Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Exploring for stratigraphic traps

  | chapter = Exploring for stratigraphic traps

  | frompg  = 21-1

  | frompg  = 21-15

  | topg    = 21-68

  | topg    = 21-17

  | author  = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks

  | author  = John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch21/ch21.htm

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

During a third-order sea level change, cycle amplitude is great enough (approximately 50–150 ft) to expose the shelf. Depositional sites range from coastal plain to deep basin. The unit of strata deposited during a third-order cycle is called a '''depositional sequence'''. A depositional sequence has three subdivisions: highstand systems tract (HST), transgressive systems tract (TST), and lowstand systems tract (LST). [[:file:exploring-for-stratigraphic-traps_fig21-8.png|Figure 1]] shows a schematic cross section of a third-order sequence and its various systems tracts.

During a third-order sea level change, cycle amplitude is great enough (approximately 50–150 ft) to expose the shelf. Depositional sites range from coastal plain to deep basin. The unit of strata deposited during a third-order cycle is called a '''depositional sequence'''. A depositional sequence has three subdivisions: highstand systems tract (HST), transgressive systems tract (TST), and lowstand systems tract (LST). [[:file:exploring-for-stratigraphic-traps_fig21-8.png|Figure 1]] shows a schematic [[cross section]] of a third-order sequence and its various systems tracts.

==Third-order sequence deposition==

==Third-order sequence deposition==

[[file:exploring-for-stratigraphic-traps_fig21-8.png|300px|thumb|{{figure number|1}}. Copyright: Hyne, 1995; courtesy Tulsa Geological Society.]]

[[file:exploring-for-stratigraphic-traps_fig21-8.png|300px|thumb|{{figure number|1}}Schematic cross section of a third-order sequence and its various systems tracts. Copyright: Hyne;<ref>Hyne, N. J., 1995, Sequence stratigraphy: a new look at old rocks, in N. J. Hyne, ed., Sequence Stratigraphy of the Mid Continent: Tulsa Geological Society Special Publication 4, p. 5–20.</ref> courtesy Tulsa Geological Society.]]

The schematic cross section in [[:file:exploring-for-stratigraphic-traps_fig21-9.png|Figure 2]] is a third-order sequence model based on observations of the Tertiary of the Gulf of Mexico passive margin basin.<ref name=ch21r47>Van Wagoner, J., C., Mitchum, R., M., Campion, K., M., Rahmanian, V., D., 1990, Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops: Concepts for High-Resolution Correlation of Time and Facies: [http://store.aapg.org/detail.aspx?id=1196 AAPG Methods in Exploration Series No. 7], 55 p.</ref> Although different basin types, i.e., foreland basins or active margin basins, require adjustments to the model, the Gulf of Mexico model still is useful for understanding third-order sequence deposition.

The schematic [[cross section]] in [[:file:exploring-for-stratigraphic-traps_fig21-9.png|Figure 2]] is a third-order sequence model based on observations of the [[Tertiary]] of the [[Gulf of Mexico]] passive margin basin.<ref name=ch21r47>Van Wagoner, J., C., Mitchum, R., M., Campion, K., M., Rahmanian, V., D., 1990, Siliciclastic Sequence Stratigraphy in Well Logs, Cores and Outcrops: Concepts for High-Resolution Correlation of Time and Facies: [http://store.aapg.org/detail.aspx?id=1196 AAPG Methods in Exploration Series No. 7], 55 p.</ref> Although different basin types, i.e., foreland basins or active margin basins, require adjustments to the model, the Gulf of Mexico model still is useful for understanding third-order sequence deposition.

[[file:exploring-for-stratigraphic-traps_fig21-9.png|300px|thumb|{{figure number|2}}. Copyright: Haq, 1988; courtesy SEPM.]]

[[file:exploring-for-stratigraphic-traps_fig21-9.png|300px|thumb|{{figure number|2}}Third-order sequence model based on observations of the Tertiary of the Gulf of Mexico passive margin basin. Copyright: Haq;<ref>Haq, B. U., J. Hardenbol, and P. R. Vail, 1988, Mesozoic and Cenozoic chronostratigraphy and cycles of sea-level change in C. K. Wilgus, B. S. Hastings, H. W. Posamentier, J. Van Wagoner, C. A. Ross, and G. C. St. C. Kendall, eds., Sea-Level Change: An Integrated Approach: Society of Economic Paleontologists and Mineralogists Special Publication 42, p. 71–108.</ref> courtesy SEPM.]]

The order of deposition for the sequence shown in [[:file:exploring-for-stratigraphic-traps_fig21-9.png|Figure 2]] is as follows:<ref name=ch21r47 />

The order of deposition for the sequence shown in [[:file:exploring-for-stratigraphic-traps_fig21-9.png|Figure 2]] is as follows:<ref name=ch21r47 />

* Transgressive systems tract deposition

* Transgressive systems tract deposition

** Rate of rise is at a maximum.

** Rate of rise is at a maximum.

** During brief slowdowns in the rate of rise, parasequences (fourth-order sequences) prograde; but overall they stack in a backstepping pattern.

