3D Architecture of Kodiak Butte as Evidence of Fluvial or Shoal‐Water Environments in Jezero Crater, Mars

Abstract

The Mars 2020 mission has explored depositional environments recorded in a fan‐shaped deposit on the western side of Jezero crater. Kodiak butte is an isolated outcrop of sedimentary rock ∼1 km south of the western fan scarp and may be an erosional remnant of said fan. Sedimentary strata of Kodiak butte were first interpreted to represent Gilbert delta foresets and a lake depth of at least 10 m. Subsequent closer‐range images of the northern face of Kodiak have resolved additional details of stratal geometries, permitting alternative interpretations of depositional environments. Rover visible‐wavelength images, a three‐dimensional digital outcrop model, and principal component analysis‐based plane‐fitting allow detailed facies mapping and measurements of stratal geometries in Kodiak. We observed three sets of gravel‐bearing, steeply inclined beds ∼3, ∼7, and ∼10 m thick with local accretion directions ranging from ∼NW clockwise to ∼SW (covering ∼230° azimuth). These sets are interpreted as deposits from downstream‐migrating bars with lobate geometries, consistent with mid‐channel bars in a braided river or mouth bars in a shoal‐water delta. The geometry of the inclined beds indicate channelized bankfull flow ∼4.2 m deep under persistent currents flowing south‐southeast to south‐southwest. The proposed hydrodynamic conditions, potentially continuous with the rest of the western fan succession, are high energy with limited settling of fine‐grained sediment from suspension in a quiescent setting, indicating a lower biosignature preservation potential than previously hypothesized.