Changes

==Example: the GOM basin==

==Example: the GOM basin==

[[file:sedimentary-basin-analysis_fig4-6.png|thumb|{{figure number|4-6}}Modified. Copyright: Buffler (1991); courtesy New Orleans Geological Society.]]

 

Tectonic evolution of the [[basin::Gulf of Mexico basin]] has resulted in five primary tectonostratigraphic phases (A–E), each with a different sediment accumulation and deformation history. Figure 4-11 is a schematic diagram showing a series of cross sections representing the four phases of Late Triassic to Early Cretaceous evolution of the GOM basin (see Figure 4-6 for the location).

[[file:sedimentary-basin-analysis_fig4-11.png|thumb|{{figure number|1}}Modified. Copyright: Buffler (1991); courtesy New Orleans Geological Society.]]

 

Tectonic evolution of the [[basin::Gulf of Mexico basin]] has resulted in five primary tectonostratigraphic phases (A–E), each with a different sediment accumulation and deformation history. [[:file:sedimentary-basin-analysis_fig4-11.png|Figure 1]] is a schematic diagram showing a series of cross sections representing the four phases of Late Triassic to Early Cretaceous evolution of the GOM basin (see [[:file:sedimentary-basin-analysis_fig4-6.png|Figure 2]] for the location).

 

===Phase A===

===Phase A===

[[file:sedimentary-basin-analysis_fig4-11.png|thumb|{{figure number|4-11}}Modified. Copyright: Buffler (1991); courtesy New Orleans Geological Society.]]

[[:file:sedimentary-basin-analysis_fig4-11.png|Figure 1A]] consists of Late Triassic to Early Jurassic rifting along linear zones within brittle crust with deposition of synrift nonmarine sediments and volcanics within half-grabens.

(Figure 4-11A) consists of Late Triassic to Early Jurassic rifting along linear zones within brittle crust with deposition of synrift nonmarine sediments and volcanics within half-grabens.

===Phase B===

===Phase B===

(Figure 4-11B) of Middle Jurassic age is characterized by rifting and attenuation of the crust, with formation of transitional crust and the associated basement highs and lows that form the basic architecture. The outer periphery of the basin underwent moderate stretching and the crust remained thick, forming broad arches and basins. The central basin underwent considerable stretching and subsidence to form a large area of thin transitional crust over which thick salt was deposited. Nonmarine terrigenous sediments continued to be deposited within the peripheral grabens.

[[:file:sedimentary-basin-analysis_fig4-11.png|Figure 1B]] of Middle Jurassic age is characterized by rifting and attenuation of the crust, with formation of transitional crust and the associated basement highs and lows that form the basic architecture. The outer periphery of the basin underwent moderate stretching and the crust remained thick, forming broad arches and basins. The central basin underwent considerable stretching and subsidence to form a large area of thin transitional crust over which thick salt was deposited. Nonmarine terrigenous sediments continued to be deposited within the peripheral grabens.

===Phase C===

===Phase C===

(Figure 4-11C) of Late Jurassic age consists of emplacement of oceanic crust as mantle upwelling concentrated along the generally east–west-trending weakness in the continental crust. As the crust underlying the basin began to cool, subsidence resulted in the relative rise of sea level. The basin margins were transgressed by broad shallow-to-deep shelfal marine environments with deposition of thick carbonate successions. Locally, thick, terrigenous clastic prisms prograded into the basin. Potential and known reservoirs occur within both the carbonate and clastic depositional systems of this tectonostratigraphic phase. During the Late Jurassic maximum transgression, the deep basin was sediment starved, and thick, organic-rich shales accumulated in lowoxygen environments (source-rock types 6 and 7).

