Bathymetric mapping of the coastal and offshore geology and structure of the Jurassic Coast, Weymouth Bay, UK

Abstract

Four hundred square kilometres of 1 m binned, full coverage swath bathymetry data, integrated with similar resolution onshore topography, have been used to generate a seamless onshore to offshore bedrock map covering an extensive area adjacent to the ‘Jurassic Coast’ World Heritage site. Analysis of these data provides new insights into the structural development of the Purbeck Monocline Cenozoic inversion structure; in particular, variations in the expression of strain between the hanging-wall block and the fault inversion zone. The footwall to the basin-bounding faults compartmentalized deformation and uplift, and acted as a buttress to compression. The data also show a limited thickness changes within the major lithostratigraphical divisions, and a notable absence of basin-related extensional faulting in the offshore area that is in marked contrast to the more extensively studied onshore region. This indicates that prior to inversion, the basin evolved by intermittent activity on a few major extensional faults. This improved understanding of the development of the basin and inversion structures results from our ability to integrate and quantitatively manipulate these high-resolution and spatially extensive offshore and onshore datasets.