Terrestrial Deposits Research Articles

Mineralogical and Spectral (Near-Infrared) Characterization of Fe-Rich Vermiculite-Bearing Terrestrial Deposits and Constraints for Mineralogy of Oxia Planum, ExoMars 2022 Landing Site.

Oxia Planum is a Noachian plain on Mars. It was chosen as the final landing site for in situ studies by ExoMars 2022 rover. The main scientific objectives of the mission are to understand the mineralogy and aqueous evolution of ancient Mars with relevance to habitability. Oxia is covered by vast deposits of Fe,Mg-phyllosilicates, but the exact nature of these deposits is not yet fully understood. We performed a survey of potential terrestrial analog rocks, and here we show combined mineralogical characterization of these rocks with their near-infrared spectral analysis. Samples from two terrestrial sites were studied: (1) vermiculitized chlorite-schists from Otago, New Zealand, which underwent an alteration process without significant oxidation; and (2) basaltic tuffs from Granby, Massachusetts, USA, with Fe-rich clays filling amygdales of supposedly hydrothermal origin. Both analogues are incorporated into the newly built Planetary Terrestrial Analogue Library (PTAL) collection. Oxia bedrock clay-rich deposits are spectrally matched best by a well-crystallized trioctahedral vermiculite/saponite mixture from the basaltic tuff, although the contribution of saponite must be minor. Otago vermiculite is a good analogue to Oxia vermiculite in terms of overall mineralogy and Fe content. However, spectral inconsistencies related to the Al content in the Otago clays indicate that illitization of vermiculite, which results from postalteration oxidation, did not occur at Oxia. This implies limited water/rock interactions and reducing conditions during deposition of sediments now constituting the bedrock at Oxia. Whereas the spectral match does not conclusively imply the mineralogy, trioctahedral vermiculite should be considered a likely mineral component of the bedrock unit at Oxia Planum. Vermiculite has great potential to store organic matter, and the postdeposition geological context of Oxia Planum derived from understanding of environmental conditions in analog sites is promising for organic matter preservation.

Carbon isotope stratigraphy across the Triassic-Jurassic boundary in the high-latitude terrestrial Junggar Basin, NW China

Carbon isotope stratigraphic records across the Triassic-Jurassic (Tr-J) boundary show carbon isotope excursions in both marine and terrestrial sections, indicating frequent perturbations of the global carbon cycles, which are linked to the ~600 kyr pulsed emplacement of the Central Atlantic Magmatic Province (CAMP). However, few detailed carbon isotope stratigraphic reports from high-latitude terrestrial deposition have been documented in contrast to the contemporaneous low- to mid-latitude records. It hampers the understanding of the climatic response in the high-latitude terrestrial areas and the modeling global carbon cycles triggered by CAMP volcanisms. Here, we present high-resolution organic carbon isotope data primarily originated from C3 plants in the Haojiagou section in the paleo-high-latitude Junggar Basin, NW China. Combined with previously published biostratigraphic and geochemical results, carbon isotope stratigraphy with distinct “initial negative carbon isotope excursions” (I-CIE) and “main negative carbon isotope excursions” (M-CIE) is built in the Junggar Basin and allows a global stratigraphic correlation. The end-Triassic mass extinction (ETE) and the Tr-J boundary is then well identified. The excursion magnitude is similar to that in Greenland and Poland where the sections are also terrestrial. Climatic pattern recorded in the Junggar Basin rapidly changed across the Tr-J transition and coincides with a bloom of fern spores, increased wildfire activities, enhanced hydrological cycles and soil loss.

