GSA Connects 2021 in Portland, Oregon

Paper No. 226-9
Presentation Time: 9:00 AM-1:00 PM


ALWMARK, Sanna, Lund University, Department of Geology, Sölvegatan 12, Lund, 22362, Sweden; University of Copenhagen, Niels Bohr Institute, Blegdamsvej 17, Copenhagen, 2100, Denmark, KAH, Linda, Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, GARCZYNSKI, Bradley, Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN 47907, SCHELLER, Eva L., California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA 91125, SMITH, Rebecca J., Department of Geosciences, Stony Brook University, Stony Brook, NY 11790, STACK MORGAN, Kathryn, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 and QUANTIN, Cathy, Universite de Lyon, Lyon, France

Jezero crater, landing site for the M2020 Perseverance rover mission, is filled by a series of geomorphically distinct units. Understanding relationships between units in Jezero crater is critical to understanding the history of the region, with implications for the broader evolution of Martian environments.

Here we explore map-scale relationships between geologic units that are exposed at the crater floor. These units include: Crater floor fractured rough (Cf-fr), which is a regional, roughly planar, crater-retaining unit with lobate margins; and two morphologically distinct units (lower and upper Séítah) that lie outside of the lobate margins. In a new orbital mapping effort, we further characterize relationships between these units. First, we identify that the basal 2-6 meters of Cf-fr contain discrete layers that are exposed either inside or outside of the lobate margin, depending on topographic relief of the substrate. Séítah rocks consist of two distinct regional units, including a lower, polygonally fractured unit with strong spectral signatures of olivine in CRISM, and a spectrally distinct, higher-standing pinnacled unit.

Layering within the basal Cf-fr permits Cf-fr to be distinguished from laterally exposed Séítah rocks and shows the Cf-fr to overlie Séítah. Layering within Cf-fr also changes in overall thickness and in the number of observed layers along the lobate margin, indicating that layered strata were likely deposited over pre-existing topographic relief associated with an erosional unconformity between the units. Higher-standing portions of the upper Séítah also occur at a variety of topographic positions with respect to polygonally fractured lower Séítah, suggesting the potential for an unconformable relationship between upper and lower Séítah units. Together, these relationships suggest a complex geologic history within Jezero crater characterized by periods of deposition separated by periods of erosion.