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The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, volcanoclastic rocks, and gabbro dikes/sills, thus being inserted in the Serra Sul district in the Mineral Province of Carajás, Pará. This study aimed to understand the igneous processes involved in the genesis of these basalts from both geological formations, supported by field, petrographic, and geochemical data. Inserted in the metavolcanosedimentary sequence of the Grão Pará Group (Carajás Domain), the basalts and basalt andesites, the most abundant types of the Parauapebas and Igarapé Cigarra Formations, occur as successions of massive and amygdaloidal lava flows. The study of core samples from nine stratigraphic holes that intersected basaltic rocks of the two geological formations in body S11D (Serra Sul) showed that these rocks reach thick layers with different characteristics, ranging from aphanitic to phaneritic. The basalts are dark green, aphanitic, phaneritic, thin to medium, and hypocrystalline. They show preserved igneous texture being commonly seriated as inequigranular, intersertal, ophitic, subophytic, intergranular, branching, and swallow tail. Its essential primary constituents are plagioclase, orthopyroxene, and clinopyroxene, and its accessory constituents are titanite and apatite. Chlorite, epidote, quartz, and calcite occur as secondary phases and are interpreted as the products of ocean-bottom hydrothermal alteration and/or incipient metamorphism. In general, the studied volcanic rocks stand out for SiO2 content between 47.00 and 56.04%, high alkali contents (4.70-7.50%), K2O contents between 0.40 and 3.97%, TiO2 (< 1.0%), and MgO between 4.90 and 8.16%. In the classification diagrams, the samples are situated in the fields of basalts, basalt andesites, trachyandesite, and trachybasalt basalts, in the transition of the toleitic and calc-alkaline series. The basalts of the Parauapebas and Igarapé Cigarra Formations were probably formed in an intraplate continental environment influenced by subduction zones. Therefore, the Grão-Pará Basin was probably formed in a convergent regime related to a subduction-type environment. The geochemical data indicate that the studied rocks of the Parauapebas Formation and the Igarapé Cigarra Formation correspond to basalts of calc-alkaline affinity. Two facies were identified in the Parauapebas Formation, namely, the Amendoim and Violão facies. In the Igarapé Cigarra Formation as well, the following facies were identified: Jacaré and Três Marias. Based on the geochemical interpretation, it is assumed that the rocks studied are arc-like continental basalts, which are formed in a subduction environment with influence from a possible asthenospheric source and modified by crustal contamination. [ABSTRACT FROM AUTHOR]

Copyright of Instituto Superior de Correlacion Geologica, Serie Correlacion Geologica is the property of Instituto Superior de Correlacion Geologica (INSUGEO-CONICET) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In their article on the Rutbah and the Hussainiyat Formations, Tamar Agha et al. (2016) interpreted the depositional environments of the Cenomanian Rutbah Formation of the Western Desert of Iraq as that of continental meandering fluvial setting. On a recent study of the same outcrops by the present authors, we could not find a single evidence to support a continental, fluvial deposition interpretation. Instead, all available evidence (both physical and biogenic sedimentary structures) seen in the sandstones outcropped in these locations overwhelmingly suggests deposition in shallow marine transgressive shelf, dominated by tidal currents. Below, we will describe our field observations in detail and advance a radically different interpretation to that of Tamar Agha et al. (2016). [ABSTRACT FROM AUTHOR]

The objective of the gravity investigation in Saghro is to follow the depth of the causative sources and to examine the continuity of the geological formation boundaries. To achieve these objectives, the Bouguer anomaly data was subjected to a subtraction of the regional component and, then, interpreted in the light of three mathematical transformations. The upward-continuation enabled classifying the causative features to deep and shallow sources. Source-Parameter-Imaging allowed us to determine the depth and distribution of the basement uplifts, while the horizontal gradient was used to detect subsurface linear discontinuities, which correspond to geological lineaments. The horizontal gradient enabled revealing several faults trending mainly E-W, NE-SW, and NW-SE; these lineaments are linked to the Anti-Atlas tectonic events. The gravity analysis outcomes were validated by field investigations and interpreted in the light of the previous geological studies carried out in Saghro. The distribution of the basement uplifts is related to tectonics, which transformed the basement into high and low areas, and subsequently influenced posterior sediments distribution. The Saghro southern flank registers a thick and complete sedimentary sequence, whereas the sequence on its northern flank is thin, indicating relatively higher subsidence on the southern flank due to various faulting systems. [ABSTRACT FROM AUTHOR]

The study of sedimentary organic matter (SOM) is essential for understanding paleoenvironmental conditions and depositional settings of geological formations. This paper explores the Devonian strata of the Paraná Basin, utilizing SOM analysis to reconstruct paleoenvironments and identify global events. The Devonian period is notable for significant geological and biological changes, including mass extinctions and extensive organic-rich sediment deposition. By examining the composition, distribution, and diagenesis of SOM in this region, we aim to elucidate the paleoenvironmental dynamics and depositional history. The Devonian outcrops in the state of Mato Grosso do Sul, Brazil rocks reveal distinct depositional characteristics, when compared to those found on the eastern border of the basin. The palynofacies analysis was conducted on 59 samples from four outcrops (MS-26, MS-29, MS-30 and MS-70), which age spans from Pragian to Givetian. The main groups and subgroups of the SOM were identified: amorphous organic matter (AOM) ("amorphous organic matter" and pseudoamorphous), phytoclasts (opaques, non-opaque-non biostructured, cuticles, membranes and Spongiophyton) and palynomorphs (spores, freshwater algae, scolecodonts, chitinozoan and acritarchs). The SOM was grouped into three palynofacies associations: opaques, land-derived and marine+AOM. In the Pragian—Emsian interval (MS-26, MS-29 and MS-30), a prevalent occurrence of phytoclasts and marine microphytoplankton is noted, with their distribution exhibiting distinct alternations in each section suggesting a deposition in the marine environment ranging from onshore to offshore. In the Givetian (MS-70 outcrop), we detected a progressive increase and diversification of marine elements (e.g., acritarchs), indicating a transgressive phase probably related with the Kačák event. • Comprehension of the Devonian period within the Paraná Basin, situated in the southwestern part of Gondwana. • Paleoenvironmental reconstruction from Pragian to Givetian in SW Gondwana • Palynofacies [ABSTRACT FROM AUTHOR]

The mineralogical studies of clay from the onshore mud volcanoes discovered in parts of the Upper Benue Trough of Nigeria provide a clue about the geological formation from which the extruded mud originates. The study area is a part of the Cretaceous Upper Benue Trough filled with Early Cretaceous continental deposits and Late Cretaceous marine deposits, having a history of magmatism dating from the Albian to the Pleistocene. The study approach involves integrated inorganic geochemical analysis of the samples to reveal their composition and origin. The results of XRD analysis of the fresh clays from the mud volcano revealed the presence of quartz, kaolinite, and other clay minerals (illite-smectite), feldspars, and in a much lower quantities, other accessory minerals including muscovite, evaporites, calcite and dolomite, trona, barite, goethite. The saprolite samples are composed mainly of quartz, kaolinite, smectite-illite associations, and feldspars, traces of goethite, calcite, and evaporate minerals (sylvite, halite). The presence of calcite, dolomite, sylvite, and halite suggests the marine origin of the rocks, while trona mineral is a non-marine evaporate. The coexistence of these minerals in some of the analyzed samples suggests the deposition of sediments in a transitional environment of deposition. Traces of marine minerals are present in some of the samples but completely absent in others collected from another site. This suggests that the source rock formations from which the material originated are within the Upper Bima Sandstone interpreted as being deposited in a non-marine environment or the Yolde Formation, which is known as a transitional unit (transitional between the outcropping continental Upper Bima Sandstone and marine Pindiga Formation). [ABSTRACT FROM AUTHOR]

Copyright of EMERG: Energy. Environment. Efficiency. Resources. Globalization is the property of Romanian National Committee of World Energy Council and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The rare earth elements (REE) in the clay fraction of sediments in 15 rivers and their estuaries along the east coast of India were analysed in this study. The total REE content (∑REE) varied from 130.98 to 289.85 μg/g and from 70.89 to 352.61 μg/g in rivers and estuaries respectively. The ∑REEs of estuarine clays (except the Brahmani and Baitarani) was lower than in rivers. The Post-Archean average Australian Shale-normalized REE patterns in rivers and estuaries were similar and categorized into three types. The REE patterns reflect the composition of dominant geological formations in river basins and extent of sediment mixing from different sources during transport. Hydrodynamic conditions controlled the abundance and fractionation of REE in the estuaries. The Sm/Nd ratios of clays were largely controlled by mineral composition and Y/Ho ratios were affected by sedimentary processes in the estuaries. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyze the assemblage of trilobites in the Silurian sequences of Iran by exploring stratigraphic section of the Silurian Niur Formation (Asadli section). Based on comprehensive field studies and laboratory investigations three Trilobite genera were identified in the study area including Calymene blumenbachii, Gravicalymene convolva, Dalmanites brevigladiolus and Calymene sp. according to this trilobite assemblage a Rhuddanian to Telychian stages (Llandovery) is suggested for deposition of the study strata. The recognized trilobite fauna will be used as a base for future geological studies on the Silurian strata in Kopeh-Dagh Basin. This is the first report of trilobites from the Silurian (Llandovery) Niur Formation in Asadli section, north- east, Iran. [ABSTRACT FROM AUTHOR]

The evolution of peat deposits of the Vydrino bog (southern Baikal region) and concentration of elements in them are discussed. The bog peat massif more than 4 m in thickness formed mostly during the Holocene. The beginning of peat formation dates back to the late Allerød (13.1 ka). At present, the Vydrino bog is a biogeocoenosis of the high-moor type with a transitional peat deposit. We have established that the bog nonuniformly accumulated chemical elements during its formation. Concentration of Pb, Sn, Cd, Zn, and Sb in recent vegetation and in the upper layer of the peat bog is mainly due to forest fires and anthropogenic air pollution. The anomalous enrichment of peat with Zn and Cu in the Early Holocene (12.1-8.8 ka) horizons proceeded through the periodic inflow of thermal groundwater into the bottom part of the peat deposit. Authigenic Zn and Cu sulfides formed on the inner membrane of the cell wall of sphagnum moss. Geochemical modeling has shown that Zn and Cu sulfides can form abiotically. [ABSTRACT FROM AUTHOR]

The petrographic study is based on 88 samples obtained from 18 surface sections. The aim of this study is to shed more light on the facies, and the environment deposition for Nfayil formation, which is results depositional environments are interpreted as categorized by Flugel (2004). Show restricted carination on marine platform, deposited in very shallow hypersalline lagoon, was deposited in shallow marine environment with normal salinity. The age of Nfayil Formation, depending on the fossils content (Peneroplisfarsensis, Ammonia beccarii, Elphidiumsp., Textulariasp., Miliolids, rotalids). The assemblage fauna above the typical is Middle Miocene which is equivalent to Fatha Formation. [ABSTRACT FROM AUTHOR]

The middle Eocene Fulra Limestone Formation of the Kachchh Basin, western India was investigated to interpret depositional environments and sources of limestones based on facies analysis, mineralogy, and major, trace, and rare earth elements (REEs) geochemistry. Facies stacking pattern of the Fulra Limestone Formation exhibits an overall shallowing‐upward sedimentary succession developed in the middle to inner ramp to lagoonal set‐up. Staining of the thin sections and X‐ray diffraction patterns show dominance of calcite mineral. The CaO, ranging from 40.45% to 49.69%, is the dominant oxide among the major oxides followed by SiO2 (4.04–10.3%). The dominance of CaO over MgO suggests that the major mineral phase has been calcite and no dolomitization occurred during the deposition of the Fulra limestone. The low proportion of SiO2 and Al2O3 suggests low siliciclastic input during the precipitation of the Fulra limestone that is confirmed by the positive correlation of ∑REE with Al2O3, Fe2O3, Ni, Th, Sc, and Y and the negative correlation of SiO2, Al2O3, and Sr with CaO. The average value of REE contents in the Fulra Limestone Formation are lower (*16.02 ppm) than the average value of typical marine carbonates (*28 ppm). The Post‐Archean Australian Shale‐normalized REE + Y patterns of the Fulra limestone exhibit seawater like shale‐normalized REE + Y pattern, whereas slightly lower average value of Y/Ho ratio (34.60) than the typical seawater value (~44–74) suggests modification of the seawater, to some extent, by input of freshwater in a coastal environment. The REEs of the Fulra Limestone Formation have similarity with the carbonates of the Arabian Sea and/or shallow marine carbonates with exception of a few elements. It is envisaged from this study that the Fulra limestone was deposited in a shallow marine to coastal set‐up where mixing of the continental material in seawater was feasible. [ABSTRACT FROM AUTHOR]

Abstract The exceptionally organic-rich rocks of the 1.98 Ga Zaonega Formation deposited in the Onega Basin, NW Russia, have refined our understanding of Earth System evolution during the Paleoproterozoic rise in atmospheric oxygen. These rocks were formed in vent- or seep-influenced settings contemporaneous with voluminous mafic volcanism and contain strongly 13C-depleted organic matter. Here we report new isotopic (δ34S, Δ33S, Δ36S, δ13C org) and mineralogical, major element, total sulphur and organic carbon data for the upper part of the Zaonega Formation, which was deposited shortly after the termination of the Lomagundi-Jatuli positive carbon isotope excursion. The data were collected on a recently obtained 102 m drill-core section and show a δ13C org shift from −38‰ to −25‰. Sedimentary sulphides have δ34S values typically between +15‰ and +25‰ reflecting closed-system sulphur isotope behaviour driven by high rates of microbial sulphate reduction, high sulphate demand, hydrothermal activity and hydrocarbon seepage. Four intervals record δ34S values that exceed +30‰. We interpret these unusually 34S-enriched sulphides to be a result of limited sulphate diffusion into pore waters due to changes in sedimentation and/or periods of basinal restriction. Additionally, there are four negative δ34S excursions that are interpreted to reflect changes in the open/closed-system behaviour of sulphate reduction or availability of reactive iron. Our findings highlight the influence of basinal processes in regulating sulphur isotope records and the need for care before interpreting such signals as reflecting global conditions. Highlights • Zaonega Formation Δ33S-δ34S data track basin-specific rather than global processes. • Opposing Δ33S-δ34S relationship relates to rapid microbial sulphate reduction. • Positive δ34S excursions reflect partial basinal restriction. [ABSTRACT FROM AUTHOR]

The existence of an early Upper Palaeolithic culture at the transition from the Middle Palaeolithic to the Upper Palaeolithic in North African cave sites is currently under debate. We studied Ifri n‘Ammar in North-East Morocco, which is one of the oldest settlement sites of anatomically modern humans (AMH) in the Maghreb and contains several sediment layers which are attributed to Middle and Upper Palaeolithic occupations. In order to investigate processes of sediment accumulation and postdepositional alteration, we studied thin sections from these levels. According to micromorphological analysis, aeolian input considerably contributed to sediment accumulation and postdepositional mixing by bioturbation occurred. We compared multiple and single-grain quartz and multiple-grain feldspar luminescence dating of three samples from corresponding sediment layers to achieve a comprehensive chronology. The single-grain dose distributions scatter strongly and the source of the scatter is unclear. We used an arithmetic mean to calculate the equivalent doses. Archaeological evidence and age control from radiocarbon dating was essential to interpret the data. Quartz and feldspar multiple-grain luminescence ages are between 15 and 80 ka. The central part of the profile shows an intermediate accumulation, which lacks specified lithic artefacts. This supports the idea of an occupational gap between Middle and Upper Palaeolithic layers. [ABSTRACT FROM AUTHOR]

