Basin Research最新文献

This study aims to investigate the structure and petroleum habitat of salt-related structures in the Kosyu–Rogov Trough, which is a part of the Uralian fold-and-thrust belt in the Timan–Pechora Basin. The structures produced by the upper Ordovician salt are thought to have a much wider distribution in the Kosyu–Rogov Trough and the adjacent Chernyshev Swell than was previously believed. The sedimentary cover of the Kosyu–Rogov Trough is decoupled along the salt layer, resulting in the long-distance transfer of contraction in the post-salt deposits. Based on an integrated interpretation of subsurface data, including 2D and 3D seismic surveys, two types of salt structures are recognised: (1) salt pillows and (2) squeezed diapirs. The salt pillows are distributed in the mildly disturbed central part of the Kosyu–Rogov Trough above the layer-parallel flat of the salt detachment. The squeezed diapirs are clustered within the external part of the study area in the highly disturbed Chernyshev Swell, where the salt layer is passing into basin margin carbonate equivalents. The squeezing of the massive salt diapirs of the Chernyshev Swell has produced large, salt-detached backthrusts in the external part of the Kosyu–Rogov Trough. The horizontal displacement of the backthrust can reach 15 km. Stratigraphic thinning over diapirs and angular unconformities indicate that the initiation of the salt tectonics preceded the onset of the Uralian collision shortening in the late Artinskian. Salt diapirism episodically influenced the facies distribution in the post-salt deposits, predetermining the location of carbonate banks, reefs, oolitic shoals and karstified areas. The large thickness of the sedimentary cover has resulted in early hydrocarbon migration, peaking before the Uralian shortening. This explains why previous exploration projects targeting thrust-related traps that postdated the main migration were largely unsuccessful. It is proposed that traps associated with long-lived salt structures, which were able to receive a hydrocarbon charge during the peak of hydrocarbon migration, are of primary exploration interest.

The intricate interplay of post-collisional magmatism, deformation and related exhumation has reshaped the basin–range system at convergent plate boundaries, as exemplified by the South Tianshan (STS) and the northern part of the Tarim basin (i.e., the Kuqa basin). However, how magmatism, deformation and exhumation interact to control the evolution of the basin–range system remains unclear. This study applies multisystem thermochronometry to elucidate the links between exhumation and post-collisional magmatism, sedimentary burial, thrusting, and deformation at the boundary of the STS–Kuqa basin. Our results reveal that the eastern Kuqa basin experienced rapid exhumation during Permian–early Triassic times, coinciding with volcanic eruptions (ca. 293–288 Ma and ca. 262–254 Ma) and accelerated tectonic subsidence in the western region. The early Permian exhumation was driven by post-collisional continental extension, whereas the late Permian–early Triassic exhumation was associated with regional-scale transpressive strike–slip faults. From the late Triassic to Early Cretaceous, the Kuqa basin experienced continuous burial reheating, corresponding to continuous denudation in the STS during that period. Subsequently, long-term slow denudation in the STS region continued until the early Cenozoic. During the Oligocene–early Miocene, southward thrusting along the North Tarim Fault resulted in the growth and denudation of the STS, coupled with sedimentary burial reheating in the Kuqa basin. Then, deformation continued towards the Tarim basin and intensified since the late Miocene (ca. 5 Ma). The late Cenozoic deformation and exhumation were synchronous with the reactivation of preexisting faults in the STS, and exhibited a progressive westward increase, which can be linked to the clockwise rotation of the Tarim block during the India–Asia collision.

Beef calcite veins in the Green River Formation of the Uinta Basin, Utah, were geochemically characterised to test two hypotheses: (1) that beef calcite veins can form during extensional tectonism and (2) that fluid overpressure can develop in open or partially restricted hydrologic systems. Laser ablation U–Pb geochronology yielded three precipitation ages, with the most precise at 24.8 ± 4.8 Ma (2σ), consistent with maximum burial of the formation and coinciding with uplift of the Uinta Basin segment of the Colorado Plateau. Clumped isotope thermometry indicates precipitation temperatures between 55°C and 72°C—substantially lower than the estimated host rock temperatures of 110°C to 140°C based on a ~30°C/km geothermal gradient. δ¹³C and δ¹⁸O values of beef calcite range from 1.6‰ to −1.2‰ and −10.7‰ to −11.5‰ (VPDB), respectively, with calculated δ¹⁸O of the precipitating fluid (VSMOW) ranging from −3.3‰ to −5.2‰. These values are consistent with a mixed meteoric and shallow connate water source, suggesting the downward invasion of cold, evolved meteoric fluids along faults and fractures during post-Laramide extensional tectonic deformation. The overpressure required for beef calcite formation may have been generated by hydraulic head associated with these downward-migrating fluids and the subsequent lateral displacement of basin brines along stratigraphic interfaces beneath regionally continuous mudstone and evaporite seals.

The influence of transversal crustal discontinuities on the development of continental rift systems remains poorly constrained, especially because their connection with shallow normal faults is often unclear. Nonetheless, these basement faults likely affect the dynamics and the kinematics of the rifting, especially during the early stages of extension. Our study focusses on the Porcupine Basin, offshore west of Ireland, an aborted rift propagator that experienced a 220 Myr-long geological evolution with several rifting episodes. Detailed seismic analysis, integrated with exploration well data, illustrates the regional complexity of the structural patterns across the basin, with faults running subparallel or transverse to its axis. This tectonic framework controlled the northward migration of the crustal stretching during the Late Jurassic, followed by crustal thinning during the Early Cretaceous. Pre-existing, orogenic-derived structures bound crustal terranes that control deformation pulses when rifted apart. This suggests structural barriers that either slowed the northward rifting migration during the Oxfordian, Kimmeridgian and Tithonian when crosscutting through the Variscan and Caledonian fold-and-thrust belts, or stopped the rifting by the end of the Barremian when it encountered Caledonian and Grenvillian crystalline basements. We propose that this structural inheritance led to the formation of a typical rift propagator of continental nature, and that the Porcupine Basin constitutes a remarkable example of a termination of rifting processes in a well-formed oceanic rift system.

Sills are fundamental elements of volcanic plumbing systems emplaced in sedimentary basins. Even though sills are commonly considered simple, planar concordant igneous sheets, they are actually complex 3-dimensional objects. Detailed knowledge of the 3D structure of sills and their host rocks is of primary relevance to better constrain the emplacement mechanisms and the impacts of sills on sedimentary basins. This study describes the results of 3-dimensional geological mapping of a large (~14 × 9 km), well-exposed Early Cretaceous dolerite sill in Central Spitsbergen, Svalbard, Arctic Norway, using a combination of digital outcrop modelling and field mapping. The sill was emplaced within Upper Palaeozoic sedimentary formations of Svalbard. It is made of distinct segments emplaced at different stratigraphic levels of the host rock stratigraphy. The mapping shows a clear stratigraphic control on the intrusion morphology. Sill segments emplaced at the boundary between two formations, which mark a strong lithological and rheological boundary, are straight and concordant. Conversely, segments emplaced within a more homogeneous formation exhibit more irregular, locally discordant shapes. The sill segments emplaced at distinct stratigraphic levels are connected by steeply dipping steps, which formed through dilatant shearing between the tips of the sill segments. The preferred NW-SE orientation of the steps and the thinning of the sill towards the SE suggests a propagation direction of the magma towards the SE. Our study shows how 3-dimensional knowledge of igneous intrusions is key for revealing their emplacement mechanisms.