Palaeoenvironmental and climatic changes during the Late Glacial and Holocene in the Mongolia and Baikal region: A review

Multilayer sections in lake bottom sediments and continental sections of loose sediments in Mongolia and the Baikal region provide rich palaeontological material and radiocarbon dating for palaeoenvironmental reconstructions of the Late Pleistocene (Late Glacial) to Holocene. Multidisciplinary data from lacustrine bottom sediments provide evidence of past lake level and vegetation dynamics in the watersheds. Palaeontological data from terrestrial deposits indicate a mosaic landscape structure and a temperate warm and humid climate during the Late Glacial and Holocene, with some regional variability.Global and regional climatic changes at the end of the Pleistocene resulted in the mass extinction of components of the Mammoth faunistic complex, such as the woolly mammoth, cave lion, cave hyena, and big-horned deer; the number of tundra species decreased and migrated to the north, and arid animal species migrated to the south. During the Holocene, four vegetation types (steppe, forest, taiga, and desert) did not show radical changes, but their ratio and spatial distribution changed. Steppe landscapes were replaced by desert steppes during the arid phases of the Holocene. In contrast, the area of taiga forests expanded during humid Holocene phases, but the steppe landscapes remained dominant in the studied territory.

A ~130 ka terrestrial-marine interaction sedimentary history of the northern Jiangsu coastal plain in China

Coastal deposits are ideal archives to decipher the history of terrestrial-marine interactions in response to sea-level changes. Over the last decades, numerous investigations have been implemented to uncover the stratigraphic framework and the paleoenvironment evolution of the Jiangsu coastal plain (JCP), China. However, there have been limited studies on the sedimentary history over the glacial-interglacial timescales because of the lack of reliable chronostratigraphy. Here, we selected a 30-m-long sediment core in the northern JCP for luminescence dating, and carried out comprehensive sedimentological and paleontological analyses to ascertain the sedimentary history. Multiple luminescence dating techniques, including quartz optically-stimulated luminescence (OSL) and feldspar (polymineral) post-infrared (IR) IR stimulated luminescence (pIRIR) dating, were applied to determine the chronology of the sediment core. The obtained chronostratigraphy of core JCP01 spanning ~130 ka reveals that terrestrial deposition occurred in Marine Isotope Stage (MIS) 6, MIS 4–2 and the late stage of MIS 1. In contrast, marine influenced deposition is identified in MIS 5e and early MIS 1. The terrestrial interval of core JCP01 mainly consists of stiff clay and floodplain facies occurring at depths of 30–24 m, 12–5 m and 2–1 m, formed in relation to sea-level lowstands; whereas marine-influenced sediments at depths of 24–12 m and 5–2 m correspond to sea-level highstands, respectively. Our results highlight two sets of marine influenced sedimentary stratigraphy (T1, T2) dated to ~7 ka and around 130–120 ka, but no obvious MIS 3 transgression recorded in this core. In general, the conclusion is consistent with previous studies in East Asia and beyond, but not with previous work in this region that relied on radiocarbon dating. This suggests that re-dating with luminescence techniques is required for deposits correlated with the MIS 3 transgression in the northern JCP. Our reconstructed terrestrial-marine alternation sedimentary history of the northern JCP also shows a strong linkage with changes in the relative sea-level over the glacial-interglacial cycles.

Map-view restorations of the South Island, New Zealand: a reappraisal of the last 10 Myr of evolution of the Alpine and Wairau faults

ABSTRACT Retro-deformation of horizontal and vertical displacements is used to reconstruct the evolution of the South Island plate boundary faults since the Late Miocene. Finite dextral offset across the Alpine Fault is estimated from a system of N-S reverse faults displaced from Otago to the Glenroy-Matakitaki area, where the N-S tectonic trends are generally interpreted as a ‘bend’ of the Alpine Fault. Increasing dextral offset on the Alpine Fault was accompanied by a NE-migrating wave of exhumation and uplift of its hanging wall, tracked by syntectonic terrestrial deposits. Strike-slip and dip-slip components both decrease near the ‘bend’, where deformation is transferred to the Wairau and Marlborough faults. The Wairau Fault offsets dextrally by c. 50 km the N-S faults of the Glenroy-Matakitaki area, correlated with the Waimea-Flaxmore Fault System of Nelson. Finite dextral separation along the Alpine Fault is 410 km, and the N-S ‘bend’ is interpreted as a transpressive stepover between the Alpine and the Wairau faults. The lack of connection between the Alpine and Wairau faults, combined with slip transfer to the Hope Fault over the last 2 Myr, do not favour propagation of coseismic rupture from the Alpine Fault to the Wairau Fault across the ‘bend’.

