Stratigraphy and structure of interior layered deposits in west Candor Chasma, Mars, from High Resolution Stereo Camera (HRSC) stereo imagery and derived elevations

Abstract

Interior layered deposits (ILDs) within western Candor Chasma were studied by mapping lithologies, measuring layer attitudes and comparing the stratigraphy of two adjacent mounds. Layering tends to dip in the same direction as the local topographic slope, although at different angles. Regionally consistent attitudes do exist, suggesting postdepositional block rotations. The stratigraphy of two adjacent mounds correlates, but the thicknesses of the units differ. Most layered material appears to have been deposited conformably, with one late major unconformity. Several fault populations are identified and correlate well with regional faults associated with the formation of Valles Marineris. The data suggest that here the ILDs predate the faulting and may be early basin fill. According to our model for ILD formation, ILDs are deposited syntectonically during early basin collapse. Subsequent subsidence of surrounding areas, accompanied by little or no sedimentation, left the early deposits as individual mounds, remnants of the former subbasins. Stratigraphic differences between mounds resulted from different subsidence rates of subbasins. A significant change in depositional environment, from depositional to a near cessation of deposition and the onset of a major erosion event, possibly coincided with the opening of the main Valles Marineris troughs. We further suggest that groundwater played an important role in the formation of sulfates. The youngest unit identified, not including surficial deposits, is likely the result of a posttectonic, regionally limited volcanic event. If basin collapse continued following the cessation of deposition, this model can also account for mounds within closed basins, such as Hebes.

Interpretation and analysis of planetary structures

“…wr.usgs.gov/), and characterizing the styles, extent, and timing of deformation within these deposits). Accordingly, much work has been conducted to characterize regional bedrock and deformational structure using topography derived from data sets such as HRSC (Fueten et al, 2006(Fueten et al, , 2008 and MOLA (Fueten et al, 2005). Results from these investigations have identified several locales that call for further structural mapping at yet higher resolutions in order to provide more detailed characterizations of the local structure and thereby improve current understanding of the area's geologic history.…”

Erosion rate and previous extent of interior layered deposits on Mars revealed by obstructed landslides

“…3.7-3.0 Ga) (Schultz, 1991). ILD formation postdates the opening of the canyons with plausible formation ages that span the Hesperian (Fueten et al, 2008) through the entire Amazonian (Okubo, 2010). Previous studies have also attempted to date individual landslides using impact crater statistics, providing ages for Valles Marineris examples that range from 3.5 Ga to 50 Ma.…”

Quantifying geological processes on Mars—Results of the high resolution stereo camera (HRSC) on Mars express

“…While layering was generally shallow, layer attitudes varied between mounds. Fueten et al (2008) were able to demonstrate a simple correlation of stratigraphy and at least one major unconformity representing a significant period of erosion. They proposed a model for ILD formation in which the collapse of W Candor proceeded through the collapse of smaller sub-basins and postulated that a significant erosion event that produced free standing mesas could be correlated with the linking of chasmata during VM opening.…”

“…Layers were found to be continuous and planar parallel for up to several kilometers. Layer dips are generally shallow to subhorizontal (Fueten et al, 2008;Roach et al, 2009;Sowe et al, 2011;Wendt et al, 2011) and in most cases dip in the same direction as the erosional slope (Fueten et al, 2008(Fueten et al, , 2010(Fueten et al, , 2011Wendt et al, 2011). A spectacular exception to this general trend was presented by Okubo (2010) using HiRISE digital elevation models and orthoimages.…”

“…In a study more aimed to understand the geometry and stratigraphy of ILDs within West Candor Chasma, Fueten et al (2008) measure layer attitudes of several mounds and attempt to correlate the stratigraphy. While layering was generally shallow, layer attitudes varied between mounds.…”