Basin Architecture Research Articles

Structural evolution of the resource-rich Proterozoic western greater McArthur Basin: A focus on the Daly Waters Fault Zone, northern Australia

Proterozoic basins cover vast cratonic areas on every continent. Their basin architecture preserves considerable information that can unravel the tectonic evolution of large parts of the world, yet many do not yet have the resolution of seismic data across them to reveal their internal structure. The ca. 1820–1320 Ma greater McArthur Basin, in the North Australian Craton, is a data-rich exception. Surface exposures in the west (Birrindudu Basin), south (Tomkinson Province) and north (McArthur Basin sensu stricto) are linked together in seismic profiles through the Beetaloo Sub-basin that allow the full basin evolution to be determined.A key feature of the basin is the Daly Waters Fault Zone, a north–south-oriented structural formation about 200 km in length. This fault zone serves as a boundary, dividing the Birrindudu Basin and the western Beetaloo Sub-basin from the eastern Beetaloo Sub-basin. It is a complex fault zone with multiple phases of structural extension and compression that have influenced the greater McArthur Basin fill from the Redbank Package (ca. 1820–1700 Ma) to the Wilton Package (ca. 1500–1320 Ma).Two dimensional seismic lines and 17 well penetrations in an area encompassing the Birrindudu Basin to the western portion of the Beetaloo Sub-basin and across the Daly Waters Fault Zone are re-interpreted to better understand the evolution of the basin and the role of the Daly Waters Fault Zone. We reveal at least five tectonic events that controlled deposition and exhumation in the region: 1) Extension during the early Redbank Package (ca. 1820–1750 Ma), followed by compression that inverted the Redbank Package (ca. 1740–1700 Ma). 2) Extension during the Glyde Package (ca. 1660–1620 Ma). 3) Compression after deposition of the Glyde Package (ca. 1620–1520 Ma). 4) Extension during the lower Wilton Package (ca. 1500–1400 Ma), and 5) compression after deposition of the Wilton Package (after ca. 1320 Ma).

Tectonostratigraphic models of an extensional back-arc basin: inferences for the evolution of the Pannonian Basin System

The subsidence history and sedimentary architecture of extensional basins are controlled by the interplay between tectonics, mantle dynamics and climatic variations. Observations from outcrop to regional seismic scales coupled with numerical modelling techniques, including basin-scale stratigraphic, crustal-scale tectonic and mantle-scale subduction models, contribute to the quantification of basin evolution. Here, we review and discuss both tectonic and stratigraphic applications of such models and compare them with observations from the Pannonian Basin system of Central Europe. We show that diachronous localization of back-arc extension, crustal thinning, asthenospheric upwelling and subsequent thermal relaxation are superimposed on an overall slow plate convergence. These processes result in contrasting subsidence and uplift patterns and a variable heat flow evolution in different parts of the basin system. The crustal stress-field of the sub-basins does not always reflect their contrasting vertical motions. Extensional deformation generally migrates from the basin margins towards the basin centre. Structural inversion is localized along hot and weak inherited zones from the Middle Miocene to Present. Tectonic subsidence focuses sedimentation along deep depocentres, sourced by exhumed footwalls and from the neighbouring orogens. The overall post-rift sediment progradation is influenced by inherited bathymetries from the preceding syn-rift stage and by enhanced differential vertical motions.

Development of detachment fault system associated with a mature metamorphic core complex: Insight from the Kaiping Sag, northern South China Sea rifted margin

AbstractDetachment fault system associated with a mature metamorphic core complex (MCC) is still not well understood. Using high‐resolution 3D seismic data, we analyse the geometries and kinematic development of detachment fault system associated with a mature and exhumated MCC in the northern South China Sea rifted margin, with an emphasis on the MCC‐associated faults within the supra‐detachment basin. Faults within the supra‐detachment basin can be classified into three stages, the pre‐MCC, syn‐MCC and post‐MCC faults, based on their formation time relative to the MCC. The NE to NEE‐striking pre‐MCC faults developed in the early syn‐rift 1 stage, and the NW to WNW‐striking post‐MCC faults were both dominated by the regional tectonics and are perpendicular to the extension directions. While the syn‐MCC faults, synchronous with the MCC development in the late syn‐rift 1 stage, show overall EW‐striking, consistent with the long axis of the KP MCC. These syn‐MCC faults were well developed and are significant in shaping the basin architecture. Besides, the syn‐MCC faults are regularly distributed in the four zones overlying the convex‐upward master detachment fault surface, and are defined in this study as a synthetic fault zone, an upper collapse synformal‐graben fault zone, a lower collapse antiformal‐graben fault zone and an antithetic fault zone respectively. These four fault zones show distinct features and evolutionary patterns, and have a closed relationship with the rolling‐hinge process of the KP MCC. An evolutionary model is established for the development of MCC‐associated detachment fault system which should have global implications.

