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AAPG Bulletin, V.
Burial history and thermal evolution of the southern and western Saharan basins: Synthesis and comparison with the eastern and northern Saharan basins
1Departement de Geologie Sedimentaire, Laboratoire de Stratigraphie, Universit Pierre et Marie Curie-Paris VI, Tour 15/16, 4ime tage, C 117-4, place Jussieu, 75252 Paris Cedex 05, France; present address: 35, place des saisons, Paris-La Dfense 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 obtained engineering and M.Sc. degrees 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 other Doctorates of Science 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 in 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 obtained engineering and M.Sc. degrees (1962) and his 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.
A quasi-two-dimensional analysis of burial history and thermal evolution was carried out along eight profiles for sedimentary sections in 24 wells in the southern and western Saharan basins with the aid of one-dimensional nonsteady numerical reconstructions. The modeling shows that thermal activation during the Permian–Triassic–Jurassic was most intense in the Timimoun basin and the northern part of the Ahnet and Mouydir basins, with a heat flow of about 70–80 mW/m2 and a lithosphere thickness of 40–50 km. Activation was more moderate in the Sbaa subbasin and Reggane basin, with a heat flow of approximately 63–67 mW/m2 and a crustal thickness of 55–60 km. These values are comparable to those for the eastern Saharan basins, where the intensity of the Triassic activation decreased considerably from north to south. The present-day thermal regime of the Ahnet and Reggane basins and the central part of the Timimoun basin is comparable to that of the Illizi basin, where the present-day lithosphere is as thin as 25 km, and recent volcanism has occurred. Moderate extension of the lithosphere with a maximum total amplitude of about 1.16 during the Cenozoic is assumed in our modeling in the Reggane basin and the southern half of the Timimoun basin, as well as in the central and eastern part of the Illizi basin. Thermal analysis of the Saharan basins has shown that the Hercynian erosion can account for only a minor part of the jumps observed in the vitrinite profiles (Ro). Intrusive activity and the associated hydrothermal heat transfer during the Triassic and Early Jurassic accurately explain the steplike character of maturation profiles in the Saharan basins. In particular, the lower level of catagenesis and conservation of oil deposits in the relatively hot Sbaa subbasin are the result of less-intensive hydrothermal-intrusive heating of the basin during the Jurassic as compared to that in neighboring basins. This could also be ascribed to a deeper location of the lithosphere and probably deeper intrusions in the Sbaa subbasin. This relatively moderate thermal regime of the Sbaa subbasin might be connected to its structural position of, as it was, a "shoulder" to neighboring deeper depressions.
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