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In the Tethys region, the evolution of North Africa and the Arabian Plates are intimately involved with the occurrence of hydrocarbons in both regions. In the Early Paleozoic, paleogeography was characterized by the breakup of Rodinia and by the re-arrangement of the major continental plates in the Pangea supercontinent. During the assemblage of Pangea, a major role was played by the transformation from Pangea B to Pangea A during Permian time by means of dextral motion of Laurasia relative to Gondwana, which changed the relative position of the Paleozoic and Mesozoic domains facing the east-west oriented Tethys Gulf.<ref name=Muttonietal_2009a /> <ref name=Muttonietal_2009b />

In the [[Tethys region]], the evolution of North Africa and the Arabian Plates are intimately involved with the occurrence of [[hydrocarbon]]s in both regions. In the Early Paleozoic, [[paleogeography]] was characterized by the breakup of Rodinia and by the re-arrangement of the major continental plates in the [[Pangea]] supercontinent. During the assemblage of Pangea, a major role was played by the transformation from Pangea B to Pangea A during Permian time by means of dextral motion of Laurasia relative to Gondwana, which changed the relative position of the [[Paleozoic]] and [[Mesozoic]] domains facing the east-west oriented Tethys Gulf.<ref name=Muttonietal_2009a /> <ref name=Muttonietal_2009b />

Since late Paleozoic time, the southern margin of the Tethys was affected by the time-transgressive opening of the Neo-Tethys, which gave origin to a complex mosaic of peri-Gondwanan terranes. They gradually collided, during Mesozoic and Cenozoic times, with the northern margin of the Tethys, as the oceanic lithosphere of the Paleo-Tethys Ocean was subducted below Laurasia. Collisions were distributed irregularly along the northern margin of the Tethys. The spreading of the Neo-Tethys balanced the subduction of the oceanic lithosphere along the northern margin of the Paleo-Tethys, preserving the Tethys Ocean until the beginning of Cenozoic time. The subduction of the Paleo-Tethys led to the accretion of microplates that today characterize the Middle East outside of Arabia. Accretion started in Triassic time with the Cimmerian orogeny and persisted up to today, with the collision of Arabia along the Zagros suture. The present day relationships among orogenic belts are further complicated by the presence of important strike-slip movements, which accommodated the different convergence rates among plates, from the Alps to the Himalayas.

Since late Paleozoic time, the southern margin of the Tethys was affected by the time-transgressive opening of the Neo-Tethys, which gave origin to a complex mosaic of peri-Gondwanan terranes. They gradually collided, during Mesozoic and [[Cenozoic]] times, with the northern margin of the Tethys, as the oceanic lithosphere of the Paleo-Tethys Ocean was subducted below Laurasia. Collisions were distributed irregularly along the northern margin of the Tethys. The spreading of the Neo-Tethys balanced the subduction of the oceanic lithosphere along the northern margin of the Paleo-Tethys, preserving the Tethys Ocean until the beginning of Cenozoic time. The subduction of the Paleo-Tethys led to the accretion of microplates that today characterize the Middle East outside of Arabia. Accretion started in [[Triassic]] time with the Cimmerian [[orogeny]] and persisted up to today, with the collision of Arabia along the Zagros suture. The present day relationships among orogenic belts are further complicated by the presence of important [[strike]]-slip movements, which accommodated the different convergence rates among plates, from the Alps to the Himalayas.

The Mesozoic and Cenozoic evolution of the Tethys Oceans was also affected by the plate reorganizations caused by the breakup of Pangea. The opening of the Atlantic Ocean further complicated the geodynamic settings of the Laurasian and Gondwanan margins due to the changes in stress fields during different stages that characterized the breakup of Pangea. In particular, the movement and rotation of Africa, controlled by the opening of the central and southern Atlantic oceans, heavily controlled the relative motions among the numerous plates (which suffered alternatively both extensional and compressional tectonic regimes) in the Tethys. The present-day setting of south Mediterranean and Middle East regions is therefore the result of the global reorganization derived from the closure of the Tethys Ocean(s) and the time-transgressive opening of the Atlantic Ocean.

The Mesozoic and Cenozoic evolution of the Tethys Oceans was also affected by the plate reorganizations caused by the breakup of Pangea. The opening of the Atlantic Ocean further complicated the geodynamic settings of the Laurasian and Gondwanan margins due to the changes in stress fields during different stages that characterized the breakup of Pangea. In particular, the movement and rotation of Africa, controlled by the opening of the central and southern Atlantic oceans, heavily controlled the relative motions among the numerous plates (which suffered alternatively both extensional and compressional tectonic regimes) in the Tethys. The present-day setting of south Mediterranean and Middle East regions is therefore the result of the global reorganization derived from the closure of the Tethys Ocean(s) and the time-transgressive opening of the Atlantic Ocean.

Different and sometimes incompatible reconstructions exist for some intervals and, as data can be either contradictory and/or scarce, it is frequently a matter of interpretation which of several alternative reconstructions should be favored, and which should be discarded. For these reasons, paleogeographic maps should always be viewed as a work in progress, and should be continually revised and reconsidered in the light of new data. Also, differences mainly increase with the detail of the maps. Therefore, the maps presented here constitute just one of the possible solutions and do not aim to represent definitive paleogeographic reconstructions. In our opinion, these maps generally honor the available data, which mainly summarize long, complex, and multidisciplinary studies from regions that are not always easily accessible (sometimes for political reasons).

Different and sometimes incompatible reconstructions exist for some intervals and, as data can be either contradictory and/or scarce, it is frequently a matter of interpretation which of several alternative reconstructions should be favored, and which should be discarded. For these reasons, paleogeographic maps should always be viewed as a work in progress, and should be continually revised and reconsidered in the light of new data. Also, differences mainly increase with the detail of the maps. Therefore, the maps presented here constitute just one of the possible solutions and do not aim to represent definitive paleogeographic reconstructions. In our opinion, these maps generally honor the available data, which mainly summarize long, complex, and multidisciplinary studies from regions that are not always easily accessible (sometimes for political reasons).

The distribution of giant oil and gas fields in North Africa, Arabia, and the Middle East is the result of the interplay between the paleogeography of oceanic and continental areas, which favored the creation of source rocks, and the geodynamic evolution of Pangea and the Tethys Oceans during the Phanerozoic. There is a range of different basin types, with a dominance of rift and sag basins, passive margin basins, and collision-related basins, often evolving from one type to another. The interplay between sedimentation and tectonics controlled both basin development and post-depositional deformation, favoring the creation of a large number of structural and stratigraphic traps that store a significant percentage of the world’s oil and gas reserves.

The distribution of giant oil and gas fields in North Africa, Arabia, and the Middle East is the result of the interplay between the [[paleogeography]] of oceanic and continental areas, which favored the creation of source rocks, and the geodynamic evolution of Pangea and the Tethys Oceans during the [[Phanerozoic]]. There is a range of different basin types, with a dominance of rift and sag basins, passive margin basins, and collision-related basins, often evolving from one type to another. The interplay between sedimentation and [[tectonic]]s controlled both basin development and post-depositional deformation, favoring the creation of a large number of structural and [[stratigraphic trap]]s that store a significant percentage of the world’s oil and gas reserves.

==Paleogeographic reconstructions==

==Paleogeographic reconstructions==

Paleogeographic maps have been reconstructed for selected time intervals: Cambrian, Late Ordovician, Early Devonian, Early Permian, Permian-Triassic boundary, Norian, Callovian, Aptian, Cretaceous-Cenozoic boundary, and Late Eocene. For each time interval both the general picture of the major plate tectonic configuration and a detail of the paleogeography and paleoenvironment of North Africa to the Middle East are presented. On these maps, the major paleoenvironmental settings (from continental to shallow marine and deep ocean) are shown for the area stretching from North Africa to Afghanistan in all the selected time slices. Besides the major tectonic events, the global climate evolution and their interplay are discussed, which in some cases led to significant biotic turnovers or even to mass extinctions (e.g., Late Ordovician, Permian-Triassic boundary, Cretaceous-Cenozoic boundary). Paleogeographic maps have been compiled from literature, selecting those based on sound paleomagnetic/paleobiogeographic data. Each map is accompanied by the description of the major tectonic events that characterized the considered time interval. When contrasting paleogeographic reconstructions were available, their differences have been discussed. In general, major differences concern the interpretation of the setting and positioning of the microplates and terranes between the major continental plates.  

Paleogeographic maps have been reconstructed for selected time intervals: Cambrian, Late Ordovician, Early Devonian, Early Permian, Permian-Triassic boundary, Norian, Callovian, Aptian, Cretaceous-Cenozoic boundary, and Late Eocene. For each time interval both the general picture of the major plate tectonic configuration and a detail of the paleogeography and [[paleoenvironment]] of North Africa to the Middle East are presented. On these maps, the major paleoenvironmental settings (from continental to shallow marine and deep ocean) are shown for the area stretching from North Africa to Afghanistan in all the selected time slices. Besides the major tectonic events, the global climate evolution and their interplay are discussed, which in some cases led to significant biotic turnovers or even to mass extinctions (e.g., [[Late Ordovician]], Permian-Triassic boundary, [[Cretaceous]]-Cenozoic boundary). Paleogeographic maps have been compiled from literature, selecting those based on sound paleomagnetic/paleobiogeographic data. Each map is accompanied by the description of the major tectonic events that characterized the considered time interval. When contrasting paleogeographic reconstructions were available, their differences have been discussed. In general, major differences concern the interpretation of the setting and positioning of the microplates and terranes between the major continental plates.  

[[file:M106Ch01Fig01.jpg|thumb|300px|{{figure number|1}}Time-position of the paleogeographic maps. Each map is displayed in the context of the evolution of the sea-water chemistry (aragonite vs. calcite sea, KCl vs. MgO₄ evaporites), the global sea-level curve, the major volcanic events, the global climate, the major geodynamic events, and the ages of the five big extinctions of the Phanerozoic.]]

[[file:M106Ch01Fig01.jpg|thumb|300px|{{figure number|1}}Time-position of the paleogeographic maps. Each map is displayed in the context of the evolution of the sea-water chemistry (aragonite vs. calcite sea, KCl vs. MgO₄ evaporites), the global sea-level curve, the major volcanic events, the global climate, the major geodynamic events, and the ages of the five big extinctions of the Phanerozoic.]]

The paleogeography of the Earth during the Phanerozoic reflects the breakup of Rodinia and the formation of Pangea and its later breakup. Sedimentation was affected by the latitudinal position of the continents, the global climate conditions, and the seawater chemistry at the largest scale, and at the basin scale by the gradual changes in the local tectonic environment that accompanied the formation and destruction of the Tethyan oceans. Each global map is coupled with a more detailed map of North Africa and the Middle East. On these maps, the major depositional settings (emerged land, continental, shallow marine, and deep marine environments) are shown. These maps are a simplified view of the Western Tethys region, whereas the detailed facies distribution of the major domains is described in the chapters that follow in this book. The time-position of these paleogeographic maps is framed by the Phanerozoic history, so each map is viewed in the context of the evolution of the sea-water chemistry (aragonite vs. calcite sea, KCl vs. MgO₄ evaporites), the global sea-level curve, the major volcanic events, the global climate, the major geodynamic events, and the age of the five major extinctions of the Phanerozoic ([[:file:M106Ch01Fig01.jpg|Figure 1]]). The interplay between these changing parameters is important as it controls and explains the distribution of climate belts (and thus the distribution of the climate-sensitive depositional environments), the depth and area of the submerged shelves, and the biogenic contribution to sediment production.

The paleogeography of the Earth during the Phanerozoic reflects the breakup of Rodinia and the formation of Pangea and its later breakup. Sedimentation was affected by the latitudinal position of the continents, the global climate conditions, and the seawater chemistry at the largest scale, and at the basin scale by the gradual changes in the local tectonic environment that accompanied the formation and destruction of the Tethyan oceans. Each global map is coupled with a more detailed map of North Africa and the Middle East. On these maps, the major [[depositional setting]]s (emerged land, continental, [[shallow marine environment|shallow marine]], and [[deep marine environment]]s) are shown. These maps are a simplified view of the Western Tethys region, whereas the detailed [[facies distribution]] of the major domains is described in the chapters that follow in this book. The time-position of these paleogeographic maps is framed by the Phanerozoic history, so each map is viewed in the context of the evolution of the sea-water chemistry (aragonite vs. calcite sea, KCl vs. MgO₄ evaporites), the global sea-level curve, the major volcanic events, the global climate, the major geodynamic events, and the age of the five major extinctions of the Phanerozoic ([[:file:M106Ch01Fig01.jpg|Figure 1]]). The interplay between these changing parameters is important as it controls and explains the distribution of climate belts (and thus the distribution of the climate-sensitive depositional environments), the depth and area of the submerged shelves, and the biogenic contribution to sediment production.

