Tectonic Framework of Parecis Basin, Brazil

Abstract:

The Parecis basin is located in the Midwestern portion of Brazil, in the southeast sector of the Amazon Craton, between the basins of Solimões and Paraná, with an area of approximately 450,000 square kilometers. The basin is a frontier for exploration with complex geology and few studies about its origin and evolution. With three wells drilled between the 80s and 90s of last century combined with the modest exploratory efforts through potential and seismic reflection methods, the existing tectonic-sedimentary model can be further refined. As well as its sedimentary thickness is not well known, the two stratigraphic wells did not reach its basement. It is known as a Palaeozoic basin, but recent reinterpretation of old and new stratigraphic wells as well as new geophysical data such as seismic, lead to a suggestion for a Mesoproterozoic basin.

New and old gravity and magnetic data, aero and ground, are processed and interpreted aiming to contribute on the tectonic framework of this basin. The objectives are achieved by mapping the subsurface structures and crustal domains besides depth estimation for the basement.

Matched filtering was applied on gravity and magnetic data and permited the interpretation for 3 interfaces for both methods. Mean sedimentary thickness is, approximately, 6 km deep, an intermediate depth is observed at 15 km, and deeper layer is at 41 km for gravity and 26 km for magnetic data. We interpret the 41 km as Moho with is in accordance with receiver function results for region. We believe the 26 km for magnetic data may represent the Curie depth although more investigation is necessary about this interface.

Tilt depth and Euler deconvolution were applied for sedimentary thickness estimates; in general, the basement is deeper than the maximum values presented in previous works. According to the results of these methods basement is as deep as 12 km in some of the grabens.