Paper No. 19-12
Presentation Time: 11:20 AM
THE GEDIZ VALLIS RIDGE: CURIOSITY’S IN-SITU INVESTIGATIONS OF A REMNANT LATE-STAGE DEBRIS-FLOW DOMINATED FAN ON MARS (Invited Presentation)
BRYK, Alexander1, DIETRICH, William E.2, FEDO, Christopher M.3, CARAVACA, Gwénaël4, DAVIS, Joel M.5, LAMB, Michael P.6, GRANT, John A.7, WIENS, Roger C.8, GASNAULT, Olivier9, GROTZINGER, John P.10, VASAVADA, Ashwin R.11, STACK, Kathryn M.12, ARVIDSON, Raymond E.13, LE MOUELIC, Stephane14, FOX, Valerie K.15, BENNETT, Kristen A.16, GUPTA, Sanjeev17, WILLIAMS, Rebecca M.E.18, SHEPPARD, Rachel Y.19, LEWIS, Kevin W.20, RUBIN, David M.21, RAPIN, William22, FRAEMAN, Abigail A.23, BANHAM, Steven G.24, HUGHES, Madison N.13, TURNER, Madison20, WILSON, Sharon A.25 and KITE, Edwin S.26, (1)Department of Earth and Planetary Science, University of California, Berkeley, CA 94720-4767, (2)Department of Geography, University of California, Berkeley, Berkeley, CA 94720, (3)Earth and Planetary Sciences, University of Tennessee, Knoxville, Knoxville, TN 37996, (4)Institut de Recherche en Astrophysique et Planétologie, 9 Avenue du Colonel Roche, Toulouse, 31400, France, (5)Department of Earth Science and Engineering (ESE), Imperial College, London, UK, London, South Kensington SW7 2AZ, UNITED KINGDOM, (6)Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, (7)Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Independence Ave at 6th St. SW, Washington, DC 20560, (8)Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, Lafayette, IN 47907, (9)Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UPS-CNRS-OMP, Toulouse, France, (10)Division of Geological and Planetary Sciences, Caltech, 1200 E California Blvd, Pasadena, CA 91125, (11)Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, (12)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, (13)Earth and Planetary Sciences, Washington University IN St. Louis, 1 Brookings Drive, St. Louis, MO 63130, (14)Laboratoire De Planétologie Et Géodynamique, U. Nantes, Nantes, 44322, France, (15)University of MinnesotaEarth Sciences, 2949 4th St SE Unit 535, Minneapolis, MN 55414-4322, (16)US Geological Survey, 2255 N Gemini Dr, Flagstaff, AZ 86001-1698, (17)Imperial College London, London, SW7 2AZ, United Kingdom, (18)Planetary Science Institute, Tucson, AZ 85719, (19)Institut d’Astrophysique Spatiale (IAS), Universite Paris-Saclay, Bures-sur-Yvette, 91122, France, (20)Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, MD 21210, (21)Earth and Planetary Sciences, UC Santa Cruz, 1156 High St, Santa Cruz, CA 950604, (22)IRAP - CNRS, Toulouse, BP 44346 31028, France, (23)NASA Jet Propulsion Laboratory, Pasadena, CA 91109, (24)Earth Science and Engineering, Imperial College London, London, SW7 2AZ, United Kingdom, (25)Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Independence Ave at 6th St, SW, Washington, DC 20560, (26)Dept. Geophysical Sciences, University of Chicago, 5734 S. Ellis Avenue Chicago, Chicago, IL 60637
Recent studies using orbital imagery (HiRISE and CTX) have identified widespread fan-shaped deposits, interpreted as resulting from a combination of fluvial and debris-flow processes, across the surface of Mars that likely formed during the Hesperian and Amazonian periods. Curiosity’s in-situ observations of the Gediz Vallis Ridge (GVR) now provide our first cross-sectional observation of a fan on Mars. The deeply eroded landform lies near the base of Mt. Sharp at the outlet of a 127 km2 catchment. The fan was deposited unconformably on top of the Stimson formation – a laterally extensive aeolian sandstone that unconformably mantles the Greenheugh pediment. The stratigraphy of the remnant fan consists of a discontinuous fine-grained (≤ gravel size) basal unit above the Stimson that is unconformably onlapped by layered boulder-rich deposits. Onlapping boulder-rich strata are laterally discontinuous and exhibit bed thicknesses ranging from ~0.25 to 3 m, with a mean dip of four degrees (much gentler than the slope of the basal contact) oriented parallel to the ridge axis. Boulder-rich strata consist of two facies with variable occurrence and lateral extent up-section: 1) a light-toned, typically matrix-supported, boulder conglomerate with scattered erosionally resistant dark-toned cobble-to-boulder sized clasts and 2) a dark-toned, typically clast-supported, cobble-boulder conglomerate facies with occasional isolated light-toned clasts. Grain-size analysis from RMI data indicates similar median grain sizes (170-190 mm) in both facies with isolated 1-3 m boulders scattered throughout. The light-toned strata are interpreted to be debris flow deposits. The dark-toned strata are more likely fluvial in origin, probably derived from surface runoff that concentrated dark-toned boulders from the light-toned unit into channels and sheetflood deposits while destroying the relatively weaker light-toned boulders during transport. Such water-driven deposits call for a water source derived from Mt. Sharp, the eroded 5 km mountain at the center of Gale Crater. The fan is composed five distinct on-lapping depositional units, marked by changes in the frequency of the two facies. These changes likely record significant changes in the magnitude and frequency of surface runoff and sediment supply that may be a response to variable climate conditions.
![[Visit Client Website]](/img/gsa/banner.jpg)