Structural and depositional controls on the distribution of the Upper Jurassic shallow marine sandstones in the Fife and Angues fields area, Quadrants 31 & 39, UK Central North Sea

摘要

An integrated evaluation of the tectonic and depositional history of the Upper Jurassic of the Fife and Angus area of UK Quadrants 31 and 39 has been carried out through 3D seismic interpretation and a range of geological studies. Sedimentological and petrologial data indicate that the Upper Jurassic sands in the study area are the lateral equivalents of the Fulmar Formation. They can be divided into three group of sandstones, deposited by different processes during an interval of almost 10 million years: (1) open shelf, Group 1 sandstones comprise sands dominated by storm/wave activity, which accumulated in fault-bounded mini-basins ('embayments'); (ii) Group 2 sandstones, possibly deposited by storm-induced flows; and (iii) Group 3 sandstones, which may represent subsqueous dunes deposited in a tidally-influenced, shallow marine environment. Sedimentological and heavy mineral studies suggest that the sands in the study area were sourced from the adjacent Mid North Sea High and were transported along the probably by wave, storm and tide-generated currents. Biostratigraphic dating indicates that the Upper Jurassic sands in the Fife/Angus area were deposited during Late Kimmeridgian to upper Middle Volgian. An earlier depositional period with a possible Callovian age is also inferred. Deposition of Jurassic sediments in the study area occurred during two transgression periods (Callovian and upper Late Jurassic), separated by an erosionalon-depositional phase (Oxfordian to Middle Kimmeridgian). The accumulation of Late Jurassic sands started in the Fife embayment and progressed northwards. It was confined, however, to the eastern side of the embayments, possibly due to the hydrodynamic conditions of the area.