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Four reservoir intervals are productive in the East Breaks 160-161 minibasin: ''Glob alt, Glob M, Hyal B'', and ''Trim A'' horizons. Reservoir intervals are named for the regionally useful bioevent species stratigraphically above the reservoir. These bioevents most often occur within condensed sections. All four reservoir intervals are interpreted to be gravity-flow sand deposits.<ref name=ch04r7>Armentrout, J., M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, in Weimer, P., Link, M., H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref> Only the ''Glob alt'' reservoir is considered here.

Four reservoir intervals are productive in the East Breaks 160-161 minibasin: ''Glob alt, Glob M, Hyal B'', and ''Trim A'' horizons. Reservoir intervals are named for the regionally useful bioevent species stratigraphically above the reservoir. These bioevents most often occur within condensed sections. All four reservoir intervals are interpreted to be gravity-flow sand deposits.<ref name=ch04r7>Armentrout, J. M., 1991, Paleontological constraints on depositional [[modeling]]: examples of integration of biostratigraphy and seismic stratigraphy, Pliocene–Pleistocene, Gulf of Mexico, in Weimer, P., Link, M., H., eds., Seismic Facies and Sedimentary Processes of Submarine Fans and Turbidite Systems: New York, Springer-Verlag, p. 137–170.</ref> Only the ''Glob alt'' reservoir is considered here.

==''Glob alt'' sequence deposition==

==''Glob alt'' sequence deposition==

[[File:Sedimentary-basin-analysis fig4-44.png|thumbnail|left|{{figure number|1}}.]]

[[File:Sedimentary-basin-analysis fig4-44.png|thumbnail|left|{{figure number|1}}See text for explanation.]]

[[file:sedimentary-basin-analysis_fig4-47.png|thumb|{{figure number|2}}After Armentrout et al.<ref name=ch04r7 /> Copyright: Springer-Verlag.]]

[[file:sedimentary-basin-analysis_fig4-47.png|thumb|{{figure number|2}}After Armentrout et al.<ref name=ArmentroutEtAl_1991>Armentrout, J. M., S. J. Malacek, P. Braithwaite, and C. R. Beeman, 1991, Seismic facies of slope basin turbidite reservoirs, East Breaks 160-161 field: Pliocene-Pleistocene, northwestern Gulf of Mexico, ''in'' P. Weimer and M. J. Link, eds., Seismic facies and sedimentary processes of submarine fans and turbidite systems: New York, Springer-Verlag, p. 223-239. /> Courtesy Springer-Verlag.]]

The ''Glob alt'' depositional sequence of Late Pliocene age (mapped below) is part of depositional cycle 2 in [[:file:sedimentary-basin-analysis_fig4-44.png|Figure 1]]. The sequence, deposited on a relatively open slope with only slightly undulating sea-floor topography, thins rapidly basinward due to sediment starvation in the most distal areas of the High Island-East Breaks depocenter ([[:file:sedimentary-basin-analysis_fig4-47.png|Figure 2]]). Subsequent progradation resulted in differential loading of the allochthonous salt and formation of local depocenters between downloaded growth fault sediment prisms and differentially displaced salt-cored anticlines.

The ''Glob alt'' depositional sequence of Late Pliocene age (mapped below) is part of depositional cycle 2 in [[:file:sedimentary-basin-analysis_fig4-44.png|Figure 1]]. The sequence, deposited on a relatively open slope with only slightly undulating sea-floor topography, thins rapidly basinward due to sediment starvation in the most distal areas of the High Island-East Breaks depocenter ([[:file:sedimentary-basin-analysis_fig4-47.png|Figure 2]]). Subsequent progradation resulted in differential loading of the allochthonous salt and formation of local depocenters between downloaded growth fault sediment prisms and differentially displaced salt-cored anticlines.

==Well-log cross section==

==Well-log cross section==

[[file:sedimentary-basin-analysis_fig4-46.png|left|thumb|{{figure number|3}}After Armentrout et al.<ref name=ch04r7 />). Copyright: Springer-Verlag. Original map by Charles R. Beeman, Mobil Oil, 1987.]]

