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The Neoproterozoic basement of the Parnaíba Basin (NE Brazil) from combined geophysical-geological analysis: A missing piece of the western Gondwana puzzle
•New tectonic map of the Neoproterozoic basement of Phanerozoic Parnaiba basin.•Updated crustal thickness map of Parnaiba basin and new seismic interpretations.•Two main pre-Brasiliano inliers surrounded by mobile belts under the basin.•Mid-crustal reflectivity interpreted as a suture zone in centra...
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Published in: | Precambrian research 2022-09, Vol.379, p.106784, Article 106784 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | •New tectonic map of the Neoproterozoic basement of Phanerozoic Parnaiba basin.•Updated crustal thickness map of Parnaiba basin and new seismic interpretations.•Two main pre-Brasiliano inliers surrounded by mobile belts under the basin.•Mid-crustal reflectivity interpreted as a suture zone in central Parnaiba basement.•Two different pre-Silurian basin systems prior to Parnaiba basin sedimentation.
A regional Pre-Silurian unconformity marks the erosive planar base of the Phanerozoic Parnaíba Basin (PB), and indistinctly truncates key tectonic units for the understanding of the Neoproterozoic evolution of western Gondwana in northeastern Brazil. We present a comparative analysis of geophysical and geological datasets in the PB and propose a new tectonic configuration for its pre-Silurian basement, composed of different terranes amalgamated during the Brasiliano orogeny. Using integrated seismic interpretation and gravity modelling, constrained by an updated crustal thickness map, well data and a compilation of recent geophysical studies, we have identified two main blocks in the center of the basin. They represent pre-Brasiliano inliers, surrounded by Brasiliano mobile belts, and assigned to two major crustal building blocks of western Gondwana: the Amazonian-West Africa (AWB; to the west/north) and the Central African blocks (CAB; to the east/northeast). The Grajaú block belongs to the AWB and is characterized by low gravity anomaly, thicker crust (41–45 km), transparent seismic character of the basement and a high velocity lower crust. The Teresina block belongs to the CAB and is characterized by slightly thinner crust (39–41 km), higher values of gravity and magnetic anomalies and by the presence of mid-crustal reflectors (MCR), observed in seven seismic lines and here interpreted as a remnant of a paleosuture zone between the two blocks. Along a NE-SW 500-km seismic and gravity profile, we interpreted the MCR as composed of crustal-scale thrust faults verging westwards and defining the Barra do Corda belt, which was formed by the closure of the Goiás-Pharusian ocean along the Transbrasiliano-Kandi corridor and subsequent collision of the Grajaú and Teresina blocks. This belt deforms the eastern margin of the Ediacaran Riachão foreland basin (RB), observed in seismic and well data beneath the SW portion of PB and overlying the southern Grajaú block. The western margin of RB is bounded by eastwards verging thrust faults, interpreted as a zone of back-thrus |
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ISSN: | 0301-9268 1872-7433 |
DOI: | 10.1016/j.precamres.2022.106784 |