CRUSTAL THICKNESS VARIATIONS IN THE SOUTHEASTERN MEDITERRANEAN REGION, INCLUDING NORTHEASTERN PART OF EGYPT, AS DEDUCED FROM 3D GRAVITY MODELING | ||
| Journal of Egyptian Geophysical Society | ||
| Volume 11, Issue 1, 2013, Pages 57-74 PDF (1.78 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jegs.2013.384996 | ||
| Author | ||
| S. Saleh | ||
| National Research Institute of Astronomy and Geophysics (NRIAG), 11421, | ||
| Abstract | ||
| Crustal thickness of the Southeastern Mediterranean Basin region, which extends from the off-shore northeastern part of Egypt (northern Sinai) to the southern part of Cyprus, was gravimetrically determined, using the 3D Bouguer data analysis. The gravity data have improved both the mass geometry and the density distribution in the 3-D calculated gravity profiles. The oceanic-continental boundary occurred beyond the North African continental margin, the basement relief (sedimentary section thickness) and the Moho depth maps were defined. The regional and residual Bouguer anomaly maps were also evaluated to show more detailed pictures for the deep and shallow structures. Generally, the regional field in the area under study is considered to be mainly influenced by the density contrast variations between the crust and the upper mantle. In the northern part of Egypt, the regional anomaly shows an increase from -30 to +40 mGal. This indicates that, the crustal thickness decreases towards the Mediterranean Sea. The residual negative anomalies with minimum values of -30 and -25 mGal in the Nile Delta and the Levantine Basin respectively, are due to their association with thick sedimentary covers, as well as the negative anomalies of -35 mGal around Southern Cyprus are related to the structures of the sedimentary sequences and the related basement relief geometry. The results also show the occurrence of thick continental crustal parts with a thickness of approximately 21 km in Northern Egypt and at least in some areas of Northern Sinai, covered by thin sediments. A few kilometers farther to the north, especially below the coastal parts regions, the thickness of crust decreases abruptly (transition zone). An inverse correlation between the sediment densities and the crustal thicknesses has been shown up from the study. Furthermore, our model reveals the existence of continental crustal zone below the Eratosthenes Seamount block, indicating a collision taken place between the African and Eurasian plates. Additionally, this block is in the process of actively subsiding, breaking-up and being thrusted beneath both Cyprus Island to the north and the Levantine Basin to the south. Whereas, the crustal type beneath the Levantine Basin is typically oceanic, this is covered by sedimentary sequences of more than 14 km thick. The gravity high of Cyprus, near the shear subduction zone, is possibly caused by varying combinations of ophiolites and thinning of sediments, as derived from the 3-D gravity modeling. The modeled Moho map shows a depth of 28-30 km below Cyprus and of 26-28 km beneath South Florence Rise to the northwest. However, the Moho lies at a constant shallow depth of 22 to 24 km below the Levantine Basin, which indicates thinning of the crust beneath this region. Finally, the Moho map reveals also a maximum depth of about 33-35 km beneath both Northern Egypt and Northern Sinai, with continental crust | ||
| Keywords | ||
| 3-D gravity modeling; Bouguer Map; Southeastern Mediterranean; Northern Egypt | ||
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