EXHUMED PALEOCHANNELS IN UTAH: INSIGHT FOR INVESTIGATION OF RAISED CURVILINEAR FEATURES ON MARS

Bifurcating ridge networks, termed ‘raised curvilinear features' (RCFs), covering areas ranging from tens to hundreds of square kilometers have been identified at nearly two hundred sites on Mars in high resolution (<100 m/pix) images. Many RCFs are interpreted as paleochannels preserved in inverted relief based on similarity to terrestrial fluvial landforms and continuity relationships with negative-relief valley networks. The global distribution of RCF locations preserves a record of the history of aqueous flow on Mars.

Exhumed paleochannels in east-central Utah have similar morphology to comparably sized, ridge landforms on Mars. The Colorado Plateau is a unique geologic setting where multiple exposures of exhumed paleochannels are preserved. Following uplift of the region in middle to late Cenozoic time, erosion by the Colorado River and its tributaries stripped away younger rock strata, revealing Late Jurassic and Early Cretaceous fluvial sediments at several sites in east-central Utah. The present-day arid climate has inhibited the development of thick soil horizons and pervasive vegetative cover, both of which would obscure these sedimentary bodies. Exhumed paleochannels expose fluvial sediments and internal sedimentary structures in three dimensions.

Field work to date has focused on an extensive (spanning ~12 km) inverted paleochannel system which consists of four carbonate-cemented, sandstone-capped ridges within the Early Cretaceous Cedar Mountain Formation located 11 km southwest of the town of Green River, Utah. Morphologic and sedimentologic observations of the exhumed paleochannels are used to evaluate multiple numerical models for reconstructing paleofluvial hydrological parameters. Preliminary analysis shows a wide envelope of discharge values is generated, with the Limerinos (1970) approach producing a discharge value tending toward the center (median and mean) of the range. Although there are likely variations in the formation history between the terrestrial inverted paleochannels and the martian RCFs, including differences in cement composition and erosional agent, further study of these landforms on Earth will help elucidate the magnitude and relative timing of fluvial activity on Mars.