The ongoing exploration for shale oil and gas has focused sedimentological research on the transport and deposition mechanisms of fine-grained sediments, and more specifically on fine-grained mass-flow deposits. It appears, however, that no easily applicable classification scheme for gravity-flow deposits exists, and that such classifications almost exclusively deal with sandy and coarser sediments. Since the lack of a good classification system for fine-grained gravity flow deposits hampers scientific communication and understanding, we propose a classification scheme on the basis of the mud content in combination with the presumed transport mechanism. This results in twelve types of gravity-flow deposits. In order to show the practical applicability of this classification system, we apply it to the Triassic lacustrine Yanchang Formation in the southern Ordos Basin (China), which contains numerous slumps, debris–flows deposits, turbidites and hyperpycnites. The slumps and debrites occur mostly close to a delta front, and the turbidites and hyperpycnites extend over large areas from the delta slopes into the basin plain. The case study shows that (1) mud cannot only be transported but also deposited under active hydrodynamic conditions; (2) fine-grained gravity-flow constitute a significant part of the lacustrine mudstones and shales; (3) muddy gravity flows are important for the transport and deposition of clastic particles, clay minerals and organic matter, and thus are important mechanisms involved in the generation of hydrocarbons, also largely determining the reservoir capability for unconventional petroleum. [ABSTRACT FROM AUTHOR]

The Middle Marker – horizon H1 of the Hooggenoeg Formation – is the oldest sedimentary horizon in the Barberton greenstone belt and one of the oldest sedimentary horizons on Earth. Herein, we describe a range of carbonaceous microstructures in this unit which bear resemblance to phototrophic microbial biofilms, biosedimentary structures, and interpreted microfossils in contemporaneous greenstone belts from the Early Archaean. Post-depositional iron-rich fluid cycling through these sediments has resulted in the precipitation of pseudo-laminated structures, which also bear resemblance, at the micron-scale, to certain microbial mat-like structures, although are certainly abiogenic. Poor preservation of multiple putative microbial horizons due to coarse volcaniclastic sedimentation and synsedimentary fragmentation by hydrothermal fluid also makes a conclusive assessment of biogenicity challenging. Nonetheless, several laminated morphologies within volcaniclastic sandstones and siltstones and coarse-grained volcaniclastic sandstones are recognisable as syngenetic photosynthetic microbial biofilms and microbially induced sedimentary structures; therefore, the Middle Marker preserves the oldest evidence for life in the Barberton greenstone belt. Among these biosignatures are fine, crinkly, micro-tufted, laminated microbial mats, pseudo-tufted laminations and wisp-like carbonaceous fragments interpreted as either partially formed biofilms or their erosional products. In the same sediments, lenticular objects, which have previously been interpreted as bona fide microfossils, are rare but recurrent finds whose biogenicity we question. The Middle Marker preserves an ancient record of epibenthic microbial communities flourishing, struggling and perishing in parallel with a waning volcanic cycle, an environment upon which they depended and through which they endured. Direct comparisons can be made between environment-level characters of the Middle Marker and other Early Archaean cherts, suggesting that shallow-water, platformal, volcanogenic-hydrothermal biocoenoses were major microbial habitats throughout the Archaean. [ABSTRACT FROM AUTHOR]

A 2400 m-thick sedimentary column belonging to the Toro Negro Formation was recorded along the Quebrada del Yeso, Sierra de Los Colorados (Vinchina Basin), La Rioja province, NW Argentina. The Vinchina basin is a good example of a closed basin surrounded by the Precordillera fold and thrust belt to the west and basement-cored blocks to the north, south (Western Sierras Pampeanas) and east (Sierra de Famatina). Seven facies associations (FA) are described and interpreted to represent fluvial, lacustrine and alluvial environments developed in the southern part of the Vinchina basin from the Late Miocene until the earliest Pleistocene. The depositional evolution of the formation was divided in four phases. Phase I (∼7–6.6 Ma) represents sedimentation in medial (FA I) to distal (FA II) parts of a southward directed distributive fluvial system with a retrogradational pattern. During phase II (6.6–6.1Ma), the distributive fluvial system was replaced by a mixed clastic-evaporitic shallow lake (FA III) in a high aggradational basin. In phase III (∼6.1–5 Ma) the eastward progradation of a fluvial system (FA IV) was recorded as a distal clastic wedge. Finally, phase IV (∼5-2.4Ma) records two depositional cycles of proximal clastic wedge progradation of fluvial-dominated piedmonts (FAV, FAVII) from the southwest (Sierra de Umango) and/or the west (Precordillera) with an intervening playa lake (FA VI). Two new U-Pb ages obtained from zircons in volcanic ash layers confirm the Late Miocene age of the lower member of the Toro Negro Formation and permit a tight correlation with the central part of the basin (Quebrada de La Troya section). The sedimentation rate calculated for the dated lacustrine-fluvial interval is higher than the corresponding one in La Troya area suggesting a higher subsidence in the southern part of the basin. During the Late Miocene (∼7-6.6Ma) the ephemeral drainage was controlled by an arid to semiarid climate and initially dissipated mostly internally as terminal fan/distributive fluvial systems descending from the north. A thick lacustrine interval developed in the southern part of the basin between ∼6.6 and 6.1 Ma during a period of high subsidence and closed drainage. Besides, this interval coincides with increased aridity recorded in other basins in the Northwest of Argentina. By ∼6.1 Ma the area started to receive the first coarse-grained sediments heralding the progradation of a clastic wedge from the southwest-west (Sierra de Umango and Precordillera) which fully developed during the rest of the Pliocene to the earliest Pleistocene (∼5–2.4 Ma). The 6.1–2.4 Ma interval records ameliorating climate conditions. [ABSTRACT FROM AUTHOR]

The Paleoproterozoic Great Oxidation Event (GOE) marks the first significant oxidation of atmosphere and surface environments, and is causally associated with the global disappearance of mass-independent sulfur isotope fractionation (MIF-S). However, fundamental sedimentary aspects of successions recording this event (e.g. depositional environment, tectonic setting and stratigraphic correlation) are poorly constrained and often debated, restricting full understanding of causes and effects related to the GOE. In South Africa, MIF-S disappears across the ‘mid-Duitschland unconformity’ (MDU) in the Duitschland Formation (Transvaal Supergroup). New sedimentological observations of the lower Duitschland Formation have identified up to 5 times thicker and more diverse chert-pebble conglomerates than previously documented. New facies observed include lenticular conglomerates which incise cross-bedded dolomites, and imbricated conglomerates. The overlying MDU is angular in nature, recording an ∼15° N dip of the lower Duitschland strata; elsewhere it possesses a disconformable geometry. A new depositional model is proposed where shallow-marine carbonate (ramp) deposition interfaced with wave-influenced Gilbert-type fan deltas in an isolated depocentre produced during synsedimentary faulting. There is no evidence that the MDU formed due to direct glaciation as proposed previously. However, glacio-eustatic changes may have had an influence. This study supports the lithostratigraphic correlation of the Duitschland and Rooihoogte formations. This interpretation challenges the idea that they are separate lithostratigraphic units that record oscillations in MIF-S; this apparent oscillation in MIF-S is a stratigraphic artefact. The correlation proposed in this study implies a unique MIF-S signal and has important consequences for differentiating true spatiotemporal oscillations in MIF-S chemistry from artificial variations caused by unresolved stratigraphic relations. [ABSTRACT FROM AUTHOR]

Comprehensive studies of cores from 7 boreholes drilled in the Pal’yanovo area provided insight into the Bazhenovo Horizon in southwestern Siberia represented by the lower subformation of the Tutleim Formation. The work presents a typification of organic-rich biogenic-terrigenous rocks. The Bazhenovo Horizon is divided into 11 lithotypes grouped into 5 large members. Members I‒IV correspond to the lower subformation of the Tutleim Formation; member V, to the upper subformation. The identified members are traced explicitly over the Pal’yanovo area, making it possible to examine the whole vertical succession of the Tutleim Formation and reconstruct its evolution based on the proposed sedimentation model. [ABSTRACT FROM AUTHOR]