Crustal extension and necking at central Campos rifted margin: The Marlim Detachment System

Detachment faults play a crucial role in accommodating crustal thinning and controlling basin architecture in extensional tectonic settings. This study focuses on the characterization of extensional structures at the Necking Domain of the central Campos Rifted Margin, southeast Brazil. Based on seismic reflection and magnetic data we interpreted a system of long offset detachment faults, here named as the Marlim Detachment System. This system is characterized by three distinct large-displacement detachment faults which systematically root at subhorizontal intracrustal reflectors, interpreted as middle crust ductile shear zones, indicating a depth-dependent accommodation of extensional strain. The detachment fault systems resulted in highly tilted upper crustal blocks, which lead to intense erosion of the footwall and the pre-salt sequences eastward. The large horizontal displacement of the hanging wall blocks by most of the detachment faults created deep and wide half-grabens resulting in thick syn-rift sedimentary wedges. The basement structural framework seems to reflect a northward strike-rotation from NE-to NS-direction of the fault systems. That rotation promoted the segmentation of the Marlim Detachment System and points out an oblique-slip extensional kinematics during rifting. We propose that the observed tectonic style at the Necking Domain of central Campos is the result of its interaction with the Vitória-Colatina Transfer Zone to the north and the Araruama Transfer Zone to the south, configuring the Marlim area as a structurally transition zone. The tectonostratigraphic analysis suggests a migration of the deformation from continent to ocean from Hauterivian to Aptian, and a polyphase and/or tardi-tectonic deformation of the Necking Domain in the central Campos Rifted Margin.

Multiphase growth and basin control of main faults on Northern sub-basin, Beibuwan basin, Northwestern South China sea

The basement-involved faults and multiphase extension control the three-dimensional (3-D) fault geometries and kinematics, producing different fault growth models in continental rift basins. In this paper, we apply qualitative and quantitative fault analysis techniques to 3D high-resolution seismic data from the Northern sub-basin of Beibuwan basin, building the tectonic-stratigraphic framework and proposing the evolutionary meachanisms of main normal faults. The results suggest that extensional stress changed from NW-SE direction during Paleocene-Middle Eocene to N-S direction in Late Eocene-Oligocene, leading to the ENE or E-W directed propagation of fault networks together with lateral and vertical linkage of fault segments. This includes three conceptual models: (1) F1 originated from propagation, interaction, linkage and failure of initial seven ENE-directed isolated faults, and grows following isolated fault growth model; (2) F2 nucleated as a normal fault before buried in Late Eocene, and reactivated as dextral strike-slip fault in Oligocene, therefore experienced vertical segmentation and linkage; (3) F3 activated as a long-term constant-length fault with generally increased displacement in Paleogene. Our study proposes that the T83 interface (the top of the second member of the Liushagang Formation) is a tectonic stress transition interface, while the T60 interface is both a tectonic inversion interface and a post-rift unconformity interface. Furthermore, the growth of extensional faults commonly accompanied single breached, transfer-fault breached or double breached relay ramps and fault-related folds, thereby exerting a significant influence on the basin architecture and sediment distribution.

Drainage reorganization and alluvial architecture of endorheic basins: The Lower Cretaceous record of the Chubut Group in the Golfo San Jorge Basin (Patagonia, Argentina)

The size, shape, and organization of depositional systems in endorheic basins are controlled by the tectonic and climatic history of the sedimentary basin and its boundaries. We evaluate the changes in the alluvial architecture of the Matasiete (Aptian) and Castillo (Albian) formations of the Chubut Group (Cretaceous) in the endorheic Golfo San Jorge Basin (Patagonia, Argentina) analyzing a ∼150 km transect along the San Bernardo Fold Belt, subsurface data, and coeval fluvial successions of the Los Adobes Formation in the nearby Cañadón Asfalto Basin. The Aptian Matasiete Formation represents an externally-sourced, high-accommodation fluvial system with its headwaters in the current Cañadón Asfalto Basin, flowing toward the alkaline lake of the Pozo D-129 Formation through N–S oriented sedimentary corridors of tectonic origin. Low sinuosity, fixed channels with ribbon geometries (mean thickness 7.3 m, W/T ratio 14) are encased in red-colored floodplain fines, whereas stratigraphic intervals rich in resedimented tuffs contain braided rivers with W/T ratio up to 90. Deposition of the overlying Albian Castillo Formation occurred in a W-E elongated basin disconnected from the Cañadón Asfalto Basin, comprising aggradational, volcaniclastic floodplain deposits and smaller-scale fluvial channels of narrow-sheet geometries (mean thickness ∼ 3m, mean W/T ratio 45). The Castillo Formation shows spatial variation in fluvial styles and channel sizes, with intermittent to ephemeral rivers of small scale near the headwaters and seasonal, perennial rivers in downstream positions. Alluvial architecture changes between the Matasiete and Castillo formations reflect changes in the configuration of the basin boundaries, subsequent re-organization of the channel networks, and variable supply of volcaniclastic particles to drainage catchments of different hierarchy that evolved in areas with large variation of the preserved thickness. Comparable geomorphic scenarios in the Okavango Macrobasin show multiple base levels (lacustrine, ephemeral pans), several drainage catchments of variable orientation, scale, and behavior (perennial, intermittent to ephemeral), and exotic rivers adjacent to minor-scale courses.

Integration of Large Multielement Geochemical, Aeromagnetic, and Gravity Data to Geologically Map a Largely Covered Area: A Case Study from the Central African Copperbelt in Northern Zambia

Abstract This study provides a method to map lithology, stratigraphy, and structures in areas with limited outcrop using mineral exploration data from multielement soil geochemical surveys, airborne and ground geophysical surveys, and drill hole data sourced from multiple exploration companies and campaigns. The 45- by 50-km study area is located in the southern portion of the Congolese Copperbelt, where the regional geology, structure, and overall basin architecture were not well understood, partly due to thick saprolite cover. The results demonstrate that the integration of such data sets allows the creation of a geologically coherent map, which can then be used to investigate basin architecture and identify basin-forming structures.

Volcanic-controlled basin architecture variation and dynamic sediment filling in the South Lufeng Sag, South China Sea

Volcanic-controlled changes of basin architectures and sediments have given rise to diverse and rapidly evolving “dynamic geomorphology,” which poses challenges to successful petroleum development. Nonetheless, the accompanying volcanic deposits and landforms often produce rich and distinct seismic responses within conventional sedimentary layers, offering vital support in addressing this critical issue. Based on this, we compared the volcanic activity stages, evolution of geomorphology, and sediment dispersal processes to determine the process of basinal evolution by analyzing the episodes and distribution of volcanic-related deposits, sub-stages, seismic facies, and attributes of deposits of the South Lufeng Sag in the Pearl River Mouth Basin, South China Sea. The widespread development of strong amplitude attributes and chaotic reflection variance cube attribute spatial perspectives reveal the evolution of both intrusive and effusive facies in the lower Wenchang Formation across three stages of volcanic activity. The seismic amplitude difference of the andesite and andesitic tuff unveils the transition of the depositional pathway from north to south in the west depression with change of depocenters, lays the foundation for the dynamic geomorphic evolution of the “transitional basin” in the region. In the middle Huizhou-Lufeng uplift, the chaotic reflection with weak amplitude and obvious diapir structures revealed by andesite constrain the distribution of sedimentary space and the transformation of sedimentary pathways within the basin, and the evolution process of the “restricted basin” is summarised in terms of sedimentary filling processes. The seismic amplitude differences of basalt and andesitic tuff - related sediments in the east depression record the process of transformation from a single sedimentary channel to multi-pathway transport, which is summarised as the evolutionary model of the “diffusive basin”. This study offers a meticulous exploration into the evolutionary trajectory of dynamic geomorphology and sedimentary accumulation in a basin regulated by volcanic activity. The findings pave the way for the extensive application of this methodology in petroleum development across various geographic regions.

