HR: 10:20h
AN: P42A-01    [Abstracts]
TI: Major Rifts on Venus: Lithospheric Properties and Formation of Parga and Hecate Chasmata
AU: * Smrekar, S
EM: ssmrekar@jpl.nasa.gov
AF: Jet Propulsion Laboratory/Caltech, 4800 Oak Grove Dr. MS 183-501, Pasadena, CA 91109, United States
AU: Hoogenboom, T
EM: trudi.hoogenboom@exxonmobil.com
AF: ExxonMobil, Upstream Research Company 3319 Mercer, Houston, TX 77027, United States
AU: Johnston, S
EM: sjohnsto@centenary.edu
AF: Centenary College of Louisiana, 2911 Centenary Blvd Box 429, Shreveport, LA 71104, United States
AU: Stofan, E
EM: ellen@proxemy.com
AF: Proxemy Research, 20528 Farcroft Lane, Laytonsville, MD 20882, United States
AU: Buck, R
EM: buck@ldeo.columbia.edu
AF: Lamont-Doherty Earth Obs. Columbia Univ., Rt. 9w, Palisades, NY 10964, United States
AU: Martin, P
EM: paula.martin@durham.ac.uk
AF: Durham University, Department of Earth Sciences South Road, Durham, DH1 3LE, United Kingdom
AB: Parga and Hecate Chasmata are complex rift systems each approximately 10,000 km in length. Each chasmata has multiple branches at varying angles to the main trend, and over a hundred associated coronae. Their admittance signatures are distinct from the surrounding plains, and from each other. At Hecate Chasmata, admittance signatures and estimated elastic thicknesses are relatively uniform along several of the rift segments, while at Parga, most of the rift segments display variable admittance signatures. In addition, at Hecate, thinner elastic lithosphere correlates with coronae that are stratigraphically younger than the rift. The correlation between lithospheric properties and rift segments at Hecate suggests that rift formation at this location may be influenced by lithospheric properties, as occurs on Earth. Applying simple models of rift formation based on uniform regional extension (Buck, 1991) and comparing with estimated crustal and elastic thicknesses shows that both these rifts should be considered as wide rifts, which is favored for a strong crustal rheology. This is consistent with their average widths of approximately 150 km and even wider zones of fractures. The implication of the wide rift designation is that spreading velocities are on the order of 1 cm/yr, which is faster than might be expected for a stagnant lid convective regime. Agreement between models, lithospheric properties and stratigraphy at Hecate suggests that uniform extension may explain rifting at Hecate. However Parga does not display such correlations, possibly indicating modification since rifting occurred. The relationship between coronae and rifts remains enigmatic, and could have a significant effect on lithospheric properties.
DE: 5470 Surface materials and properties
DE: 6299 General or miscellaneous
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting