INITIAL FORENSIC GEOLOGY MODEL OF SOUTHERN MID-CONTINENT RIFT

In the Southern Mid-Continent Rift (SMCR) area I built a representative regional 3D geology model and an expected density distribution as a proxy for the Earth’s in situ density distribution. All observed gravity data is the result of measuring the gravity field of the in situ density distribution. The free air anomaly (Faye) of the Southern Mid-Continent Rift (SMCR) region shows complex in situ density distribution (geology). For example, there are areas of positive Faye gravity coincident with the south extension of the SMCR from central Kansas into the 14,000 meter deep Anadarko Basin in southern Oklahoma, while the 12,000 meter deep Arkoma Basin in southeastern Oklahoma and southwestern Arkansas shows an expected negative Faye anomaly of a basin. The modeled (expected) Faye gravity at each gravity station location is calculated using this 3D geology model of the SMCR area from the topographic surface to 100 km below mean sea level including expected geology boundaries within the sedimentary and crystalline basement, deep crust, and mantle. The initial 3D sedimentary model is based on the geology interpretation published in the AAPG, Petroleum Geology of the Mid-Continent Atlas. The atlas represents the sedimentary geology and structure of the Southern Mid-Continent region as a sequence of isopach maps. My initial regional geology model does not fully reflect the complexity of the in situ structure or density distribution; though it is in close elevation agreement with local small scale well log based 3D geology models. This initial regional geology model is a reasonable framework to test interpretation hypotheses using Bayesian inversion techniques. I recover the estimated Faye gravity and rock densities along with their goodness of fit. The residual, between the observed and estimated gravity holds insight to where the geology model warrants geologic study and updating. This initial 3D geology model is the base of a “living” interpretation where updating the model is a recursive process allowing piecewise updating of the interpretation with new geologic insight, geophysical data, or to test alternative 3D geology interpretations.