Links between hydrographic restriction, redox conditions, and organic matter accumulation in the Early Cambrian intrashelf basin, South China

There was a strong relationship between paleo-oceanic conditions and organic matter accumulation during the critical period of the Early Cambrian. The Yangtze Platform in South China provides an opportunity to study this relationship, but the basin architecture and paleo-hydrographic dynamics remain poorly understood, which hinders one’s understanding of the evolution in oceanic redox state and its relationship to organic matter accumulation. To fill the knowledge gap, a newly obtained data set from the Lower Cambrian Niutitang Formation shales (Late Cambrian Stage 2-Stage 3) of the intrashelf basin is used. Results show that the molybdenum–uranium covariation, along with the abnormally low Mo contents and Mo/TOC ratios in the anoxic (ferruginous and euxinic) Niutitang shales of the intrashelf basin, indicate a hydrographic circulation that is moderately to strongly restricted. The hydrographic evolution at different stages, influencing redox conditions to a certain extent, in conjunction with variations in primary productivity, controls the enrichment of organic matter. In particular, the relatively low sea level during Interval I (Late Stage 2) resulted in weak connectivity between the intrashelf basin and open ocean; this, coupled with high primary productivity and enhanced chemical weathering, formed stable stratified water (euxinic bottom-water) conditions that were favorable for organic matter enrichment. In contrast, Interval II (Early–Middle Stage 3) and Interval III (Late Stage 3) involved less organic matter enrichment due to weakened restricted hydrographic circulation (Interval II) and oxic bottom-water conditions (Interval III). This study highlights how hydrodynamic processes affected the marine environment during the Early Cambrian and reveals that sluggish oceanic circulation combined with high primary productivity led to anomalous enrichment of organic matter. This may be a common feature of basins with restricted hydrographic circulation in deep time.

The discrimination of tidal- and fluvial-dominated sedimentary systems based on quantifying the degree of serration in gamma-ray logging curves: East China Sea Shelf Basin

Using quantitative methods to distinguish tidal- and fluvial-dominated sedimentary systems is currently a challenge in sedimentological research. This paper establishes and verifies a new quantitative method through the degree of serration of gamma-ray logging curves. This method depends on the fundamentals of core-based and gamma-ray logging pattern interpretation of the depositional environment, using one-dimensional continuous wavelet transform to denoise the initial curve to enhance the effects of tides and rivers processes, and then expands to an analysis of the degree of serration in noise-reduced gamma-ray curves. The results may then be used to constrain a single best-boundary value to distinguish a tidal- or fluvial-dominated area, avoiding subjectivity and uncertainty. A case study of the Pinghu Formation showed that the degree of serration (defined here as DeltaGr) of the fluvial-dominated sediments was less than 10 in the depth dimension and that the average degree of serration (defined here as the average square of DeltaGr) was less than 7 in the layer dimension. Values that deviate from these imply a close relation to tide-dominated sedimentary systems, which provides a quantitative basis for the interpretation of sedimentary environments in both the depth and layer dimensions in the Pingbei Slope. Seismic attribute-based sedimentary analysis, relative sea-level changes, and the basin architecture of the Pingbei Slope clarify the reason for these changes and verify that this method is reliable. However, owing to the limitations of logging and core samples, the criteria remain an approximation of the actual situation. This study may, however, enable the discrimination of other similar sedimentary systems dominated by tidal and fluvial processes and therefore provide a further constraint on the reconstruction of the filling of basins.

