STRATIGRAPHY AND PALEOHYDROLOGY OF DELTA CHANNEL DEPOSITS, JEZERO CRATER, MARS

Decades of planetary exploration have revealed an abundance of geomorphic evidence for ancient fluvial activity on the surface of Mars; however, only in the past ~15 years have remote sensing data sets existed with the necessary resolution to study the details of the martian sedimentary rock record. Coastal transition zones are amongst the diverse depositional environments identified on Mars, and here we present observations of the large-scale sedimentary structures of a martian delta deposit within the Jezero crater paleolake basin.

We map the channel-related stratigraphy of this deposit using high-resolution orbital images and stereo-derived digital elevation models (DEMs). The exposed channel stratigraphy is interpreted to be the exhumed topset of the deposit, and records evidence of a distinct change in the style of channelization associated with the evolution of this fluvio-lacustrine delta. The stratigraphically lowest channel-related structures are eroded point bar strata deposited on the inner banks of meandering channel bends. Above the point bar strata are relatively straight, stacked channel deposits preserved as inverted topography. Finally, the entire deposit is incised by a younger valley.

We use DEMs to extract quantitative characteristics of the geometries of these unique types of channel stratigraphy (e.g., point bar radius of curvature, stacked channel body thickness, valley incision depth) to help constrain the paleohydrology of the flows associated with their formation. We also integrate our results to develop a self-consistent stratigraphic framework for this deposit, and reconstruct a scenario for the evolution of the Jezero crater delta and paleolake in which it formed.

The Jezero crater delta deposit provides a record of a dynamic fluvio-lacustrine sedimentary system that evolved through time, including secular shifts in the style(s) of channelization and associated sedimentation. This deposit is a representative example of ancient fluvial stratigraphy on Mars; however, few martian basins contain such readily identifiable fluvial deposits. Therefore, the Jezero crater delta deposit has the potential to improve our understanding of martian fluvial systems, including the evolution of the climate and hydrologic cycles on early Mars.