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In this paper, geophysical technique ERT (Electrical Resistivity Tomography) supported by geological methods (macroscopic and microscopic observations) have been used to study shallow structure of the southern margin of the Krzeszowice Graben in the vicinity of Nawojowa Góra (southern Poland). The fieldwork was focus on the characterizing facies of the Upper Jurassic sediments that crops out in the selected quarry. Special attention was also paid on its microfacies development in order to broadly characterise these sediments. Geological studies of the exposed sediments have revealed that in this site calciturbidites and debris-flow deposits are present. The 2D ERT survey has been developed over the quarry exposure and within adjacent area, with the aim of identifying the 2D subsurface geology. Separate ERT survey lines have been performed and in the case of each profile, combined array configuration has been applied. In all obtained 2D ERT cross-sections, gradient analysis (showing the distribution of the maximum vertical and horizontal gradients of the interpreted resistivity) was carried out. These data provides additional information about spatial distributions of the various geoelectrical/geological layers. Beyond the Upper Jurassic sediments, which prevail in the research area, several lithological units were outlined on the ERT profiles that contain both the Upper Cretaceous sediments, Oligocene-Miocene karst deposits as well as Quaternary deposits. The use of the both geological and geophysical methods has allowed also delineating the zones which could be interpreted as fault zones. Geological interpretation has been considerably enhanced by forward 2D ERT modeling, by which it was possible to resolve some of the hypothesis derived from the interpretation of the field data. The distribution of the gravity flow deposits of different types in the marginal southern part of the Krzeszowice Graben reflects Late Jurassic fault activity. All obtained data have ultimately lead to a better understanding of the sediment distributions and the presence of tectonics in the geological context of the southern margin of the Krzeszowice Graben, supplying relevant information to its geological interpretation. • Characterization of the southern margin of the Krzeszowice Graben (Poland) based on geoelectrical and geological studies. • Analysis of the Upper Jurassic limestones microfacies development. • Maximum gradient of the interpreted resistivity analysis applied to structural boundaries detection. • The numerical forward 2D ERT modeling as a supplementary geophysical tool. [ABSTRACT FROM AUTHOR]

Abstract Two breccia layers occur directly stacked upon each other in a silty/sandy Saalian glaciolacustrine succession near Ujście (western Poland). This complex is exceptional because of two aspects: the two breccia layers consist of distinctly more fine-grained material (mainly silt) than the rest of the succession, and they contain numerous soft-sediment clasts of sandy silt with irregular shapes. The silty clasts are interpreted to represent fragments of eroded sediment from the more marginal (proximal) bottom of the lake. The fine-grained character of the breccia matrix excludes that the process responsible for their deposition had a sufficiently high erosional capability to erode the embedded clasts. The only feasible explanation is that this enigmatic breccia consists of a mixture of sediments: the silty matrix must first have been deposited on the bottom of a lake and afterward have been eroded and redeposited by gravity flows that initially had sufficient power to erode the lake margin over which they ran down. The source of the gravity-flow silt remains enigmatic because no sediments with similar lithology are currently present nearby at a higher topographic level. We must therefore deduce that such sediments existed previously but were entirely eroded away, probably by the Weichselian ice mass that had reached this area during the next glaciation. The probable trigger of the gravity flows is evidenced by the presence of soft-sediment deformation structures in two levels around 4.5 m below the breccias. These two levels show intense folding, collapse, and load structures indicative of liquefaction and fluidization. The deformation is ascribed to shocks, most probably resulting from earthquakes that were induced by glacioisostatic rebound during the Saalian deglaciation. Similar seismic shocks are likely to have triggered the mass flows that resulted in the breccia layers. Graphical abstract Unlabelled Image Highlights • Two silty glaciolacustrine gravity-flow deposits contain numerous soft-sediment clasts. • The frozen clasts became plastic during transport by the higher temperature of the water. • The same Saalian glaciolacustrine succession contains two seismites. • The flows were likely induced by seismic shocks due to glacio-isostatic rebound. [ABSTRACT FROM AUTHOR]