Shallow crustal imaging beneath NW Indian terrane from teleseismic P-wave coda using a Bayesian approach

Deciphering the crustal architecture of the Cretaceous Barmer-Sanchore Basin (BSB) and Neoproterozoic provinces in the NW Indian Shield presents significant challenges due to extensive sediment deposition and widespread felsic igneous rocks. To address such intricacies, we employ a transdimensional Bayesian joint inversion of teleseismic P-wave polarizations and receiver functions to resolve the detailed structure of the upper 10 km of the crust beneath 29 seismic stations deployed in the study area. The new data is analyzed separately within each of the three different backazimuthal groups to identify any strong variations in the shallow subsurface structure and derive a more robust, averaged model for every station site. The resulting 1-D models reveal heterogeneous sediment cover in BSB and Marwar Basin, with respective thicknesses ranging from ∼1.3–5.5 km and 1–1.5 km. Remarkably low shear-wave velocities (Vs < 1.0 km/s) of sediments with increased Vp/Vs (>2.3) are observed in BSB and adjacent areas, which are related to highly unconsolidated Quaternary-Tertiary deposits. The Marwar Basin is imaged to have 0.3–0.5 km of uncompacted sediments that overlie 0.5–1 km thick Marwar Supergroup sequence. The Erinpura Granites (EG) and Malani Igneous Province (MIP) are characterized by a variably thick sediment blanket, typically ranging within 1 km in thickness. The Vs of the sediments in these regions exceeds 2.4 km/s that possibly corresponds to Mesozoic and older sediments. The basement beneath EG exhibits Vs faster than 3.4 km/s, consistent with moderately metamorphosed granites. In MIP, the basement is characterized by non-uniform shear velocities, suggesting the influence of intrusions linked to magmatic episodes in NW India.

The Ancient Configuration of the Southern Central Andes and Paleogeographic Reconstruction of the Late Cretaceous Foreland Basin at 34°40’S

AbstractThe early stages of Andean construction have been barely recognized due to a long history of tectonic superposition during the growth of the orogen. In this work, we present a multi‐method approach integrating sedimentological, geochronological, structural, and provenance analyses to reconstruct the architecture of the Late Cretaceous foreland basin at 34°40’S. We identified a new depocenter located in an inner position of the Late Cretaceous foreland basin, a strategic location to understand the sedimentation dynamics near the topographic front of the orogen. Two sandstone samples from the basal and upper sections of the Diamante Formation were collected for detrital zircons dating, which yielded maximum depositional ages between 98 Ma and 91 Ma. The provenance analyses based on U‐Pb zircons ages indicated a main source area located to the west, in the incipient orogenic belt, with a complementary contribution from basement rocks, located to the east. Moreover, growth strata documented in these deposits were compared with structural kinematic models, which suggest that some of these deposits are associated with inherited structures, reactivated during the tectonic inversion of the extensional Jurassic Atuel depocenter. Our paleogeographic model comprises an Andean Cordillera flanked by a hinterland basin to the west and a foreland basin to the east, with a deformational front positioned further east compared to previous models.

Møre–Vøring Composite Tectono-Sedimentary Element, Norwegian Rifted Margin, Norwegian Sea

Abstract The Møre and Vøring basins at the mid-Norwegian margin were affected by a series of rift phases separated by periods of tectonic quiescence from Caledonian collapse in the Devonian to final continental break-up in the earliest Eocene. The tectonic phases were mostly extensional in nature, and the pre-drift extension across the Møre and Vøring basins since mid-Permian time has been estimated to be of the order of 200–250 km. The pre-Cretaceous basin configuration is poorly constrained due to limited seismic resolution at great depths and a lack of borehole control. A fundamental change occurred in the crustal deformation regime: from Late Jurassic distributed stretching of the upper crust to Early Cretaceous thinning at lower-crustal levels located along the axis of the Møre and Vøring basins. A westward migration of Late Cretaceous–Paleocene depocentres in the Vøring Basin reflects the focus of deformation towards the time and line of break-up. The basin architecture and evolution are summarized in relation to tectono-sedimentary elements corresponding to the main tectonic and depositional phases, and represent characteristic megasequences in the seismic data. Finally, the exploration history and main petroleum systems of the Møre and Vøring basins are presented.

