Changes

North Africa experienced several stages of alternating passive margin (e.g., Devonian, Carboniferous) and rift settings, related to different geodynamic events (e.g., effects of the Tethys opening in late Paleozoic) which recurred in this area. Rift and passive margin stages are commonly separated by local or regional compressional events (e.g., Cretaceous) with reactivation/inversion of extensional structures (Boote et al., 1998). Favorable environmental conditions controlled the deposition of major source rocks, such as the Hot Shale during the Silurian. This unit reflects the environmental changes (warming and sea-level rise) that postdated the Ordovician glaciations (Figure 3). The history of repeated rifting, sag stage, and folding favored the creation of a large number of stratigraphic and tectonic traps that store, at different stratigraphic levels, several giant fields.<ref name=Booteetal_1998>Boote, D., Clark-Lowes, D., and Traut M., 1998, Palaeozoic petroleum systems of North Africa, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 7–68.</ref> <ref name=Macgregor_1998>Macgregor, D., 1998, Giant fields, petroleum systems, and exploration maturity of Algeria, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 79–96.</ref> The presence of a wide, shallow-water shelf in an arid environment (Triassic-Jurassic) led to the deposition of thick and widespread salt layers, which represent an effcient seal at the regional scale.<ref name=Booteetal_1998 />

North Africa experienced several stages of alternating passive margin (e.g., Devonian, Carboniferous) and rift settings, related to different geodynamic events (e.g., effects of the Tethys opening in late Paleozoic) which recurred in this area. Rift and passive margin stages are commonly separated by local or regional compressional events (e.g., Cretaceous) with reactivation/inversion of extensional structures (Boote et al., 1998). Favorable environmental conditions controlled the deposition of major source rocks, such as the Hot Shale during the Silurian. This unit reflects the environmental changes (warming and sea-level rise) that postdated the Ordovician glaciations (Figure 3). The history of repeated rifting, sag stage, and folding favored the creation of a large number of stratigraphic and tectonic traps that store, at different stratigraphic levels, several giant fields.<ref name=Booteetal_1998>Boote, D., Clark-Lowes, D., and Traut M., 1998, Palaeozoic petroleum systems of North Africa, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 7–68.</ref> <ref name=Macgregor_1998>Macgregor, D., 1998, Giant fields, petroleum systems, and exploration maturity of Algeria, in D. Macgregor, R. Moody, and D. Clark-Lowes, eds., Petroleum geology of North Africa: GSL Special Publication 132, p. 79–96.</ref> The presence of a wide, shallow-water shelf in an arid environment (Triassic-Jurassic) led to the deposition of thick and widespread salt layers, which represent an effcient seal at the regional scale.<ref name=Booteetal_1998 />

If in North Africa the basins are mainly related to rift basins followed by passive margin, the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia led to the formation of a major concentration of giant fields along the northern passive margin of the peri-Gondwanan blocks and in the overlying peripheral basins related to their collision. In the southern Caspian Sea area, the giant fields are mainly stored in collision-related basins<ref name=Mannetal_2003 /> whose origin was controlled by the docking of the peri-Gondwanan along the southern margin of Eurasia (e.g., Cimmerian orogeny). A similar origin is suggested for the Northern Caucasus Basins,<ref name=Mannetal_2003 /> whereas a complex history (from cratonic backarc extension and rifting followed by a sag basin stage) is recorded in the Pricaspian Basin.<ref name=Weberetal_2003>Weber, L. J., Francis, B. P., Harris, P. M., and Clark, M., 2003, Stratigraphy, facies, and reservoir distribution, Tengiz Field, Kazakhstan, in W. M. Ahr, P. M. Harris, W. A. Morgan, and I. D. Somerville, eds., Permo- Carboniferous carbonate platforms and reefs: SEPM Special Publication 78 and AAPG Memoir 83, p. 351–394.</ref>

If in North Africa the basins are mainly related to rift basins followed by passive margin, the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia led to the formation of a major concentration of giant fields along the northern passive margin of the peri-Gondwanan blocks and in the overlying peripheral basins related to their collision. In the southern Caspian Sea area, the giant fields are mainly stored in collision-related basins<ref name=Mannetal_2003 /> whose origin was controlled by the docking of the peri-Gondwanan along the southern margin of Eurasia (e.g., Cimmerian orogeny). A similar origin is suggested for the Northern Caucasus Basins,<ref name=Mannetal_2003 /> whereas a complex history (from cratonic backarc extension and rifting followed by a sag basin stage) is recorded in the Pricaspian Basin.<ref name=Weberetal_2003>Weber, L. J., Francis, B. P., Harris, P. M., and Clark, M., 2003, Stratigraphy, facies, and reservoir distribution, Tengiz Field, Kazakhstan, in W. M. Ahr, P. M. Harris, W. A. Morgan, and I. D. Somerville, eds., Permo- Carboniferous carbonate platforms and reefs: SEPM Special Publication 78 and [http://store.aapg.org/detail.aspx?id=868 AAPG Memoir 83], p. 351–394.</ref>

In the Arabian peninsula, Mann et al.<ref name=Mannetal_2003 /> identified three basin types preserving giant fields: continent–continent collision for the elongate fields along the Zagros Mountain front; passive margin basins of the southern shore of the Neo-Tethys (central Arabian peninsula and Persian Gulf area); and continental rifts with overlying sag basins on the eastern Arabian Peninsula. Source rocks and reservoirs are present at different stratigraphic levels, reflecting a complex interaction of depositional and tectonics events.<ref name=Foxandahlbrandt_2002>Fox, J. E., and Ahlbrandt, T. S., 2002, Petroleum geology and total petroleum systems of the Widyan Basin and Interior Platform of Saudi Arabia and Iraq: USGS Bulletin 2202-E, http://geology.cr.usgs.gov/pub/bulletins/b2202-e.</ref> <ref name=Pollastro_2003>Pollastro, R. M., 2003, Total petroleum systems of the Paleozoic and Jurassic, Greater Ghawar Uplift and adjoining provinces of Central Saudi Arabia and Northern Arabian-Persian Gulf: USGS Bulletin 2202-H, http://pubs.usgs.gov/bul/b2202-h.</ref>

In the Arabian peninsula, Mann et al.<ref name=Mannetal_2003 /> identified three basin types preserving giant fields: continent–continent collision for the elongate fields along the Zagros Mountain front; passive margin basins of the southern shore of the Neo-Tethys (central Arabian peninsula and Persian Gulf area); and continental rifts with overlying sag basins on the eastern Arabian Peninsula. Source rocks and reservoirs are present at different stratigraphic levels, reflecting a complex interaction of depositional and tectonics events.<ref name=Foxandahlbrandt_2002>Fox, J. E., and Ahlbrandt, T. S., 2002, Petroleum geology and total petroleum systems of the Widyan Basin and Interior Platform of Saudi Arabia and Iraq: USGS Bulletin 2202-E, http://geology.cr.usgs.gov/pub/bulletins/b2202-e.</ref> <ref name=Pollastro_2003>Pollastro, R. M., 2003, Total petroleum systems of the Paleozoic and Jurassic, Greater Ghawar Uplift and adjoining provinces of Central Saudi Arabia and Northern Arabian-Persian Gulf: USGS Bulletin 2202-H, http://pubs.usgs.gov/bul/b2202-h.</ref>