Paleoarchean terrestrial to shallow marine sedimentation on Singhbhum Craton, eastern India (the Western Iron Ore Group)

Distinguishing shallow-marine and terrestrial (fluvial) sedimentary deposits is often difficult in the absence of fossils and challenging in deformed and metamorphosed early Precambrian terrains. Herein we report for the first time a > 3.4 Ga shallow marine to terrestrial deposit from the Western Iron Ore Group (WIOG), Singhbhum Craton, India. The WIOG sedimentary succession, lying below a ~ 3.4 Ga banded iron formation, has been divided into three facies associations: a lower alluvial fan-fluvial association, a middle shallow-marine association, and an upper fluvial association. The bottommost conglomerate–very coarse- to coarse-grained sandstone constitutes the alluvial fan-braided fluvial association. Sandstones of the facies association two bears mud drapes and herringbone cross-stratification and thus indicates tidal influence. These shallow-marine sandstones bear wave ripples, ladderback ripples, and adhesion structures and indicate an intertidal depositional environment. The overlying fluvial facies association is characterized by several fining-upward cycles of conglomerate–coarse- to medium-grained sandstones with large-scale trough cross beds, parallel lamination and penecontemporaneous deformation structures and minor shale, indicating the braided nature of the postulated river system. The WIOG succession indicates an overall shallowing-up trend because of sea level fall. The sedimentary structures and texture of the WIOG fluvial deposit are very similar to recent fluvial deposits and are likely to have formed by similar sediment transportation and depositional processes in a tectonically stable sedimentary basin.

The Iron Age in the Plastic Age: Anthropocene signatures at Castell Henllys

Abstract

Археологические раскопки на могильниках «Скальная» в 2021 году (Республика Хакасия)

In 2021, an excavation team from the Institute of Archaeology and Ethnography SB RAS carried out rescue archaeological works at the “Skalnaya” burial complex (Askiz district of the Republic of Khakassia) as a part of the Preservation project of the archaeological heritage objects during the construction of the second railway line at the Kamyshta - Uytag section of the Krasnoyarsk railway. According to the project requirements, 3 burial mounds were examined; 4296 sq. m. were excavated to terrestrial deposits; 7 burials (grave pits) yielded more than 100 individual finds (items made of bronze, iron, clay, gypsum and organic materials). All collective human burials in earthen grave pits with wooden log cabins were constructed inside stone fences under overhead stone and wooden coverings. Objects from the crypts and the diagnostic features of the funeral rite allow these burials to be dated to the Podgornovskiy (Skalnaya 7) Saragashenskiy (Skalnaya 6) and “Tesinskiy” stages (Skalnaya 5). Single kurgan Skalnaya 5 is an elite complex. This is evidenced by a massive aboveground and intra-grave structures, clay-plaster death masks, and preserved grave goods. Despite the serious robbery, the burial is very valuable because of all the details of two-levelled burial bed (boards, posts, support beams and traces of their attachment) preserved in the crypt. Burnt wood from the burial structures of the mound was analyzed in 2021. Comparison with the other materials obtained enabled us to establish clear chronological frame for mentioned in this article sites. Fence slabs of the Tagar kurgans with various embossed decorations (humanoidfigures, animals, hunting scenes, etc.) are very important objects of study.

Late Toarcian continental palaeoenvironmental conditions: An example from the Cañadón Asfalto Formation in southern Argentina

