassinoides. These BIFM units demonstrate burrow percentages ranging from 10% to 45%, featuring interconnected networks. The identified units reflect diverse depositional settings, ranging from open marine to restricted lagoon, and distinct stratigraphic positions. By highlighting the sedimentological and stratigraphic controls on the petrophysical properties of carbonate strata containing Thalassinoides with large burrows, this research contributes to the prediction of super-permeability zones in analogous settings.

About the so-called «Bug series» of the Middle Bug region (Ukrainian Shield). Article 3. Problems of origin and age.

The name «Bug Series» was introduced into the Precambrian stratigraphic scheme of the Ukrainian Shield more than half a century ago. During this period, ideas about the composition and age of the series changed several times, but at the same time, until recently, the opinion of various studies about its stratigenic nature remained unchanged. In recent years, a number of publications have appeared in which other views on the origin of the «Bug series» are expressed. Initially, they concerned only individual petrographic groups, such as carbonate and magnetite-bearing rocks, which were attributed to endo­genous (magmatic) origin. Later, an opinion was expressed about the nonstratigenic origin of the entire «Bug Series», and some authors propose to abandon the dismemberment of the Early Precambrian granulite complexes into suites altogether. These ideas are based only on the materials of the study of local objects obtained by drilling and geophysical methods, and they do not take into account the results of regional geological and stratigraphic studies. Simultaneously with new ideas about the genesis of the «Bug series», an attempt is being made to link its origin with faults and to revise its age.
 In order to discuss the problem of the «Bug series», a series of publications has been prepared, in which the main generalized data of many years of regional geological and thematic studies on the composition, structure, stratigraphic and structural position of the units belonging to the «Bug series» are presented. The cycle consists of three separate articles. The first article [Kyrylyuk, 2022a] characterizes the composition of subdivisions and rock associations included in the «Bug series» in the current Precambrian stratigraphic scheme of the Ukrainian Shield. In the second article of the series [Kyrylyuk, 2022б], the ideas about the structural position of the «Bug series» and its subdivisions are considered. This final article is devoted to consideration of ideas about the primary nature of the «Bug series» and its age. As for the Kosharo-Aleksandrovskaya and Khashchevo-Zavalyevskaya suites, the composition, structure, and structural-stratigraphic position of these suits in the stratotype region unambiguously testify to their original stratigenic nature. The problem is only the origin of the rock association of magnetic anomalies, which are erroneously included in the Khashchevo-Zavalievskaya suite. But this association, according to the sum of the signs that are given in the article, also has the most probable lithogenic origin. All subdivisions of the «Bug series» are part of the unified Pobug granulite-gneiss complex of the Lower Archean. Its «stratigraphic age» is not younger than 3.8 Ga, and all younger dates indicate a long-term granulite metamorphism of the complex up to 2.0—1.9 Ga.

