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\section{Geological setting of the Variscan faults and vein fill}  The geographic location and regional geology of the Peak District area of the southern Pennines is shown in Figure 1. During the mid-Devonian to the end of the lower Carboniferous Britain was subject to a general north-south back arc stretching as a result of subduction of the Rheic ocean to the south. Extension was largely accommodated by the development of a series of graben and half graben deep water basins bounded by normal growth faults and with foot wall topographic highs. In the Peak District the main basins are the Edale Gulf, Goyt Trough and Widmerpool Gulf. Visean shallow water platform and ramp carbonates accumulated on the topographic highs of the Derbyshire platform whilst deep water facies limestones and shales of the Bowland-Hodder group were deposited in the basins, Figure 1. The end of the Visean is marked by the cessation of extension and carbonate sedimentation on the platform and the onset of thermal subsidence. Subsequent sedimentation included a thin blanket of Namurian shales and later a range of Westphalian river and deltaic sandstone facies. The total thickness of post Visean sediment accumulation is close to 2km. between one and two km.  A regional inversion during the Variscan orogeny resulted in significant uplift and exhumation with removal of the Upper Carboniferous cover. During this period earlier extensional faults were reactivated with both strike slip and reverse components of movement. Whilst there is little field evidence for a subsequent Mesozoic and Cenozoic cover of the platform platform,  apatite fission track analysis suggests that a significant late-Palaeozoic and Mesozoic cover up to 1.4km thick may have existed and was subsequently removed during Cenozoic uplift associated with the Alpine orogeny \citep{Hillis_2008}