[[file:sedimentary-basin-analysis_fig4-46.png|left|thumb|{{figure number|3}}After Armentrout et al.<ref name=ArmentroutEtAl_1991 />. Courtesy Springer-Verlag. Original map by Charles R. Beeman, Mobil Oil, 1987.]]

The following figure is a well-log cross section of the ''Glob alt'' reservoir interval; datum is a mudstone within the GA-2 sandstone (well locations are shown on [[:file:sedimentary-basin-analysis_fig4-46.png|Figure 3]]). All logs are spontaneous potential with true vertical depth displays. The GA-4 reservoir sand is below the displayed interval. Log profiles are annotated: arrow C = funnel-shaped, coarsening-upward sandstone; arrow F = bell-shaped, fining-upward sandstone; parallel lines B = blocky profile of relatively thick sandstones and thin mudstone interbeds.

The following figure is a well-log cross section of the ''Glob alt'' reservoir interval; datum is a mudstone within the GA-2 sandstone (well locations are shown on [[:file:sedimentary-basin-analysis_fig4-46.png|Figure 3]]). All logs are spontaneous potential with true vertical depth displays. The GA-4 reservoir sand is below the displayed interval. Log profiles are annotated: arrow C = funnel-shaped, coarsening-upward sandstone; arrow F = bell-shaped, fining-upward sandstone; parallel lines B = blocky profile of relatively thick sandstones and thin mudstone interbeds.

[[file:sedimentary-basin-analysis_fig4-48.png|thumb|{{figure number|4}}After Armentrout et al.<ref name=ch04r7 />). Copyright: Springer-Verlag.]]

[[file:sedimentary-basin-analysis_fig4-48.png|thumb|{{figure number|4}}After Armentrout et al.<ref name=ArmentroutEtAl_1991 />. Courtesy Springer-Verlag.]]

==Net sandstone isopachs==

==Net sandstone isopachs==

[[file:sedimentary-basin-analysis_fig4-49.png|left|thumb|{{figure number|5}}. Copyright: Armentrout et al. (1991); courtesy Springer-Verlag.]]

[[file:sedimentary-basin-analysis_fig4-49.png|left|thumb|{{figure number|5}}From Armentrout et al.<ref name=ArmentroutEtAl_1991 />. Courtesy Springer-Verlag.]]

Well-log correlations within the ''Glob alt'' isochron thick show a succession of aggrading sandstone bodies ([[:file:sedimentary-basin-analysis_fig4-48.png|Figure 4]]). [[:file:sedimentary-basin-analysis_fig4-49.png|Figure 5]] shows net sandstone isopachs for reservoir units of the ''Glob alt'' sandstone interval. The stratigraphic succession from top to bottom reservoir sandstone is 1, 1.1, 2, 2.2, 3, and 4. Maps of each sandstone interval document lobate deposition within the minibasin. Individual lobe development shows compensation lobe switching as progressively younger deposits infill the mud-rich/sand-poor intralobe areas of the preceding lobe.

Well-log correlations within the ''Glob alt'' isochron thick show a succession of aggrading sandstone bodies ([[:file:sedimentary-basin-analysis_fig4-48.png|Figure 4]]). [[:file:sedimentary-basin-analysis_fig4-49.png|Figure 5]] shows net sandstone isopachs for reservoir units of the ''Glob alt'' sandstone interval. The stratigraphic succession from top to bottom reservoir sandstone is 1, 1.1, 2, 2.2, 3, and 4. Maps of each sandstone interval document lobate deposition within the minibasin. Individual lobe development shows compensation lobe switching as progressively younger deposits infill the mud-rich/sand-poor intralobe areas of the preceding lobe.

==Depositional model diagram==

==Depositional model diagram==

[[file:sedimentary-basin-analysis_fig4-50.png|thumb|{{figure number|6}}. Copyright: Armentrout et al. (1991); courtesy Springer-Verlag.]]

[[file:sedimentary-basin-analysis_fig4-50.png|thumb|{{figure number|6}}From Armentrout et al.<ref name=ArmentroutEtAl_1991 />. Courtesy Springer-Verlag.]]

