The geomorphology and evolution of Hecate Chasma, Venus

Hecate Chasma is a discontinuous trough and fracture system extending from Atla Regio through Asteria Regio. A detailed examination of Hecate Chasma using Magellan image and altimetry data reveals morphologic features such as normal faults (including graben), compressional ridges, a variety of volcanic edifices, and coronae, There is no evidence for a systematic age progression among coronae in chains, thus a single, stationary thermal anomaly underlying a moving lithosphere is an unlikely origin for the chains, A comparison of the observed features with two possible models of evolution, subduction/delamination or lithospheric extension with limited rifting, shows some similarities between the predicted morphologies of each model and Hecate Chasma, The dominance of features related to upwelling and extensional tectonism strongly favor an extensional origin for this zone. The corona chain may have been formed by upwellings related to Rayleigh-Taylor instabilities, similar to those observed at terrestrial mid-ocean ridges, but in an environment of limited spreading. (C) 1996 Academic Press, Inc.