In the present study, we carried out trace element analyses of black shales of the Ediacaran Doushantou Formation from two sections (Jiulongwan, Baiguoyuan) in Hubei Province, South China. Mo-U characteristics of black shales from the two sections and compiled Mo-U data of Doushantuo black shales from sections of a variety of sedimentary facies described the temporal/spatial variability in the redox conditions of paleo-seawater during deposition of the Doushantuo Formation. Changes in Mo-U patterns of the Doushantuo Member II (DST2) shales of open marine environments are consistent with a shift from a predominately oxic to a predominately anoxic ocean during their deposition. Mo-U patterns of the DST2 black shales from intra-shelf sections reflect basin restriction may have happened in the intra-shelf basin and are compatible with the redox-stratified model of the intra-shelf basin. Mo-U patterns of black shales of the Doushantuo Member IV (DST4) reveal that the shales from intra-shelf sections have more pronounced Mo enrichment and more significant enrichment of Mo over U than the slope shales, indicating the operation of a Mn particulate shuttle in the intra-shelf basin. High Mo/TOC ratios of the DST4 at the intra-shelf sections, in combination with similar Mo-TOC patterns of the DST4 from both intra-shelf and slope sections, indicate the intrashelf basin was well connected to the open ocean during deposition of the DST4. [ABSTRACT FROM AUTHOR]

Rare earth element (REE) and Y concentrations, and 87Sr/86Sr ratios were analyzed in 33 carbonate samples from the Paleogene Shahejie Formation in the Qikou depression, eastern China, with the goal of determining depositional environments and post-depositional conditions of carbonates in the region. The REE and Y concentrations were normalized to the post-Archean Australian shale (PAAS) standard. The La*PAAS/Yb*PAAS ratios of 0.35-1.52, where *PAAS indicates values for the PAAS standard, show light REE enrichment and heavy REE depletion in most samples. Values of La*PAAS (0.775-1.284) and Ce*PAAS (0.822-1.224), coupled with a relatively flat REE distribution, indicate that the Shahejie carbonates were deposited in lacustrine environments. Values of Y anomalies (1.009-1.527) and Y/Ho ratios (28.43-45.00) in the Shahejie Formation are greater than those of lacustrine carbonates and closer to those of marine carbonates, indicating that diagenetic fluids were probably influenced by seawater. In the carbonates from Well Kou-42, Eu anomalies (1.171-1.604), 87Sr/86Sr ratios (0.708 001-0.710 893), and high homogenization temperatures (104-151 ºC) suggest that the carbonates were affected by hydrothermal fluids. The REEs and Sr isotope ratios show that the carbonates from the Shahejie Formation in the Qikou depression were deposited in lacustrine environments, and were influenced by seawater and hydrothermal fluids. [ABSTRACT FROM AUTHOR]

The Proterozoic Oonah Formation comprises a thick sequence of turbidites and mafic rocks that is widely exposed in western and northern Tasmania. The regional significance of the Oonah Formation is poorly understood as its contacts are faulted and estimates of its depositional age range from 1450 Ma to 700 Ma. Here we refine the depositional age of the Oonah Formation and clarify its relationship to other Proterozoic sequences in Tasmania. Magmatic apatite from the syn-sedimentary Cooee Dolerite has a 207Pb-corrected 238U/206Pb age of 733 ± 9 Ma that provides a robust estimate of the depositional age of the Oonah Formation. The Oonah Formation contains abundant 750 Ma detrital monazite and has detrital zircon age populations at 1800-1700 Ma, 1590 Ma, and 1450 Ma. The new age and provenance data support the interpretation that the Oonah Formation is a lateral equivalent of the base of the Togari Group and correlatives in Tasmania. We demonstrate that the stratigraphy and provenance of Neoproterozoic strata in Tasmania differ from time-equivalent sequences in Adelaide Rift Complex but are similar to the Pahrump Group (Death Valley, California) and the Cobham Formation (Transantarctic Mountains), which supports a southwest Laurentia—Tasmania—East Antarctica connection within supercontinent Rodinia. [ABSTRACT FROM AUTHOR]

Lower Paleocene deposits in the San Juan Basin document one of the best records of mammalian change and turnover following the Cretaceous-Paleogene mass extinction and is the type area for the Puercan (Pu) and Torrejonian (To) North America Land Mammal age (NALMA). One of the largest mammalian turnover events in the early Paleocene occurs between the Torrejonian 2 (To2) and Torrejonian 3 (To3) NALMA interval zones. The Nacimiento Formation contains the only deposits in North America where the To2-To3 mammalian turnover can be constrained; however, the precise age and duration of the turnover is poorly understood due to the lack of a precise chronostratigraphic framework. We analyzed paleomagnetic samples, produced a 40Ar/39Ar detrital sanidine age, and developed a detailed lithostratigraphy for four sections of the upper Nacimiento Formation in the San Juan Basin, New Mexico (Kutz Canyon, Escavada Wash, Torreon West and East) to constrain the age and duration of the deposits and the To2-To3 turnover. The polarity stratigraphy for the four sections can be correlated to chrons C27r-C26r of the geomagnetic polarity time scale (GPTS). Using the local polarity stratigraphy for each section, we calculated a mean sediment accumulation rate and developed a precise age model, which allows us to determine the age of important late Torrejonian mammalian localities. Using the assigned ages, we estimate the To2-To3 turnover was relatively rapid and occurred over ~120 kyr (-60/+50 kyr) between 62.59 and 62.47 Ma. This rapid duration of mammalian turnover suggests that it was driven by external forcing factors, such as environmental change driven by the progradation of the distributive fluvial system across the basin and/or changes in regional or global climate. Additionally, comparisons of the mean sediment accumulation rates among the sections that span from the basin margin to the basin center indicate that sediment accumulation rates equalized across the basin from the end of C27r through the start of C26r, suggesting an accommodation minimum in the basin associated with the progradation of a distributive fluvial system into the basin. This accommodation minimum also likely led to the long hiatus of deposition between the Paleocene Nacimiento Formation and the overlying Eocene San Jose Formation. [ABSTRACT FROM AUTHOR]

The coarse-grained, upper Cambrian Owen Group of western and northern Tasmania is a prominent feature of the Tasmanian landscape and regional map series. The group has previously been divided into four informal formations (Lower Owen Conglomerate, Middle Owen Sandstone, Middle Owen Conglomerate and Upper Owen Sandstone) that have been correlated across the state over tens to hundreds of kilometres. The deposition of these sediments is largely believed to have occurred during extensional tectonics, but some authors continue to argue a compressional tectonic regime. Detailed mapping and sedimentological work around Proprietary Peak on the Mount Jukes massif, 10 km south of Queenstown, Tasmania, has identified significant depositional variations controlled by early growth faulting and paleotopography. Discontinuity of stratigraphic units (L6-L13) across two growth faults on the north face of Proprietary Peak shows the strong effect on sediment deposition in the area. Paleotopography is also evident with most stratigraphic units (L8-L13 and U1) gradually onlapping basement during their deposition. Significant paleotopography has also been identified on East Jukes Peak, where lower Owen Group sedimentary units onlap basement volcanics, with no evidence for tectonically controlled deposition. Field evidence strongly supports the deposition of the Owen Group during extensional tectonics, after a period of prolonged erosion of the underlying Mount Read Volcanics. The distinct variation in vertical and lateral extent of stratigraphic units within the Owen Group in the Proprietary Peak area suggests that widespread lithostratigraphic correlation of older Owen Group sedimentary units across Tasmania may not be feasible. [ABSTRACT FROM AUTHOR]

The HC-rich Upper Cretaceous rocks in the West Siberian petroliferous basin comprise genetically heterogeneous sediments, resulting in the specificity of morphology, structure, and properties of natural reservoirs therein. One of the possible techniques for more reliable predictions of reservoir rock characteristics is the utilization of results of sedimentation modeling based on the complex interpretation of borehole and seismic data. The paper presents an example of the realization of such approach for refining the structure of oil-and-gas pools in the Pokur Formation of the Russko-Chasel megaswell. [ABSTRACT FROM AUTHOR]

