HR: 1340h
AN: P13D-1565    [Abstracts]
TI: CRISM Analyses of Noachian Stratigraphy in Argyre Basin
AU: * Buczkowski, D
EM: Debra.Buczkowski@jhuapl.edu
AF: JHU Applied Physics Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723,
AU: Murchie, S
AF: JHU Applied Physics Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723,
AU: Seelos, F
AF: JHU Applied Physics Lab, 11100 Johns Hopkins Rd, Laurel, MD 20723,
AU: Malaret, E
AF: Applied Coherent Technology, 112 Elden St, Herndon, VA 20170,
AU: Hash, C
AF: Applied Coherent Technology, 112 Elden St, Herndon, VA 20170,
AU: Team, a C
AB: The Argyre basin is a >1500 km, well preserved impact basin in the southern highlands of Mars and the geologic units associated with the basin are mostly Noachian in age (Scott and Tanaka, 1986). Thus, Argyre is an ideal location to characterize the stratigraphy of ancient highland rocks. We analyzed 72-channel CRISM multispectral data that had been map projected to 256 ppd into 40 5-degree map tiles. The data were corrected for illumination by dividing by the cosine of the solar incidence angle. A multiplicative correction for atmospheric gas absorption was applied (Bibring et al., 2005). Spectrally distinct regions were identified by calculating summary parameters (Pelkey et al., 2007); spectra of key areas were examined in detail. A scarp is roughly associated with a contact between the Hpl3 and Npld units in NW Argyre. At the top of the scarp (unit Hpl3) CRISM has detected an olivine signature associated with a depression. Phyllosilicates have been identified extending laterally along the scarp, related to unit Npld (dissected impact breccias). Below the phyllosilicates are found deposits of high-Ca pyroxene hugging scarps in unit Npld. High-Ca pyroxene is also identified in unit Npl1 (undissected impact breccias), at the same stratigraphic level of the Npld pyroxenes. A high-standing knob in Npl1 has a phyllosilicate signature. CRISM investigations also support previous studies by OMEGA, which identified olivine and pyroxene in north Argyre (Gondet et al., 2007). A correlation appears between the low-Ca pyroxene/olivine exposures and the hills of unit Nplh, the oldest geologic unit in Argyre interpreted as uplifted by tectonism during the formation of the impact basin (Scott and Tanaka, 1986). We suggest that as a group these deposits reveal the stratigraphy of the Noachian crust in this region. At the bottom of the stratigraphic column are olivine and low-Ca pyroxene associated with uplifted ancient rocks (unit Nplh). Above these deposits are high-Ca pyroxenes associated with lavas and impact breccia (unit Npl1 and Npld). Within these same units but stratigraphically above the pyroxene are phyllosilicates, preserved in freestanding knobs and along scarp walls. At the top of the stratigraphic column in NW Argyre is olivine associated with the early Hesperian Hpl3 unit.
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting