Development of three genetically related basins associated with detachment-style faulting: Predicted characteristics and an example from the central Mojave Desert, California

Abstract

Three types of sedimentary basins may develop in large-magnitude detachment-type extensional systems. Possible early Miocene examples of these basin types have been identified in association with northeast-directed extension on the central Mojave metamorphic core complex, southern California. From west to east the basins are (1) the Tropico basin, a flexural basin formed on the unextended footwall behind, and bounded by, the detachment breakaway zone; (2) the Pickhandle basin, a supradetachment half graben bounded to the southwest by the detachment breakaway and to the northeast by the hanging wall; and (3) the Clews basin, an intra-hanging-wall basin that formed on the upper plate of the detachment system. Different basin types may be recognized by the nature and geometry of their strata. The footwall flexural basin should be shallow and areally extensive, with basin fill dominated by fine-grained, low-energy deposits. The supradetachment basin typically will be elongate normal to the extension direction and characterized by a thick sequence of volcanic and coarse-grained deposits that reflect its fault-controlled margins. Intra-hanging-wall basins may be of half- or full-graben geometry and will vary in dimension depending on the spacing of the transfer elements. Recognition of these basin types is potentially useful in delineating features of the extensional system that are important to its reconstruction, including the detachment breakaway zone and the boundaries of the extensional system parallel and normal to the extension direction.