Abstract
Recently an ambitious experiment combining deep seismic surveys from near-vertical and wide-angle acquisition methods was carried out in Brazil. The seismic lines are essentially coincident and crossed the Parnaiba Basin from west to east near latitude 5 degrees S. Here, the wide-angle reflection and refraction (WARR) and deep seismic reflection (DSR) results, which were previously interpreted independently, are compared by directly correlating WARR interfaces converted to TWTT with the major reflective horizons identified in the zero-offset image and by considering coincident reflectivity patterns displayed in both data sets. This integrated WARR and DSR analysis allowed a spatial association of the apparently acoustically featureless crust imaged in the DSR profile to the high reflectivity observed in the WARR data. Numerical tests and elastic modelling show that variations of the elastic properties of the crust, particularly as they are characterized by low Vp and Vs contrasts with a possible increase of the Vp/Vs ratio, can only weakly explain the observed reflectivity patterns but that fine-scale lithological heterogeneity within the crust is capable of replicating the observed contrasting seismic responses. The segment of the Parnaiba Basin crust that is characterized by fine-scale lithological heterogeneity lies directly above a mafic crustal underplate defined by the WARR model and was named as the Grajau domain on the basis of WARR-derived velocity model. The applied methodologies allow added value to be taken from the independent seismic data sets and provide new information about crustal structure that may have important implications for overlying intracontinental basin evolution.
Original language | English |
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Pages (from-to) | 1652-1664 |
Number of pages | 13 |
Journal | Geophysical Journal International |
Volume | 218 |
Issue number | 3 |
Early online date | 16 May 2019 |
DOIs | |
Publication status | Published - Sept 2019 |
Bibliographical note
ACKNOWLEDGEMENTSThe authors thank the two reviewers Randy Keller and Nicky White for their constructive and valuable comments and their careful revision of the manuscript. Marcus Vinicius Lima thanks the PBAP program for the availability of WARR and DSR data and for the postdoctoral fellowship (Project 5547: BP ENERGY/FUB/FINATEC—PARNAIBA BASIN REFRACTION EXPERIMENT) and also
thank the School of Geosciences from University of Aberdeen (specifically the Geophysics & Tectonics group of the Department of Geology and Petroleum Geology) for academic facilities
and advisory support provided during research fellowship activities. RAF acknowledges CNPq research grants (46.5613/2014-4, 30.1065/2016-0).
Keywords
- Composition and structure of the continental crust
- South America
- Controlled source seismology
- Crustal imaging
- Crustal structure
- CRATONIC BASIN
- REFRACTION
- BASEMENT
- GRAVITY
- BENEATH