Gravity signature of the western Parana Basin, Brazil

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doi: 10.1016/S0012-821X(98)00070-3
Authors:Vidotti, R. M.; Ebinger, C. J.; Fairhead, J. D.
Author Affiliations:Primary:
University of Leeds, Department of Earth Sciences, Leeds, United Kingdom
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 159(3-4), p.117-132. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:1998
Note:In English. Includes an appendix. 36 refs.; illus., incl. sketch maps
Summary:Volcanism in the Parana basin, one of the largest continental flood basalt provinces on Earth, was contemporaneous with the Early Cretaceous opening of the South Atlantic Ocean. Problematic is the lack of crustal extension associated with this flood basalt event, although three Palaeozoic-Jurassic extensional episodes have been reported in parts of the basin. Gravity measurements at 185 new stations were established to constrain the geometry and magnitude of Bouguer anomalies that characterise the poorly understood western portion of the Parana basin, and to interpret new and existing data in light of its poly-phase extensional history. The Bouguer map of the Parana basin is characterised by two gravity lows (up to -100 mGal) in the eastern and western portions with a relative high in its centre (around -50 mGal). The spectral characteristics of the N-S-oriented western gravity lows and flanking regions suggest density contrasts at 7.4-4 km, which we interpret as variable depth to basement beneath the Palaeozoic-Cretaceous sedimentary and Cretaceous volcanic rocks. Forward modelling (2.5 D) of two profiles across the N-S-trending western gravity low shows that the low can be explained by shallow, steeply deepening structures, bounding what we believe to be a rift basin buried beneath the Mesozoic flood basalts and sedimentary strata. Comparison with other gravity data, heat flow, contour maps of crustal extension, basement and structural maps all support our interpretation of a pre-Cretaceous rift basin. We also compare our results to Palaeozoic-Mesozoic rift basins in Brazil, the North Sea and Central Africa with similar gravity signatures and better subsurface control. These comparisons also support a 3-5 km-deep, thick rift sequence beneath the western Parana basin sequences. Abstract Copyright (1998) Elsevier, B.V.
Sections:Physical properties of rocks and minerals
Subjects:Basalts; Basins; Bouguer anomalies; Continental crust; Crust; Flood basalts; Geophysical methods; Geophysical surveys; Gravity anomalies; Gravity methods; Heat flow; Igneous rocks; Mapping; Rifting; Surveys; Volcanic rocks; Brazil; Parana Basin; South America
Abstract Numbers:99M/1080
Record ID:1998044232
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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