Abstract: The Lobo Formation of southwestern New Mexico consists of spatially variable continental successions attributed to the Laramide orogeny (80–40 Myr), although its age and provenance are virtually undocumented. This study combines sedimentological, magnetostratigraphical and geochronological data to infer the timing and origin of the Lobo Formation. Measured sections of Lobo strata at two locations, Capitol Dome in the Florida Mountains and in the Victorio Mountains, indicate significant differences in depositional environments and sediment provenance. At Capitol Dome, where Lobo strata were deposited above a syncline developed in Palaeozoic strata, deposition took place in fluvial, palustrine and marginal lacustrine settings, with alluvial‐fan deposits only at the top of the formation. Combined magnetostratigraphy and a young U–Pb detrital zircon age suggest deposition of the section at Capitol Dome from ~60 to 52 Ma. The Lobo Formation in the Victorio Mountains was deposited in alluvial‐fan and fluvial settings; the age of deposition is poorly bracketed between 66 ± 2 Ma, the weighted‐mean age of two young zircons, and middle Eocene (~40 Ma), the approximate age of overlying volcanic rocks. U–Pb zircon ages from sandstones at the Victorio and Capitol Dome localities indicate that different source rocks provided sediment to the Lobo Formation. Local Proterozoic basement (~1.47–1.45 Ga) dominated the source of the Lobo Formation in the Victorio Mountains, consistent with abundant granitic clasts that are present in the proximal facies there; a diverse range of grain ages suggest that recycled Lower Cretaceous strata provided the dominant source for Lobo Formation sediment at the Capitol Dome locality. The U–Pb data suggest that the depositional systems at the two sites were not connected. Contrasts in depositional setting and detrital zircon provenance indicate that the Palaeogene Lobo Formation in southwest New Mexico was deposited in an assemblage of local depositional settings, possibly in separate structural basins, as a consequence of Laramide tectonics in the region. [ABSTRACT FROM AUTHOR]

This study focuses on the causes, modalities and obstacles of sediment transfer in the longest cell of littoral sand drift documented on Earth so far. Sand derived from the Orange River is dragged by swell waves and persistent southerly winds to accumulate in four successive dunefields in coastal Namibia to Angola. All four dunefields are terminated by river valleys, where aeolian sand is flushed back to the ocean; and yet sediment transport continues at sea, tracing an 1800 km long submarine sand highway. Sand drift would extend northward to beyond the Congo if the shelf did not become progressively narrower in southern Angola, where drifting sand is funnelled towards oceanic depths via canyon heads connected to river mouths. Garnet-magnetite placers are widespread along this coastal stretch, indicating systematic loss of the low-density feldspatho-quartzose fraction to the deep ocean. More than half of Moçamedes Desert sand is derived from the Orange River, and the rest in similar proportions from the Cunene River and from the Swakop and other rivers draining the Damara Orogen in Namibia. The Orange fingerprint, characterized by basaltic rock fragments, clinopyroxene grains and bimodal zircon-age spectra with peaks at ca 0·5 Ga and ca 1·0 Ga, is lost abruptly at Namibe, and beach sands further north have abundant feldspar, amphibole-epidote suites and unimodal zircon-age spectra with a peak at ca 2·0 Ga, documenting local provenance from Palaeoproterozoic basement. Along with this oblique-rifted continental margin, beach placers are dominated by Fe-Ti-Cr oxides with more monazite than garnet and thus have a geochemical signature sharply different from beach placers found all the way along the Orange littoral cell. High-resolution mineralogical studies allow us to trace sediment dispersal over distances of thousands of kilometres, providing essential information for the correct reconstruction of 'source to sink' relationships in hydrocarbon exploration and to predict the long-term impact of man-made infrastructures on coastal sediment budgets. [ABSTRACT FROM AUTHOR]

The hematite- and manganese-rich Hotazel iron formation, Griqualand West basin, South Africa, was deposited at a key moment in time, close to the GOE between 2.4 and 2.3 Ga. It stratigraphically overlies the Ongeluk Formation, comprising thick flood basalts, which in turn interfinger with and cover the Makganyene Formation diamictites, the inferred remnants of the first Paleoproterozoic Snowball Earth interval. No extensive research has been conducted to date on the basal part of the Hotazel Formation due to poor exposure, though it constitutes an important link between a period of large-scale ice cover, extensive volcanism and the onset of atmospheric oxygenation. Here, we present a detailed petrographic, geochemical and Fe isotope study of a roughly 3-metre-long drill-core exposing the Ongeluk to Hotazel contact. Our results show that after the cessation of Ongeluk volcanism, primary precipitation of Fe(III) oxyhydroxides from the photic surface zone of the original basin became the dominant sedimentation mechanism. Negative δ 56 Fe values (between −0.26 and −0.50‰) in micro-drilled hematite-rich chert indicate that surface water δ 56 Fe compositions at the time of deposition were depleted. Yet, δ 56 Fe and bulk-rock Fe/Mn values are still substantially higher (1–2‰) than those reported higher up in the Mn-rich layers of the Hotazel sequence, suggesting that redox potentials were still comparatively limited during the earliest stages of the Hotazel depositional environment. The base of the Hotazel Formation thus forms a transitional interval between precipitation from essentially ferruginous seawater, as recorded in the Ghaap Group BIFs, and from isotopically and chemically highly evolved surface waters, as demonstrated by the Hotazel Mn-rich layers. In the absence of Fe(II) as a strong reducing agent, large volumes of photosynthetic oxygen may have eventually escaped into the atmosphere, leading to the onset of atmospheric oxygenation. Our results thus contradict previous models that place the onset of the GOE before the Hotazel Formation, concurrent with and mechanistically linked to the Makganyene and Ongeluk events. Instead, we show that the Hotazel basal sediments are still pre-GOE, consistent with their circa 2.4 Ga age and the continuation of MIF-S higher in the stratigraphic record. [ABSTRACT FROM AUTHOR]

Stratigraphic units exposed on Akpatok Island, Ungava Bay, Nunavut, were previously recognized as Boas River and Akpatok formations; their biostratigraphic ages and correlations, in particular the stratigraphic position and age of the organic rich 'Boas River' Formation, were largely based on limited data. New detailed field observations have recognized three stratigraphic units, namely the Amadjuak, Akpatok, and Foster Bay formations, in which extensive microfossil sampling recovered over 22 000 conodont elements from 66 productive samples from both outcrops and rubble at over 20 localities in four areas. Four Upper Ordovician conodont zones and one unzoned interval are established for the three redefined formations: Belodina confluens and Oulodus velicuspis Interval zones are confined to the exposed Amadjuak Formation and correlated to Edenian and Maysvillian; Amorphognathus ordovicicus - Plegagnathus dartoni Concurrent-range Zone occurs with the Akpatok Formation and correlated to lower Richmondian; Rhipidognathus symmetricus Taxon-range Zone is retained in the Foster Bay Formation and correlated to upper Richmondian; and an 'Unzoned Interval' is defined between the last two zones in the lower Foster Bay Formation. The conodont Amorphognathus ordovicicus occurs in both Akpatok and lower Foster Bay formations, and it is also recovered from the bituminous, argillaceous limestone rubble, based on which the stratigraphic position of the previously named 'Boas River' Formation is most likely positioned within the lower Foster Bay Formation. The biostratigraphy and lithostratigraphy are combined with geographic information systems (GIS) to establish the thicknesses of the three formations and revise the geologic map of the island. [ABSTRACT FROM AUTHOR]

Turbidity currents are underflows responsible for sediment deposits that generate geological formations of interest for the oil and gas industry. LibMesh-sedimentation is an application built upon the libMesh library to simulate turbidity currents. In this work, we present the integration of libMesh-sedimentation with in situ visualization and in transit data analysis tools. DfAnalyzer is a solution based on provenance data to extract and relate strategic simulation data in transit from multiple data for online queries. We integrate libMesh-sedimentation and ParaView Catalyst to perform in situ data analysis and visualization. We present a parallel performance analysis for two turbidity currents simulations showing that the overhead for both in situ visualization and in transit data analysis is negligible. We show that our tools enable monitoring the sediments appearance at runtime and steer the simulation based on the solver convergence and visual information on the sediment deposits, thus enhancing the analytical power of turbidity currents simulations. [ABSTRACT FROM AUTHOR]

