Provenance of Lower Cretaceous clastic reservoirs in the Middle East

Some of the world's largest oilfields contain reservoirs in Lower Cretaceous (Hauterivian-Albian) clastic successions of the Middle East. They comprise sandstone-prone intervals of hundreds of metres thickness deposited in non-marine to paralic settings on a very shallow gradient, otherwise carbonate-dominated, passive margin. This study integrates petrography, X-ray powder diffraction, heavy mineral analysis, mineral chemistry, zircon geochronology and palaeodrainage basin scale calculations to determine the likely provenance of the clastic deposits. Regional geological considerations are then used to suggest the likely driving mechanisms for the clastic influx. The sediments are highly texturally and chemically mature with low-diversity heavy mineral assemblages, suggesting extensive weathering and sediment recycling. The mixture of heavy minerals derived from metapelitic, metamafic and granitic domains at variable metamorphic grades is consistent with erosion of a complex heterogeneous basement or recycling of multiple earlier cycle sediments. Comparison with published data suggests an Arabian Shield provenance, with input from Precambrian basement and Palaeozoic sedimentary cover both possible. This is consistent with drainage basin scaling calculations. Large-scale tectonic reorganization associated with opening of the South and Equatorial Atlantic together with mantle plume related uplift in the northern Arabian Shield is postulated as the main driving mechanism of clastic influx.