[[:file:sedimentary-basin-analysis_fig4-50.png|Figure 6]] is a block diagram of the depositional model for the ''Glob alt'' reservoir interval. The model shows a 40-50-mi-long (60-80 km) transport system from a shelf-edge delta basinward to the East Breaks 160-161 minibasin. Depositional water depths exceeded [[depth::1000 ft]] (320 m) (upper bathyal), suggesting transport was by gravity-flow processes. Sandstone deposition in the minibasin may have resulted from subtle variations of sea-floor topography, perhaps related to early salt withdrawal.<ref name=ch04r53>Kneller, B., 1995, Beyond the turbidite paradign: physical models for deposition of turbidites and their implications for reservoir prediction, in Hartley, A., J., Prosser, D., J., eds., Characterization of Deep Marine Clastic Systems: Geological Society, London, Special Publication 94, p. 31–49.</ref> Mass-wasting processes occurred on the slope well to the north of the field, as shown by slump facies on Figure 4-39. The areal extent of the basin-floor sheet is restricted by the areal extent of the East Breaks 160-161 intraslope minibasin.

[[:file:sedimentary-basin-analysis_fig4-50.png|Figure 6]] is a block diagram of the depositional model for the ''Glob alt'' reservoir interval. The model shows a 40-50-mi-long (60-80 km) transport system from a shelf-edge delta basinward to the East Breaks 160-161 minibasin. Depositional water depths exceeded [[depth::1000 ft]] (320 m) (upper bathyal), suggesting transport was by gravity-flow processes. Sandstone deposition in the minibasin may have resulted from subtle variations of sea-floor topography, perhaps related to early salt withdrawal.<ref name=ch04r53>Kneller, B., 1995, Beyond the turbidite paradigm: Physical models for deposition of turbidites and their implications for reservoir prediction, ''in'' Hartley, A. J., and D. J. Prosser, eds., Characterization of Deep Marine Clastic Systems: Geological Society, London, Special Publication 94, p. 31–49.</ref> Mass-wasting processes occurred on the slope well to the north of the field, as shown by slump facies on Figure 4-39. The areal extent of the basin-floor sheet is restricted by the areal extent of the East Breaks 160-161 intraslope minibasin.

==Accommodation space==

==Accommodation space==

===Structural trap formation===

===Structural trap formation===

Structural trap formation is related to differential rotation of the ''Glob alt'' sand-prone interval. This rotation occurred between 1.3 Ma and the present. The result was the development of the rollover anticline downthrown to fault A′, which is a splay off regional fault A (Figures 4-42 and 4-43). (See ;<ref name=ch04r5>Apps, G., M., Peel, F., J., Travis, C., J., Yeilding, C., A., 1994, Structural controls on Tertiary deep water deposition in the northern Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 15th Annual Research conference, p. 1–7.</ref><ref name=ch04r9>Armentrout, J., M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio–Pleistocene, in Howell, J., Aiken, J., eds., High Resolution [[Sequence stratigraphy]]: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65–86.</ref><ref name=ch04r53 /> and Weimer and Bouma, 1995, for discussions on structural control of deepwater deposition.)

Structural trap formation is related to differential rotation of the ''Glob alt'' sand-prone interval. This rotation occurred between 1.3 Ma and the present. The result was the development of the rollover anticline downthrown to fault A′, which is a splay off regional fault A (Figures 4-42 and 4-43). (See<ref name=ch04r5>Apps, G. M., F. J. Peel, C. J. Travis, and C. A. Yeilding, 1994, Structural controls on Tertiary deep water deposition in the northern Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 15th Annual Research conference, p. 1–7.</ref>, <ref name=ch04r9>Armentrout, J. M., 1996, High-resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio–Pleistocene, ''in'' Howell, J., and J. Aiken, eds., High Resolution [[Sequence stratigraphy]]: Innovations and Applications: The Geological Society of London Special Publication 104, p. 65–86.</ref>, <ref name=ch04r53 />, and Weimer and Bouma, 1995, for discussions on structural control of deepwater deposition.)

==See also==

==See also==