Fault pattern delineation and structural interpretation of the Gafsa trough (onshore central Tunisia) using gravity data
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ORIGINAL PAPER
Fault pattern delineation and structural interpretation of the Gafsa trough (onshore central Tunisia) using gravity data Mohamed Dhaoui & Hakim Gabtni
Received: 18 June 2011 / Accepted: 29 September 2011 / Published online: 13 October 2011 # Saudi Society for Geosciences 2011
Abstract The purpose of this investigation was to identify subsurface lineaments in Gafsa trough (onshore central Tunisia) after gravity data analysis. The Bouguer and residual gravity maps show a gravity values decrease from west to east associated with subsidence variation and confirmed by a regional seismic reflection profile. The deep structural map of the study area is elaborated after the application of two methods: (1) the automatic lineament tracing after horizontal gravity gradient and (2) 3D Euler method. The dominant trends show approximately NW–SE, E–W, and NE–SW directions. Some of these trends are well correlated with the major faults systems. We can qualify the deep structuration model as a mosaic of quadratic blocks bounded by significant deep flower fault corridors. The elaborated structural map of the study area constitutes also a useful document for rationalizing the future petroleum exploration in the Gafsa trough. Keywords Tunisia . Gafsa . Gravity . HGM method . Delineation . Structural . Quadratic blocks . Petroleum implications
Introduction Gravity data have been traditionally thought of as regional screening tools capable of providing basin definitions and basement mapping. However, in recent years, the application of potential field data has been greatly expanded to include global palaeotectonic modeling through to modelM. Dhaoui : H. Gabtni (*) Laboratoire de Géoressources, Centre de Recherches et des Technologies des Eaux, Technopôle Borj-Cedria, B.P. 73, 8020 Soliman, Tunisia e-mail: [email protected]
ing of prospect-level targets. One of the most important phases of any exploration screening program, particularly, in areas that lack seismic and well data, is the integration of potential field data with various geological datasets to define structural elements, continental block outlines, and crustal types, with the aim of producing a detailed, digital structural and geological coverage. The Gafsa trough sedimentary basin is a frontier area for petroleum exploration, with limited seismic coverage and only two deep exploration wells. Gravity surveys were conducted to assist with the structural interpretation of the basin. An evenly spaced grid of potential field data provided relatively cheap structural information, compared with the cost of acquiring seismic data, and an opportunity to test the relative effectiveness of gravity in a sedimentary basin. Gravity anomalies provide reliable definition of the structures at basement level and within the sedimentary sequence. As with all geophysical interpretation, the analysis of gravity data has two distinct aspects: qualitative and quantitative. The qualitative process is largely map-based and dominates the early stages of a study. The resultant pr
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