Changes

==Numerical ages==

==Numerical ages==

Rate-dependent analyses such as subsidence analysis, deposition rate, and [[maturation]] modeling require age-depth pairs as input data. Numerical ages are critical to accurate analyses and ideally should be based on high-resolution biostratigraphic control calibrated to a standard [http://www.britannica.com/EBchecked/topic/229486/geochronology geochronology], such as Harland et al.<ref name=ch17r44>Harland, W., B., Armstrong, R., L., Cox, A., V., Craig, L., E., Smith, A., G., Smith, D., G., 1990, A Geologic Time Scale—Revised Edition: Cambridge, Cambridge University Press, 263 p.</ref> Berggren et al.<ref name=ch17r15>Berggren, W., A., Kent, D., V., Swisher, C., Aubry, M.-P., 1995, A revised Cenozoic geochronology and chronostratigraphy, in Berggren, W., A., Kent, D., V., Aubry, M.-P., Hardenbol, J., eds., Geochronology, Time Scales, and Global Stratigraphic Correlation: Society for Sedimentary Geology (SEPM) Special Publication 54, p. 127–208.</ref> or Gradstein et al.<ref name=ch17r42>Gradstein, F., M., Agterberg, F., P., Ogg, J., G., Hardenbol, J., Van Veen, P., Thierry, J., Huang, Z., 1995, A Triassic, Jurassic, and Cretaceous time scale, in Berggren, W., A., Kent, D., V., Aubry, M.-P., Hardenbol, J., eds., Geochronology, Time Scales, and Global Stratigraphic Correlation: Society for Sedimentary Geology (SEPM) Special Publication 54, p. 93–125.</ref>

Rate-dependent analyses such as subsidence analysis, deposition rate, and [[maturation]] modeling require age-depth pairs as input data. Numerical ages are critical to accurate analyses and ideally should be based on high-resolution biostratigraphic control calibrated to a standard [http://www.britannica.com/EBchecked/topic/229486/geochronology geochronology], such as Harland et al.<ref name=ch17r44>Harland, W. B., R. L. Armstrong, A. V. Cox, L. E. Craig, A. G. Smith, and D. G. Smith, 1990, A Geologic Time Scale—Revised Edition: Cambridge, Cambridge University Press, 263 p.</ref> Berggren et al.<ref name=ch17r15>Berggren, W. A., D. V. Kent, C. Swisher, and M.-P. Aubry, 1995, A revised Cenozoic geochronology and chronostratigraphy, in W. A. Berggren, D. V. Kent, M.-P. Aubry, and J. Hardenbol, eds., Geochronology, Time Scales, and Global Stratigraphic Correlation: Society for Sedimentary Geology (SEPM) Special Publication 54, p. 127–208.</ref> or Gradstein et al.<ref name=ch17r42>Gradstein, F. M., F. P. Agterberg, J. G. Ogg, J. Hardenbol, P. Van Veen, J. Thierry,and Z. Huang, 1995, A Triassic, Jurassic, and Cretaceous time scale, in W. A. Berggren, D. V. Kent, M.-P. Aubry, and J. Hardenbol, eds., Geochronology, Time Scales, and Global Stratigraphic Correlation: Society for Sedimentary Geology (SEPM) Special Publication 54, p. 93–125.</ref>

==Systems tract interpretation==

==Systems tract interpretation==

[[file:applied-paleontology_fig17-24.png|thumb|300px|{{figure number|2}}Depositional systems tracts and the bounding surfaces of a stratigraphic sequence depositional model.<ref name=ch17r43 /> Courtesy SEPM.]]

[[file:applied-paleontology_fig17-24.png|thumb|300px|{{figure number|2}}Depositional systems tracts and the bounding surfaces of a stratigraphic sequence depositional model.<ref name=ch17r43 /> Courtesy SEPM.]]

