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.