Evolution Of Sedimentary Basins Research Articles

3D reconstruction of the Lapis Tiburtinus (Tivoli, Central Italy): The control of climatic and sea‐level changes on travertine deposition

Abstract3D modelling is a fundamental tool to visualize and understand the history of sedimentary basin filling and to reconstruct the geobody architecture. Spatial distribution of discontinuity surfaces and geobody characteristics provide valuable information on the factors controlling the sedimentary evolution of basins. Several Neogene‐Quaternary basins of central‐western Italy are controlled by extensional and strike‐slip tectonics and characterized by travertine deposition, related to hydrothermal fluids rising up along discontinuities and fractured carbonate bedrocks. This study presents the 3D modelling results of the quarry area within the tectonically controlled Acque Albule Basin (Tivoli, Central Italy) that hosts the Pleistocene Lapis Tiburtinus travertine. The 3D reconstruction of the different surfaces bounding the travertine units shows a complex architecture composed of depressions, reliefs and channels as predominant morphological elements related to four different depositional environments (subaqueous, palustrine, slope and travertine channel). The reconstructed surface maps highlight the presence of laterally migrating, E–W‐oriented lens‐shaped geometries, with a drainage system persistent through time oriented towards the southern part of the study area in the direction of the Aniene River, bordering the Acque Albule Basin in the South. The Lapis Tiburtinus travertine developed in an area of 28 km2, accumulated in a system composed of sub‐basins (approximately 1–2 km2 wide) with subaqueous conditions interconnected by a hydrographic network, controlled through time by fluctuations of the Aniene River base level. Based on the results obtained, base‐level fluctuations of the Aniene River, related to glacio‐eustatic sea‐level oscillations of the last 115 kyrs associated with alternation of humid and arid climatic conditions, arise as the most important factor affecting the architecture of the travertine geobodies.

Evolution of parallel, oblique and triple-junction rifts: Insights from analogue modelling

The study of extensional structures such as normal faults, grabens and rift systems using analogue modelling techniques has been widely used to understand the evolution of sedimentary basins. These have been particularly helpful to understand the generation of oil reservoirs and structural traps. The present work was inspired by the discussion on the origins of two sub-parallel grabens located in the intracratonic Parecis Basin in the centre-west of Brazil. Parallel, oblique or intersecting grabens may form by the reactivation of inherited basement weaknesses that can act as velocity discontinuities, with their geometry and proximity controlling the evolution of the resulting grabens. In this work, we use sandbox analogue experiments to investigate the geometric and kinematic evolution of two nearby, sometimes intersecting, grabens. We do this by varying the distance and the geometry of two basal velocity discontinuities (VDs). In all experiments, an extension of 3 cm (scaling to 12 km) was prescribed to affect a 3 cm thick sand pack. The materials were deformed using a plexiglass box with two basal velocity discontinuities attached to two lateral movable walls. In a first set of experiments, we varied systematically the distance between the VDs. In the second set, we varied the angles between the VDs with different configurations, including situations in which the VDs intersect forming triple junctions. The results show that when the VDs are initially close (<2 cm, corresponding to ~8 km in nature) there is the formation of a wide graben composed of two sub-grabens that interfere with each other, while if the spacing between the VDs is >2 cm, the grabens develop independently and do not interfere. Furthermore, it is possible to conclude that whenever (not interfering) VDs are prescribed to the base of a sand pack it always leads to the formation of asymmetric grabens, except when the two VDs are initially close to each other. In the experiments with conjugate triple-junction VDs, the extension was shared between two independent asymmetric grabens where the VDs were at a certain distance from each other, and always led to the formation of a wide graben where the VDs were close or intersect each other.

Focused methane migration formed pipe structures in permeable sandstones: Insights from uncrewed aerial vehicle‐based digital outcrop analysis in Varna, Bulgaria

AbstractFocused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas.