Effects of crustal rheology and fault strength on the formation of the Qaidam Basin: Results from 2-D mechanical modeling

The Cenozoic Qaidam Basin on the northern Tibetan Plateau is bounded by the foreland thrust belts of the East Kunlun Mountains to the south and Qilian Mountains to the north. In this basin, the maximum thickness of the accumulated sedimentary strata is ∼17 km near the geographic center of the basin. Such a basin architecture challenges the classic foreland-basin deformation model, wherein substantial sediments should be localized near the basin margins owing to thrust loads on a bending plate. Based on the available geological and geophysical constraints, we built a two-dimensional viscoelastoplastic finite element model to investigate whether the unique pattern of the Qaidam Basin was mechanically related to the rheological structure of the crust and frictional strength of the basin-bounding thrust fault. By testing reasonable bounds on the viscosity of the ductile crust and effective frictional coefficient of the thrust faults, we modeled a basin framework that fits well with that of Qaidam Basin. The model parameters include a layered rheological structure, with the viscosity of the ductile crust of the basin being two orders of magnitude greater than that of the adjacent mountain belts and an effective frictional coefficient of >0.2. Furthermore, the initial width of the basin significantly affected its deformation style. Therefore, the layered rheological structure of the crust and frictional strength of the basin-bounding thrust faults played important roles in the formation of the Qaidam Basin. Our findings suggest that the inelastic behavior of the crust affects foreland deformation, highlighting that the classic foreland basin model must be revised for some tectonic settings.

3D modeling of the stratigraphic and structural architecture of the Crotone basin (southern Italy) using machine learning with Python

The 3D modeling and representation of geological data have experienced significant growth within last years, due to the use of new technologies derived from advancements in land representation methods. These technologies enable interactive, intuitive and clear geological visualizations. This paper shows how, by using the open-source Python software (operable with a simple internet browser) for machine learning (linear and KNN interpolations), together with Geographic Information Systems (GIS), it is possible to achieve interactive 3D visualizations of geological features in sedimentary basins. This study is performed in the onshore-offshore Crotone area (southern Italy) where a large amount of stratigraphic datasets are available from core perforation and seismic profiles due to the presence of a natural gas extraction field. Thanks to a database of 63 drilling lithologic records and 43 check points obtained from 9 interpreted seismic sections, several 3D HTML models were constructed defining three stratigraphic units (Pre-Messinian, Messinian, and Post-Messinian). An overlap of the Post-Messinian top surface and an erosional truncation of the Messinian top surface toward the N were observed, together with a rising of the Pre-Messinian top surface in the northwestern area. This stratigraphic architecture may indicate differential subsidence and/or uplifting due to syn-sedimentary fault kinematics in the whole studied area. The 3D models with the stratigraphic unit boundary surfaces obtained with KNN interpolation (showing stepped and abrupt edges) allowed the interpretation in terms of structural architecture and syn-sedimentary fault kinematics. Three main sets of faults were deduced: N–S; NNW-SSE, and ENE-WSW. A minorly represented E-W set was added to the main sets. These faults generated a horsts-grabens structure, and in many cases a determinate set of faults caused a progressive lowering or rising of some areas with an “en echelon” arrangement. According to previous works, these deduced sets of faults (most of them strike-slip faults) have a good agreement with the general structural architecture and defined faults in the area.

Architecture and sedimentary evolution of the Ladinian Kobilji curek basin (External Dinarides, central Slovenia)

The study area is located in cental Slovenia, and geologically located at the junction between the Alps and the Dinarides. The Middle Triassic of this region is characterised by intense rifting manifested by differential subsidence and volcanism. This led to a major paleogeographic reorganisation of the region, where three paleogeographic domains formed in the Upper Triassic: The Julian Carbonate Platform in the north, the intermediate Slovenian Basin, both parts of the Southern Alps, and the Dinaric (Adriatic, Friuli) Carbonate Platform in the south, which today is a part of the External Dinarides that host the area of investigation. Prior to the installation of the Dinaric Carbonate Platfrom, i.e. in the Ladinian, the entire area of the preset-day External Dinarides broke up into numerous tectonic blocks that were exposed to either erosion or continental, shallow-marine, and deep-marine sedimentation. In this study, we analyse at small scale a complex transitional area between a local carbonate platform and the Kobilji curek basin (depositional area dominated by deeper marine sediments), located in the Rute Plateau in central Slovenia south of Ljubljana. During enhanced subsidence, the basin was filled with volcanic material (tuffs and volcanogenic clays and subordinate extrusive material), while the adjacent platform aggraded. The slope was positioned above active paleofaults. During relative sea level lowstand, the platform prograded across the basin. The study area is divided into four major tectonic paleoblocks. The NW paleoblock experienced the most enhanced subsidence, and the platform prograded twice in this area and was submerged again by the rejuvenated subsidence and/or sea-level rise. The second and third paleoblocks subsided only during discrete major subsidence events, and the carbonates of the platform and slope were soon reinstated therein. In the fourth paleoblock to the east the platform persisted during the Ladinian. In the Carnian, the entire study area became emerged, and continental clastics were deposited. These were then replaced by a uniform shallow marine/intertidal Hauptdolomit (Dolomia Principale) formation at the onset of the Norian. This study provides the first detailed reconstruction of the sedimentary evolution of small-scale Ladinian basin and platforms system in the northern External Dinarides.

Integrated geophysical approach for detection and size-geometry characterization of a multiscale karst system in carbonate units, semiarid Brazil

Abstract The karstification of carbonate rocks creates 3D maze voids that are normally controlled by fracture networks and sedimentary bedding. The spatial distribution and density of karst systems are usually complex and difficult to predict, demanding multidisciplinary studies at different scales of investigation to determine the spatial distribution and density of karst features and their possible links with cave systems controlled by the regional structural setting. The present study integrates geophysical datasets (gravity, electrical resistivity tomography - ERT, and ground penetrating radar - GPR) with a digital elevation model to investigate a karst system in the Irecê basin, a semiarid region of Brazil. Morphostructural lineaments reveal a NNW-SSE- and E-W-oriented structural setting of the crystalline basement, which is imprinted on the internal basin architecture, and surface drainage network. Negative gravity anomalies and high-gradient gravity zones indicate the main karstic zone, where karst landforms are concentrated. In addition, 2.5D gravity modeling provides the internal basin geometry, demonstrating that the karst system has evolved in the thickest sector of the basin. ERT profiles delineate the underground passages that connect dolines at depth. Finally, GPR data image shallow subsurface ghost-rock karstification that spread out from the surface to depth and that took advantage of vertical fractures and slightly arched bedding planes. Our results point out the role of the fracture corridors in channelizing hydrodynamic energy at a sufficiently high level to create caves by the total removal of dissolved material, whereas in the surrounding areas under low hydrodynamic conditions, overall shallow ghost-rock karstification took place, creating residual weathered rocks (alterites).

The origin and tectonic evolution of the late Neoproterozoic rift basin in the Tarim Craton, NW China

The Cryogenian-early Paleozoic succession in the Tarim Craton is generally regarded as a continuous rift sequence that followed the prolonged superplume-related breakup of Rodinia. However, the rift architecture and origin of the late Neoproterozoic basin are poorly known, but these are important for the understanding of the tectonic evolution of the basin and for the evaluation of the hydrocarbon potential. This paper aims to elucidate the rift architecture, distribution, origin and evolution of the late Neoproterozoic Tarim Basin by integrating outcrop investigations with well and seismic data. The late Neoproterozoic magma-rich active rifting primarily occurred in the northeastern part of the basin, whereas other areas experienced slightly younger magma-poor passive rifting. The Ediacaran succession overlaps in the northern basement uplift to show a pre-Ediacaran unconformity occurs in the northern Tarim Craton, while a sub-Cambrian unconformity traverses the entire Tarim Craton and presents a distinct truncation in the southern basement uplift. A tiered architecture exists in which narrow, deep Cryogenian grabens are overlain by a broad Ediacaran depression. Two NE-striking rift systems developed in the northeastern and southwestern Tarim. It can be inferred from the compiled data that the late Neoproterozoic rift basin evolution in the Tarim Craton can be divided into four stages: early Cryogenian rifting, late Cryogenian fault-graben, Ediacaran intracratonic depression, and end-Ediacaran regional uplifting. These results suggest that documented Neoproterozoic retreating subduction-related slab failure/detachment processes led to both active and passive rifting, which contributed to the diverse continental rift architecture and evolution of the late Neoproterozoic Tarim Basin.

Syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system, Exmouth Plateau, offshore NW Australia: The role of fault‐scarp degradation

AbstractThe syn‐rift architecture of extensional basins records deposition from and interactions between footwall‐, hangingwall‐, and axially‐derived systems. However, the exact controls on their relative contributions and the overall variable depositional architecture, and how their sediment volume varies through time, remains understudied. We undertook a quantitative approach to determine temporal and spatial changes in the contribution of fault‐scarp degradation to the syn‐rift tectono‐stratigraphic development of the Thebe‐0 fault system on the Exmouth Plateau (NW Shelf, offshore Australia), using high‐quality 3D seismic reflection and boreholes data. The magnitude of footwall erosion was measured in terms of vertical (VE) and headward (HE) erosion by calculating the volume of eroded material along the footwall scarp. A detailed seismic‐stratigraphic and facies analysis allowed us to constrain the architectural variability of the hangingwall depositional systems and the types of resulting deposits (i.e., fault‐controlled base‐of‐scarp, settling from suspension, and hangingwall‐derived). After addressing the syn‐rift tectono‐stratigraphic framework, we suggest that periods of significant erosion along the Thebe‐0 fault scarp are related to the accumulation of fault‐controlled base‐of‐scarp deposits characterised by comprising a lower wedge with chaotic to low‐continuity reflections. Footwall‐derived deposits characterised by an upward decrease in stratigraphic dip are interpreted as related to periods of reduced fault activity and sustained sediment delivery sourced from the footwall scarp and systems beyond it (e.g., antecedent systems). We then analysed the tectono‐stratigraphic framework and the volumetric comparison between material eroded from the fault‐scarp and accumulated in the basin, aiming to estimate the contribution of fault‐scarp degradation to the hangingwall syn‐rift fill. Our results suggest periods of enhanced fault activity control fault‐scarp degradation variability through time, and we agree with that described by previous researchers—fault throw variability along‐strike regulates the variability in the magnitude of erosion. However, we propose that fault‐scarp degradation timing and its spatial variability are also influenced by the interaction and linkage with adjacent normal faults and by sea level variations. Lastly, we determine broader similarities and differences with a system located in the same fault array (i.e., Thebe‐2 fault system), aiming to give insights into the tectono‐stratigraphic evolution of a broader area and the spatial variability in fault‐scarp degradation.

Continental depositional record of climate and tectonic evolution around the Eocene-Oligocene transition in southeast France: perpectives from the Vistrenque Basin (Camargue)

Based on detailed sedimentological analyses of cores, interpretation of well logs and a set of geochemical measurements performed on lacustrine sedimentary rocks, the palaeoenvironmental evolution and the sedimentary architecture of the Paleogene continental Vistrenque Basin (SE France) have been reconstructed. The analysis of sedimentary archives revealed three main stages of basin infill evolution: (1) a deep-lake basin (Priabonian-earliest Rupelian) whose sedimentation was dominated by terrigenous gravity-driven deposits during a period of high subsidence rate and strike-slip fault activity and under a prevailing humid climate; (2) an evaporative deep lake (early Rupelian) characterized by a drastic reduction in lake volume (forced-regression), terrigenous supplies and deposition of evaporites in disconnected sub-basins; (3) an overall long-term normal regressive stage (middle Rupelian to earliest Chattian) of lake infill characterized by an increase in terrigenous supplies and a vertical upward transition from deep-lake gravity-driven deposits to marginal lake and floodplain sedimentation. The onset of lake volume reduction and forced regression during the early Rupelian is associated with (1) the reworking of marginal lake carbonates into the deep lake areas, (2) the deposition of organic-rich sediments (TOC &gt; 10%) coupled with sulphate-reduction processes in the deepest areas of the lake, (3) an important decrease in terrigenous supplies and (4) a long-term increase in δ18O of matrix-supported carbonates. This early Rupelian forced regression of the Vistrenque lacustrine system is interpreted to result from a regional decrease in precipitation in response to global cooling during the Eocene-Oligocene Transition (EOT). The final infill of the Vistrenque lake system (late Rupelian-early Chattian) and the onset of a floodplain occurred in more humid conditions during a stage of decreased activity of the Nîmes Fault, prior to or during an early stage of the Liguro-Provençal rifting.