A [[Definitions_of_depositional_system_elements#Systems_tracts||systems tract]] (ST) is a linkage of contemporaneous, three-dimensional arrays of [[lithofacies]].<ref name=ch17r39>Fisher, W. L., McGowen, J. H., 1967, Depositional systems in the Wilcox Group of Texas and their relationship to occurrence of oil and gas: Transactions of the Gulf Coast Association of Geological Societies, vol. 17, p. 105–125.</ref><ref name=ch17r21>Brown, L., F., Fisher, W., L., 1977, [http://archives.datapages.com/data/specpubs/seismic1/data/a165/a165/0001/0200/0213.htm Seismic–stratigraphic interpretation of depositional systems: examples from Brazil rift and pull-apart basins], in Payton, C., E., ed., Seismic Stratigraphy—Applications to Hydrocarbon Exploration: [http://store.aapg.org/detail.aspx?id=1157 AAPG Memoir 26], p. 213–248.</ref> [[:file:applied-paleontology_fig17-24.png|Figure 2]] shows depositional systems tracts and the bounding surfaces of a stratigraphic sequence depositional model.

A [[Definitions_of_depositional_system_elements#Systems_tracts||systems tract]] (ST) is a linkage of contemporaneous, three-dimensional arrays of [[lithofacies]].<ref name=ch17r39>Fisher, W. L., and J. H. McGowen, 1967, Depositional systems in the Wilcox Group of Texas and their relationship to occurrence of oil and gas: Transactions of the Gulf Coast Association of Geological Societies, vol. 17, p. 105–125.</ref><ref name=ch17r21>Brown, L. F., and W. L. Fisher, 1977, [http://archives.datapages.com/data/specpubs/seismic1/data/a165/a165/0001/0200/0213.htm Seismic–stratigraphic interpretation of depositional systems: examples from Brazil rift and pull-apart basins], in C. E. Payton, ed., Seismic Stratigraphy—Applications to Hydrocarbon Exploration: [http://store.aapg.org/detail.aspx?id=1157 AAPG Memoir 26], p. 213–248.</ref> [[:file:applied-paleontology_fig17-24.png|Figure 2]] shows depositional systems tracts and the bounding surfaces of a stratigraphic sequence depositional model.

==Fossil assemblages in the systems tract==

==Fossil assemblages in the systems tract==

In addition to [[Seismic data|seismic]], [[lithofacies]], and [[Basic open hole tools|well log]] signatures<ref name=ch17r92 /> sequence stratigraphic surfaces and systems tracts can be recognized from paleoenvironmental trends evident from several types of paleontologic analyses:

In addition to [[Seismic data|seismic]], [[lithofacies]], and [[Basic open hole tools|well log]] signatures<ref name=ch17r92 /> sequence stratigraphic surfaces and systems tracts can be recognized from paleoenvironmental trends evident from several types of paleontologic analyses:

* '''[[Paleobathymetry]]'''—changes in [http://www.thefreedictionary.com/benthic benthic] faunal composition can help identify relative sea level changes, e.g., benthic [[Microfossils_in_exploration#Principal_microfossils|foraminifera]]l [[Fossil assemblage|biofacies]]<ref name=ch17r3>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico, in Innovative Biostratigraphic Approaches to Sequence Analysis: New Exploration Opportunities: Selected Papers and Illustrated Abstracts of the Eighth Annual Research conference of the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists Foundation, p. 6–14.</ref>

* '''[[Paleobathymetry]]'''—changes in [http://www.thefreedictionary.com/benthic benthic] faunal composition can help identify relative sea level changes, e.g., benthic [[Microfossils_in_exploration#Principal_microfossils|foraminifera]]l [[Fossil assemblage|biofacies]]<ref name=ch17r3>Armentrout, J. M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico, in Innovative Biostratigraphic Approaches to Sequence Analysis: New Exploration Opportunities: Selected Papers and Illustrated Abstracts of the Eighth Annual Research conference of the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists Foundation, p. 6–14.</ref>

* '''Distance from shoreline'''—changes in the relative abundance of marine vs. land-derived forms (e.g., [[Palynomorphs_(organic-walled_microfossils)#Dinoflagellates|dinoflagellate]]-[[Palynomorphs_(organic-walled_microfossils)#Spores_and_pollen|pollen]] ratios) may reflect shoreline advances and retreats

