Growth Faults in Upper Triassic Deltaic Sediments, Svalbard

Abstract

Abstract Growth faults, rollovers, and shale anticlines affecting Upper Triassic deltaic coarsening-upward sequences are excellently exposed in coastal cliffs on Edgeoya in southeast Svalbard. Study of photographs of the cliffs shows fault configuration, reservoir variations, and internal features of shale anticlines. On downthrown blocks the strata were tilted and rollovers were formed. Beneath the concave-upward growth faults shale anticlines developed and relative uplift of the upthrown block resulted in erosion of some of the newly deposited sands. Subsequent shale deposition formed a local angular unconformity. The faulting may have been initiated by a combination of (1) denser sands overlying less dense clays with excess pore-fluid pressure, (2) a southward prodelta slope and/or regional paleoslope, (3) differential loading associated with deltaic progradation, and (4) a triggering mechanism such as earthquakes. These structures serve as a model for the larger Gulf Coast and Nigerian structures and provide criteria for the recognition of growth faulting in other exposures of ancient deltaic sediments.