** During brief slowdowns in the rate of rise, parasequences (fourth-order sequences) [[Depocenter#Sediment_supply_rate_and_facies_patterns|prograde]]; but overall they stack in a backstepping pattern.

** Organic-rich (condensed) section moves up onto the shelf.

** Organic-rich (condensed) section moves up onto the shelf.

** Fluvial systems typically shift from braided to meandering pattern.

** Fluvial systems typically shift from braided to meandering pattern.

* Highstand systems tract deposition

* Highstand systems tract deposition

** Rate of sea level rise is at a minimum; in the late highstand, it falls slowly.

** Rate of sea level rise is at a minimum; in the late highstand, it falls slowly.

** Depositional rates exceed rate of sea level rise, causing parasequences to build basinward in aggradational to progradational parasequence sets.

** Depositional rates exceed rate of sea level rise, causing parasequences to build basinward in [[Depocenter#Sediment_supply_rate_and_facies_patterns|aggradational]] to progradational parasequence sets.

** Parasequences downlap onto the condensed section.

** Parasequences downlap onto the condensed section.

[[file:exploring-for-stratigraphic-traps_fig21-10.png|thumb|300px|{{figure number|3}}. Copyright: Weber et al., 1995; courtesy SEPM.]]

[[file:exploring-for-stratigraphic-traps_fig21-10.png|thumb|300px|{{figure number|3}}The Desmoinian of the Paradox basin, Utah, an example of a third-order depositional sequence. Copyright: Weber et al.;<ref>Weber, L. J., J. F. Sarg, and F. M. Wright, 1995, Sequence stratigraphy and reservoir delin- eation of the middle Pennsylvanian (Desmoinesian), Paradox basin and Aneth field, southwestern U.S.A., in J. F. Read, L. J. Weber, J. F. Sarg, and F. M. Wright, eds., Milankovitch Sea-Level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-House Worlds: SEPM Short Course No. 35, 79 p.</ref> courtesy SEPM.]]

==Third-order sequence example==

==Third-order sequence example==

The Desmoinian of the Paradox basin, Utah, shown in [[:file:exploring-for-stratigraphic-traps_fig21-10.png|Figure 3]], is an example of a third-order depositional sequence.

The Desmoinian of the Paradox basin, Utah, shown in [[:file:exploring-for-stratigraphic-traps_fig21-10.png|Figure 3]], is an example of a third-order depositional sequence.

==Carbonate platform third-order sequence==

==Carbonate platform third-order sequence==

The diagrams below outline the deposition of a sequence associated with a carbonate plat-form during a third-order sea level cycle. Sequence deposition begins with lowstand systems tract (2 and 3) and ends with the highstand systems tract (5).

The diagrams below<ref>Hunt, D., and M. E. Tucker, 1993, [http://archives.datapages.com/data/specpubs/carbona1/data/a044/a044/0001/0400/0409.htm The Mid-Cretaceous Urgonian platform of S. E. France], in J. A. Simo, R. W. Scott, and J. P. Masse, eds., Cretaceous Carbonate Platforms: [http://store.aapg.org/detail.aspx?id=1188 AAPG Memoir 56], p. 409-453.</ref> outline the deposition of a sequence associated with a carbonate plat-form during a third-order sea level cycle. Sequence deposition begins with lowstand systems tract (2 and 3) and ends with the highstand systems tract (5).

# Highstand

# Highstand

#* Rimmed shelf with accretionary slope apron pattern of progradation

#* Rimmed shelf with accretionary slope apron pattern of progradation

# Forced regression

# Forced [[regression]]

#* Rate of eustatic fall exceeds rate of subsidence

#* Rate of eustatic fall exceeds rate of subsidence

#* Sea level is at its lowest point and the greatest area of the platform is exposed.

#* Sea level is at its lowest point and the greatest area of the platform is exposed.

# Lowstand

# Lowstand

#* Rate of eustatic fall decreases, reaches stillstand, and rises slowly

#* Rate of eustatic fall decreases, reaches stillstand, and rises slowly

#* Lowstand wedge progrades seaward

#* Lowstand wedge [[Depocenter#Sediment_supply_rate_and_facies_patterns|progrades]] seaward

# Maximum flooding

# Maximum flooding

#* Most of shelf drowns as sedimentation outpaced by relative sea level rise

#* Most of shelf drowns as sedimentation outpaced by relative sea level rise

==See also==

==See also==

* [[Sequence stratigraphy]]

* [[Sequence stratigraphy]]

* [[Hierarchy of sequences]]

* [[Hierarchy of sequences]]

* [[Fourth- and fifth-order sequences (Parasequences)]]

* [[Fourth- and fifth-order sequences (Parasequences)]]

[[Category:Exploring for stratigraphic traps]]

[[Category:Exploring for stratigraphic traps]]

[[Category:Pages with problematic figures]]

[[Category:Pages with problematic figures]]