The Cañadón Asfalto continental Basin preserves terrestrial deposits interbedded with volcanic rocks, providing a unique opportunity for palaeoenvironmental reconstructions of the Jurassic continental realm. This study presents a sedimentological, mineralogical, and geochemical analysis of three lacustrine successions in the Cerro Cóndor area of the Cañadón Asfalto Basin, Argentina. New CA ID-TIMS U–Pb data from tuffaceous deposits indicate a late Toarcian age (179.481 ± 0.059, 179.41 ± 0.13, and 177.27 ± 0.40 Ma), suggesting that the palaeolakes developed contemporaneously to the Chon Aike volcanic activity. The sedimentary successions are composed of carbonate, organic matter-rich mudstone — with up to 8 wt% total organic carbon (TOC) content — sandstone and conglomerate, all with an important contribution of volcanic and volcanogenic material. The clay mineral assemblage dominated by corrensite (chlorite-vermiculite mixed layers), smectite and vermiculite is likely related to hydrothermal activity and alteration of volcanic material, rather than to change in weathering processes and climate. Organic matter preserved in the sedimentary successions has a lacustrine and terrestrial/reworked origin. Changes in the source of carbon dioxide (CO2) and in the type and/or degree of preservation of the organic matter had a major impact on the δ13Corg values. This further exemplifies the necessity to evaluate the influence of the depositional environment before interpretation of the organic carbon isotope records. The combined high phosphorus and TOC contents suggest that episodes of increased nutrient availability into the basin enhanced lacustrine primary productivity, which favoured the development of oxygen-depleted conditions bottom waters and ultimately organic matter preservation and burial. High Corg/Ptot ratios indicate that phosphorus was likely released back into the water column in a positive feedback loop, further sustaining primary productivity. This study provides an important clue to understand the palaeoenvironmental conditions prevailing on land during the late Toarcian and on how volcanism exerted a control on the depositional conditions.

B–Tm Ash of a Catastrophic Eruption of Baitoushan Volcano in Terrestrial Deposits of Primorye as an Age Marker of the Medieval Warm Period in the Holocene

The first finds of B–Tm volcanic ash of the catastrophic eruption of Baitoushan Volcano in the 10th century (946/947 AD) in the terrestrial deposits of Primorye are reported. The ash layer is found in 17 cross sections of lacustrine–boggy sediments at nine observation sites, both on the coast and in the internal areas of Sikhote-Alin. Identification of the volcanic source is carried out based on the study of macroelement composition of volcanic glass. Radiocarbon dating is used for age determination. The tephra distribution and the changes in the grain size depending on the distance from the source are analyzed. A comparative analysis of the volcanic glass composition and the data on pyroclastics of the proximal zone and the results of distal tephra study has been performed. It proved that the ash layer in Primorye was formed in the final phase of the eruption, but an exception was the coast of Kit Bay and the Shkotovskoe Plateau, where glass of rhyolitic composition corresponding to the maximum phase at the beginning of the eruption is found. For the reconstruction of the environmental development, the ash is used as an age marker of the Medieval Warm Period in the Holocene, which makes it possible to compare reliably the data on the cross sections located on the coast and in the mountains, to refine the chronology of paleogeographical events of historical time, and to perform interregional correlations.

Source-to-sink system for peat accumulation in marginal basins of the South China Sea with the Qiongdongnan Basin as an example

In the coal-bearing deposits of the Qiongdongnan Basin in the South China Sea, coal seams are for the most part extremely thin, typically less than 0.5 m. Coal streaks are commonly observed but are not concentrated. In addition, the ash content of the coal components is very high, indicating that the geological conditions of peat accumulation and coal formation were very unstable. For these reasons, it can be speculated that at the time of development, peat mires were relatively poor, in terms of inheritance and continuity, and were commonly not preserved. Coal measures, coal seams (in situ peat accumulation over long distances) and dispersed terrigenous sedimentary organic matter, which together constitute a type of complex coal source-to-sink system found in basin-marginal basins, include three aspects. (1) The material is homologous: whether autochthonous accumulation, allochthonous accumulation or dispersed organic matter is present, the total organic matter source is homologous, i.e. suitable for development and plant growth. (2) The process of organic matter transport (channel) is divided into three forms: vertical accumulation in situ, transport to relatively fixed areas by flowing water, and transport by other mechanisms with long-distance dispersion and drift. (3) There are three types of aggregation forms: vertical accumulation in situ, transport from flowing water to relatively fixed areas away from where plants grow and aggregate, and deposition in deep-water basins fixed with other substances; the latter type requires a period of time for long-distance dispersion and drift, including channel flow and surface flow. KEY POINTS From plant growth to peat formation, the ‘source–channel–sink system’ of coal formation is ‘sensitivity to sedimentary environments and complexity of distribution’. Convergence of coal-series, coal seam (in situ peat aggregation and allochthonous aggregation), and terrestrial dispersed organic matter deposition, constitute a complex coal-measure source–sink system. Source includes substance homology, channels include in situ vertical accumulation and dispersion drift in short and long distances, with convergence forms including in situ vertical accretion, remote sink and dispersion in deep-water basin.

