Utility of Gravity and Magnetic Data for Mapping Phanerozoic Faults, Fractures, Folds, and Facies Transitions Caused by Reactivation of Precambrian Basement Structures
Joseph M. Kruger. Lamar University, Department of Earth and Space Sciences, Beaumont, Texas [email protected]
Regional gravity and magnetic maps have proven extremely useful for determining the Precambrian structural framework of the midcontinent. This is particularly true when these maps are combined with other geological and geophysical data such as deep well control and seismic data. In this study, the gravity and magnetic maps of Kansas are integrated with maps from previous geologic studies, well control, and oil and gas field outlines using GIS software. An interpretation of the gravity and magnetic anomalies using this method show a remarkable correlation with geologic trends and boundaries in both the Precambrian basement and Phanerozoic strata, as well as trends in numerous oil and gas fields.
It is believed that the excellent correlation between the gravity, magnetic, and Precambrian geologic data is due to the density and magnetic susceptibility differences between various Proterozoic igneous, metamorphic, and sedimentary rocks created, deposited, and deformed in the Central Plains orogen, Southern Granite-Rhyolite Province, and southern midcontinent rift system. Relatively steep gravity and magnetic gradients form along major boundaries between these lithologies, indicating the location of faults, shear zones, and intrusive margins.
Deformation of the midcontinent since the Proterozoic has been relatively subtle, so reactivation of these Precambrian structures, and differential compaction over Precambrian paleotopography, can have a dramatic impact on the formation of faults, folds, and fractures in the relatively flat-lying Phanerozoic cover. In addition, subtle topographic differences due to differential uplift or subsidence of a gently sloping continental platform can have a dramatic effect on carbonate and clastic depositional facies. Therefore, reactivated basement structures are also likely candidates for Phanerozoic facies boundaries, which can create stratigraphic traps and control the location of good reservoirs.
AAPG Search and Discover Article #90067©2007 AAPG Mid-Continent Section Meeting, Wichita, Kansas