TOPOGRAPHIC ANALYSIS OF DEVANA CHASMA, VENUS: IMPLICATIONS FOR RIFT SYSTEM SEGMENTATION AND PROPAGATION

Abstract

Devana Chasma is a rift system on Venus formed in association with the Beta Regio and Phoebe Regio volcanic highlands, which are interpreted as mantle plumes. We present a new analysis of a 2500-km-long segment of Devana. Based on the rift topography, the horizontal extension across the rift boundary faults is 3-9 km. This is a lower bound on the total rift extension because the altimetry does not resolve the topographic relief across the numerous faults that are visible in radar images of the rift floor. The total extension across Devana is approximately 20 km, similar in magnitude to continental rift systems on Earth. Rift flank elevations are up to 3.1 km in the regions nearest the mantle plumes and decay strongly with increasing distance from the plumes, indicating a strong thermal component to the rift flank topography, unlike the situation usually reported for terrestrial rifts. As on Earth, there is also a flexural uplift component to the flank topography. Rift depths are up to 2.5 km below the surrounding plains, with considerable along-strike variability. There is a 600 km lateral offset along Devana Chasma near the mid-point between the two mantle plumes. Devana most likely formed as two distinct rifts due to the horizontal stresses created by outflow from the upwelling plumes. The offset zone formed as a result of the interaction between the two rift tips, which requires that upwelling at the two mantle plumes overlapped in time. © 2005 Elsevier Ltd. All rights reserved.