[[file:M106Ch01Fig02.jpg|thumb|300px|{{figure number|2}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Cambrian (about 500 Ma), modified after Cocks and Torsvik.<ref name=Cocksandtorsvik_2002>Cocks, L. M. R., and Torsvik, T. K., 2002, Earth geography from 500 to 400 million years ago: A faunal and palaeomagnetic review: Journal of the Geological Society, v. 159, p. 631–644.</ref> Proto-Tethys concept sensu Stampfli and Borel.<ref name=Stampfliandborel_2002>Stampfli, G. M., and Borel, G. D., 2002, A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons: Earth and Planetary Science Letters, v. 196, p. 17–33.</ref> The Proto-Tethys waters encroached northern Gondwana, extending over parts of the present day African-Arabian plate margin as evidenced by facies distribution across these regions. The position of major Late Precambrian–Cambrian faults and rift zones (inactive at the time of this paleogeographic reconstruction), where salt deposition occurred, is indicated by the dashed faults.]]

[[file:M106Ch01Fig02.jpg|thumb|300px|{{figure number|2}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Cambrian (about 500 Ma), modified after Cocks and Torsvik.<ref name=Cocksandtorsvik_2002>Cocks, L. M. R., and Torsvik, T. K., 2002, Earth geography from 500 to 400 million years ago: A faunal and palaeomagnetic review: Journal of the Geological Society, v. 159, p. 631–644.</ref> Proto-Tethys concept sensu Stampfli and Borel.<ref name=Stampfliandborel_2002>Stampfli, G. M., and Borel, G. D., 2002, A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons: Earth and Planetary Science Letters, v. 196, p. 17–33.</ref> The Proto-Tethys waters encroached northern Gondwana, extending over parts of the present day African-Arabian plate margin as evidenced by facies distribution across these regions. The position of major Late Precambrian–Cambrian faults and rift zones (inactive at the time of this paleogeographic reconstruction), where salt deposition occurred, is indicated by the dashed faults.]]

===Cambrian (late Cambrian, about 500 Ma)===

===Cambrian (late Cambrian, about 500 Ma)===

During Cambrian time ([[:file:M106Ch01Fig02.jpg|Figure 2]]) most of the continents were gathered in the southern hemisphere.<ref name=Cocksandtorsvik_2002 /> <ref name=Torsvikandcocks_2009>Torsvik, T. H., and Cocks, L. R. M., 2009, The Lower Palaeozoic palaeogeographical evolution of the northeastern and eastern peri-Gondwanan margin from Turkey to New Zealand: GSL Special Publications, v. 325, p. 3–21.</ref> Gondwana stretched from the equator (Australia) to the South Pole (North Africa). Tectonic movement was active mainly as a consequence of the relative rotation of the different cratons that built Gondwana.<ref name=Veevers_2004>Veevers, J. J., 2004, Gondwanaland from 650-500 Ma assembly through 320 Ma merger in Pangea to 185-100 Ma breakup: Supercontinental tectonics via stratigraphy and radiometric dating: Earth-Science Reviews, v. 68, p. 1–132.</ref> Extensional tectonics that controlled the deposition of major evaporitic successions in the Arabic peninsula (Hormuz Salt Basin) and surroundings (e.g., Punjab Salt Basin) close to the Precambrian–Cambrian boundary (see dashed faults in [[:file:M106Ch01Fig02.jpg|Figure 2]]) came to an end, and no important tectonic activity is observed in the late Cambrian (500 Ma). Laurentia lay astride the equator in both hemispheres and was separated from Gondwana by the Iapetus Ocean. Avalonia, Armorica, Perunica, Baltica (180&deg; geographically inverted), North and South China, and all the Cimmerian blocks fringed peripheral Gondwana at moderate to high southern latitudes. Torsvik and Cocks<ref name=Torsvikandcocks_2009 /> show that South China was located close to the Equator. According to von Raumer and Stampfli,<ref name=Vonraumerandstampfli_2008>von Raumer, J. F., and Stampfli, G. M., 2008, The birth of the Rheic Ocean - Early Palaeozoic subsidence patterns and subsequent tectonic plate scenarios: Tectonophysics, v. 461, p. 9–20.</ref> the Proto-Tethys ocean, which separated North China (to the north) from the other blocks along the peripheral Gondwana, was subducting toward the south and backarc extension, which is suggested by oceanic Cambrian seaways between the peripheral Gondwanan blocks. Torsvik and Cocks<ref name=Torsvikandcocks_2009 /> recognized that their concept of the Ran Ocean used for the Cambrian-Ordovician ocean existing between Baltica and Gondwana is comparable to that of the Proto-Tethys (sensu Stampfli and Borel<ref name=Stampfliandborel_2002 />), and herein we prefer to use the latter term. Siberia was positioned at low latitudes and was separated from Laurentia and Baltica by oceanic crust. Avalonia rifted off Gondwana in the Early Ordovician with the opening of the Rheic Ocean,<ref name=Nys&aelig;theretal_2002>Nys&aelig;ther, E., Torvik, T. H., Feist, R., Walderhaug, H. J., and Eide, E.A., 2002, Ordovician palaeogeography with new palaeomagnetic data from the Montagne Noire (Southern France): Earth and Planetary Science Letters, v. 203, p. 329–341.</ref> although some authors suggest even older ages for its opening.<ref name=Torsvikandcocks_2009 />

