Abstract

Synopsis

Basin subsidence and thermal history models of the eastern part of the Midland Valley of Scotland have been constructed to characterize the development of the Midlothian-Leven synclinal basin from the mid Mississippian to the present day. Two modelling programs were used: BasinMod and HotPot. BasinMod models are based on thermal maturity at borehole sites; HotPot models operate on stacks of 2D layer grids using a mechanical compaction method. The thermal and burial history modelling indicates up to 1.9 km of additional burial of Carboniferous strata compared to present day levels: up to 660 m deposited by the end of the Carboniferous period, subsequently removed by Variscan uplift and erosion, followed by up to 1.9 km of burial by sedimentary rocks deposited during the Permian to the Palaeogene periods. Temperatures greater than 130 °C were reached by the most deeply buried Carboniferous sedimentary rocks. Mississippian (Lower Carboniferous) rocks reached the oil generation window during the mid Carboniferous, with Pennsylvanian (Upper Carboniferous) rocks reaching the oil generation window during the Cretaceous. Sedimentation rates were of 0.03–0.63 m ka−1 (metres per thousand years) with changes in the rate and the positions of depocentres consistent with both extensional and strike-slip basin formation.

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