Basin Research最新文献

Buried pockmarks are features associated with fluid seepage through ancient seafloors. In this work, high-quality 3D seismic reflection and well data are used to investigate the geometry, distribution and significance of listric faults and associated pockmarks in a salt minibasin from offshore Espírito Santo, SE Brazil. The results show that six out of ten pockmarks interpreted in the study area have crescent, elliptical, or elongated shapes. They occur along the trace of listric faults and on their immediate hanging-wall blocks, with pockmarks' long axes being nearly parallel to the strike of the faults. The pockmarks are approximately 1300–6200 m long, 600–4000 m wide, 30–139 m deep, and buried 50 to 500 m below the modern seafloor. They can be divided into fault-strike (type I) and fault hanging-wall (type II) pockmarks based on their spatial relationships. Type I represents pockmarks developed along the trace of listric faults, which acted as fluid conduits. Type II pockmarks were developed away from fault traces on their hanging-wall blocks. Their occurrence near listric faults was controlled by multiple factors, including the relative depth, length, area, and maximum displacement of listric faults. In addition, listric faults below horizon H4—an Upper Paleogene unconformity—do not show pockmarks around them. Listric faults with greater length, area, and maximum displacements were more likely to form pockmarks. In conclusion, the studied pockmarks are evidence for local hydrocarbon escape occurring in the Espírito Santo Basin since the Miocene. The results presented here can be applied to other regions around the world prone to geohazards and where carbon and hydrogen storage solutions are being proposed.

Orogenic wedges juxtapose tectonic units that originated far from each other, and tracing these back to their origin is often difficult. We have studied two contrasting serpentinite–sediment associations of the Alpine-Apennine orogenic wedge of eastern Elba Island with the help of a detrital zircon study of the sediments and a geochemical comparison of the relic phases of their associated serpentinites. We demonstrate that these very likely originated in different branches of the Ligurian Ocean and in contrasting tectonic settings, one during opening of Alpine Tethys and the other during Apenninic contraction-exhumation. First, the Early Cretaceous Palombini shales are associated with abyssal ocean floor serpentinite–ophicalcites of a Ligurian ophiolite (LO) that originated in the western branch of the Ligurian Ocean during ultraslow spreading. They have an Adria/African zircon provenance, indicating proximity to Adria rather than Corsica-Europe and the associated serpentinites are highly depleted and relatively little deformed. The second sediment–serpentinite association has a tectonised serpentinite band in contact with highly deformed, Miocene blueschist facies metasediments. Detrital zircons of these metasediments (Acquadolce (AD) and Pseudomacigno) record major Eocene–Oligocene U–Pb zircon age peaks, with an igneous provenance in the western and central Alps respectively. An age peak at ca. 38 Ma links the Pseudomacigno sediments to calc-alkaline volcanic rocks of the central Adamello massif, whilst an Oligocene age peak at ca. 32 Ma indicates western Alpine sources for the AD Unit. The associated massive, highly tectonised AD serpentinite represents most likely a mantle sliver of subcontinental lithospheric mantle, which together with Oligocene blueschist facies rocks underwent synorogenic Apenninic tectonic extrusion during W-directed subduction–rollback of the eastern branch of the Ligurian Ocean.

Stratigraphy and its associated grain size preserve a record of the dynamic behaviour of source-to-sink systems over time. Sediment supply and available accommodation space primarily control downstream grain-size fining preserved in stratigraphy. In principle, these grain-size trends can be inverted to quantify temporal and spatial variation in these driving forces. Here, we illustrate how grain size and stratigraphic thickness can be used to quantify fault growth and interaction using the early-mid Pleistocene Pirgaki-Mermoussia (P-M) fault, Gulf of Corinth, Greece, as a natural laboratory. A 2.5 km long exposed cliff section of the uplifted Kerinitis Gilbert-type delta, which lies in the hanging wall of the P-M fault, was selected for study. In the field, we traced out stratigraphic units in the lower part of the Kerintis delta, which are bounded by flooding surfaces, and measured their thickness to reconstruct hanging wall subsidence. We collected down-system grain-size data at 31 measurement sites using the Wolman point count method. Our results show the observed grain-size fining rate increase from 11 to 17 mm.km⁻¹ for the lower delta deposits over a timescale of up to 120 kyr. Using a self-similarity-based grain-size fining model and considering a minimum increase in accommodation generation from 0.6 to 1 mm year⁻¹ over this period, we reconstruct an increase in delta sediment supply from ca. 170 to 460 m³ year⁻¹. The integration of stratigraphic thickness measurements with grain-size fining trends enables quantitative reconstruction of temporal variations in fault-driven accommodation space and sediment supply, thereby demonstrating fault slip rate evolution. We show an increase in the P-M fault slip rate during its early history from 1 to 2 mm year⁻¹, reflecting early interaction of the P-M fault segments over ca. 120 kyr. Reconstructed catchment-averaged erosion rates are ca. 20% of the footwall uplift, implying a transient response of the landscape to the P-M fault growth. These analyses demonstrate how grain-size data from a well-constrained geological example can be used to reconstruct landscape dynamics quantitatively in fault-controlled sedimentary systems with high temporal and spatial resolution.

The Levant Basin of the Eastern Mediterranean accumulated voluminous siliciclastic sediments during the Oligocene–Miocene. The deep-sea section has attracted significant interest as it contains world-class hydrocarbon reservoirs (‘Tamar Sands Play’). Our recent sandstone provenance study revealed that the hydrocarbon-bearing, lower Miocene ‘Tamar Sands’ were recycled from older quartz-rich sandstones that covered the Arabian flank of the Red Sea Rift. However, sandstones constitute just a third of the thickness of the Oligocene–Miocene siliciclastic section in the Levant Basin, with the rest being mainly composed of shales. Unravelling the provenance of the shale fraction is therefore essential for a comprehensive reconstruction of the Oligocene–Miocene source-to-sink system of the Levant Basin. In the present study, we examined the mineralogy and Sr-Nd isotopes of clay samples retrieved from deep-sea boreholes that penetrated the Oligocene–Miocene siliciclastic section. The isotopic composition of most clay fractions resembles that of Nile Delta sediments, indicating that unlike the ‘Tamar Sands’, their dominant provenance lay in NE Africa. Our investigations show that they were derived from Neoproterozoic basement rocks of the Arabian-Nubian Shield and Tertiary continental flood basalts. The absence of chlorite and serpentine negates detrital contribution from the Arabia-Eurasia suture in the north. Compilation of the available thermochronology data and major geologic events shows that the accumulation of the siliciclastic section in the Levant Basin coalesced with uplift of the continental areas around the Red Sea. The marked switch to shale deposition recognised in the basin during the late early Miocene signifies the downfall of the ‘quartzose’ Arabian sediment transport system, when it was partially captured by the evolving Dead Sea Transform valley. Our study highlights the strength of coupling sand and clay provenance investigations in source-to-sink studies of sedimentary basins.

In this contribution, we document changes in detrital zircon ages in the upper Devonian (Famennian) to lower Carboniferous (Mississippian) Billefjorden Group on Bjørnøya, the southernmost island of Svalbard. This alluvial, coal-bearing clastic succession is widely distributed across the archipelago and the Barents Shelf. The sediments were deposited in subsidence-induced lowlands that formed just after regional post-Caledonian collapse-related extension, which created the classical ‘Old Red Sandstone’ basins during the Devonian, and prior to localised rift-basin development in the middle Carboniferous (Serpukhovian–Moscovian). Moreover, the succession is little affected by Ellesmerian compressional deformation, which occurred in the latest Devonian. However, little is known of the provenance and regional sediment routing in this tectonically transitional period between the post-Caledonian structuring events in the Devonian and the middle Carboniferous rifting. It has previously been invoked that a regional fault running parallel to the western Barents Shelf margin, the West Bjørnøya Fault, controlled sedimentation in the area. Here, we combine detrital zircon U–Pb ages and sedimentological data to investigate stratigraphic provenance variations and test whether tectonics controlled deposition of the Billefjorden Group on Bjørnøya. Sedimentological investigations demonstrate changes in fluvial style with intercalations between successions dominated by meandering channel fills and abundant overbank fines to sandstone-dominated sheet-like successions of braided stream origin. Palaeocurrent data show that two competing drainage directions accompany the changes in fluvial architecture. Northeasterly transport directions, recorded in the braided stream deposits, indicate possible fault-transverse drainage. The detrital zircon content in these deposits indicates sourcing from Caledonian terranes in Northeast Greenland. Northwest-oriented transport directions, measured in the meandering channel deposits, are inferred to represent axially positioned drainage systems. These may have been sourced from either Northeast Greenland, a more localised source, or Baltica. The latter would require long-distance sourcing, which, given the tectonic setting of the region, seems unlikely. Although our sedimentological observations point to syn-tectonic deposition, this is not clearly captured in the detrital zircon data, suggesting a common source for the Late Devonian–Mississippian fluvial systems of Bjørnøya. Thus, combined with previously published provenance data from Svalbard and Greenland, we demonstrate that the East Greenland Caledonides formed a long-lived and significant source area which provided sediments to nearby basins from the Devonian to the Early Cretaceous.

The exhumed hydrocarbon traps of East Greenland provide a superb opportunity to study the evolution of fluid flow in the petroleum systems of the North Atlantic. Following basin inversion during the Cenozoic these structures were exhumed and deeply incised which has allowed them to be observed and mapped in great detail. This study examines the diagenetic history of the Mols Bjerge and Laplace Bjerg exhumed hydrocarbon traps, from the initial charge of Triassic and Jurassic reservoirs, to their eventual uplift and destruction. Detailed petrographic analysis was undertaken on 67 samples collected at representative intervals throughout the structures. Variations in the distribution of diagenetic phases and remnant porosity were investigated. Twenty three samples were also subjected to helium porosity measurement. Bitumen, up to 18%, was recognised in 34 samples, 6 of which were analysed for their form and reflectance. Fluid inclusion data, collected from the nearby Bjørnedal region, helps to constrain the thermal history of the region. Helium porosity and permeability measurements are low, largely below 10% and 2 mD respectively. However, the abundance of bitumen highlights the presence of significantly higher porosity and permeability during hydrocarbon charge. A synthesis of fluid inclusion data and bitumen reflectance, alongside a detailed examination of the paragenetic sequence, demonstrate that hydrocarbon charge occurred in the Eocene, during maximum burial, at which time only a minor reduction in original intergranular porosities had taken place. The destruction of the pore systems occurred due to the degradation of hydrocarbons to bitumen, resulting from heat flow during intrusive events, and subsequent carbonate and limonite cementation during uplift. The original source of the hydrocarbons is unclear. This work highlights that where unaffected by intrusives and uplift, the largely untested Triassic play may still contain viable reservoir intervals at depth on the Norwegian Continental Shelf.

Paleo source to sink system analysis requires a complete earth systems model approach, utilising regional geology, tectonics, climate and modern-day source to sink analogues. This study examines the Cretaceous source to sink systems of Senegal, NW Africa, integrating a broad regional dataset using a multidisciplinary mineralogical approach. The most significant regional geological and tectonic events to affect Senegal since the Pan-African Orogenies (800–520 Ma) are the Hercynian Orogeny (320–290 Ma), Pangea break-up and rifting between S. America and Africa, with associated Central Atlantic Magmatic Province volcanism (200 Ma) and uplift of the Mauritanide hinterland (113–66 Ma). In addition to tectonic controls, climate is the principal driver for paleo-drainage reorganisation. During the Cretaceous an antithetical shift in climate from warm and arid (145–115 Ma), to hot and humid (100–88 Ma), increased fluvial catchment and energy. Antecedent paleo-drainage of the Cretaceous Senegalese Basin is governed by subsurface grabens striking hundreds of kilometres into the continent formed during Atlantic rifting. Early Cretaceous aridity restricted fluvial catchments to recycling pre-Cretaceous basinal sediments. Climate change triggered expansion of paleo-drainage catchments during the Aptian caused fluvial incision and erosion of the Gaouâ Group Hercynian to Pan-African age source rocks along the western flank of the Mauritanides. Exhumation increased significantly throughout the Cretaceous Thermal Maximum during the Cenomanian–Turonian, with exhumation of the Gadel Group Pan-African source rocks, evidenced from a shift between a garnetiferous to staurolitic basin mineralogy. Inclusion of 200 Ma zircons into the central Senegalese Basin during the Albian is evidence of possible catchment shifts to include CAMP detritus from the Fouta Djallon Plateau. Cretaceous basinal sediments are almost exclusively sourced from the Mauritanide belt which includes Hercynian metamorphic host rocks and Palaeozoic sediments ultimately derived from the erosion of the Pan-African orogenic belts. During the Maastrichtian, the central fluvial systems breached the southern Mauritanides, sourcing Cambrian zircons from the south.

The submarine Miocene Central Canyon and Pleistocene channel systems in the Qiongdongnan Basin constitute valuable sedimentary records that provide insight into the depositional processes and sediment routing from the hinterland to the deep sea. However, the primary source of sediment for the Pleistocene channel systems and the variation in relative sediment contributions since the Miocene from potential source terranes remain unknown. We have integrated new and published detrital zircon U–Pb ages and rare earth elements (REEs) from Pleistocene channel sands and late Miocene Central Canyon sands in the Qiongdongnan Basin to analyse the sediment routing system of these channel systems since the Miocene. Qualitative analyses of REEs, comparisons of detrital zircon age spectra, and multidimensional scaling plots suggest that the Red River is a significant source of sediment supply. The quantitative analysis of sediment mixing models indicates that the Pleistocene channel sands were mainly sourced from the Red River (62.8%–85.7%), followed by Central Vietnam rivers (4.8%–27.1%), with a minor amount derived from rivers in Hainan Island, Northern Vietnam and Southern Vietnam. Sand sediments, mainly from the Red River system, were deposited in the Yinggehai Basin, then transported and deposited again in the Qiongdongnan Basin. The relatively stable and major sediment supply from the Red River since the Miocene may have been driven by the uplift of the Tibetan Plateau. This study quantifies the relative provenance contributions to submarine channel systems in the Qiongdongnan Basin since the Miocene. It provides crucial geological implications for tectonic responses to channel migrations and the prediction of gas hydrates in sandy reservoirs.