Physics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.g51a0803m&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #G51A-0803
Physics
1219 Gravity Anomalies And Earth Structure (0920, 7205, 7240), 1221 Lunar And Planetary Geodesy And Gravity (5417, 5450, 5714, 5744, 6019, 6250), 1517 Magnetic Anomalies: Modeling And Interpretation, 5475 Tectonics (8149), 6225 Mars
Scientific paper
Gravity and magnetic anomalies along the well-preserved Martian dichotomy boundary between 105° and 180° E are studied in order to better understand the origin of the dichotomy and magnetization of the crust. We estimate elastic and crustal thicknesses using admittances based on the spectral representations of gravity and topography observations. Admittance values indicate crustal and elastic thicknesses of 15-40 km and 15-35 km for Amenthes West (105° to 135° E), and 0-30 km for Amenthes East (110° to 140° E), respectively. In the Aeolis region (145° to 180° E) however, elastic thickness (0-15 km) is smaller than crustal thickness (15-35 km). Admittance modeling of the Amenthes West region indicates bottom loading, while the Amenthes East and Aeolis regions show top loading. The bottom loading signature for Amenthes West could be due to the proximity of Isidis or a broad valley feature southeast of Isidis. Low elastic thickness estimate ranges are consistent with isostatic compensation. We calculate Bouguer and isostatic anomalies to examine the spatial variability in the gravity field and subsurface structure. The Bouguer gravity has steep gradients parallel to the dichotomy boundary. The derived lithospheric properties along the dichotomy, including the Ismenius region (50° to 90° E), are uniform except near Isidis. The uniformity of estimated lithospheric properties suggests a similar boundary formation mechanism for each region (except at Amenthes West, which may have experienced subsequent modification). Magnetic and gravity anomalies show similar spatial scales and amplitude ratios along the boundary suggesting that the creation or modification of the magnetized crust also created density anomalies via intrusion and/or local thinning or thickening of the crust. We model the sources for the magnetic and gravity anomalies as correlated and anticorrelated. Positive correlations between the magnetic anomalies and density variations are most likely to be a result of subsurface magmatic intrusions. Anticorrelated anomalies are consistent with discrete, high-density intrusions causing demagnetization of the crust.
Milbury Colleen A.
Raymond Carol A.
Schubert Gerald
Smrekar Suzanne E.
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