Latest Miocene restriction of the Mediterranean Outflow Water: a perspective from the Gulf of C\xe1diz

The Mediterranean-Atlantic water mass exchange provides the ideal setting for deciphering the role of gateway evolution in ocean circulation. However, the dynamics of Mediterranean Outflow Water (MOW) during the closure of the Late Miocene Mediterranean-Atlantic gateways are poorly understood. Here, we define the sedimentary evolution of Neogene basins from the Gulf of Cádiz to the West Iberian margin to investigate MOW circulation during the latest Miocene. Seismic interpretation highlights a middle to upper Messinian seismic unit of transparent facies, whose base predates the onset of the Messinian salinity crisis (MSC). Its facies and distribution imply a predominantly hemipelagic environment along the Atlantic margins, suggesting an absence or intermittence of MOW preceding evaporite precipitation in the Mediterranean, simultaneous to progressive gateway restriction. The removal of MOW from the Mediterranean-Atlantic water mass exchange reorganized the Atlantic water masses and is correlated to a severe weakening of the Atlantic Meridional Overturning Circulation (AMOC) and a period of further cooling in the North Atlantic during the latest Miocene.

Paleo‐thermal constraints on the origin of native diagenetic sulfur in the Messinian evaporites: The Northern Apennines foreland basin case study (Italy)

AbstractRecent studies on the genesis of sedimentary native sulfur deposits indicate diagenetic mid‐low temperature Bacterial Sulfate Reduction (BSR) as the main process, involving organic compounds (kerogen/hydrocarbons), bacterial colonies and gypsiferous rocks. In the peri‐Mediterranean area (Southern Spain, Sicily, Northern Apennines, Israel), the main sulfur accumulations are always associated with late Miocene sulfates and organic‐rich successions encompassing the Messinian salinity crisis (MSC). In particular, the Messinian successions of the Apennine‐Adriatic foreland basin system, due to a large amount of high‐resolution stratigraphic data, represent a perfect case study for understanding the diagenetic conditions controlling the development of the BSR process during sedimentary basin evolution. In this work, thermal models performed in three sub‐basins in a sector of the Northern Apennines comprised of the Sillaro and Marecchia rivers (Italy), calibrated by means of organic and inorganic geothermometers, indicate a general thermal immaturity of the studied successions attained as a result of a constant heat flow similar to the present day one (ca. 40 mW/m2) since Late Tortonian and lithostatic loads between 615 and 1,710 m depending on different sub‐basins. These results suggest that the MSC deposits experienced maximum temperatures between about 39°C and 65°C. Temperatures derived from thermal models have been used to constraint occurrence of the diagenetic BSR associated with evaporitic deposits providing thermal constraints in sulfur genesis as well as new useful thermal‐constraints for basin analysis studies.

Sedimentary basin evolution and its implications for outward expansion of the northeastern Tibetan Plateau: Insights from the Tongxin Basin, China

The basin history of the northeastern Tibetan Plateau provides an ideal record for understanding the tectonic evolution of the plateau. We present high-resolution magnetostratigraphy and cosmogenic 10Be/26Al burial chronology from the Tongxin Basin in the Arcuate Ranges area in the northeastern Tibetan Plateau and reconstruct a long depositional history ranging from >21.7 to 4.6 Ma. Our new chronologic data suggest that a broad N-S-trending elongated basin existed during the Late Oligocene-Early Miocene (>21.7–16.5 Ma). WNW-trending faulting initiated at ca. 16.5 Ma and resulted in the formation of some fault-bounded basins outward from the western margin of the broad basin, but did not strongly affect the deposition within the basin region. Subsequently, intense northeastward compression elevated both WNW- and NWN-trending mountain ranges at ca. 7.6 Ma. Thrust-induced surface uplift elevated basin sediments and formed piggy-back basins in the hanging-wall blocks, reflecting the northeastward expansion of the northeastern Tibetan Plateau.