Based on core observations, well logs and test results of siderite-bearing mudstone from the Benxi Formation to the Member 2 of the Shanxi Formations in the Linxing block, northeastern Ordos Basin, a logging identification model for siderite-bearing mudstone (key layer) was established. The porosity characteristics and sealing property were quantitatively evaluated by logging data. Sedimentary control on the formation of multi-superimposed gas-bearing system in the development of key layers in the sequence framework was also discussed. The results showed that the siderite-bearing mudstone has obvious logging response characteristics, e.g., high photoelectric absorption cross-section index (PE), high density (DEN), high amplitude natural gamma ray (GR), low acoustic (AC), low resistivity (M2RX) and low neutron porosity (CNCF). The quantitatively evaluated results of the porosity characteristics and sealing property for the key layer showed that the key layer has the characteristics of low porosity (with an average of 1.20 percent), low permeability (with an average of 2.29 × 10 −8 μm 2 ), and high breakthrough pressure (with an average of 12.32 MPa) in the study area. This layer acts as an impermeable gas barrier in a multi-superimposed gas system. The results also indicated that the material composition of the multi-superimposed gas-bearing system can be established by the sequence stratigraphic framework. The sedimentary evolution results in a cyclic rhythm of material composition vertically. The spatial distribution of the corresponding transgressive event layer near the maximum flooding surface (MFS) in the sequence framework restricts the spatial distribution of the key layer with high breakthrough pressure and low porosity, which constitutes the gas-bearing system boundary. The siderite-bearing mudstone formed near the MFS in the second-order sequence and constitutes a stable comparison of the first-order gas-bearing system boundary, which has a wide range of regional distribution and stable thickness. The siderite-bearing mudstone formed near the MFS in the third-order sequence is often incompletely preserved due to the late (underwater) diversion channel erosion and cutting. This layer forms the coal-bearing reservoirs, which we termed as a second-order gas-bearing system in adjacent third-order sequences to form a uniform gas-bearing system. [ABSTRACT FROM AUTHOR]

Hybrid beds, the deposits of sediment gravity flows that show evidence for more than one flow regime (turbulent, transitional and/or laminar), have been recognized as important components of submarine lobe deposits. A wide range of hybrid bed types have been documented, however, quantitative analysis of the stratigraphic and geographic distribution of these enigmatic bed types is rare. Here, extensive exposures integrated with research borehole data from Unit A of the Laingsburg Formation and Fan 4 of the Skoorsteenberg Formation, Ecca Group, South Africa, provide the opportunity to examine geographical and stratigraphic patterns over a range of hierarchical scales. For this purpose, >23,000 individual beds have been evaluated for deposit type and bed thickness. On average, hybrid beds make up < 5% of all events and <10% of the cumulative thickness. Lobe complex 1 (LC1) of Fan 4,Skoorsteenberg Formation, preserves a prominent geographical trend of hybrid beds becoming more prevalent towards the frontal fringes of a lobe complex (up to 33.2% of beds), whereas their proportion in proximal and medial lobe complex settings is <10%. Data from Unit A, Laingsburg Formation, show hybrid beds are less common in the basal (A.1) and top (A.6) subunits compared to A.2-A.5 in both core data sets. The bases and tops of some lobe complexes (A.2, A.3 and A.5.7) are observed to be slightly enriched in hybrid beds, whereas others (A.5.1, A.5.5 and A.6.1) show no hybrid beds in their bases, which does not conform to expected allogenically-driven distributions that predict more hybrid beds during the initiation of lobe complexes. Instead, the occurrence and distribution of hybrid beds in lobe complexes are interpreted to be controlled by autogenic processes, including flow transformation processes on the basin-floor meaning enrichment in frontal lobe fringe settings. Therefore, the 1D distribution of hybrid beds in lobe complexes reflects the dominant stacking pattern of lobes within a lobe complex, with enrichment at the base and top of lobe complexes due to overall progradational to retrogradational stacking patterns. Individual lobes show a wide range of hybrid bed distributions, due to stacking patterns of the component lobe elements. These findings highlight the importance of autogenic processes rather than allogenic controls in the distribution of hybrid beds, which has implications for reservoir evaluation and the assessment of lobe stacking patterns in 1D core data sets. [ABSTRACT FROM AUTHOR]

Market places remain underrepresented in studies of archaeological soil micromorphology. In Lier, micromorphology was applied to gain understanding of the stratigraphy and formation processes of the medieval “Grote Markt”. Block samples were obtained from a sediment profile that spanned the 11 th -15th century and contained three separate phases of thick, dark-coloured, humic, homogeneous layers - so-called ‘dark earth’. Combined with textural and archaeobotanical analyses (seeds, fruits and phytoliths), the results shed light on the formation processes that shaped this site. The oldest dark earth, dated to the 11th century, was characterised by agricultural activities. The second dark earth (12–13th century) formed as a result of intensive human activities, witnessing the site's transformation to an urban space. This layer contained large amounts of organic matter and anthropogenic inclusions and developed gradually in situ . It probably represents an early market or open space close to dwellings or small courtyards. Units that contain evidence for intensive building activity separate the second and third dark earth, and are possibly the result of a spatial re-organisation of the square. The formation of the third dark earth, which started in the 14th century, is characterised by an intensification of traffic and craftworking activities. Surfaces may have been maintained by spreading organic matter such as leaves, sand and hearth detritus. However, there is no evidence for a kept, empty urban square before a thick layer of levelling sand was deposited (in the second half of the 14th century at earliest) and the market was cobbled. The analysis shows that mixed market activities took place in this intensively used zone, and presents a number of micromorphological characteristics and inclusions typical of a medieval market place in a temperate climate. [ABSTRACT FROM AUTHOR]

The study area refers to the class of highly complex geotechnical conditions. Hazardous geological processes (HGP) are active here, including high seismicity up to 7 points MSK-64, karst, suffosion, subsidence and collapses of land surface, underflooding and flooding, erosion, ecological processes, etc. Large industrial plants with hazardous production and complex infrastructure are in operation here. One such plant is the First Berezniki Potassium Production Mine (BPPM-1), which have been operated since 1954. Its mine field extends below the industrial zone and the residential quarters of the town. An accident took place here in 2006, resulting in the inundation of the entire mined-out space with a volume of more than 80 million m3 and the formation of huge collapses of land surface in 2007, 2010, 2011, and 2015. The geological structure of a mine in the Verkhnekamskoe deposit of potassium salts is used as an example to discuss the effect of two leading groups of geological factors on the formation of karst sinkholes. Analysis is given to the hydrodynamic conditions and geomechanical structure of the above-salt rock stratum, whose synergy determines the diversity of models of possible development of deformations and collapses of land surface. The article gives the possible development schemes of land surface collapses above the mined-out space. The objective of the study is to assess and forecast the development of hazardous geological processes in the territory of Berezniki T. based on the geotechnical interpretation of the available materials of geological works, engineering surveys, and integral monitoring observations. [ABSTRACT FROM AUTHOR]

The concentration and distribution of organic matter, phosphate nodules, and framboidal pyrite preserved in shales are controlled by organic matter decomposition and the cycles of phosphorus, sulfur, and iron, which, in turn, are controlled by bottom-water redox conditions. The organic-rich shale in the 7th member of the Upper Triassic Yanchang Formation (Ch7) contains high organic carbon concentrations and abundant phosphate nodules and pyrite framboids, providing an opportunity to better understand the redox conditions at the time of deposition. Framboidal pyrite in the Ch7 organic-rich shales are composed of octahedral, pyritohedral, and spherulitic microcrystals with uniform crystal size. SEM photographs and statistical data suggest that pyrite framboids have large mean diameters (10.0 to 18.1 μm) and standard deviations (2.8 to 5.9 μm). This may indicate that the organic-rich shale was deposited under oxic-suboxic bottom-water conditions. The C org :P ratios of the organic-rich shale exhibit considerable variation, ranging from 7.2 to 216, but the majority of them (83.2%) belong to the lower-intermediate range (< 130), suggesting that the redox conditions were predominantly oxic-suboxic and intermittently anoxic. The C org :P ratios also show periodic vertical variation, which suggests that redox conditions fluctuated between oxic-suboxic and anoxic. Additional support for the trends based on C org :P ratios is provided by DOP T values, which show similar vertical variation and redox patterns. All evidence shows that the redox conditions during deposition of the Ch7 organic-rich shale was predominantly oxic-suboxic accompanied by intermittent anoxic environments. The result of this study will be helpful in better understanding the formation mechanism of the Ch7 organic-rich shale. [ABSTRACT FROM AUTHOR]

