Curiosity in Situ Observations at Kylie, a Preview of the Kimberley Drill Site Geology

Abstract:

After passing through Dingo Gap, Curiosity turned south and explored the Kylie outcrop on sols 550 to 555. Kylie is topographically higher (by ~10 meters) than the Kimberley located ~300 m to the south, and shares the same succession of geomorphic units identified in satellite images. Thus, in situ observations at Kylie provided context for the subsequent drilling campaign at the Kimberley. Additionally, comparisons of the stratigraphy exposed at Kylie with stratigraphic sections observed at other locations along the traverse (including Darwin, Cooperstown, and Dingo Gap) enable regional correlations and the development of working hypotheses for the former depositional environments.

The sedimentary facies exposed at Kylie include pebble-rich conglomerates and sandstones that vary in bedding orientation and stratification. Exposed on the basin walls is a fining upward stratigraphic succession with a basal pebble conglomerate, flat-bedded sandstone, and a resistant, dark-grey massive to crudely stratified sandstone capping facies. The conglomerate facies forms a prominent bench that rims the western side of the basin. ChemCam data indicate that the pebble-rich conglomerates have mafic and felsic elements and appear similar in composition to the conglomerates previously encountered during the mission. Within the basin, the sedimentary deposits appear to drape pre-existing topography. The most voluminous facies has decimeter-thick south-dipping beds of cross-bedded sandstone that correspond to distinct NE-SW trending linear bands in orbital images. In the southern portion of the basin, these south-dipping cross-bedded sandstones are overlain by thin-bedded, sub-meter cross-bedded sandstone and a poorly exposed, scree-covered butte forming facies. The Kylie deposits are consistent with a complex scenario of dominantly fluvial activity, although the nature and magnitude of flows is still being investigated.