Geological control of young orogenic mountain morphology: From geomorphological analysis to reinterpretation of geology of the Outer Western Carpathians

The paper presents a new concept of geological control of the Outer Western Carpathians (OWC) morphology. The establishment of the Carpathians' morphology dates back to the stage of evolution of sedimentary basin, when huge blocks of solidified rock massifs were gravitationally displaced into the foreland sedimentary basins, forming finally isolated hills. The altitudinal difference between the Beskidy Mts. and the Carpathian foothills is caused by the structural positions of these two segments of rock massifs within the orogenic megastructure during the compressional stage. Indeed, the tectonic elements that formed during the earliest stage of compression took (and still take) the highest structural and altitudinal position, whereas the elements incorporated into the orogen as the last have taken a lower topographic position, forming a belt of foothills. Therefore, this difference in topography is not related to rock resistance only, as was previously thought. The rotation of the Carpathian blocks during the orogenic thrusting and the formation of strike-slip fault zones parallel to the Carpathian tectonic thrusts formed a flower structure, which has played a significant role in morphology (insular character of). During the stage of secondary tectonic deformation – including the rotation of the Carpathian tectonic segments, strike-slip faulting and the radial extension and large extensional collapse of the Carpathian massifs – the principal features of the Carpathian relief as well as the main river valleys were formed. Gravitational collapse resulted in back-thrusting and the tectonic exhumation of the Carpathian massifs, which helps to explain the problem of seemingly large denudation of the Carpathian overburden of a thickness estimated at several kilometres. Chaotic complexes (synsedimentary and syntectonic mélanges), which frequently occur in the Carpathians, are very important for the Carpathian morphology and river valley development (controlled not only by faults) as well as the formation of isolated hills. Analysis of the Carpathian morphology supported by the Bouguer's gravity anomalies map, and geological data allow us to present a new hypothesis that the Carpathians were formed as a huge regional flower structure, without the participation of subduction, which has formerly been considered to play the crucial role in the formation of the Carpathian orogen.

Fossil eggshells of amniotes as a paleothermometry tool

Raman spectroscopic analyses of thermally altered organic materials can be used to assess the paleothermometry of the sedimentary deposits. Although this technique has been widely applied to diverse microfossils, macroscopic vertebrate fossils have been neglected. In this paper, we show that fossil eggshells can be used for this purpose by demonstrating the paleothermometric potential of diverse amniotic eggshells from the Wido Volcanics (Upper Cretaceous, South Korea) that contain thermally altered organic material. We estimate the maximum paleotemperature recorded in the eggshells using Raman spectroscopic data and the spectrum deconvolution technique, which was invented and developed by organic geochemists. The results show that the same type of eggshells record different paleotemperature gradients depending on their spatial distribution in the fossil locality, whereas different types of eggshells from similar locations show similar paleotemperature gradients (except for one specimen with a peculiar microstructure). These findings are further supported by Fourier transform infrared spectroscopic results, which focus on thermally altered organic materials, and electron backscatter diffraction data, which focus on calcite twinning. This study suggests that fossil eggshells are useful and reliable materials for paleothermometry because thermally altered organic materials and calcites of eggshells provide independent opportunities to assess paleothermometry. We propose that fossil eggshells may be useful for evaluating the thermal evolution of sedimentary basins.

Results of Modeling of Generation and Accumulation Hydrocarbon Systems in the Sedimentary Basins of the Sea of Okhotsk

The paper presents the results of modeling of generation and accumulation hydrocarbon systems in the sedimentary basins of the sea of Okhotsk. The results of modeling HC migration showed that the most likely zones of hydrocarbon accumulation are the side parts of sedimentary basins. The anticline zones located on the border of two or more basins have the most favorable conditions. These areas, in general, are among the most promising in terms of hydrocarbon prospecting. However, such zones are characterized by complex conditions for the formation and preservation of deposits due to the non-synchronous evolution of adjacent sedimentary basins. This leads to uncertainties when assessing their prospects at the regional research level, for example, when predicting the type of fluid in deposits. For example, Vostochno-Shmidtovsk (East Schmidt) anticline zone is located on the border of two large centers of oil and gas generation: Severo-Sakhalinsky (North-Sakhalin) and Deryugin basin. The results of numerical modeling of the regional level allowed us to establish that HC migration towards the anticline zone occurs from the East (from the Deryugin basin) and the West (from the Severo-Sakhalinsky (North-Sakhalin) basin). The type of fluid in the predicted clusters is controlled by the type and maturity of the organic matter of the generation centers.