We study the transition from passive margin to foreland basin sedimentation now exposed in the High Zagros belt to provide chronological constraints on the initial stage of Arabia–Eurasia collision and closure of the Neo-Tethys. We performed magnetostratigraphy and strontium isotope stratigraphy along two sections near the Zagros suture which expose the oldest preserved foreland deposits: the Shalamzar section in the west and the Dehmoord section in the east. The top of the passive margin Asmari formation has an age of 28–29 Ma in the High Zagros and is overlain by foreland deposits with a major basal unconformity representing 7 Myr of hiatus. The base of the foreland deposits has an age of 21.5 Ma at Dehmoord and ca. 26 Ma at Shalamzar. The sedimentation rate increased from 30 m/Myr in the passive margin to 247 m/Myr in the foreland. Combined with available age constraints across the Zagros, our results show that the unconformity is diachronous and records the southwestward migration of the flexural bulge within the Arabian plate at an average rate of 24 ± 2 mm/yr over the last 27 Ma. The time evolution of sediment accumulation in the Zagros foreland follows the prediction from a flexural model, as the foreland is thrust beneath the orogenic wedge and loaded by the wedge and basin fill. We detect the onset of forebulge formation within the Asmari Formation around 25 Ma. We conclude that closure of the Neo-Tethys formed the Zagros collisional wedge at 27 ± 2 Ma. Hence, the Arabia–Eurasia collision was probably not the main driver of global cooling which started near the Eocene–Oligocene boundary (ca. 33.7 Ma). We estimate 650 km of forebulge migration since the onset of the collision which consists of 350 km of shortening across the orogen, and 300 km of widening of the wedge and increasing flexural rigidity of Arabia. We conclude the average rate of shortening across the Zagros to be ca. 13 mm/yr over the last 27 Myr; a value comparable to the modern rate. Palinspastic restoration of structural cross-sections and crustal volume conservation comprise only ca. 200 km of shortening across the Zagros and metamorphic Sanandaj–Sirjan belt implying that at least 150 km of the Arabian crust was underthrust beneath Eurasia without contributing to crustal thickening, possibly due to eclogitization. [ABSTRACT FROM AUTHOR]

Serious discrepancies exist in the correlation between North American, West European and East European chronostratigraphic classifications of the Pennsylvanian Subsystem. Asketch map (text-fig. 1) shows tectono-stratigraphic zones/areas in their paleogeographic relationship. The complexity of western Europe is noted with regard to eastern Europe and North America. Regional stratigraphic histories are discussed for revised correlations leading to modified charts as included in the present paper (text-figs. 2, 3). Reasons are given for lowering the base of the Moscovian in the Donbass to conform to Moscovian in its conceptual stratotype in the Moscow Syneclise. There may be an overlap between the upper Bashkirian in its South Urals (Gornaya Bashkiria) stratotype and the lower Moscovian in the Moscow Syneclise. It is also noted that American authors have assumed that a major extinction event coincides with the Desmoinesian-Missourian boundary in North America, where abrupt changes in paleontological composition have been recorded. No such 'extinction event', however, is apparent in NW Spain where a continuous stratigraphic succession from uppermost Westphalian to a full lower Stephanian representation shows only gradual changes in faunal and floral composition. An alternative explanation of the American record would be a stratigraphic gap at the Desmoinesian-Missourian boundary. This gap is regarded herein as widespread in North America as well as in northern Europe, where most of Stephanian time is unrepresented. A general interpretation of paleogeographic zones is proposed herein based on shared geological histories, which are briefly discussed. Paleogeographical areas are recognized as follows: (1) a large northern continental region (Laurasia) with epicratonic basins from the Moscow Basin in the east to the North American Midcontinent in the west; (2) the Paralic Coal Belt of northern Europe extending WNWinto the Appalachian region in eastern North America; (3) a Mid-German Crystalline Rise which provoked the Variscan Orogeny; (4) the Saxothuringian Zone in central Europe with strike-slip controlled basins; (5) a Moldanubian Zone defined on criteria independent of the Pennsylvanian record; (6) the Massif Central of south-central France; (7) Montagne Noire and Pyrenees extending eastwards into the western and southern Alps; (8) Cantabrian Mountains at the western end of a Paleotethyan area, which is also represented in the Carnic Alps, the Donbass, and central Anatolia; (9) aWest Iberian area characterized by terrane assembly by major strike-slip movements in Pennsylvanian times; and (10) South European areas including southeastern Iberian Peninsula, most of Morocco, SE France, Tuscany (Italy) and Corsica/Sardinia. Alternating marine and terrestrial deposits in the most nearly complete successions in the Cantabrian Mountains and the Donbass are the key to a fully integrated set of chronostratigraphic units of global validity within the context of a Pennsylvanian paleoequatorial belt. [ABSTRACT FROM AUTHOR]

The type section of the Hume Formation (114.6 m), located along the Hume River in western Northwest Territories, is examined in detail for its conodonts and benthic fossils. For the most part it consists of a late Eifelian (early Middle Devonian) kockelianus Zone age, with short intervals of australis and ensensis zones at its base and top, respectively. Three benthic assemblage zones are recognized, in ascending order, Eoschuchertella adoceta, Carinatrypa dysmorphostrota, and Eliorhynchus castanea. The ranges of selected benthic fossils suggest transgression and regression, which are in agreement with three T-R cycles of Johnson, Klapper and Sandberg (1985) and Johnson andKlapper (1992), namely Id, Ie, and If. Cycle Id occurs at the base of the Hume Formation, at contact with the underlyingGossage Formation, and iswithin the australis Zone. Cycle Ie is about midway in the Hume Formation, within the kockelianus Zone. Cycle If, at the top of theHume Formation, signals the entry of the ensensis Zone and the Kačák Episode,with the deposition of the overlying Hare Indian Formation. [ABSTRACT FROM AUTHOR]

The Afar region is a triangular area located at the triple junction between the African, Somalia, and Arabian plates, which are currently diverging at different rates. Currently, the extension vector is roughly oriented in a NE-SW direction in the Afar, Red Sea and Gulf of Aden, in respect to Arabia plate, whereas the Nubian–Somalian divergence, evidenced by the Main Ethiopian Rift (MER), is approximately WNW-ESE (N95-100°E). This study focuses on the tectono-sedimentary evolution of a sector from Massawa to the north up to the continental Early-Middle Pleistocene Dandiero Basin to the south. This basin is filled with approximately 500 m thick fluvial-lacustrine deposits and includes six formations. Sedimentation occurred mainly along the basin axis and allowed accumulation of sand and mud deposits with subordinate gravels close to the basin margin. The age of the basin infill succession is well constrained through integration between paleomagnetic and paleontological data and ranges between ~ 1.2 and 0.75 Ma. The Dandiero Basin is controlled by two main roughly NNW-SSE trending, east dipping normal faults. The westernmost fault delimits the basins from the plateau, whereas the easternmost marks the limit between the basin succession and the Late Pleistocene Samoti Plain. We infer that the NNW-trending faults were progressively activated as a consequence of the Danakil Block counter clockwise rotation and were superimposed to the N-S trending faults that delimited the basin at the time of its inception as a marginal graben roughly aligned to the Eritrean-Ethiopian plateau. The timing of deformation (1.2 Ma up to Present) is well constrained by the age of syntectonic sediments of the Dandiero Basin and volcanic products of the Alid Volcano. These relations allowed us to refine the timing and evolution of this sector of Afar and giving some insights on the geodynamics of the area. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination of groundwater is often caused by As leaching from geological formations. This study focused on factors affecting As content in unconsolidated sediments by using three sediment cores in the Ishikari plain, Hokkaido, Japan. The geochemical properties of the sediments were characterized by the chemical and mineral compositions as well as leaching experiments and sequential extractions of As. The results showed that higher As content of 4-9 mg/kg was observed in peat layers with organic matter content > 10 wt%, and that higher As contents deeper than 8 m below the surface were also observed. The deeper sediments were likely to be formed in brackish water conditions due to lower weight ratios of organic carbon content to sulfur content (C/S < 10). The results of the leaching experiments showed that As was mobilized at slightly alkaline region. These indicate that the distribution of As depended on the organic content in the sediments and sedimentation condition, and that the mobility of As in the sediment was affected by pH. [ABSTRACT FROM AUTHOR]

