The decompensative gravity anomaly and deep structure of the region of the Rio Grande rift

Journal Article · Wed Apr 10 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JB00008· OSTI ID:5387460

Cordell, L ^[1]; Zorin, Y A ^[2]; Keller, G R ^[3]

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1. Geological Survey, Denver, CO (USA)
2. Inst. of the Earth's Crust, Irkutsk (USSR)
3. Univ. of Texas, El Paso (USA)

An isostatic correction is commonly made to Bouguer anomaly gravity data to remove the gravity effect of isostatic compensation of topographic loads. In the USSR a decompensative correction has then been made to the isostatic gravity anomaly to remove the gravity effect of isostatic compensation of geologic loads as well. The authors employ here calculations in the wave number domain, leading to an efficient and exact solution. In a 1,200 {times} 1,200 km region centered on the Rio Grande rift the decompensative correction ranges from about {minus}35 to +25 mGal. The decompensative anomaly, highlights an arcuate gravity low and a system of gravity highs inferred to reflect prerift welts of mass concentration which have indirectly influenced the position of the rift and its segmentation and zones of accommodation. Under the assumptions made, if the decompensative anomaly is subtracted from the Bouguer anomaly, then the residual is the gravity anomaly field of deep structure, without gravity effects of shallow sources in the upper crust. Using available seismic data to (weakly) constrain the Moho surface, they invert the residual gravity field for topography of the base of the lithosphere. Lithosphere is found to be 200 km thick in the High Plains; 40-50 km in the eastern Great Basin; 75-100 km in the Colorado Plateau, and as thin as 40 km in the southern Rio Grande rift. In the area studied, the thickness of the lithospere is everwhere greater than that of the crust. The separation of gravity effects made possible by the decompensative correction shows how the rift is fundamentally controlled by thinning of the lithosphere, yet in detail is deflected by long-lived tectonic welts in the shallow, brittle crust.

• OSTI ID: 5387460
• Journal Information: Journal of Geophysical Research; (United States), Vol. 96:B4; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
RIO GRANDE RIFT
GEOMORPHOLOGY
BOUNDARY CONDITIONS
CALCULATION METHODS
CONTINENTAL CRUST
CORRECTIONS
DATA PROCESSING
DENSITY
DEPTH
EARTH MANTLE
GEOLOGIC STRUCTURES
GRAVITY SURVEYS
INTERFACES
SEISMIC SURVEYS
THICKNESS
TOPOGRAPHY
USSR
ASIA
DEVELOPED COUNTRIES
DIMENSIONS
EARTH CRUST
EUROPE
GEOLOGY
GEOPHYSICAL SURVEYS
PHYSICAL PROPERTIES
PROCESSING
SURVEYS
580000* - Geosciences