Manganese-Iron Phosphate Nodules at the Groken Site, Gale Crater, Mars

The MSL Curiosity rover investigated dark, Mn-P-enriched nodules in shallow lacustrine/fluvial sediments at the Groken site in Glen Torridon, Gale Crater, Mars. Applying all relevant information from the rover, the nodules are interpreted as pseudomorphs after original crystals of vivianite, (Fe2+,Mn2+)3(PO4)2·8H2O, that cemented the sediment soon after deposition. The nodules appear to have flat faces and linear boundaries and stand above the surrounding siltstone. ChemCam LIBS (laser-induced breakdown spectrometry) shows that the nodules have MnO abundances approximately twenty times those of the surrounding siltstone matrix, contain little CaO, and have SiO2 and Al2O3 abundances similar to those of the siltstone. A deconvolution of APXS analyses of nodule-bearing targets, interpreted here as representing the nodules’ non-silicate components, shows high concentrations of MnO, P2O5, and FeO and a molar ratio P/Mn = 2. Visible to near-infrared reflectance of the nodules (by ChemCam passive and Mastcam multispectral) is dark and relatively flat, consistent with a mixture of host siltstone, hematite, and a dark spectrally bland material (like pyrolusite, MnO2). A drill sample at the site is shown to contain minimal nodule material, implying that analyses by the CheMin and SAM instruments do not constrain the nodules’ mineralogy or composition. The fact that the nodules contain P and Mn in a small molar integer ratio, P/Mn = 2, suggests that the nodules contained a stoichiometric Mn-phosphate mineral, in which Fe did (i.e., could) not substitute for Mn. The most likely such minerals are laueite and strunzite, Mn2+Fe3+2(PO4)2(OH)2·8H2O and –6H2O, respectively, which occur on Earth as alteration products of other Mn-bearing phosphates including vivianite. Vivianite is a common primary and diagenetic precipitate from low-oxygen, P-enriched waters. Calculated phase equilibria show Mn-bearing vivianite could be replaced by laueite or strunzite and then by hematite plus pyrolusite as the system became more oxidizing and acidic. These data suggest that the nodules originated as vivianite, forming as euhedral crystals in the sediment, enclosing sediment grains as they grew. After formation, the nodules were oxidized—first to laueite/strunzite yielding the diagnostic P/Mn ratio, and then to hematite plus an undefined Mn oxy-hydroxide (like pyrolusite). The limited occurrence of these Mn-Fe-P nodules, both in space and time (i.e., stratigraphic position), suggests a local control on their origin. By terrestrial analogies, it is possible that the nodules precipitated near a spring or seep of Mn-rich water, generated during alteration of olivine in the underlying sediments.

First record of abelisaurid theropods and a peirosaurid crocodyliform from the Upper Cretaceous of Precordillera of La Rioja, NW Argentina

Extra-Patagonian records of Cretaceous theropod dinosaurs in Argentina are limited. When it comes to the Northwest of Argentina, most of the records come from the Cretaceous rocks of Salta Province, which yielded ceratosaurian abelisauroids like Noasaurus and Guemesia. Preliminary studies of the Los Llanos Formation at Eastern La Rioja Province recognized bone remains of Upper Cretaceous undetermined Abelisauridae and Coelurosauria. Recent surveys in the Northwest of the same province, in the outcrops of the Upper Cretaceous Ciénaga del Río Huaco Formation, at Quebrada Santo Domingo (Precordillera), resulted in the discovery of six isolated shed tooth crowns of putative abelisaurid theropods and crocodyliforms. They were found in association with partial skeletons of titanosaurid sauropod dinosaurs from two quarry sites, in the lower and upper sections of the same unit. Here we corroborate the taxonomic assignment of these specimens and their phylogenetic relationships. Five out of six teeth were assigned to Abelisauridae, whereas the remaining is considered to belong to a peirosaurid crocodyliform. Thus, the first occurrence of abelisaurid theropods and peirosaurid crocodyliforms in the Upper Cretaceous of the Precordillera of La Rioja is confirmed. Even though the teeth cannot be assigned to a less inclusive taxon, the difference in their stratigraphic position might indicate the presence of more than a single abelisaurid species in this region. The new results offer an optimistic perspective for future expeditions in this area, which intend to recover more skeletal elements.

A new specimen of Solnhofia parsonsi from the Upper Jurassic (Kimmeridgian) Plattenkalk deposits of Painten (Bavaria, Germany) and comments on the relationship between limb taphonomy and habitat ecology in fossil turtles.

The limestones of the Solnhofen area in southern Germany are one of the most important fossil Lagerstätten from the entire Mesozoic era, especially famous for the exquisitely preserved vertebrates. The turtles from the Solnhofen Limestone have been always of special interest because they include some of the best-preserved specimens from the Mesozoic. Here, we describe a new turtle specimen from the Torleite Formation (Kimmeridgian) of Painten and refer it to the thalassochelydian turtle Solnhofia parsonsi based on the presence of a unique combination of characters. The far majority of morphological differences from previously published specimens can be explained by ontogeny as the new specimen represents a larger, more ossified, and presumably older individual. Additionally, the specimen from Painten is the first described specimen of S. parsonsi preserving the largely complete and articulated limbs, the preservation of which indicates that the taxon did not possess stiffened paddles present in more pelagic marine turtles and is consistent with a previously inferred nearshore marine lifestyle. Contrary to previous inferences, we argue that taphonomic preservation of digits in articulated fossil turtles from laminated deposits cannot be used alone to infer marine or freshwater habitat. Finally, the new specimen from Painten is only the second, for which detailed information on its stratigraphic position and locality of origin are known.

Age and Stratigraphic Position of a Supracrustal Complex (Kaskama Block, Inari Terrane, Northeastern Kola–Norwegian Region of the Fennoscandian Shield)

Age and Stratigraphic Position of a Supracrustal Complex (Kaskama Block, Inari Terrane, Northeastern Kola–Norwegian Region of the Fennoscandian Shield)

Mercury stratigraphy of early Danian sediments from the Rio Grande Rise and the timing of Deccan volcanism

The Maastrichtian - Danian transition is characterized by one of the largest mass extinctions recorded in the geological history of Earth, the Cretaceous-Paleogene (K-Pg boundary). Chemostratigraphic indicators (e.g. Mercury) are of fundamental importance for understanding the causes of this extinction and its effects on the environment in which life after the K-Pg boundary flourished. This study presents a new mercury (Hg) concentrations and Hg/TOC dataset for Deep Sea Drilling Project (DSDP) Site 516F (Rio Grande Rise), in the framework of carbon cycle proxies that depict the Dan-C2 event within the ∼500 kyr that followed the K-Pg event, from 66.05 to 65.55 Ma, and their temporal relationship with the Deccan Traps (DT) volcanic event. Enriched Hg and Hg/TOC values were observed between ∼65.89 Ma (963.45 mbsf) and 65.98 Ma (963.73 mbsf), ∼60 kyr before (or 40 cm below) the Dan-C2 event. Furthermore, the stratigraphic position with the highest Hg and/or Hg/TOC values is ∼40 kyr after the K-Pg boundary. Our results suggest that the DT volcanism is unrelated with the Dan-C2 event observed at Site 516, and that the highest Hg/TOC appear to be coeval with the eruption of the Deccan Ambenali Formation lavas at about ∼65.90–65.95 Ma.

Nearctic Pleistocene ungulates from the Pampean region (Argentina) in the historical collections of Santiago Roth in Switzerland: an overview

Nearctic ungulates such as artiodactyls, perissodactyls, and proboscideans arrived in South America during the Great American Biotic Interchange. Among them are camelids, cervids, tayassuids, equids, tapirids and gomphotherids. A historical collection of Nearctic ungulates from Pleistocene deposits of the Pampean region in Argentina is here studied and described. The collection consists of specimens collected by Santiago Roth in the nineteenth century and brought to Europe, where they are housed in the paleontological collections of the University of Zurich and the Natural History Museum of Geneva. Among the taxa reported here are Notiomastodon platensis,Lama guanicoe, Hemiauchenia paradoxa, Tayassu pecari, Morenelaphus sp., Hippidion cf. H. principale, Equus cf. E. neogeus, and other indeterminate gomphotherids, camelids, tayassuids, cervids, and equids. The exact stratigraphic position of these fossils collected more than 130 years ago is in many cases uncertain. The historical collection is still relevant for taxonomic studies and for offering new insights into palaeobiogeography and palaeobiology of mammalian fauna of the region during the Pleistocene.

