Normal faulting vs regional subsidence and sedimentation rate

Normal faults occur in a variety of geodynamic environments, both in areas of subsidence and uplift. Normal faults may have slip rates faster or slowe r than regional subsidence or uplift rates. The total subsidence may be def ined as the sum of the hangingwall subsidence generated by the normal fault and the regional subsidence or uplift ate. Positive total subsidence obvio usly increases the accommodation space (e.g., passive margins and back-are basins), in contrast with negative total subsidence (e.g., orogens). Where the hangingwall subsidence rate is faster than the sedimentation rate in ca ses of both positive and negative total subsidence, the facies and thicknes s of the syntectonic stratigraphic package may vary from the hangingwall to the footwall. A hangingwall subsidence rate slower than sedimentation rate only results in a larger thickness of the strata growing in the hangingwal l, with no facies changes and no morphological step at the surface. The iso static footwall uplift is also proportional to the amount and density of th e sediments filling the half-graben and therefore it should be more signifi cant when the hangingwall subsidence rate is higher than sedimentation rate . (C) 1998 Elsevier Science Ltd. All rights reserved.