The meeting place of backarc and foreland rifting: The example of the offshore western Sicily (Central Mediterranean)

Coeval rifting processes affecting both backarc, thrust belt and foreland occurred in offshore western Sicily (Central Mediterranean) as indicated by the analysis of a large seismic data set calibrated with well data, onshore data and dredges in a dedicated GIS software environment. Structural pattern of the investigated area, 3-D geological models and a Pliocene-Lower Pleistocene evolution of extensional sedimentary basins have been reconstructed. In detail, two zones characterized by basins with different directions of extension have been recognized: one trending NE-SW, located south of the Egadi Islands; another trending E-W, positioned north of the Egadi Islands. The first group of basins represents the continuation of those of the Africa foreland basin (Pelagian Block), as the second one characterizes the opening of the backarc (southern Tyrrhenian margin). Both basins affect the collisional chain (Maghrebian thrust belt). An eastward progression of extension, from lower Pliocene to lower Pleistocene, based on different onset of the basin fill, has been documented in the Southern Tyrrhenian margin. The study area represents the meeting place of backarc and foreland rifting that affected the late Miocene thrust belt. The recognized pattern of extensional deformation of the upper plate adds some constraint on the geodynamic evolution of the African and Eurasia plates and supports a model of westward dipping slab in the Central Mediterranean. It is hypothesized that the along-trench variation of the nature of the plates, due to paleo-margin configuration, has a profound impact on the upper crustal deformation during the convergence and thus the meeting place of backarc and foreland rifting could represent the surficial signature of the slab detachment since Pliocene times. • 3D models are constructed from geological and subsurface data • The study area represents the meeting place of backarc and foreland rifting affecting the late Miocene thrust belt. • A lower Pliocene-lower Pleistocene eastward progression of extension has been documented in the Southern Tyrrhenian margin. • The geological signature of slab detachment during Pliocene times is where backarc and foreland rifting meets.

Modeling of Mineral Parageneses and Thermobarometry of Metavolcanic Rocks of the Ruker Group in the Southern Prince Charles Mountains, East Antarctica

Diverse geological complexes that form the crystalline basement of the East Antarctic Platform crop out in the Prince Charles Mountains. The Ruker Group is a member of the metasedimentary complexes that make up the Paleoproterozoic through Neoproterozoic suprastructure of the Ruker Terrane. It is divided into two sequences consisting of highly deformed and greenschist facies metamorphosed sedimentary and volcanic rocks. The mineral and major element compositions of metavolcanic rocks have been studied and physicochemical modeling of mineral parageneses has been performed to reconstruct the P–T parameters of metamorphism. The dependence of the mineralogy of metabasic schists on the protolith composition and the ratio of components in the H2O–CO2 fluid involved in the phase reactions were analyzed. The calculated mole fraction of CO2 in the fluid equilibrated with carbonate-bearing parageneses is 0.13–0.27. It is assumed that chloritoid schist consists of metamorphosed laterites derived from basalt. Modeling and the data of chlorite–phengite thermobarometry indicate that the Ruker Group rocks were metamorphosed under conditions of the high-pressure part of the greenschist facies (300–450°C, 7–8 kb). These conditions are significantly higher than the stable continental geotherm and are close to those in the zone of a slow subduction geotherm. According to the available geological data, a similar geodynamic setting could be caused by the evolution of the Neoproterozoic intraplate sedimentary basin in connection with deep-sinking basement blocks as a result of tectonic aggregation during the closure of the basin.