Earliest evidence of Inostrancevia in the southern hemisphere: new data from the Usili Formation of Tanzania

ABSTRACT Gorgonopsia is an iconic group of saber-toothed, carnivorous therapsids. They have a rich fossil record in the Karoo Basin of South Africa, but are also relatively common components of coeval Malawian, Tanzanian, Zambian, and Russian assemblages. Phylogenetic analyses have demonstrated that African gorgonopsians form a monophyletic subclade distinct from their Russian relatives, which all fall out near the root of the cladogram, thus suggesting a northern hemisphere origin for the clade as a whole. Surprisingly, recent research has demonstrated that a species of Inostrancevia, a genus previously recorded solely in Russia, occurs in the upper Daptocephalus Assemblage Zone of the Karoo Basin, perhaps the result of immigration following the demise of endemic rubidgeine gorgonopsians in the lower subzone of that unit. Here we describe a large, isolated gorgonopsian premaxilla from a bone-rich, conglomeratic interval at the base of the Usili Formation of Tanzania’s Ruhuhu Basin. Based on its stratigraphic position and fossil content, this unit likely correlates with the Cistecephalus Assemblage Zone. The premaxilla can be confidently referred to the genus Inostrancevia on the basis of its four incisors, a feature unique to Inostrancevia among gorgonopsians. In contrast to the disjunct distribution of inostranceviines and rubidgeines in the uppermost Permian of South Africa, the Tanzanian Inostrancevia likely overlapped with large-bodied rubidgeines such as Dinogorgon and Rubidgea.

Timescale of Emplacement and Rheomorphism of the Green Tuff Ignimbrite (Pantelleria, Italy)

AbstractWe present a multidisciplinary study based on Differential Scanning Calorimetry (DSC), paleomagnetic analysis, and numerical modeling to gain information on the timescales of syn‐ and post‐depositional ductile deformation of the strongly welded and rheomorphic Green Tuff ignimbrite (GT; Pantelleria, Italy). DSC measurements allow the determination of glass fictive temperatures (Tf; i.e., the parameter accounting for the cooling dependence of glass structure and properties). Using a Tf‐based geospeedometry procedure, we infer the cooling rate (qc) experienced by the glassy phases in different lithofacies within the GT formation. Glass shards from the basal pumice fall deposit record a fast qc of ∼10°C/s. In contrast, the ignimbrite body returns slow qc values depending on the stratigraphic position and lithofacies (basal/upper vitrophyres, fiamme‐rich and rheomorphic layers), ranging from ∼10−2 to ∼10−6 °C/s. Moreover, paleomagnetic analyses of the natural remanent magnetization of ignimbrite matrix and embedded lithic clasts indicate an emplacement temperature higher than 550–600°C. By integrating calorimetric and paleomagnetic datasets, we constrain a conductive cooling model, describing the ignimbrite's temperature‐time‐viscosity (T–t–η) evolution from the eruptive temperature to below Tf. Outcomes suggest that the upper and basal vitrophyres deformed and quenched over hours, indicating that the entire GT underwent intense syn‐depositional ductile deformation. Furthermore, the central body remained above Tf for a much longer timespan (>1 month), enabling post‐emplacement rheomorphic flow. Lastly, we discuss the critical role of mechanisms such as shear heating and retrograde solubility of volatiles, in locally controlling the rheological behavior of the GT.

GEOLOGICAL CHARACTERISTICS OF BOLKARDAĞI BAUXITE DEPOSITS IN AYRANCI, THE TAURUS MOUNTAIN, TURKEY

The aim of this study is to determine the stratigraphic position of the bauxite deposits in the Ayrancı region, where the most important bauxite mineralization of the Bolkardağı region is located. In this context, the age of bauxite will be determined by determining the erosion surface associated with stratigraphic features during the formation of bauxite and the age of bauxite according to its side rocks. In the region, there are Permian-Cretaceous aged rocks belonging to the Bolkardağı Union, one of the main tectonic units forming the Central Taurus Mountains. Miocene units covering these rocks are surfaced in the study area. Karamanoglu ophiolite and older units are uncomfortably covered by Miocene aged Mazı and Divlek formations. Bauxite deposits are clearly seen in the Upper Permian aged Dedeköy formation. According to the field studies, the bauxites were formed in the Late Triassic - Early Jurassic interval, on the Upper Permian aged carbonate rocks and Lower Triassic aged shale - sandstone - limestone units and then deposited in caves and dolines within the carbonate rocks. The fact that bauxites are located above dolomites and below, within and above limestones is thought to be due to the different behavior of carbonate rocks.