During Cambrian time ([[:file:M106Ch01Fig02.jpg|Figure 2]]) most of the continents were gathered in the southern hemisphere.<ref name=Cocksandtorsvik_2002 /> <ref name=Torsvikandcocks_2009>Torsvik, T. H., and Cocks, L. R. M., 2009, The Lower Palaeozoic palaeogeographical evolution of the northeastern and eastern peri-Gondwanan margin from Turkey to New Zealand: GSL Special Publications, v. 325, p. 3–21.</ref> Gondwana stretched from the equator (Australia) to the South Pole (North Africa). Tectonic movement was active mainly as a consequence of the relative rotation of the different cratons that built Gondwana.<ref name=Veevers_2004>Veevers, J. J., 2004, Gondwanaland from 650-500 Ma assembly through 320 Ma merger in Pangea to 185-100 Ma breakup: Supercontinental tectonics via stratigraphy and radiometric dating: Earth-Science Reviews, v. 68, p. 1–132.</ref> Extensional tectonics that controlled the deposition of major evaporitic successions in the Arabic peninsula (Hormuz Salt Basin) and surroundings (e.g., Punjab Salt Basin) close to the Precambrian–Cambrian boundary (see dashed faults in [[:file:M106Ch01Fig02.jpg|Figure 2]]) came to an end, and no important tectonic activity is observed in the late Cambrian (500 Ma). [[Laurentia]] lay astride the equator in both hemispheres and was separated from Gondwana by the Iapetus Ocean. Avalonia, Armorica, Perunica, Baltica (180&deg; geographically inverted), North and South China, and all the Cimmerian blocks fringed peripheral Gondwana at moderate to high southern latitudes. Torsvik and Cocks<ref name=Torsvikandcocks_2009 /> show that South China was located close to the Equator. According to von Raumer and Stampfli,<ref name=Vonraumerandstampfli_2008>von Raumer, J. F., and Stampfli, G. M., 2008, The birth of the Rheic Ocean - Early Palaeozoic subsidence patterns and subsequent tectonic plate scenarios: Tectonophysics, v. 461, p. 9–20.</ref> the Proto-Tethys ocean, which separated North China (to the north) from the other blocks along the peripheral Gondwana, was subducting toward the south and backarc extension, which is suggested by oceanic Cambrian seaways between the peripheral Gondwanan blocks. Torsvik and Cocks<ref name=Torsvikandcocks_2009 /> recognized that their concept of the Ran Ocean used for the Cambrian-Ordovician ocean existing between Baltica and Gondwana is comparable to that of the Proto-Tethys (sensu Stampfli and Borel<ref name=Stampfliandborel_2002 />), and herein we prefer to use the latter term. Siberia was positioned at low latitudes and was separated from Laurentia and Baltica by oceanic crust. Avalonia rifted off Gondwana in the Early Ordovician with the opening of the Rheic Ocean,<ref name=Nys&aelig;theretal_2002>Nys&aelig;ther, E., Torvik, T. H., Feist, R., Walderhaug, H. J., and Eide, E.A., 2002, Ordovician palaeogeography with new palaeomagnetic data from the Montagne Noire (Southern France): Earth and Planetary Science Letters, v. 203, p. 329–341.</ref> although some authors suggest even older ages for its opening.<ref name=Torsvikandcocks_2009 />

The scanty fossil record makes reconstruction of Cambrian paleobiogeography difficult. This fauna mostly comprises pelagic trilobites and articulated brachiopods.<ref name=Cocksandtorsvik_2002 /> Cocks and Torsvik<ref name=Cocksandtorsvik_2002 /> recognized Laurentia, Siberia, and peri-Gondwana as distinct faunal provinces. Few data are available on climate, which based on the general character of the sedimentary section was probably temperate warm to temperate cool, but arid at low latitudes. No ice seems to have been present at the poles.

The scanty fossil record makes reconstruction of Cambrian paleobiogeography difficult. This fauna mostly comprises pelagic trilobites and articulated brachiopods.<ref name=Cocksandtorsvik_2002 /> Cocks and Torsvik<ref name=Cocksandtorsvik_2002 /> recognized Laurentia, Siberia, and peri-Gondwana as distinct faunal provinces. Few data are available on climate, which based on the general character of the [[sedimentary]] section was probably temperate warm to temperate cool, but arid at low latitudes. No ice seems to have been present at the poles.

Along North Africa and North Arabia, clastic continental deposits fringed a shallow water platform comprising both shales and mixed siliciclastic and carbonate facies.<ref name=Guiraudandbosworth_1999>Guiraud, R., and Bosworth, W., 1999, Phanerozoic geodynamic evolution of northeastern Africa and the northwestern Arabian platform: Tectonophysics, v. 315, p. 73–108.</ref> <ref name=Konertetal_2001>Konert, G., Abdulkader, M. A., Al-Hajri, A. A., and Droste, H. J., 2001, Paleozoic stratigraphy and hydrocarbon habitat of the Arabian Plate: GeoArabia, v. 6, p. 407–442.</ref>

Along North Africa and North Arabia, clastic continental deposits fringed a shallow water platform comprising both [[shale]]s and mixed [[siliciclastic]] and [[carbonate facies]].<ref name=Guiraudandbosworth_1999>Guiraud, R., and Bosworth, W., 1999, Phanerozoic geodynamic evolution of northeastern Africa and the northwestern Arabian platform: Tectonophysics, v. 315, p. 73–108.</ref> <ref name=Konertetal_2001>Konert, G., Abdulkader, M. A., Al-Hajri, A. A., and Droste, H. J., 2001, Paleozoic stratigraphy and hydrocarbon habitat of the Arabian Plate: GeoArabia, v. 6, p. 407–442.</ref>

[[file:m106Ch01Fig03.jpg|thumb|300px|{{figure number|3}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Late Ordovician time (about 440 Ma), modified after Cocks and Torsvik<ref name=Cocksandtorsvik_2002 />]]

[[file:m106Ch01Fig03.jpg|thumb|300px|{{figure number|3}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Late Ordovician time (about 440 Ma), modified after Cocks and Torsvik<ref name=Cocksandtorsvik_2002 />]]

Late Ordovician paleogeography ([[:file:M106Ch01Fig03.jpg|Figure 3]]) is represented by Cocks and Torsvick,<ref name=Cocksandtorsvik_2002 /> Robardet,<ref name=Robardet_2003>Robardet, M., 2003, The Armorica “microplate": Fact or fiction? Critical review of the concept and contradictory palaeobiogeographical data: Palaeoeography, Palaeoclimatology, Palaeoecology, v. 195, p. 125–148.</ref> and Ruban et al.,<ref name=Rubanetal_2007>Ruban, D. A., Al-Husseini, M. I., and Yumiko, I., 2007, Review of Middle East Palaeozoic plate tectonics: GeoArabia, v. 12, no. 3, p. 35–56.</ref> and shows that most continental blocks/terranes were located in the southern hemisphere except for Siberia and Tarim, which were entirely within the northern hemisphere. South China lay across the equator. The major oceans were not too large to prevent biotic exchange; thus the biota is quite cosmopolitan.

Late Ordovician paleogeography ([[:file:M106Ch01Fig03.jpg|Figure 3]]) is represented by Cocks and Torsvick,<ref name=Cocksandtorsvik_2002 /> Robardet,<ref name=Robardet_2003>Robardet, M., 2003, The Armorica “microplate": Fact or fiction? Critical review of the concept and contradictory palaeobiogeographical data: Palaeoeography, Palaeoclimatology, Palaeoecology, v. 195, p. 125–148.</ref> and Ruban et al.,<ref name=Rubanetal_2007>Ruban, D. A., Al-Husseini, M. I., and Yumiko, I., 2007, Review of Middle East Palaeozoic plate tectonics: GeoArabia, v. 12, no. 3, p. 35–56.</ref> and shows that most continental blocks/terranes were located in the southern hemisphere except for Siberia and Tarim, which were entirely within the northern hemisphere. South China lay across the equator. The major oceans were not too large to prevent biotic exchange; thus the biota is quite cosmopolitan.