Gravity-flow deposits are important hydrocarbon exploration targets in most basins. In this study, an integration of geological, geophysical, and geochemical analysis is used to investigate the gravity-flow deposits and their petroleum prospects in the Oligocene Dongying Formation (E 3 d), Bozhong Subbasin, Bohai Bay Basin. Mass-transport deposits (MTDs) and channel-lobe complexes are the main gravity-flow depositional units. The mass-transport deposits (MTDs) show hummocky and chaotic reflections with poor continuity and variable amplitude. The channels display linear geomorphology with weak root-mean-square (RMS) amplitude, and the lobes are dominated by high-continuous and high-amplitude reflection at the terminal channels. The formation of gravity-flow deposits is primarily controlled by high sedimentation rate during a relative lowstand of lake level. The E 3 d 3 source rock has TOC contents in the range of 0.6–3.1%, Rock-Eval S 2 values in the range of 0.7–19.8 mg HC/g rock, and Hydrogen indices (HI) in the range of 100–600 mg/g TOC. The E 3 d 2 L source rock has TOC contents ranging from 0.5 to 1.9%, Rock-Eval S 2 values from 0.4 to 7.8 mg HC/g rock, and HI from 40 to 480 mg/g TOC. Both E 3 d 3 and E 3 d 2 L source rocks have good hydrocarbon-generation potential. The E 3 d 3 and E 3 d 2 L source rocks have entered the oil-generation peak window with the vitrinite reflectance (R o ) higher than 1.0%. Oils generated from the underlying source rocks shortly migrated to the overlying gravity-flow lithologic traps. The gravity-flow reservoirs could serve as potential and effective hydrocarbon exploration targets. [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 late Early Jurassic Toarcian Stage represents the warmest interval of the Jurassic Period, with an abrupt rise in global temperatures of up to ∼7 °C in mid-latitudes at the onset of the early Toarcian Oceanic Anoxic Event (T-OAE; ∼183 Ma). The T-OAE, which has been extensively studied in marine and continental successions from both hemispheres, was marked by the widespread expansion of anoxic and euxinic waters, geographically extensive deposition of organic-rich black shales, and climatic and environmental perturbations. Climatic and environmental processes following the T-OAE are, however, poorly known, largely due to a lack of study of stratigraphically well-constrained and complete sedimentary archives. Here, we present integrated geochemical and physical proxy data (high-resolution carbon-isotope data ( δ 13 C ), bulk and molecular organic geochemistry, inorganic petrology, mineral characterisation, and major- and trace-element concentrations) from the biostratigraphically complete and expanded entire Toarcian succession in the Llanbedr (Mochras Farm) Borehole, Cardigan Bay Basin, Wales, UK. With these data, we (1) construct the first high-resolution biostratigraphically calibrated chemostratigraphic reference record for nearly the complete Toarcian Stage, (2) establish palaeoceanographic and depositional conditions in the Cardigan Bay Basin, (3) show that the T-OAE in the hemipelagic Cardigan Bay Basin was marked by the occurrence of gravity-flow deposits that were likely linked to globally enhanced sediment fluxes to continental margins and deeper marine (shelf) basins, and (4) explore how early Toarcian ( tenuicostatum and serpentinum zones) siderite formation in the Cardigan Bay Basin may have been linked to low global oceanic sulphate concentrations and elevated supply of iron (Fe) from the hinterland, in response to climatically induced changes in hydrological cycling, global weathering rates and large-scale sulphide and evaporite deposition. [ABSTRACT FROM AUTHOR]

In the Upper Cretaceous Balcones Igneous Province in South and Central Texas, numerous small volcanoes developed during Austin Chalk and Anacacho deposition that are similar to the recent Surtsey volcano offshore of Iceland. The volcanoes formed topographic highs on the deep-water (500–900 ft [150–275 m]), earlier-drowned Comanche Platform. The Elaine field in South Texas is associated with one of these relict volcanic highs and integration of a 3D-seismic dataset and cores permitted a detailed analysis of the deeper-water carbonate depositional systems of the field and associated carbonate reservoir development. This reservoir description extends the understanding of petroleum systems associated with relict, open-marine, deep-water, volcanic highs. In the shallow water at the top of the volcanic topographic highs, a carbonate factory developed that produced coarser-grained carbonate sediments that sourced the deeper-water flanks and toe-of-slope of the mound. Finer-grained carbonate chalk was deposited in the open-marine, deep-water environment adjacent to the volcanic mound. The coarser-grained carbonate sediments sourced from the mound top were transported downslope by gravity-flow processes that formed debrites and hyperconcentrated density-flow deposits. The gravity-flow deposits are composed of a mixture of shallow- and open-marine, deep-water biota indicating they are not shallow-water deposits, but are deeper-water mound-flank and toe-of-slope deposits. In the Anacacho Elaine field, the coarser-grained carbonates (i.e., skeletal packstones and grainstones) associated with the volcanic mound are the oil-producing reservoirs. The Elaine volcanic mound itself is tight and not productive. The Anacacho chalk immediately above the mound are also tight and form the top seal for the Elaine field. Associated with the relict volcanic mounds in the Balcones Igneous Province are a spectrum of carbonate plays. The relict volcano can be a reservoir, but not all the relict volcanic mounds are porous. The coarser-grain carbonates on the top, flanks, and at the base of the volcanic mounds are reservoirs in the area of the Balcones Igneous Province. The chalks deposited penecontemporaneously on the open-marine, deep-water platform can also be tight carbonate reservoirs. • Integration of 3D-seismic data and cores to define volcanic mound paleogeomorphology • Carbonate lithofacies associated with volcanic mounds. • Recognition of depositional environments associated with volcanic mounds. • Hydrocarbon reservoirs associated with volcanic mounds in open-marine settings. [ABSTRACT FROM AUTHOR]

Understanding the flow processes that form gravity-flow deposits is vital for modeling and predicting sandstone bodies in the subsurface, which is of great significance for conventional and unconventional oil and gas exploration and development in lacustrine basins. This study analyses gravity-flow deposits of the Late Triassic Chang 7 oil member of the Yanchang Formation in the Ordos Basin, using a combination of well-log analysis, core observations, thin-section analysis, and laboratory measurements. The sedimentary facies, formation mechanisms, distribution patterns, and depositional models of gravity-flow deposits are investigated. Thirteen facies and eight bed-types are recognized in the gravity-flow deposits. Bed types represent deposits of sandy slides, sandy slumps, debrites, high-density turbidites, hybrid event beds, transitional flow deposits, surge-like low-density turbidites, and quasi-steady low-density turbidites. Gravity-flow deposits, particularly those caused by sediment failure, are composed of slides, slumps, debrites, high-density turbidites, hybrid event beds, transitional flow deposits, and surge-like low-density turbidites. These deposits form as isolated lenticular sand bodies, with retrogradational internal stacking patterns. In contrast, gravity-flow deposits caused by flooding rivers are composed of high-density turbidites, hybrid event beds, transitional flow deposits, and quasi-steady low-density turbidites. These deposits exhibit elongate morphologies with progradation stacking patterns internally. The collision between the North China Block and the South China Block, which occurred during the closing of the Qinling Ocean, lead to frequent volcanic eruptions and earthquakes. These activities promoted the development of gravity-flow deposits associated with sediment failure from delta fronts in both the northeastern and southwestern parts of the basin. Concurrently, extremely humid climatic conditions promoted increased fluvial drainage, leading to enhanced hyperpycnal flows into the deep-lacustrine basin depocenters in the Late Triassic. This study emphasized that detailed facies analysis and distribution pattern analysis are the fundamental way to identify the formation mechanisms of gravity flow deposits in lacustrine depression basins. • Thirteen facies and eight bed-types are recognized amongst the gravity-flow deposits in the Late Triassic Chang 7 oil member of the Yanchang Formation in the Ordos Basin, which are composed of sandy slide, sandy slump, muddy debrites, sandy debrites, hybrid event beds, transitional flow deposits, surge-like low-density turbidite, quasi-steady low-density turbidite. • Gravity-flow deposits in the late Triassic Chang 7 oil member of the Yanchang Formation in the Ordos Basin are due to both sediment failure and flooding river. • The collision between the north China block and the south China block during the closing of Qinling Ocean, and extremely humid environment in the Late Triassic promotes the development of gravity-flow deposits in the Ordos Basin. [ABSTRACT FROM AUTHOR]

Integrated in the peri-Adriatic domain, the Ionian Basin extended along a NW-SE direction during the Late Cretaceous, limited on its sides by the Apulian and the Kruja platforms. The basinal/slope succession was studied in seven outcrops exposed in the Albanian fold-and-thrust belt. Sedimentological investigations, supported by bio- and chronostratigraphy were performed on calcareous Upper Cretaceous hemipelagites, gravity-flow deposits and slumps. The western part of the basin was studied, revealing a strong influence of the Apulian margin, alternatively shedding sediment basinward, by means of a tectonically controlled edge. The Late Albian to Cenomanian period is characterized by the settling of muddy debrites along the margin. A deep basinal environment characterizes this period which prolongs until the Santonian, with no significant influx of the platform basinward. This sedimentary setting abruptly changed at the end of the Santonian, with an important influx derived from both platforms. Coarsening and thickening upward sequences show a progressive increase in sediment shedding during the Campanian. The Late Campanian-Early Maastrichtian period points out a major change on the resedimentation processes with the settling of several slumped units reworking thick sediment packages. The latter can be traced along the Apulian margin, testifying of instabilities along the edge of Apulia. [ABSTRACT FROM AUTHOR]

The Perbla Formation represents typical Toarcian clay-rich pelagic sediment of the southern Tethyan passive continental margin. It was deposited in the Slovenian Basin, located in present-day western Slovenia. During the Early Jurassic the basin was surrounded by the Dinaric (Friuli) Carbonate Platform to the south and by the Julian Carbonate Platform to the north. Today, the transitional areas between the platforms and basin are not preserved due to intense Cainozoic thrusting and erosion, with the only record of the evolution of these areas stored in gravity-flow deposits of the Perbla Formation. Coarser turbidites were deposited on the margins of the basin, with other types of gravity-flow deposits, observed mainly in the central part of the basin. These intercalations reflect regionally recognized events that characterized the sedimentary evolution of western Slovenia at the end of the Early Jurassic. Slumps that occasionally developed into debris-flows reflect uneven sea-bottom palaeotopography that originated during a pre- to early-Toarcian phase of accelerated subsidence. The early Toarcian transgression caused drowning of the adjacent carbonate platforms, an event reflected in the composition of coarser turbidites which consist almost exclusively of echinoderm fragments and thin-shelled bivalves. These turbidites originated from drowned platform margins and/or slopes and were subsequently redeposited in proximal parts of the basin.

The tight sandstone of gravity-flow deposits in Miocene Mbr 2 of the Huangliu Fm, Ledong area is one of the focuses future exploration in the Yinggehai Basin. Reservoirs have complex sedimentary and diagenesis processes, experienced multi-stage fluid influence. However, the influence of different diagenesis on reservoir quality, and distribution patterns of different diagenetic facies in Mbr 2 of the Huangliu Fm are still short in research. In this paper, a variety of methods, such as thin sections analysis, electron microscopy (SEM), electron probe micro-analyzer (EPMA), cathode luminescence (CL), x-ray diffraction measurement (XRD), in situ carbon and oxygen isotopes composition of cements (SIMS), fluid inclusion homogenization temperature, and high-pressure mercury injection (HPMI), are used to analyze reservoir quality, diagenetic evolution stages, diagenesis, fluid filling processes, etc. Studies have shown that there are obvious differences in diagenetic evolution process, including carbonate cementation, organic acid and hydrothermal dissolution, etc. Which ultimately leads to large differences in physical properties. Although sandstone texture has an impact on reservoir quality, strong compaction and early carbonate cementation were the main reasons for reservoir densification. Early calcite was precipitated in alkaline seawater, and later ferrocalcite was formed by the recrystallization of calcite and polyframboidal pyrites and euhedral pyrites formed under organic acid charged. After hydrothermal fluid charged, dolomite, iron dolomite, cement pyrites and dispersed granular pyrites precipitated. Besides, illite filled the throat. The dissolution of organic acids and late CO 2 -rich hydrothermal fluids improved the quality of reservoirs. According to the difference of diagenetic process and the quality of the reservoirs, Mbr 2 of the Huangliu Fm is divided into 4 types of diagenetic facies. High-quality reservoirs are mostly developed in H2-Ⅰ, H2-Ⅱ, and H2-Ⅴ sand formation near faults. Early carbonate cements were less developed, which could support primary intergranular pores. Feldspar, rock fragments, and early carbonate cements were strongly dissolved. It includes two diagenetic facies, low cementation - strong dissolution reservoirs and slightly cementation - weaken dissolution reservoirs. On the contrary, tight reservoirs mostly develop in H2-Ⅲ, H2-IV, and H2–V sand formation far away from faults, including late compacted tight reservoirs and early carbonate cementation tight reservoirs. The research results are helpful to analyze the diagenetic evolution of tight sandstone reservoirs, and conducive to the study of similar gravity-flow reservoir quality with the influence of hydrothermal fluids. • The diagenesis characteristics of N 1 h 2 shows obvious heterogeneity. • The diagenetic evolution stages and genesis of carbonate cements are revealed. • Gravity flow deposition and fluid charging have effect on reservoir quality. • Diagenetic facies distribution model of Mbr 2 of the Huangliu Fm is established. [ABSTRACT FROM AUTHOR]

The Middle Triassic (Anisian) Leidapo Member of the Qingyan Formation, which crops out in southwestern China, consists of basin-floor and slope deposits with abundant benthic fossils and records two transgressions and one regression. The well-preserved bivalves are grouped into four assemblages. The allochthonous Cassianella–Elegantinia and Protostrea–Cassianella assemblages as well as the autochthonous Palaeonucula assemblage are found in slope deposits. The allochthonous assemblages exhibit several modes of occurrence in sediment gravity-flow deposits. The parautochthonous Posidonia assemblage is preserved in slope and basin deposits. The genus-level compositions of these bivalve assemblages are similar to those from the Early Carnian of Tethyan Europe. It is probable that a significant diversification of bivalves took place in the Anisian. [Copyright &y& Elsevier]

A comparative study of the Middle Liassic series in the south western part of the Middle Atlas system leads to the definition of three new formations called Fellat 1, 2 and 3. They mainly involve gravity-flow deposits related to the breakup of the regional carbonate platform in a subsiding area, the Selloum Basin. The creation of this basin provides evidence for a rifting stage during the Carixian–Domerian interval, inducing the separation of the Selloum unit with respect to the Middle Atlasic trough and its possible connection with the High Atlasic sedimentary domain. [Copyright &y& Elsevier]