[[:file:sedimentary-basin-analysis_fig4-11.png|Figure 1C]] of Late Jurassic age consists of emplacement of oceanic crust as mantle upwelling concentrated along the generally east–west-trending weakness in the continental crust. As the crust underlying the basin began to cool, subsidence resulted in the relative rise of sea level. The basin margins were transgressed by broad shallow-to-deep shelfal marine environments with deposition of thick carbonate successions. Locally, thick, terrigenous clastic prisms prograded into the basin. Potential and known reservoirs occur within both the carbonate and clastic depositional systems of this tectonostratigraphic phase. During the Late Jurassic maximum transgression, the deep basin was sediment starved, and thick, organic-rich shales accumulated in lowoxygen environments (source-rock types 6 and 7).

===Phase D===

===Phase D===

(Figure 4-11D) of Early Cretaceous age is characterized by broad carbonate platforms rimmed by reef buildups along the margins established at the boundary of differential subsidence between thin and thick crust. Fine-grained carbonates were deposited in the adjacent deep basin. Terrigenous clastics continued to be input at local points along the northern margin. Known and potential reservoirs occur within both carbonate and clastic depositional systems of these early Cretaceous rocks.

[[:file:sedimentary-basin-analysis_fig4-11.png|Figure 1D]] of Early Cretaceous age is characterized by broad carbonate platforms rimmed by reef buildups along the margins established at the boundary of differential subsidence between thin and thick crust. Fine-grained carbonates were deposited in the adjacent deep basin. Terrigenous clastics continued to be input at local points along the northern margin. Known and potential reservoirs occur within both carbonate and clastic depositional systems of these early Cretaceous rocks.

 

===Phase E===

===Phase E===

(Figure 4-9) began during the mid-Cenomanian with a rapid fall and rise of sea level superimposed on a long-term rise that terminally drowned the outer margins of the carbonate platforms, causing the margins to retreat landward. Widespread submarine erosion created a prominent mid-Cretaceous unconformity. Subsequent deposition was dominated by terrigenous sedimentation as large clastic prisms prograded first from the west and northwest in the Late Cretaceous and early Cenozoic and then from the north (Mississippi River drainage) during the late Cenozoic. Most of the offshore and many onshore reservoirs occur within these Late Cretaceous and Cenozoic siliciclastic deposits. The prograding prisms of siliciclastic sediment differentially loaded the underlying salt, resulting in deformation by both salt mobility and down-to-the-basin growth faulting along the shelf-slope break.<ref name=ch04r24>Bruce, C., H., 1973, Pressured shale and related sediment deformation: mechanism for development of regional contemporaneous faults: AAPG Bulletin, vol. 57, p. 878–886., 10., 1306/819A4352-16C5-11D7-8645000102C1865D</ref><ref name=ch04r117>Winker, C., D., Edwards, M., B., 1983, Unstable progradational clastic shelf margins: SEPM Special Publication 33, p. 139–157.</ref>

[[:file:sedimentary-basin-analysis_fig4-9.png|Figure 3]] began during the mid-Cenomanian with a rapid fall and rise of sea level superimposed on a long-term rise that terminally drowned the outer margins of the carbonate platforms, causing the margins to retreat landward. Widespread submarine erosion created a prominent mid-Cretaceous unconformity. Subsequent deposition was dominated by terrigenous sedimentation as large clastic prisms prograded first from the west and northwest in the Late Cretaceous and early Cenozoic and then from the north (Mississippi River drainage) during the late Cenozoic. Most of the offshore and many onshore reservoirs occur within these Late Cretaceous and Cenozoic siliciclastic deposits. The prograding prisms of siliciclastic sediment differentially loaded the underlying salt, resulting in deformation by both salt mobility and down-to-the-basin growth faulting along the shelf-slope break.<ref name=ch04r24>Bruce, C., H., 1973, Pressured shale and related sediment deformation: mechanism for development of regional contemporaneous faults: AAPG Bulletin, vol. 57, p. 878–886., 10., 1306/819A4352-16C5-11D7-8645000102C1865D</ref><ref name=ch04r117>Winker, C., D., Edwards, M., B., 1983, Unstable progradational clastic shelf margins: SEPM Special Publication 33, p. 139–157.</ref>

==See also==

==See also==