The collision of Avalonia and Baltica occurred during Late Ordovician time, as documented by paleomagnetic, tectonic, isotope, and faunal data.<ref name=Cocksandtorsvik_2002 /> <ref name=Robardet_2003 /> Baltica, after the accretion of Avalonia, was positioned at intermediate latitudes NW of the Northern Gondwana margin and could have deflected the South Equatorial current southward. The Iapetus Oceanic lithosphere was subducting beneath the Laurentian active margin and its width was decreasing. The Rheic Ocean was several thousands of km wide with Perunica in the northern part, having probably detached from NW Gondwana in mid-Ordovician time. According to von Raumer and Stampfli,<ref name=Vonraumerandstampfli_2008 /> the Rheic Ocean was subducting beneath the Peri-Gondwanan blocks placed along the northern margin of Gondwana. The Panthalassic Ocean was very large and mostly covered the northern hemisphere. Cocks and Torsvik<ref name=Cocksandtorsvik_2002 /> suggest this ocean was comparable in size to today’s Pacific. Peri-Gondwanan blocks were located along the Gondwanan margin at high to intermediate southern latitudes. However, some faunal data<ref name=Villasetal_2002>Villas, E., Hammann, W., and Harper, D. A. T., 2002, Foliomena fauna (Brachiopoda) from the Upper Ordovician of Sardinia: Palaeontology, v. 45, p. 267–295.</ref> suggest lower latitudes, as well as the existence of peripheral blocks detaching from North Gondwana. The position and the architecture of the Armorica composite plate is still discussed.<ref name=Robardet_2003 /> Nysæther et al.<ref name=Nys&aelig;theretal_2002 /> suggested that by the Late Ordovician, it is possible that part of Armorica had rifted off the NW Gondwanan margin; however, Robardet<ref name=Robardet_2003 /> casted doubts on the reliability of the paleomagnetic data on which the evolution of the Armorica was based and proposed a different scenario in which the southern European blocks remained attached to the northern Gondwanan margin from Ordovician to Devonian<ref name=Robardet_2003 /> ([[:file:M106Ch01Fig09.jpg|Figure 9]]).

The collision of Avalonia and Baltica occurred during Late Ordovician time, as documented by paleomagnetic, [[tectonic]], [[isotope]], and [[fauna]]l data.<ref name=Cocksandtorsvik_2002 /> <ref name=Robardet_2003 /> Baltica, after the accretion of Avalonia, was positioned at intermediate latitudes NW of the Northern Gondwana margin and could have deflected the South Equatorial current southward. The Iapetus Oceanic lithosphere was subducting beneath the Laurentian active margin and its width was decreasing. The Rheic Ocean was several thousands of km wide with Perunica in the northern part, having probably detached from NW Gondwana in mid-Ordovician time. According to von Raumer and Stampfli,<ref name=Vonraumerandstampfli_2008 /> the Rheic Ocean was subducting beneath the Peri-Gondwanan blocks placed along the northern margin of Gondwana. The Panthalassic Ocean was very large and mostly covered the northern hemisphere. Cocks and Torsvik<ref name=Cocksandtorsvik_2002 /> suggest this ocean was comparable in size to today’s Pacific. Peri-Gondwanan blocks were located along the Gondwanan margin at high to intermediate southern latitudes. However, some faunal data<ref name=Villasetal_2002>Villas, E., Hammann, W., and Harper, D. A. T., 2002, Foliomena fauna (Brachiopoda) from the Upper Ordovician of Sardinia: Palaeontology, v. 45, p. 267–295.</ref> suggest lower latitudes, as well as the existence of peripheral blocks detaching from North Gondwana. The position and the architecture of the Armorica composite plate is still discussed.<ref name=Robardet_2003 /> Nysæther et al.<ref name=Nys&aelig;theretal_2002 /> suggested that by the Late Ordovician, it is possible that part of Armorica had rifted off the NW Gondwanan margin; however, Robardet<ref name=Robardet_2003 /> casted doubts on the reliability of the paleomagnetic data on which the evolution of the Armorica was based and proposed a different scenario in which the southern European blocks remained attached to the northern Gondwanan margin from Ordovician to Devonian<ref name=Robardet_2003 /> ([[:file:M106Ch01Fig09.jpg|Figure 9]]).