Chronology of Miocene terrestrial deposits and fossil vertebrates from Quebrada Honda (Bolivia)

At ~3500 m above sea level in the Eastern Andean Cordillera, Quebrada Honda Basin exposes more than 300 m of middle Miocene sedimentary strata, developed on distal alluvial fan sediments interstratified with volcanoclastic deposits, overlying Paleozoic basement. These deposits are rich in exotic vertebrate fauna adapted to a wetter and warmer climate at lower paleoelevation, as contrasted with the present high-elevation cold and dry Andean conditions. This study provides new magnetostratigraphic and 40Ar/39Ar age control of the Quebrada Honda, Río Rosario and Huayllajara fossiliferous areas, demonstrating that they are 13.1–12.4 Ma. Part of the succession evidences cyclical deposition of calcretes and reddish mudstones which may be a response to precessional orbital-forcing climatic processes. Paleomagnetic measurements show a significant clockwise tectonic rotation related to postdepositional tectonism, associated with evidence of an important uplift after the deposition of Quebrada Honda sediments. This uplift of the Andean Eastern Cordillera was associated with the formation of the Subandean fold-thrust belt and the development of the Amazon and La Plata drainage basins. Proposed uplift rates of >200 m/Ma are compatible with well-established rates of uplift recorded in contemporaneous alpine sections.

Geochemical and Stratigraphic Analysis of the Chisana Formation, Wrangellia Terrane, Eastern Alaska: Insights Into Early Cretaceous Magmatism and Tectonics Along the Northern Cordilleran Margin

AbstractThe Chisana Formation consists of Lower Cretaceous volcanic rocks that occur in the Nutzotin Mountains of eastern Alaska. New stratigraphic analysis indicates that the volcanic succession is >2 km thick at the Bonanza Creek type section. We present stratigraphic, geochemical, Sr‐Nd‐Pb isotope, and U‐Pb age data from samples collected from various stratigraphic levels of the Chisana Formation. We demonstrate that the Chisana Formation can be divided into a lower subaqueous unit, a middle transitional unit, and an upper subaerial unit. Chisana Formation lavas range from transitional to subalkaline basalts through andesites. Trace element geochemistry shows high field strength element depletions relative to large ion lithophile elements and hydrous mineral assemblages with calc‐alkaline to tholeiitic chemistries, all consistent with a magmatic arc origin. Chisana lavas yield geochemical compositions and isotope characteristics that overlap with magmas from volcanic suites formed within juvenile continental crust and immature island arcs. Volcanism occurred between ~131 and 117 Ma judging from previously reported lava ages and new U‐Pb ages of detrital zircons recovered from sandstones that conformably underlie the lowermost Chisana Formation lavas. Our results support existing tectonic models in which an east dipping subduction zone existed beneath Wrangellia during Early Cretaceous time. The upsection shift from marine to terrestrial depositional conditions in the Chisana Formation and the overlying ~117–93 Ma Beaver Lake Formation was coincident with regional shortening. Together, the geologic evidence for shortening and terrestrial deposition are interpreted to reflect accretion/suturing of Wrangellia against inboard terranes.

Structural analysis of syn-depositional hydrothermal veins of the 3.48 Ga Dresser Formation, Pilbara Craton, Australia