Filling of sedimentary basins and the birth of large rivers: The lower Danube network in the Dacian Basin, Romania

Large rivers typically form in the final phase of evolution of sedimentary basins. By that time the sediment supply balances out the accommodation, local rivers coalesce into larger rivers and seek pathways to flow out of the basin into areas where accommodation is available. Very often, this is controlled by tectonics controlling sediment supply and accommodation or facilitating opening inter-basinal gateways. Using subsurface data (seismic and well logs), this paper discusses the controlling factors that lead to the birth of large, continental-scale rivers using the Danube River in the Carpathians foreland basin as a study example. The Proto-Danube originated in the North Alpine Foreland basin around 19–18 Ma and prograded southwards across the Vienna basin (14–13 Ma) and Pannonian basin (10–5 Ma) before reaching the Dacian basin. The Dacian basin took shape during the mid-Miocene and initially consisted of a number of individual and loosely connected depocenters, which were subsequently filled by local sediment sources. These sources typically reflect the uplift and erosion history of the closest orogenic segment. As the accommodation filled, the fluviatile networks coalesced and merged with the Paleo-Danube around 4 Ma, which flowed closer to the Carpathians, about 100 km north of the present path. Continued subsidence in the eastern part of the foreland basin controlled the further evolution of the Paleo-Danube that formed a large delta system, a precursor of the present-day Danube Delta. Eventually, the delta depocenter advanced into the Black Sea in the Romanian/Pleistocene. We interpret this to be the result of increased sediment supply due to renewed uplift of the Carpathians. Comparing the evolution of the Danube River drainage with other continental scale rivers around the world, we can conclude that the Danube represents an uncommon river system characterized by transiting multi-basin drainages. Initially, multiple small rivers filled sub-basins from different directions and these coalesced at later stages. Most large modern rivers, similar in size, formed within a simpler tectonic frame with sediments commonly supplied along a well-defined tectonic trend.

Palaeoproterozoic turbidite deposition in the Liaodong Penisula, northeastern North China craton – Constraints from the Gaojiayu formation of the Liaohe Group

The Palaeoproterozoic sedimentary environment is difficult to reconstruct because rocks often experience multiple stages of deformation and metamorphism; however, it is critical to understand the Precambrian evolution of sedimentary basin. In this study, we report two un-metamorphosed sections in the Gaojiayu Formation of the North Liaohe Group, central part of the Jiao-Liao-Ji orogenic belt, eastern North China Craton. Rocks consist of shales, carbonaceous slates, calcareous mudstones and sandstones, marlstones, calcarenites, and brecciated limestones in these sections. Detailed field observations indicate that all kinds of original bedding and syn-depositional structure developed in these rocks. Microscope observations suggest that detritus in rocks predominantly contain feldspars, quartz, and calcites, occasionally with volcanic fragments and pyrites. Palaeocurrent study indicates that the provenance of detritus in rock of these two sections was from NW to SE. Detrital heavy minerals mainly consist of pyrite and hematite, occasionally with barite, which are all from the Li'eryu Formation that contains these minerals in sedimentary layers. The increase of percentages of pyrite in a cross-section indicate that the sedimentary environments transformed from an oxidizing to a reducing depositional environment because the depositional setting became deeper. According to the mafic intrusion dated in this study and regional geochronological data such as the age of underlying volcanic rocks, the depositional age of the Gaojiayu Formation is constrained between 2.17 and 2.16 Ga and 2.11 Ga. Archaean basement (2.5 Ga) is recognized as the major provenance providing clastic materials for the Gaojiayu Formation; volcaniclastic rocks in the Li'eryu Formation were also a significant source. Accordingly, in this paper we interpret the Gaojiayu Formation as turbiditic sedimentary rocks that were deposited in an arc-related abyssal and semi-abyssal environment, probably in an extensional back-arc basin setting. Palaeoproterozoic turbidite deposition combined with a 2.17 Ga volcanic arc developed in the study area, we conclude that the modern trench-arc-basin system may had already existed in the early Palaeoproterozoic and deeply affected the tectonic evolution of the Jiao-Liao-Ji orogenic belt, northeastern North China Craton.

