Horsts in continental rifts are classified into three types on the basis of their structural characteristics. Type 1: large horsts bounded by near-vertical, bifurcating faults at rift termini or structural nodes; a subset of this type includes horsts comprising an exceptionally uplifted rift shoulder. Type 2; generally smaller than type-1, type-2 horsts are commonly associated with graben formed in broad zones of crustal extension and thinning; in particular they are a feature of both volcanic and sedimentary basins, where they are bounded by listric faults. Type 3: small horsts occurring close to the margins of rift zones formed in a transtensional regime and bounded by near-vertical faults. The genesis of type-2 and some type-3 horsts is explained by the Vening-Meinesz isostatic model, but type-1 horsts require an additional hydraulic force acting at the base of thick, fractured crust. Small-scale convection in the asthenosphere could provide this force.
ASJC Scopus subject areas
- Earth-Surface Processes