The lower chert unit of the 3.48 Ga Dresser Formation (Pilbara Craton, Western Australia) hosts Earth’s oldest convincing evidence of life in the form of stromatolites in a depositional setting that has been interpreted as either a shallow marine lagoon, an active volcanic caldera, or a basin deposited during regional extension.Understanding the environment where early life thrived is important not only for early life studies on Earth, but in the search for life on Mars, and for understanding the setting for the origin of life.Structural analysis of the extensive network of syn-depositional hydrothermal chert-barite veins that immediately underlies the Dresser was undertaken in order to test if deposition occurred within an evolving caldera system, or during regional extension.Over 190 hydrothermal veins were mapped for their geometry and relative age relationships.Bedding orientations were recorded within nine fault-bounded structural sub-blocks and used for back-rotating the measured veins to their original orientation.The results show that:1)There are four main vein systems, including three that were emplaced during deposition of the Dresser Formation lower chert unit, and a fourth that was emplaced within syn- to post-depositional listric growth faults;2)The majority of veins were sub-vertical prior to regional tilting;3)The first three vein systems show mutually cross-cutting relationships;4)Vein densities and the number of vein systems vary between sub-blocks;5)Conjugate vein networks (NE-SW and NW-SE) dominate two middle and northern sub-blocks.These results show that the first three vein systems were emplaced through fracturing under a stress regime with a vertical σ1. Vertical conjugate fractures are consistent with sandbox models of overburden fracturing during emplacement and discharge of a magma chamber in a volcanic caldera. Areas of single vein orientations reflect marginal areas of the caldera system, dominated by radial or by ring faults. The veins in late listric growth faults represent the final period of caldera collapse, which controlled the depositional thicknesses of overlying strata, possibly during subsequent regional extension.These results document an unique setting for earliest life on Earth, within shallow water and terrestrial deposits of an active, low-eruptive caldera setting.

Palynology and the Eco-Plant model of peat-forming wetlands of the Upper Triassic Haojiagou Formation in the Junggar Basin, Xinjiang, NW China

Terrestrial deposits of the Triassic-Jurassic transition are well developed in the Junggar Basin, located in the Haojiagou Valley of Urumqi, Xinjiang Uygur Autonomous Region of Northwest China. This paper describes the palynology of a 10 m thick lignite bed from the Upper Triassic Haojiagou Formation (Rhaetian) with the aim of reconstructing the palaeovegetation and palaeoenvironment of a peat-forming wetland near the Triassic-Jurassic boundary. The palynoflora contains both Eurasian and Gondwanan elements, and is dominated by the spores and pollen of Bennettitales, Corystospermales, Ginkgoales, and Gleicheniales. At the Triassic/Jurassic boundary (Hettangian), the palynoflora significantly changes as Cyatheales spores become the dominant elements. We analyze assemblages in terms of an Eco-Plant model, which assigns the parent plants of the palynomorphs into five groups based on humidity and four groups based on temperature, and uses multivariate statistical analyses to infer palaeoclimate and palaeoenvironmental conditions. Results suggest that the palaeoclimate of the Rhaetian was generally wet and subtropical with short seasonal drought periods. Our analysis shows that an Eco-Plant model may be a useful tool to reveal past vegetation patterns and climate changes, applicable to other Mesozoic assemblages.

Astronomically forced variations in multiresolution resistivity logs of lower Upper Cretaceous (Cenomanian-Coniacian) terrestrial formations from the Songliao Basin, northeastern China

Continuous and high-resolution well logs from the SK-2 east (SK-2e) borehole in the Songliao Basin provide an opportunity to understand the relationship between astronomically forced climate and electrical responses in terrestrial Cretaceous strata. Here, we present well logs, mud logs, and core measurement data of lacustrine deposits in the Upper Cretaceous Qingshankou Fm and of fluvial/deltaic deposits in the Quantou Fm. The multiresolution resistivity logs used for the cyclostratigraphic analysis include deep laterolog resistivity logs, resistivity image logs, and array induction logs. The results show that the resistivity of strata in Quantou Fm mainly reflects changes in clay content, and that resistivity logs can be used as paleoenvironmental and paleoclimate proxies in cyclostratigraphic studies of the Quantou Fm. For the Qingshankou Fm, formation resistivity is mainly affected by clay minerals, which contribute to the overall electrical conductivity, as well as nonconductive organic carbon. Increasing clay and organic carbon contents usually correspond to wetter and warmer climatic conditions. The phase relationship between resistivity logs and astronomical cyclicity depends on factors that control resistivity. Spectral analyses of lithological changes and resistivity logs indicate the presence of eccentricity, obliquity, and precession cycles throughout the Quantou Fm. This provides strong evidence that climate was the dominant control on cyclic sedimentation in the Quantou Fm. The floating astronomical timescale, which was established by calibrating extracted 405-kyr cycles from resistivity logs, reveals that the duration of Quantou Fm was approximately 5.5 Myr. Comparative analysis of power spectra reveals that the sensitivity of resistivity logs with specific resolutions to Milankovitch cycles with different frequencies is variable. Comprehensive analysis of multiresolution resistivity logs is a new method in cyclostratigraphy analysis that has the potential to be effective in detecting signals of Milankovitch cycles in terrestrial deposits.