The Lower Jurassic Huayacocotla Fm. (Upper Sinemurian), was first studied by several American and European geologist during the twentieth century (1948), whom eventually concluded that these rocks were not commercially productive. Consequently, the interest in this unit faded a long time ago. However, studies resumed in the 2000’s by Mexican researchers, this time including a wide range of paleontological, paleoenvironmental, paleoecological, geologic, and structural aspects, incorporating taphonomic, petrologic and geochemical techniques. They concluded that the Huayacocotla Fm. is not a condensed sequence, but can be better regarded as a single unit, including several facies rather than a complex unit of several formations. Today, it is well known that the Huayacocotla Fm. was deposited in a semi-restricted back arc paleobasin, with suboxic to euxinic conditions. Its protolith of igneous intermediate composition reveals tectonic features related to the Pangea collision phase and the first stages of the Gulf of Mexico opening. The paleobasin with high rate of sedimentation, generated this sequence siliciclastic, simultaneously with the process of expansion of the Gulf of Mexico. The modern biostratigraphical analyses developed in the 2000’s, accurate the biostratigraphic zonation proposed by Burckhardt and Erben. These new studies revealed that the deposition of the Huayacocotla Fm. spanned several Late Sinemurian diverse chronozones, especially Oxynotum, Densinodulum, and Raricostatum subzones. Nevertheless, some local divergences with respect to the standard biozonation were noticed, and these anomalies are tentatively explained to be the result of Early Sinemurian homotaxial events. There is a gap in the Lower Obtusum faunas, but the presence of Lower Sinemurian deposits was reported from at least one outcrop. This Jurassic field trip guide was written to lead and encourage interested researchers in this field to contribute to this subject, and maybe other related topics, as well as to encourage academic discussions about the knowledge of Early Jurassic marine paleobasins, in the context of the 10th International Jurassic Congress. [ABSTRACT FROM AUTHOR]

The Middle Permian Skoorsteenberg Formation is part of the Ecca Group (Karoo Supergroup) of South Africa. It is also known as the 'Tanqua fan complex' due to its origin as a deep-water sedimentation unit associated with a prograding deltaic system. The Skoorsteenberg Formation crops out over approximately 650 km? along the western margin of the Main Karoo Basin. It thins out in a northerly and easterly direction and therefore has a limited extent with cut-off boundaries to the south and north. It is underlain by the Tierberg Formation and overlain by the Kookfontein Formation, the latter being limited to the regional distribution of the Skoorsteenberg Formation. The Skoorsteenberg Formation has a composite thickness of 400 m and comprises five individual sandstone packages, separated by shale units of similar thickness. The sandstones are very fine- to fine-grained, light greyish to bluish grey when fresh, poorly sorted and lack primary porosity and permeability. The Tanqua fan complex is regarded as one of the world's best examples of an ancient basin floor to slope fan complex associated with a fluvially dominated deltaic system. It has served as analogue for many deep-water systems around the world and continues to be a most sought after "open-air laboratory" for studying the nature of fine-grained, deep-water sedimentation. The fan systems are essentially tectonically undeformed, outstandingly well exposed and contain an inexhaustible amount of information on the deep-water architecture of lower slope to basin floor turbidite deposits. [ABSTRACT FROM AUTHOR]

The Lower Carboniferous, probably Tournaisian, Kweekvlei Formation is part of the Witteberg Group (Cape Supergroup) of South Africa. Together with the overlying Floriskraal Formation, it forms an upward-coarsening succession within the Lake Mentz Subgroup. Sedimentary features of the Kweekvlei Formation suggest deposition in a storm-wave dominated marine setting, within the storm-influenced, distal part of an offshore transition zone environment. This predominantly argillaceous formation preserves a low diversity trace fossil assemblage. Reworked vascular plant debris (including the problematic genus Praeramunculus sp.) and a shark spine have been reported for the Kweekvlei Formation. There are no known stratigraphic equivalents in South Africa. [ABSTRACT FROM AUTHOR]

The Permian Kookfontein Formation forms part of the upper Ecca Group in the southwestern part of the main Karoo Basin of South Africa. It occupies a stratigraphic position between the underlying Skoorsteenberg Formation and the overlying Waterford Formation, with its regional extent limited to the cut-off boundaries of the Skoorsteenberg Formation. The Kookfontein Formation has an average thickness of 200 m, coarsens upwards, and predominantly comprises dark grey shale, siltstone and thin- to thick-bedded, fine- to very fine-grained, feldspathic litharenite. Characteristic upward-coarsening and thickening successions and syn-sedimentary deformation features reflect rapid deposition and progradation of a predominantly fluvially-dominated prodelta and delta front slope environment. The upward increase in the abundance of wave-ripple marks further indicates a gradual shallowing of the depositional environment through time. The upper contact with theWaterford Formation is gradational, which indicates a transition from deposition in an unstable upper slope/shelf margin environment to a more stable shelf setting. [ABSTRACT FROM AUTHOR]

The Pamir Salient and Southwestern Tien Shan belong to two different systems, which collided due to the continuous northward drift of the Indian Plate during the Cenozoic, resulting in a shortening of ~ 300 km. The uplift history and kinematic evolution of the Pamir-Southwestern Tien Shan remain unclear. In this study, we chose the 2025 m-thick Pakabulake formation in the East Wuqia section, at the southern-most margin of the Southwestern Tien Shan system, to obtain a high-resolution magnetostratigraphic record spanning ~ 16.61 Ma to ~ 9.78 Ma. Based on its high sedimentation rate, stable ca. E-W paleocurrents and stable magnetic susceptibility values, the nearby Southwestern Tien Shan was inferred to have undergone stable uplift during this period of sedimentation. Combining our results with the previous low-temperature thermochronology, magnetostratigraphy and re-calculated block rotations, we conclude that four episodic uplift events occurred in the Pamir-Southwestern Tien Shan during the Cenozoic, at times of ~ 50–40 Ma, ~ 35–16 Ma, ~ 11–7 Ma and < 5 Ma, and that the first episodic uplift only occurred in the Pamir Salient. In addition, the Pamir Salient underwent a tectonic transformation from entire- to a half-oroclinal bending rotation during the Miocene, caused by activity along the Karakorum Fault and Kashgar-Yecheng Transfer System. [ABSTRACT FROM AUTHOR]

Post-dam removal geomorphologic adjustment of a stream channel has been documented in the scientific literature at watershed, hillslope, and laboratory scales. Hillslope-scale studies in channel cross sections are most common and add significant value in the dam-removal literature. This study examines geomorphic stream channel adjustment following dam removal at the hillslope scale under natural climatic conditions. A sedimentfilled silt fence dam (1 m tall, 12.65 m wide) was removed in three stages, and the width and depth of the upstream developing channel was monitored at six transects for 15 months. Headcut retreat and changes in channel sinuosity were also recorded. After the silt fence dam was removed, channel development was initiated by headcut formation, which migrated upstream at a rate of 4 cm/d for about 10 months and then gradually reached attenuation. The channel progressed through four distinct stages: Stage 1 (Initial conditions); Stage 2 (Downcutting)--wide, shallow, meandering channel incised to a maximum depth of 0.52 m, and sinuosity decreased; Stage 3 (Floodplain development)--upon reaching base level, surface runoff began to meander within the channel, widening it through bank slumps and erosion; and Stage 4 (Quasi-equilibrium)--channel development reached dynamic (quasi-) equilibrium with only minor widening at downstream transects (maximum width of the incised channel reached 0.46 m), accompanied by sediment aggradation. The stages of upstream channel development and headcut retreat pattern in this study are consistent with the findings of other studies at the laboratory and watershed scales, indicating that channel development after dam removal is scale independent. [ABSTRACT FROM AUTHOR]