Global climate deteriorated at the end of Ordovician time, resulting in the Hirnantian glacial episode. The glaciation is documented by sedimentary evidence and isotopic data<ref name=Brenchleyetal_1994>Brenchley, P. J., Marshall, J. D., Carden, G. A. C., et al., 1994. Bathymetric and isotopic evidence for a short-lived Ordovician glaciation in a greenhouse period: Geology, v. 22, p. 295–298.</ref> and lasted about 0.5–1 million years. Peri-Gondwanan and Gondwanan glacial deposits occur in North Africa (where a N-S high was present in Egypt<ref name=Schandelmeierandreynolds_1997>Schandelmeier, H. and Reynolds, P. O., eds., 1997, Palaeogeographic-palaeotectonic atlas of north-eastern Africa, Arabia, and adjacent areas: Balkema, Rotterdam, 160 p. 17 pls.</ref>), South America, Arabia, and South Africa, and periglacial features are known also from Armorica and Avalonia. Several interpretations have been offered on the distribution of the ice caps during the Hirnantian glaciation (a single large ice cap vs. a number of smaller ice caps), as summarized in Veevers.<ref name=Veevers_2004 /> This glaciation followed a period of climatic amelioration along the Northern Gondwana margin, evidenced by deposition of temperate bioclastic limestones and pelmatozoan-bryozoan mud-mounds, which overlie a very thick terrigenous succession of Early-Middle Ordovician age. The change from pre-Hirnantian “greenhouse” climates to Hirnantian “icehouse” conditions was rapid and was not preceded by any climatic fluctuations, which might have helped acclimatize the biota to the climate change.<ref name=Brenchleyetal_1994 /> If the pre-Hirnantian benthos was widespread in epicontinental seas and inland basins, the Hirnantian shelly fauna<ref name=Sutcliffeetal_2001>Sutcliffe, O. E., Harper, D. A. T., Salem, A. A., Whittington, R. J., and Craig, J., 2001, The development of an atypical Hirnantia-brachiopod Fauna and the onset of glaciation in the late Ordovician of Gondwana. Transactions of the Royal Society of Edinburgh: Earth Sciences, v. 92, p. 1–14.</ref> <ref name=Jinandcopper_2008>Jin, J., and Copper P., 2008, Response of brachiopod communities to environmental change during the Late Ordovian mass extinction interval, Anticosti Island, eastern Canada: Fossils and Strata, v. 54, p. 41–52.</ref> was mostly restricted to the continental margins, due to the sea-level drop caused by the glaciations in the latest Ordovician. The Hirnantian glaciation seems to have occurred during times of very high levels of the greenhouse gas CO₂ (14–18 times the present atmospheric value). Brenchley et al.<ref name=Brenchleyetal_1994 /> considered that the onset of glaciation was the result of an early Hirnantian increment in burial rates of organic carbon acting as a major sink for the atmospheric CO₂. However, according to Villas et al.,<ref name=Villasetal_2002>Villas, E., Hammann, W., and Harper, D. A. T., 2002, Foliomena fauna (Brachiopoda) from the Upper Ordovician of Sardinia: Palaeontology, v. 45, p. 267–295.</ref> the accumulation of great volumes of carbonates in the pre-Hirnantian late Ordovician served as the sink of the atmospheric CO₂. At the end of the Hirnantian, the ice cap melting caused a rapid, eustatic sea-level rise and the development of low-oxygen conditions on the shelves.<ref name=Rongandharper_1988>Rong, J.-Y., and Harper, D. A. T., 1988, A global synthesis of the latest Ordovician Hirnantian brachiopod faunas: Transactions of the Royal Society of Edinburgh Earth v. 79, p. 383–402.</ref> <ref name=Owenandrobertson_1995>Owen, A. W., and Robertson, D. B. R., 1995, Ecological changes during the end-Ordovician extinction: Modern Geology, v. 20, p. 21–39.</ref> The end of the glaciation was followed by the deposition of organic-rich shales (Lower Silurian “hot shales”) which represent the most important source rocks in North Africa and one of the major in the Arabian peninsula.<ref name=Luningetal_2000>Luning, S., Craig, J., Loydell, D. K., Storch, P. B., and Fitches B., 2000, Lower Silurian ‘hot shales’ in North Africa and Arabia: Regional distribution and depositional model: Earth Science Review, v. 49, p. 121–200.</ref>

Global climate deteriorated at the end of Ordovician time, resulting in the Hirnantian glacial episode. The glaciation is documented by sedimentary evidence and isotopic data<ref name=Brenchleyetal_1994>Brenchley, P. J., Marshall, J. D., Carden, G. A. C., et al., 1994. Bathymetric and isotopic evidence for a short-lived Ordovician glaciation in a greenhouse period: Geology, v. 22, p. 295–298.</ref> and lasted about 0.5–1 million years. Peri-Gondwanan and Gondwanan glacial deposits occur in North Africa (where a N-S high was present in Egypt<ref name=Schandelmeierandreynolds_1997>Schandelmeier, H. and Reynolds, P. O., eds., 1997, Palaeogeographic-palaeotectonic atlas of north-eastern Africa, Arabia, and adjacent areas: Balkema, Rotterdam, 160 p. 17 pls.</ref>), South America, Arabia, and South Africa, and periglacial features are known also from Armorica and Avalonia. Several interpretations have been offered on the distribution of the ice caps during the Hirnantian glaciation (a single large ice cap vs. a number of smaller ice caps), as summarized in Veevers.<ref name=Veevers_2004 /> This glaciation followed a period of climatic amelioration along the Northern Gondwana margin, evidenced by deposition of temperate bioclastic limestones and pelmatozoan-bryozoan mud-mounds, which overlie a very thick terrigenous succession of Early-Middle Ordovician age. The change from pre-Hirnantian “greenhouse” climates to Hirnantian “icehouse” conditions was rapid and was not preceded by any climatic fluctuations, which might have helped acclimatize the biota to the climate change.<ref name=Brenchleyetal_1994 /> If the pre-Hirnantian benthos was widespread in epicontinental seas and inland basins, the Hirnantian shelly fauna<ref name=Sutcliffeetal_2001>Sutcliffe, O. E., Harper, D. A. T., Salem, A. A., Whittington, R. J., and Craig, J., 2001, The development of an atypical Hirnantia-brachiopod Fauna and the onset of glaciation in the late Ordovician of Gondwana. Transactions of the Royal Society of Edinburgh: Earth Sciences, v. 92, p. 1–14.</ref> <ref name=Jinandcopper_2008>Jin, J., and Copper P., 2008, Response of brachiopod communities to environmental change during the Late Ordovian mass extinction interval, Anticosti Island, eastern Canada: Fossils and Strata, v. 54, p. 41–52.</ref> was mostly restricted to the continental margins, due to the sea-level drop caused by the glaciations in the latest Ordovician. The Hirnantian glaciation seems to have occurred during times of very high levels of the greenhouse gas CO₂ (14–18 times the present atmospheric value). Brenchley et al.<ref name=Brenchleyetal_1994 /> considered that the onset of glaciation was the result of an early Hirnantian increment in burial rates of organic carbon acting as a major sink for the atmospheric CO₂. However, according to Villas et al.,<ref name=Villasetal_2002>Villas, E., Hammann, W., and Harper, D. A. T., 2002, Foliomena fauna (Brachiopoda) from the Upper Ordovician of Sardinia: Palaeontology, v. 45, p. 267–295.</ref> the accumulation of great volumes of carbonates in the pre-Hirnantian late Ordovician served as the sink of the atmospheric CO₂. At the end of the Hirnantian, the ice cap melting caused a rapid, eustatic sea-level rise and the development of low-oxygen conditions on the shelves.<ref name=Rongandharper_1988>Rong, J.-Y., and Harper, D. A. T., 1988, A global synthesis of the latest Ordovician Hirnantian brachiopod faunas: Transactions of the Royal Society of Edinburgh Earth v. 79, p. 383–402.</ref> <ref name=Owenandrobertson_1995>Owen, A. W., and Robertson, D. B. R., 1995, Ecological changes during the end-Ordovician extinction: Modern Geology, v. 20, p. 21–39.</ref> The end of the glaciation was followed by the deposition of organic-rich shales (Lower Silurian “hot shales”) which represent the most important source rocks in North Africa and one of the major in the Arabian peninsula.<ref name=Luningetal_2000>Luning, S., Craig, J., Loydell, D. K., Storch, P. B., and Fitches B., 2000, Lower Silurian ‘hot shales’ in North Africa and Arabia: Regional distribution and depositional model: Earth Science Review, v. 49, p. 121–200.</ref>

A very important event at the end of the Ordovician was the first of the Big Five Mass Extinctions<ref name=Raupandsepkoski_1982>Raup, D. M., and Sepkoski, J. J., 1982, Mass extinctions in the marine fossil record: Science, v. 215, p. 1501–1503.</ref> of the Phanerozoic, with disappearance of 85% of species, 61% of genera, and 12–24% of families.<ref name=Sepkoski_1997>Sepkoski, J. J., 1997, Biodiversity: Past, present, and future: Journal of Paleontology, v. 71, p. 533–539.</ref> The close correlation between the Ordovician extinction and the glaciation suggests climatic change as the proximate cause. However, the extinction was probably a complex event.<ref name=Brenchleyetal_1995>Brenchley, P. J., Carden, G. A. F., and Marshall, J. D., 1995, Environmental changes associated with the “first strike” of the late Ordovician mass extinction: Modern Geology, v. 20, p. 69–82.</ref> A sea-level fall and rise, changes in oceanic structure,<ref name=Wildeandberry_1984>Wilde, P., and Berry, W. B. N., 1984, Destabilization of the oceanic density structure and its significance to marine ‘extinction’ events: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 48, p. 143–162.</ref> nutrient fluxes,<ref name=Brenchleyetal_1995 /> and development of anoxia<ref name=Fortey_1989>

A very important event at the end of the Ordovician was the first of the Big Five Mass Extinctions<ref name=Raupandsepkoski_1982>Raup, D. M., and Sepkoski, J. J., 1982, Mass extinctions in the marine fossil record: Science, v. 215, p. 1501–1503.</ref> of the Phanerozoic, with disappearance of 85% of species, 61% of genera, and 12–24% of families.<ref name=Sepkoski_1997>Sepkoski, J. J., 1997, Biodiversity: Past, present, and future: Journal of Paleontology, v. 71, p. 533–539.</ref> The close correlation between the Ordovician extinction and the glaciation suggests climatic change as the proximate cause. However, the extinction was probably a complex event.<ref name=Brenchleyetal_1995>Brenchley, P. J., Carden, G. A. F., and Marshall, J. D., 1995, Environmental changes associated with the “first strike” of the late Ordovician mass extinction: Modern Geology, v. 20, p. 69–82.</ref> A sea-level fall and rise, changes in oceanic structure,<ref name=Wildeandberry_1984>Wilde, P., and Berry, W. B. N., 1984, Destabilization of the oceanic density structure and its significance to marine ‘extinction’ events: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 48, p. 143–162.</ref> nutrient fluxes,<ref name=Brenchleyetal_1995 /> and development of anoxia<ref name=Fortey_1989>Fortey, R. A., 1989, There are extinctions and extinctions: Examples from the lower Palaeozoic. Philosophical Transactions of the Royal Society of London. Series B, v. 352, p.327–355.</ref> <ref name=Briggsetal_1998>Briggs, D. E. G., Evershed, R. P., and Stankiewicz, B. A., 1998, The molecular preservation of fossil arthropod cuticles: Ancient Biomolecules, v. 2, p. 135–146.</ref> were all ultimately related to climatic change and may have contributed to the crisis.<ref name=Brenchleyetal_2001>Brenchley, P. J., Marshall, J. D., and Underwood, C. J., 2001, Do all mass extinctions represent an ecological crisis? Evidence from the late Ordovician: Geological Journal, v. 36, p. 329–340.</ref>

 

Fortey, R. A., 1989, There are extinctions and extinctions: Examples from the lower Palaeozoic. Philosophical Transactions of the Royal Society of London. Series B, v. 352, p.327–355.</ref> <ref name=Briggsetal_1998>Briggs, D. E. G., Evershed, R. P., and Stankiewicz, B. A., 1998, The molecular preservation of fossil arthropod cuticles: Ancient Biomolecules, v. 2, p. 135–146.</ref> were all ultimately related to climatic change and may have contributed to the crisis.<ref name=Brenchleyetal_2001>Brenchley, P. J., Marshall, J. D., and Underwood, C. J., 2001, Do all mass extinctions represent an ecological crisis? Evidence from the late Ordovician: Geological Journal, v. 36, p. 329–340.</ref>

[[file:M106Ch01Fig04.jpg|thumb|300px|{{figure number|4}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Early Devonian time (about 400 Ma).]]

[[file:M106Ch01Fig04.jpg|thumb|300px|{{figure number|4}}Global paleogeography (top) and major depositional settings in the southern margin of the Tethys (below) during Early Devonian time (about 400 Ma).]]

==Paleogeography and petroleum plays==

==Paleogeography and petroleum plays==

The paleogeographic and tectonic evolution of the southern Tethys area during the Phanerozoic plays an important role in determining the distribution of the source rocks and reservoirs as well as the origin of stratigraphic and tectonic traps, both strictly related to the geodynamic evolution of the area. This recognition of these controls on hydrocarbon resources and accumulation of oil and gas along the Tethyn margin has been the major thrust of the publications of many geologists, including Murris,<ref name=Murris_1980>Murris, R. J., 1980, Middle East: Stratigraphic evolution and oil habitat: AAPG Bulletin, v. 64, no. 5, p. 597–618.</ref> Beydoun,<ref name=Beydoun_1986>Beydoun, Z. R., 1986, The petroleum resources of the Middle East: A review: Journal of Petroleum Geology, v. 9, p. 5–29.</ref> <ref name=Beydoun_1988>Beydoun, Z. R., 1988, The Middle East: Regional geology and petroleum resources: Scientific Press, Beaconsfield, U.K., 292 p.</ref> <ref name=Beydoun_1991>Beydoun, Z. R., 1991, Arabian plate hydrocarbon geology and potential — a plate tectonic approach: AAPG v. 33, p. 77.</ref> May,<ref name=May_1991>May, P. R., 1991, The Eastern Mediterranean Mesozoic Basin: Evolution and oil habitat: AAPG Bulletin, v. 75, no. 7, p. 1215–1232.</ref> and Sharland et al.<ref name=Sharlandetal_2001>Sharland, P. R., Archer, R., Casey, D. M., Davies, R. B., Hall, S. H., Heward, A. P., Horbury, A. D., and Simmons, M. D., 2001, Arabian plate sequence stratigraphy: GeoArabia, Special Publication 2, 371 pp.</ref>

The paleogeographic and tectonic evolution of the southern Tethys area during the Phanerozoic plays an important role in determining the distribution of the source rocks and reservoirs as well as the origin of stratigraphic and tectonic traps, both strictly related to the geodynamic evolution of the area. This recognition of these controls on hydrocarbon resources and accumulation of oil and gas along the Tethyn margin has been the major thrust of the publications of many geologists, including Murris,<ref name=Murris_1980>Murris, R. J., 1980, Middle East: [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0064/0005/0550/0597.htm Stratigraphic evolution and oil habitat]: AAPG Bulletin, v. 64, no. 5, p. 597–618.</ref> Beydoun,<ref name=Beydoun_1986>Beydoun, Z. R., 1986, The petroleum resources of the Middle East: A review: Journal of Petroleum Geology, v. 9, p. 5–29.</ref> <ref name=Beydoun_1988>Beydoun, Z. R., 1988, The Middle East: Regional geology and petroleum resources: Scientific Press, Beaconsfield, U.K., 292 p.</ref> <ref name=Beydoun_1991>Beydoun, Z. R., 1991, Arabian plate hydrocarbon geology and potential — a plate tectonic approach: AAPG Studies in Geology 33, p. 77.</ref> May,<ref name=May_1991>May, P. R., 1991, [http://archives.datapages.com/data/bulletns/1990-91/data/pg/0075/0007/0000/1215.htm The Eastern Mediterranean Mesozoic Basin: Evolution and oil habitat]: AAPG Bulletin, v. 75, no. 7, p. 1215–1232.</ref> and Sharland et al.<ref name=Sharlandetal_2001>Sharland, P. R., Archer, R., Casey, D. M., Davies, R. B., Hall, S. H., Heward, A. P., Horbury, A. D., and Simmons, M. D., 2001, Arabian plate sequence stratigraphy: GeoArabia, Special Publication 2, 371 pp.</ref>

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<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 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, [http://archives.datapages.com/data/bulletns/1999/10oct/1552/1552.htm 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.

The latitude and relative position of the Pangea and the Tethys therefore favored the deposition of source rocks, whereas the continuous and time-transgressive generation and evolution of different sedimentary basins controlled the creation of reservoirs and traps (such as those related to tectonic inversion of extensional structures), leading to the impressive concentration of oil and gas fields in this area.

The latitude and relative position of the Pangea and the Tethys therefore favored the deposition of source rocks, whereas the continuous and time-transgressive generation and evolution of different sedimentary basins controlled the creation of reservoirs and traps (such as those related to tectonic inversion of extensional structures), leading to the impressive concentration of oil and gas fields in this area.

The distribution of giant oil fields is related to the nature of the sedimentary basins. According to Mann et al.,<ref name=Mannetal_2003>Mann, P., Gahagan, L, and Gordon, M. B., 2003, Tectonic setting of the world’s giant oil and gas fields, in M. T. Halbouty, ed., Giant oil and gas fields of the decade 1990- 1999: AAPG Memoir 78, 15-105.</ref> most of the giant oil and gas fields known until 2000 are related to continental passive margins facing the major ocean basins (34.66%), continental rifts and overlying sag basins (especially failed rifts at the edges or interiors of continents; 30.90%), and collisional margins produced by terminal collision between two continents (19.73%). These types of basins are common in the succession of North Africa and the Middle East. Due to the geodynamic evolution of this area, rift basins (mainly formed due to the opening of the Tethys oceans and to the extensional events affecting North Africa) rapidly evolved to passive margins (e.g., evolution of the peri-Gondwanan blocks) and then to active margins, with the development of collision-related basins (e.g., foredeep related to the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia).

The distribution of giant oil fields is related to the nature of the sedimentary basins. According to Mann et al.,<ref name=Mannetal_2003>Mann, P., Gahagan, L, and Gordon, M. B., 2003, [http://archives.datapages.com/data/specpubs/memoir78/CHAPTER_2/CHAPTER_2.HTM Tectonic setting of the world’s giant oil and gas fields], in M. T. Halbouty, ed., Giant oil and gas fields of the decade 1990- 1999: [http://store.aapg.org/detail.aspx?id=1247 AAPG Memoir 78], 15-105.</ref> most of the giant oil and gas fields known until 2000 are related to continental passive margins facing the major ocean basins (34.66%), continental rifts and overlying sag basins (especially failed rifts at the edges or interiors of continents; 30.90%), and collisional margins produced by terminal collision between two continents (19.73%). These types of basins are common in the succession of North Africa and the Middle East. Due to the geodynamic evolution of this area, rift basins (mainly formed due to the opening of the Tethys oceans and to the extensional events affecting North Africa) rapidly evolved to passive margins (e.g., evolution of the peri-Gondwanan blocks) and then to active margins, with the development of collision-related basins (e.g., foredeep related to the accretion of the peri-Gondwanan blocks to the southern margin of Eurasia).

As a consequence, different types of sedimentary basins were continuously created by the movement of continental blocks, so that at any time different basin types can be recognized (e.g., divergence on the southern side of the Tethys and convergence on the Asian margin) in North Africa and the Middle East. Therefore, favorable conditions for the development of petroleum plays were almost continually present. Though there are some differences in tectonic evolution across the margin plate scale, correlations of stratigraphy and thus petroleum systems are possible.<ref name=Murris_1980 /> <ref name=Beydoun_1986 /> <ref name=Beydoun_1988 /> <ref name=Beydoun_1991 /> <ref name=May_1991 /> <ref name=Sharlandetal_2001 />

As a consequence, different types of sedimentary basins were continuously created by the movement of continental blocks, so that at any time different basin types can be recognized (e.g., divergence on the southern side of the Tethys and convergence on the Asian margin) in North Africa and the Middle East. Therefore, favorable conditions for the development of petroleum plays were almost continually present. Though there are some differences in tectonic evolution across the margin plate scale, correlations of stratigraphy and thus petroleum systems are possible.<ref name=Murris_1980 /> <ref name=Beydoun_1986 /> <ref name=Beydoun_1988 /> <ref name=Beydoun_1991 /> <ref name=May_1991 /> <ref name=Sharlandetal_2001 />

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, [http://geology.cr.usgs.gov/pub/bulletins/b2202-e Petroleum geology and total petroleum systems of the Widyan Basin and Interior Platform of Saudi Arabia and Iraq]: USGS Bulletin 2202-E.</ref> <ref name=Pollastro_2003>Pollastro, R. M., 2003, [http://pubs.usgs.gov/bul/b2202-h 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.</ref>

==See also==

==See also==

* [[Jordan petroleum geology]]

* [[Jordan petroleum geology]]

* [[Iraq petroleum geology]]

* [[Iraq petroleum geology]]

==References==

==References==