Print this pageAbstract: A Buried Rift Beneath the Western Paraná Basin, Brazil?
Vidotti, R. M.; C. J. Ebinger and J. D. Fairhead - University of Leeds
The Paraná basin is a huge intracratonic sedimentary basin (1,700,000 km2) filled with sedimentary and volcanic rocks (Ordovician - Cretaceous), but its subsurface is not well known. The Bouguer map of the basin is characterized by two gravity lows (>-100 mGal) in the eastern and western portions with a relative high in it center (-50 mGal). The characteristics of the N-S oriented western gravity lows, which are narrow and bounded by steep gradients, suggests a shallow source structure. Depth estimates from log power spectra of Bouguer anomalies for the western Paraná basin indicate shallow depth between 7.4 and 4 km interpreted as the basement depth beneath the sediments and volcanic rocks, with an increase in depth relative to the gravity low. Forward modeling (2.5 D) of two profiles across the N-S-trending western gravity low show that the low can be explained by shallow, steeply dipping structures, bounding what we suggest to be a rift basin of unknown age buried beneath the Cretaceous flood basalts and widespread Paleozoic-Mesozoic sequences. The results are compared to Paleozoic-Mesozoic rift basins in Brazil, North Sea and Central Africa with similar gravity signatures and better subsurface control. Coherence analyses of Paraná basin and surrounding regions allow us to suggest possible models for its thermal evolution.
AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil