--> --> Reverse Magnetized Lava Dome Interpreted from 3-D Seismic, Gravity and Magnetic Data in the Turkish Black Sea

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Reverse Magnetized Lava Dome Interpreted from 3-D Seismic, Gravity and Magnetic Data in the Turkish Black Sea

Abstract

Introduction The Black Sea is an underexplored deep water basin with significant hydrocarbon potential. It evolved as a rift basin in a back-arc setting with subsequent compression events that added complexity to the structural setting. Shell acquired a recent 3D seismic survey along with gravity and magnetic data to pursue its exploration efforts in the region. The newly acquired data showed a basin centre dome like structure. Seismic and potential data were integrated to resolve its nature and origin. Method Different geological scenarios were investigated for this dome feature; like mud volcano/salt dome/”real” volcano. The magnetic data were analysed to estimate the depth to magnetic sources and 2D gravity/magnetic models were generated with various parameters; structural architecture, densities and susceptibilities to validate one geological scenario over the others. Results The Bouguer gravity data shows a moderate (2mGal) positive anomaly whereas the reduced to pole total magnetic intensity data indicates a large (-150nT) negative anomaly. The model suggests that the feature possesses slightly high density and very high magnetic susceptibility relative to the surrounding rocks. The negative magnetic anomaly can be modelled by a high Koenigsberger ratio with a large amount of remanent magnetized material which cooled down below Curie temperature at a time when the magnetic polarity was reversed. The gravity and magnetic models, integrated with the seismic interpretation, rule out mud volcanoes, salt and metamorphic rocks; and point to an igneous lava dome. Based upon geological knowledge of the area, the formation and cooling of the body below Curie temperature is estimated between late Cretaceous (Santonian) and Eocene. Paleomagnetic study shows a number of polar reversals during this period.