Evaluation of Shale Source Rocks and Clay Mineral Diagenesis in the Permian Basin, USA: Inferences on Basin Thermal Maturity and Source Rock Potential

The use of mineral diagenetic indices and organic matter maturity is useful for reconstructing the evolution of sedimentary basins and critical assessments for potential source rocks for petroleum exploration. In this study, the relationship of clay mineral diagenesis and organic matter thermal indices (Rock-Eval Tmax) and calculated vitrinite reflectance (%Ro) were used to constrain the maximum burial depths and temperatures of three distinct intervals within the northern Permian Basin, USA. X-ray diffraction of clay fractions (&lt;2 µm) consists of illite, chlorite, and illite-smectite intermediates. Primary clay mineral diagenetic changes progressively increase in ordering from R0 to R1 I-S between 2359.5 and 2485.9 m and the appearance of chlorite at 2338.7 m. Rock-Eval pyrolysis data show 0 to 14 wt% TOC, HI values of 40 to 520 mgHC/g TOC, and S2 values of 0 to 62 mg HC/g, with primarily type II kerogen with calculated %Ro within the early to peak oil maturation window. Evaluation of the potential for oil generation is relatively good throughout the Tonya 401 and JP Chilton wells. Organic maturation indices (Tmax, %Ro) and peak burial temperatures correlate well with clay mineral diagenesis (R0–R1 I-S), indicating that maximum burial depths and temperatures were between 2.5 and 4 km and &lt;100 °C and 140 °C, respectively. Additionally, the use of clay mineral-derived temperatures provides insight into discrepancies between several calculated %Ro equations and thus should be further investigated for use in the Permian Basin. Accordingly, these findings show that clay mineral diagenesis, combined with other paleothermal proxies, can considerably improve the understanding of the complex burial history of the Permian Basin in the context of the evolution of the southern margin of Laurentia.

Thermal structure and source rock maturity of the North Peruvian forearc system: Insights from a subduction-sedimentation integrated petroleum system modeling

Basin modeling is commonly used for the hydrocarbon potential evaluation of underexplored areas, taking into account the full basin history to assess its thermicity and fluid distributions. In the case of forearc basins, however, the influence of the subduction on the internal thermal structure is difficult to predict. The existing subduction thermal models usually focus on the present day lithosphere and do not consider the sediment infill history, while industrial modeling tools handle the thermal evolution of sedimentary basins but not the subduction process. In this paper, we propose a solution model in which the cooling engendered by the subduction is represented by the advective term of the heat conservation energy equation throughout the sedimentation. This study focuses on the Talara-Tumbes-Lancones petroleum province, part of the North Peruvian forearc system. Despite the long term exploration of the Talara Basin, the origin of its massive oil fields still remains questioned. The new subduction-sedimentation integrated petroleum system modeling presented here, calibrated by numerous structural and thermometric data, allows to better constrain the thermal structure and source rock maturity history of this forearc system. We show that the exposure of the sedimentary basin to the subducting cold lithosphere, the sedimentation rate and erosion are important factors impacting the maturity of the source rocks. Consequently, even in the same subduction setting, each depocenter of the North Peruvian forearc system presents a different thermal history and maturity timing, and each basin presents an independent petroleum system.