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

AbstractAlong the Dinaric–Hellenic orogen, the Late Jurassic – Early Cretaceous ophiolite obduction over the Adria continental margin was sealed by sedimentation of clastic terrestrial deposits rapidly followed by a widespread carbonate platform system since the Early Cretaceous period. These Cretaceous sediments presently crop out over areas of varying extension, from several hundred kilometre wide undeformed continuous covers to small-scale tectonic slivers involved in the tectonic stack following the latest Cretaceous–Palaeogene collision. These deposits are unconformably sedimented above the units formed by the Late Jurassic to Early Cretaceous nappe stacking above the eastern Adria continental margin. We studied these deposits in a large area between western Serbia and eastern Bosnia. In the studied area, these deposits are divided into three lithostratigraphic groups according to their age, depositional environment and type of underlying basement. The Mokra Gora Group sediments (upper Aptian–Maastrichtian) were deposited on top of previously obducted and weathered ophiolites, the Kosjerić Group (Cenomanian–Campanian) overlies composite tectonic units comprising obducted ophiolites and their underlying continental basement portions, while the Guča Group (Campanian–Maastrichtian) exclusively rests on top of continental basement. The reconstructed sedimentary evolution of these groups, together with the comparison with the syn- and post-obduction deposits at the front of the ophiolitic nappe(s) in a wider area of the internal Dinarides (e.g. Pogari Group and Bosnian flysch), allowed us to clarify the obduction mechanisms, including their tectonic context, the changes in depositional environments and the timing of depositional and tectonic events, and, in a wider view, shed light on the geodynamic evolution of the Dinaric belt.

Oldest Record of African Bagridae and Evidence from Catfishes for a Marine Influence in the Late Eocene Birket Qarun Locality 2 (BQ-2), Fayum Depression, Egypt

ABSTRACT The Birket Qarun Formation, sampling upper Eocene deposits of the Fayum Depression, has been the subject of disagreement in terms of the environmental deposition. The formation has traditionally been considered to be a marine deposit but, more recently, one particular site, Birket Qarun Locality 2 (BQ-2), has been reported to have freshwater vertebrates, indicating that at least this locality in the formation contains terrestrial deposits. We here report a new varied assemblage of fossil catfishes from BQ-2, which adds new information with which to interpret the paleoenvironment of the locality. The new BQ-2 catfish assemblage includes the earliest record of the freshwater family Bagridae in Africa, as well as the oldest records of Fajumia and Socnopaea, otherwise known only from the overlying marine deposits of the Qasr el-Sagha Formation. Notable among the finds are remains of Arius fraasi and two additional species of marine ariid catfishes, representing the first such occurrences from the Fayum deposits. These occurrences indicate that BQ-2 likely had marine influences, or perhaps that Fajumia, Socnopaea, and Arius were euryhaline. In addition, the freshwater families Claroteidae and Mochokidae are represented among our collection. The new material documents the presence of a variety of taxa, and in addition it documents the variation in body size of members of the same family. Most evidence from other vertebrate fossils indicates that BQ-2 is a freshwater deposit, but some elements of the new catfish collection suggest the presence of nearshore marine influences, indicating that a much more complex environment was present.

