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AAPG Bulletin, V.
Burial history and thermal evolution of the northern and eastern Saharan basins
1Departement de Geologie Sedimentaire, Universit Pierre et Marie Curie, Paris VI Tour 15/16, 4ime tage, C 117, 4, place Jussieu, Paris Cedex 05, France; present address: 35, Place des saisons, La Dfence 1, 92400 Courbevoie, France; email: [email protected]
2Museum of the Earth Sciences, Moscow State University, Vorobjevy gory, 119 899, Moscow, Russia; email: [email protected]
Monzer Makhous has an engineering degree and an M.Sc. degree in geochemistry (1969), a Ph.D. in geochemistry and mineral resources (1974), and a Doctor of Science in petroleum production (1993) from Moscow (Lomonosov) State University. He was awarded two Doctorate of Sciences: in petroleum exploration from Strasbourg University (1996) and in universe sciences from Paris (Sorbonne) University, as well as a habilitation for research direction (2002). He worked on the sedimentology and geochemistry of the Mesopotamia basin (Iraq, Syria) in the Middle East from 1969 to 1974. From 1975 to 1991, he worked for Sonatrach on the Saharan basins as a senior geochemist/sedimentologist at the Center of Research and Development. From 1996 to 2000 he contributed to the Peri-Tethys program within the group of Paris University. Currently, he is conducting integrated basin studies at Paris University. His interests include diagenesis, geochemistry, geodynamics, and integrated studies on sedimentary basins.
Yurii Galushkin has engineering and M.Sc. degrees (1962) and a Ph.D. (1971) in physics and mathematics from the Moscow Physical-Technical Institute. Since 1975, he has worked at Moscow State University in the Department of Geophysics. Currently, he is working at the Earth Science Museum of Moscow University. His principal fields of interest are lithosphere geothermics (computer programs on temperature distribution in continental and oceanic lithosphere, continental rifting, and oceanic ridge spreading processes) and basin modeling problems.
We gratefully thank P. K. Webb, M. K. Horn, J. Thomas (AAPG Science Director), and R. Erickson for their careful and constructive reviews, which considerably improved the manuscript. P. K. Webb's editing style was particularly helpful to improve the text.
The numerical one-dimensional reconstruction of the burial history and thermal evolution of the sedimentary section and basement was conducted for 32 wells in the East Algerian basins with the help of the Galo basin-modeling system. These reconstructions allowed the performance of a quasi-two-dimensional analysis of the burial history of the basins, changes in rock temperatures, the lithosphere thickness, and maturation conditions of organic matter during basin development along the four profiles crossing the study region. The modeling assumed that the highest thermal activation in the history of the Saharan basins, with the heat flow more than 100 mW/m2 and the thinnest lithosphere on the order of 25–35 km, took place during the Late Carboniferous to Permian in the Dahar and Oued el-Mya basins. The uplift responsible for this activation caused erosion of 2000–3000 m of Ordovician to Lower Carboniferous strata. The Ghadames and Illizi basins were subjected at the same time to more moderate erosion and thermal activation with heat flow less than 75 mW/m2. In the Triassic–Cretaceous interval, maximum subsidence occurred in the northern areas, which were characterized by maximal thermal activation and the thinnest lithosphere in the Permian. At present, the situation is opposite to that in the Permian: the highest thermal regime occurs in the southern areas of the study region and especially in the Illizi basin, where heat flow reaches and even exceeds 100 mW/m2, and the thickness of the lithosphere decreases as much as 30 km. The modeling also assumes stretching of the lithosphere in the northeastern and central parts of the Illizi basin, with maximal amplitude of about 1.16 during the Cenozoic. The analysis shows that the Hercynian erosion could account for only a few of the abrupt changes in vitrinite profiles in the Saharan basins and that Triassic and later intrusive activity and associated hydrothermal heat transfer accurately explain the steplike character of maturation profiles.
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