Data-driven identification of stratigraphic units in 3D seismic data using hierarchical density-based clustering

Seismic sequences are stratigraphic units of relatively conformable seismic reflections. These units are intervals of similar sedimentation conditions, governed by sediment supply and relative sea level, and they are key elements in understanding the evolution of sedimentary basins. Conventional seismic sequence analyses typically rely on human interpretation; consequently, they are time-consuming. We have developed a new data-driven method to identify first-order stratigraphic units based on the assumption that the seismic units honor a layer-cake earth model, with layers that can be discriminated by the differences in seismic reflection properties, such as amplitude, continuity, and density. To identify stratigraphic units in a seismic volume, we compute feature vectors that describe the distribution of amplitudes, texture, and two-way traveltime for small seismic subvolumes. Here, the seismic texture is described with a novel texture descriptor that quantifies a simplified 3D local binary pattern around each pixel in the seismic volume. The feature vectors are preprocessed and clustered using a hierarchical density-based cluster algorithm in which each cluster is assumed to represent one stratigraphic unit. Field examples from the Barents Sea and the North Sea demonstrate that the proposed data-driven method can identify major 3D stratigraphic units without the need for manual interpretation, labeling, or prior geologic knowledge.

Sedimentary characteristics and interactions among volcanic, terrigenous and marine processes in the Late Permian Kuishan Member, Eastern Block of the North China Craton

Understanding the variability of depositional environment and depositional processes of the Late Permian Kuishan Member, North China Craton, is crucial for unraveling the evolution of sedimentary basin and epicontinental sea in Shandong tectonic domain. The Kuishan Member in the Eastern Block of the North China Craton, formed in association with general regression of an epicontinental sea, is composed of abundant volcanic deposits and nearshore sedimentary deposits. Three lithofacies assemblages together with eleven lithofacies are identified in the study area, including volcanic deposits of the turbidity lithofacies assemblage, epiclastic deposits of the nearshore lithofacies assemblage, and mixed volcaniclastic and epiclastic sedimentary deposits of the terrestrial lithofacies assemblage. These alternating volcanic-epiclastic lithofacies assemblages illustrate the depositional environments induced by volcanic activities and nearshore wave influence. Syn-eruptive lithofacies, in the shallow water area, were formed by high density turbidity currents and ash fall into water introduced by rising sea levels and high rainfall due to volcanic eruptions to the north, whereas thin-bedded shallow marine silty mud developed in the distal area. Inter-eruptive lithofacies were represented by tuffaceous mudstone deposited in an exposed and oxidized setting due to falling sea level, whereas epiclastic nearshore deposits accumulated by wave or current flow regimes. Paleocurrent measurements show that the predominant regression direction changes from uniform southwest to divergent southwest and southeast during volcanic inter-eruptive periods. The Kuishan succession therefore can be regarded as a volcano-related sequence, in which the input of volcaniclastic and epiclastic deposits were significantly modulated by controls of volcanism, with frequently changing coastline position of the epicontinental sea and alternating depositional environments.

Geochronology and sedimentology of the Huashan Group in the northern Yangtze Block: implications for the initial breakup of the South China

Middle Neoproterozoic sedimentary sequences are widespread in South China and provide crucial insights into the geological evolution of sedimentary basins related to the breakup of the Rodinia supercontinent. The Huashan Group is a key Neoproterozoic stratigraphic unit in the northern Yangtze Block, South China; however, its depositional age and tectonic setting of deposition are debated. Here, we report zircon U–Pb geochronology and Hf isotope data for a tuff from the second section of the Hongshansi Formation near the bottom of the Huashan Group. Zircon U–Pb geochronology yields a 206Pb/208U age of 836 ± 4 Ma (MSWD = 0.74, n = 29). Zircon Hf isotope ratios have eHf(t) values of + 3.1 to + 5.4 and TDM2 ages range from ca. 1.5 to 1.4 Ga, which indicates that juvenile materials derived from the mantle were involved in their host magmas. Combined with previous research, the Huashan Group was deposited from ca. 830 to 800 Ma from bottom to top, and it contains alluvial fan, fan delta, and semideep to deep lacustrine facies, which represent early sedimentation into a continental rift basin. Rifting and basin formation began at ca. 830 Ma in South China, which is coeval with the initial breakup of the Adelaidean Rift in southeastern Australia. The Huashan Group was deposited during the first and the second episodes of a superplume associated with the breakup of the Rodinia supercontinent.

