Crustal taper and topography at passive continental margins

Abstract

Terra Nova, 23, 349–361, 2011 Abstract The long‐term evolution of kilometre(s) high, seaward‐facing escarpments at passive margins is linked directly to the crustal thinning gradient. The development of ‘post‐rift’ faults in the onshore parts of the margin and the associated distribution of drainage patterns, landscape types and sediment dispersal patterns reflect this linkage. For the seismically well‐imaged Norwegian margin as well as for a number of passive margins worldwide, we identify a scaling relationship that correlates escarpment height with the distance to the highly extended distal margin or, more specifically, the taper break. The highest escarpments and the most asymmetric margin topography are found inboard of sharply tapering crystalline crust, independent of margin age. Conversely, escarpments are lower where the taper is gentle. Thus, the topography of passive margins does not primarily reflect age, magmatism, climate or mantle convection, but more probably the response to loading of the laterally variable, fault‐controlled architecture of the crystalline crust.