Smoothed millennial-scale palaeoclimatic reference data as unconventional comparison targets: Application to European loess records

Millennial-scale palaeoclimate variability has been documented in various terrestrial and marine palaeoclimate proxy records throughout the Northern Hemisphere for the last glacial cycle. Its clear expression and rapid shifts between different states of climate (Greenland Interstadials and Stadials) represents a correlation tool beyond the resolution of e.g. luminescence dating, especially relevant for terrestrial deposits. Usually, comparison of terrestrial proxy datasets and the Greenland ice cores indicates a complex expression of millennial-scale climate variability as recorded in terrestrial geoarchives including loess. Loess is the most widespread terrestrial geoarchive of the Quaternary and especially widespread over Eurasia. However, loess often records a smoothed representation of millennial-scale variability without all fidelity when compared to the Greenland data, this being a relevant limiting feature in integrating loess with other palaeoclimate records. To better understand the loess proxy-response to millennial-scale climate variability, we simulate a proxy signal smoothing by natural processes through application of low-pass filters of δ18O data from Greenland, a high-resolution palaeoclimate reference record, alongside speleothem isotope records from the Black Sea-Mediterranean region. We show that low-pass filters represent rather simple models for better constraining the expression of millennial-scale climate variability in low sedimentation environments, and in sediments where proxy-response signals are most likely affected by natural smoothing (by e.g. bioturbation). Interestingly, smoothed datasets from Greenland and the Black Sea-Mediterranean region are most similar in the last ~15 ka and between ~50–30 ka. Between ~30–15 ka, roughly corresponding to the Last Glacial Maximum and the deglaciation, the records show dissimilarities, challenging the construction of robust correlative time-scales in this age range. From our analysis it becomes apparent that patterns of palaeoclimate signals in loess-palaeosol sequences often might be better explained by smoothed Greenland reference data than the original high-resolution Greenland dataset, or other reference data. This opens the possibility to better assess the temporal resolution and palaeoclimate potential of loess-palaeosol sequences in recording supra-regional climate patterns, as well as to securely integrate loess with other chronologically better-resolved palaeoclimate records.

Fallout tuffs in the Eocene Duchesne River Formation, northeastern Utah—ages, compositions, and likely source

Thin fallout tuffs are common in the terrestrial deposits of the Eocene Duchesne River Formation on the flanks of the Uinta Mountains of eastern Utah. Their ages and compositions provide new insight into the tectonic events and magmatic history of the western Cordillera and provide important constraints on the Cenozoic land mammal chronology. Whole-rock compositions of the volcanic ash show that they underwent post-emplacement argillic alteration, typical of a wetland/floodplain depositional setting. However, immobile element ratios and abundances, such as Zr/Ti, La/Nb, and Y are typical of rhyolites formed in a subduction-related setting. Glass shards preserved in one sample all had SiO2 values >75%, typical of high-silica rhyolite. Preserved phenocrysts in the ash beds include quartz, sanidine, plagioclase, and biotite with variable amounts of accessory zircon, apatite, titanite, and allanite. Biotite compositions have Fe/(Fe+Mg) ratios typical of calc-alkaline igneous rocks and clusters of chemical compositions suggest a genetic relationship to three or four separate eruptions. Sanidine compositions from five samples range from Or73 and Or79. Only one sample had preserved plagioclase with compositions ranging between An22 – An49. Allanite from the ash beds has lower total rare earth elements (REE) concentrations than allanite from other well-studied rhyolites. Titanite in one sample has lower concentrations of REE, Fe, and Al than expected of rhyolites and is probably detrital.Plagioclase and sanidine from two different tuff beds near the middle of the Duchesne River Formation yielded analytically indistinguishable 40Ar/39Ar ages of 39.47 ± 0.16 Ma and 39.36 ± 0.15 Ma, respectively. These dates, along with the compositional data seem to limit the eruptive source for these fallout tuffs to the northeast Nevada volcanic field, one of the few volcanically active regions of western North America at the time. These new radiometric ages, along with stratigraphic relations and previously published ages for tuffs in the Bishop Conglomerate (which unconformably overlies the Duchesne River Formation), constrain the timing of late Laramide uplift in the region from 39 to about 37 Ma and post-Laramide epeirogenic uplift from 34 Ma to 30 Ma. Finally, the ages also provide additional evidence that the Duchesnean North American Land Mammal Age ended in the Eocene, which was originally named and defined from the Duchesne River Formation.