An analogue of dominance of tectonic over climatic forcing in intermontane coal-bearing basins: Padul (SE Spain)

A multiproxy study based on sedimentology, mineralogy, magnetic susceptibility, organic geochemistry and fossil content allowed to establish the sedimentary evolution of palustrine basins and to study the interplay between tectonic and climatic forcings in the sedimentation and facies arrangement that can be extrapolated to other coal-bearing basins. The reinterpretation of the data from 18 cores allowed to determine the facies distribution and to model the sedimentary evolution of the Padul Basin, with the longest continuous continental Quaternary record in the Southwestern Mediterranean region. The Padul Basin sediment record and facies successions provide an outstanding example of tectonically and environmentally controlled sedimentation. The sedimentary characteristics of the cores and thickness distribution revealed that recent tectonics was a more important forcing than other processes (e.g. climate). The influence of recent tectonics was determinant in facies arrangement, that is to say that the activity of a rotated fault produced a differential subsidence, causing more than 100 m of palustrine deposits to stack. On the basis of the sedimentological record combined with data on the mineralogy, fossil content, magnetic susceptibility and total organic carbon, three main sedimentary units were identified, linked to diverse subsidence rates and paleoenvironmental oscillations. The magnetic susceptibility was likely to have been controlled by the organic matter content (TOC values), linked to oxic/anoxic conditions. In the lower part of the record, Unit A (107.0–68.7 m), shallow lacustrine conditions were dominant, with an important influx associated with considerable runoff from active alluvial fans, linked to a higher subsidence rate. Unit B (68.7–37.6 m) had a transitional character, with a considerable decrease in the influence of the alluvial fan system. The lake recharge through overland flow markedly diminished and pre-existing groundwater recharge was dominant. A sudden change to peaty materials indicated that surface runoff was directly diverted to the recently excavated Dúrcal River gorge, thereby precluding the basin from becoming a swampy environment with stagnant waters. Unit C (upper 37.6 m) was almost exclusively fed by bicarbonate groundwater and subsurface runoff through the highly permeable coarse alluvial fan deposits. Within these main sedimentary units, minor mud-peat shallowing-upward sequences were identified.

Thermal evolution of the intracratonic Paris Basin: Insights from 3D basin modelling

The thermal evolution of the Paris Basin (PB) has been widely studied using 1D, 2D and, more rarely, 3D thermal models. It is well documented that the PB experienced higher temperatures in the past compared to what is currently observed. However, a quantitative analysis of the main processes and parameters that affect the temperature distribution, at the basin scale and over time, is still not available. In this study, through basin modeling which accounts for the main processes of the thermal evolution of sedimentary basins, we analyze and quantify the role of the different geological mechanisms by discriminating the causes of abnormal temperatures during the Late Mesozoic. This is done with a 3D basin model built from base Moho to present-day topography using the TemisFlow® basin modelling software. The model includes thermal processes within an evolving upper crust defined by three main structural domains. Each crustal sector presents radiogenic heat production, conductivity and thickness values which are used as input parameters to reproduce the paleo- and present-day basal heat flow variations observed in the basin. The model calculates heat flow through time in both, crust and sedimentary column where the crust is coupled with the geological evolution of the basin. This approach allows estimating the eroded thickness during the main Tertiary uplift event and therefore the maximum temperature in the Late Cretaceous. The model is constrained by different types of paleo-thermo-chronometers and by 52 wells that are regionally distributed over the entire basin, resulting in a new regional thermal history of the PB. The amount of missing section in the Cretaceous chalk which mainly affected the eastern part of the basin is increased by up to 500m compared with previous studies and constitutes the key controlling factor of the temperature evolution. This new regional thermal history of the Paris Basin may be important for further analysis of the HC generation from the Lower Jurassic Toarcian source-rock and bring new insights into the geothermal potential of the basin.