SUMMARY
Good documentation of uncomplicated tectonic faulting in the Coal Measures of north-east Derbyshire has enabled fault planes and zones to be isolated for detailed study, both laterally and vertically. Systematic variations in throw and hade are revealed by contouring the fault planes for these properties, and typical patterns are described. The individuality shown by faults is emphasised.
The Ochil Fault, one of the most prominent tectonic features in the Midland Valley of Scotland, juxtaposes Lower Devonian volcanic rocks against late Westphalian strata, implying a possible vertical displacement of up to 4 km. The Kincardine Basin in its hanging-wall, although actively subsiding during the greater part of the Silesian, trends generally N–S, perpendicular to the Ochil Fault, and its Silesian sedimentary record shows little sign of tectonic control by that fault. It is proposed that the Ochil Fault was initiated, possibly as a sinistral strike-slip feature, in the Devonian, but acted as a sidewall fault during the early evolution of the Kincardine Basin, attributed to extension on a hypothetical pre-Brigantian fault along the Bo'ness Line on the east side of the basin until late Namurian times, when active extension ceased. Both faults were probably buried during late Namurian and Westphalian times. Reactivation of the Ochil Fault during end-Carboniferous N–S extension, dated by quartz-dolerite emplacement, was responsible for probably at least 2 km displacement. including the presently visible footwall uplift. It is suggested that the hanging wall may have contained a Permian basin, now removed.
Channel orientation and palaeoflow analyses across the British Westphalian (Carboniferous) coalfields show that three main inflow directions dominated the palaeogeography from the mid-Langsettian to the mid-Bolsovian. In eastern Scotland and NE England, flow was mainly from the N and NE. In the Pennine Basin of north central England, flow was mainly from the W and NW, whilst in South Wales, main flow from the SW was compatible with a westerly system that also branched to give the northerly inflows recorded in the Culm Basin of southwest England. The depositional area included discrete tectonic depocentres, notably the Pennine Basin, which was traversed directly and tangentially by major channel belts. These basins were essentially incidental to the main channel pathways, but sand body characteristics vary according to basin location. A new depositional model for the post-rift Pennine Basin is proposed, relating sand concentrations and connectivities to the depositional and tectonic setting. The description of dominant SW to NE flow across South Wales through much of the Langsettian and Duckmantian, in contrast to the centripetal inflows previously proposed, implies some similar channel/depocentre relationships to those described here for the Pennine Basin.
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