Sediment deformation structures and the palaeotectonic analysis of sedimentary basins, with a case-study from the Carboniferous of northern England

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Abstract
Summary: There is a close link between syn-sedimentary faulting caused by earthquakes of magnitude >5 and accompanying ‘soft’ sediment intrafolial deformation in active neotectonic settings. Certain of these intrafolial structures may also be produced by purely sedimentary processes and are termed ‘autokinetic’. Those caused by earthquake-induced stresses are termed ‘allokinetic’. Although certain structures may be caused by either mechanism, it appears that large amplitude dewatering pipes and recumbent-folded cross stratification are likely to be predominantly allokinetic in origin. These structures may be used to define the Allokinetic Deformation Number which can be systematically mapped out in particular lithofacies over outcrops in a sedimentary basin. Results of this mapping are then combined with data on lithofacies thickening and stacking (tectonically-controlled architecture), hangingwall rollover deformation etc., to establish an interdisciplinary outline of palaeotectonic evolution. This methodology of palaeotectonics is tested in the suspected extensional terrain of the Northumberland Basin with encouraging results.