Abstract
In this study, gravity data has been used in conjunction with seismic data to map and model the structural and stratigraphic elements in and around Al Hagfa Trough of central Sirt Basin. 2D seismic data show that the erosion and truncation of pre-rift strata and the thinning and onlapping of syn-depositional sequences onto fault scarp suggest that the area has experienced rifting activities and erosion during basin evolution. The mapped fault zone attached to rifting is about 150 km long and is composed of three 45 – 50 km long normal planar segments. These segments are bounded on the east by an area of local gravity high (NW-SE orientation)
which results from low contrast between the Palaeozoic basement and Mesozoic - Cenozoic rocks and defines the Zaltan Platform structural trend. The western boundaries are marked by both gravity highs and lows which includes Al Bayda Platform and Al Hagfa Trough. The gravity minima are associated to longitudinal synclines or growth nuclei best explained by recognizing that it is a thick sequence of predominantly sedimentary wedges, including syn and post-sediments. Gravity modeling demonstrates the nature and structure of the mapped troughs and platforms, for a particular fault segments. Tilted segments can be observed also on the Bouguer and horizontal gradient maps. The southern portion of the fault block has a nearly N-S trend due to tilting. The mode of extension has important consequences for the Cretaceous hydrocarbon plays associated with the rifted province of Al Hagfa Trough. A breached relay ramp as evidenced from seismic and gravity data probably has a great influence on the hydrocarbon migration and entrapment in the study area.