HR: 17:00h
AN: P34A-05    [Abstracts]
TI: Insight Into Lava Sheet Inflation and Deflation Events From the McCartys Flow, New Mexico, and Implications for Planetary Lava Flow Emplacement
AU: * Bleacher, J E
EM: Jacob.Bleacher-1@nasa.gov
AF: Planetary Geodynamics Laboratory, Code 698, NASA GSFC Bldg 33. Room G310, Greenbelt, MD 20771,
AU: Garry, W B
EM: GarryW@si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Museum Smithsonian Institution MRC 315 PO Box 37012, Washington, DC 20013-7012,
AU: Zimbelman, J R
EM: zimbelmanj@si.edu
AF: Center for Earth and Planetary Studies, National Air and Space Museum Smithsonian Institution MRC 315 PO Box 37012, Washington, DC 20013-7012,
AU: Crumpler, L S
EM: larry.crumpler@state.nm.us
AF: New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM 87104,
AB: Basaltic lavas typically form channels or tubes during flow away from a vent. However, the importance of sheet flow in the development of basaltic terrains has gained attention within the last 15 years. The McCartys lava flow field (NM) is among the youngest (~3000 yrs) basaltic lava flows in the continental United States. It was emplaced over slopes of < 1 degree, displaying features suggested to represent lava sheet inflation and deflation. Therefore, it among the most pristine examples of sheet flow morphologies in the United States. Here we present field observations of this flow field. At the meter scale the interior flow surface typically forms smooth, undulating lobes that appear to represent breakouts from adjacent lobes. These features display grooved surfaces and occasional squeeze-ups along lobe contacts. At the scale of 10s to 100s of meters the flow comprises multiple topographic platforms and depressions. Some depressions display level floors with surfaces as described above, while some are bowl shaped with floors covered in broken lava slabs. The boundaries between platforms and depressions are also typically smooth, grooved surfaces that have been tilted to angles sometimes approaching vertical. The upper margin of these tilted surfaces typically displays large cracks parallel to the boundary, sometimes containing squeeze-ups. The bottom boundary with smooth floored depressions typically shows embayment by younger lavas. The superposition relationships between platforms, depressions, and small lava flows within depressions are complex. It appears that this style of terrain represents the emplacement of an extensive, sheet, likely as one large unit. The sheet experiences inflation episodes within preferred regions, which produce platforms of varied elevations. Inflation events appear to be associated with breakouts of lava which flood the floors of accessible depressions. Depressions are the result of non-inflation, or collapse of an inflated surface as lava is drained from the sheet interior during breakout events. Such an event would comprise an extensive sheet experiencing multiple, possibly contemporaneous, dynamic episodes of inflation and deflation throughout the flow field. The resultant morphology might be analogous to surface textures seen in Tharsis province plains regions adjacent to the Tharsis Montes, Mars.
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 6225 Mars
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8486 Field relationships (1090, 3690)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting