DECIPHERING THE SEDIMENTOLOGICAL EXPRESSION OF TECTONICS, EUSTASY, AND CLIMATE - A BASINWIDE STUDY OF THE CORALLIAN FORMATION, SOUTHERN ENGLAND

Jurassic Corallian Formation outcrops along the Dorset coast, composed of carbonate and siliciclastic shallow marine facies, are classic sit es for British geologists. They have been regarded as typical of cycli cally deposited strata, characterized by repeated sandstone, mudstone, and carbonate lithologies. The stratigraphy has been interpreted as e vidence for rapid eustatic sea-level change throughout the. Oxfordian. This study's basinwide database, however, shows that study of the out crops alone has led to oversimplified conclusions. The stratigraphy re cords the migration of siliciclastic source areas through time. Pulses of terrigenous sand reflect local uplift and increased weathering, ra ther than rapid eustatic sea-level falls, The recognition of mixed sil iciclastic-carbonate beds makes an argument for rapid changes in water depth less convincing, and reveals that lateral migration of shallow- water facies is a more plausible explanation for the observed stratigr aphy, Coeval carbonate and siliciclastic deposition around the basin s hows that neither eustasy nor climatic change can be solely responsibl e for the stratigraphy, The strata reflect, instead, a complex interpl ay of episodic local tectonism, siliciclastic source area migration, a nd marine circulation patterns.