Changes

The giant fields of North Africa, Arabia, and the Middle East reflect episodes of enhanced primary productivity with high export production and storage of this organic matter in the sedimentary successions of different types of sedimentary basins.

The giant fields of North Africa, Arabia, and the Middle East reflect episodes of enhanced primary productivity with high export production and storage of this organic matter in the sedimentary successions of different types of sedimentary basins.

The factors that control primary productivity are light intensity, nutrient inputs (nitrate and phosphate), and climate.<ref name=Begonetal_1996>Begon, M., Harper, J. L., and Townsend, C. R., 1996, Ecology. Individuals, Populations and communities: Blackwell Scientific Publications, 1088 p.</ref> Today maximum productivity in the oceans is recorded on the inner shelf of the continental platforms and in ocean upwellings because of high nutrient concentration and relatively clear water.<ref name=Barnesandhughes_1982>Barnes, R. S. K., and Hughes, R. N., 1982, An introduction to marine ecology: Blackwell Scientific Publications.</ref> The paleogeographic configurations of the late Paleozoic-Mesozoic time interval is dominated by E-W oceans, particularly in North Africa, Arabia, and the Middle East, where they extended mainly from the equator to the tropics; indeed, for most of this interval the Tethyan Seaway was present at very low latitudes north of Africa and Arabia, indenting the Pangea supercontinent. Paleocurrent models for a general Pangea configuration (e.g., Kutzbach et al., 1990; Kiessling et al., 1999; Winguth et al., 2002, 2005) envisage a westward-flowing equatorial surface current which, upon reaching the continental shelves of the western Tethys Seaway, deflected southeastward and northeastward; in the meanwhile, a deep water circulation brought cold waters from high latitudes to the equator. Ocean upwellings of these cold and nutrient-rich bottom waters were created by monsoonal wind circulation<ref name=Crowleyetal_1989>Crowley T. J., Hyde, W. T., and Short, D. A., 1989, Seasonal cycle variation on the supercontinent of Pangaea: Geology, v. 17, p. 457–460.</ref> <ref name=Parish_1993>Parrish, J. T., 1993, Climate of the supercontinent Pangaea: Journal of Geology, v. 101, p. 215–233.</ref> <ref name=Peyserandpoulsen_2008>Peyser, C. E., and Poulsen, C. J. 2008, Controls on Permo-Carboniferous precipitation over tropical Pangaea: A GCM sensitivity study: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 268, p. 181–192.</ref> along the Gondwanan margin and in the lee of continental blocks scattered in the Paleo- and Neo-Tethys, as well as at the equatorial divergence zone.

The factors that control primary productivity are light intensity, nutrient inputs (nitrate and phosphate), and climate.<ref name=Begonetal_1996>Begon, M., Harper, J. L., and Townsend, C. R., 1996, Ecology. Individuals, Populations and communities: Blackwell Scientific Publications, 1088 p.</ref> Today maximum productivity in the oceans is recorded on the inner shelf of the continental platforms and in ocean upwellings because of high nutrient concentration and relatively clear water.<ref name=Barnesandhughes_1982>Barnes, R. S. K., and Hughes, R. N., 1982, An introduction to marine ecology: Blackwell Scientific Publications.</ref> The paleogeographic configurations of the late Paleozoic-Mesozoic time interval is dominated by E-W oceans, particularly in North Africa, Arabia, and the Middle East, where they extended mainly from the equator to the tropics; indeed, for most of this interval the Tethyan Seaway was present at very low latitudes north of Africa and Arabia, indenting the Pangea supercontinent. Paleocurrent models for a general Pangea configuration<ref name=Kutzbachetal_1990>Kutzbach, J. E., Guetter, P. J., and Washington, W. M., 1990, Simulated circulation of an idealized ocean for Pangaean time: Paleoceanography, v. 5, p. 299–317.</ref> <ref name=Kiesslingetal_1999>Kiessling, W., Flügel, E., and Golonka, J., 1999, Paleoreef maps: Evaluation of a comprehensive database on Phanerozoic reefs: AAPG Bulletin, v. 83, p. 1552–1587.</ref> <ref name=Winguthetal_2002>Winguth, A. M. E., Heinze, C. Kutzbach, J. E., Maier-Reimer, E., Mikolajewicz, U., Rowley, D., Rees, A., and Ziegler, A. M., 2002, Simulated warm polar currents during the middle Permian: Paleoceanography, v. 17, no. 4, p. 1057, doi:10.1029/2001PA000646.</ref> envisage a westward-flowing equatorial surface current which, upon reaching the continental shelves of the western Tethys Seaway, deflected southeastward and northeastward; in the meanwhile, a deep water circulation brought cold waters from high latitudes to the equator. Ocean upwellings of these cold and nutrient-rich bottom waters were created by monsoonal wind circulation<ref name=Crowleyetal_1989>Crowley T. J., Hyde, W. T., and Short, D. A., 1989, Seasonal cycle variation on the supercontinent of Pangaea: Geology, v. 17, p. 457–460.</ref> <ref name=Parish_1993>Parrish, J. T., 1993, Climate of the supercontinent Pangaea: Journal of Geology, v. 101, p. 215–233.</ref> <ref name=Peyserandpoulsen_2008>Peyser, C. E., and Poulsen, C. J. 2008, Controls on Permo-Carboniferous precipitation over tropical Pangaea: A GCM sensitivity study: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 268, p. 181–192.</ref> along the Gondwanan margin and in the lee of continental blocks scattered in the Paleo- and Neo-Tethys, as well as at the equatorial divergence zone.

The combination of extended continental platforms in the proximity of a nutrient-delivering supercontinent and developed ocean upwellings caused the increase of primary productivity during favorable climate conditions, particularly at low latitudes where light intensity was higher and rate of mineralization (hence greater nutrient supply) more rapid. Storage of increased production as organic matter in the sediments was in turn enhanced by high sedimentation rates and availability of accommodation space.

The combination of extended continental platforms in the proximity of a nutrient-delivering supercontinent and developed ocean upwellings caused the increase of primary productivity during favorable climate conditions, particularly at low latitudes where light intensity was higher and rate of mineralization (hence greater nutrient supply) more rapid. Storage of increased production as organic matter in the sediments was in turn enhanced by high sedimentation rates and availability of accommodation space.