* '''Distance from shoreline'''—changes in the relative abundance of marine vs. land-derived forms (e.g., [[Palynomorphs_(organic-walled_microfossils)#Dinoflagellates|dinoflagellate]]-[[Palynomorphs_(organic-walled_microfossils)#Spores_and_pollen|pollen]] ratios) may reflect shoreline advances and retreats

* '''Climatic cycles'''—fluctuations of warm- and cold-water indicators in marine environments [e.g., [[Calcareous_microfossils#Calcareous_nannofossils|calcareous nannofossils]]<ref name=ch17r78>Shaffer, B., L., 1987, The potential of calcareous nannofossils for recognizing Plio–Pleistocene climatic cycles and sequence boundaries on the shelf, in Innovative Biostratigraphic Approaches To Sequence Analysis: New Exploration Opportunities: Selected Papers and Illustrated Abstracts of the Eighth Annual Research conference of the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists Foundation, p. 142–145.</ref> or [[Microfossils in exploration|planktonic foraminifera]]<ref name=ch17r63>Martin, R., E., Neff, E., D., Johnson, G., W., Krantz, D., E., 1993, Biostratigraphic expression of Pleistocene sequence boundaries, Gulf of Mexico: Palaios, vol. 8, no. 2, p. 155–171., 10., 2307/3515169</ref>] may reflect sea level changes during periods of glacio-eustasy. Variations in arid vs. wet climates reflected in land-based flora (e.g., [[Palynomorphs (organic-walled microfossils)|palynomorphs]]) or [http://www.merriam-webster.com/dictionary/lacustrine lacustrine] fauna (e.g., [[Calcareous_microfossils#Ostracods|ostracods]]) help identify climatic changes that control the development of stratigraphic sequences.

* '''Climatic cycles'''—fluctuations of warm- and cold-water indicators in marine environments [e.g., [[Calcareous_microfossils#Calcareous_nannofossils|calcareous nannofossils]]<ref name=ch17r78>Shaffer, B. L., 1987, The potential of calcareous nannofossils for recognizing Plio–Pleistocene climatic cycles and sequence boundaries on the shelf, in Innovative Biostratigraphic Approaches To Sequence Analysis: New Exploration Opportunities: Selected Papers and Illustrated Abstracts of the Eighth Annual Research conference of the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists Foundation, p. 142–145.</ref> or [[Microfossils in exploration|planktonic foraminifera]]<ref name=ch17r63>Martin, R. E., E. D. Neff, G. W. Johnson, and D. E. Krantz, 1993, Biostratigraphic expression of Pleistocene sequence boundaries, Gulf of Mexico: Palaios, vol. 8, no. 2, p. 155–171., 10., 2307/3515169</ref>] may reflect sea level changes during periods of glacio-eustasy. Variations in arid vs. wet climates reflected in land-based flora (e.g., [[Palynomorphs (organic-walled microfossils)|palynomorphs]]) or [http://www.merriam-webster.com/dictionary/lacustrine lacustrine] fauna (e.g., [[Calcareous_microfossils#Ostracods|ostracods]]) help identify climatic changes that control the development of stratigraphic sequences.

[[:file:applied-paleontology_fig17-25.png|Figure 3]] illustrates the utility of variations in palynological assemblages, reflecting differing paleoenvironmental settings, when differentiating and identifying systems tracts.

[[:file:applied-paleontology_fig17-25.png|Figure 3]] illustrates the utility of variations in palynological assemblages, reflecting differing paleoenvironmental settings, when differentiating and identifying systems tracts.

[[file:applied-paleontology_fig17-26.png|thumb|300px|{{figure number|4}}Paleontologic and paleoenvironmental variables across a condensed section in the Upper Eocene at St. Stephens Quarry, Alabama. Copyright: Loutit et al.;<ref name=ch17r60 /> courtesy SEPM.]]

[[file:applied-paleontology_fig17-26.png|thumb|300px|{{figure number|4}}Paleontologic and paleoenvironmental variables across a condensed section in the Upper Eocene at St. Stephens Quarry, Alabama. Copyright: Loutit et al.;<ref name=ch17r60 /> courtesy SEPM.]]

The [[Definitions_of_depositional_system_elements#Maximum_flooding_surface|maximum flooding surface]] (which may in fact be a thin stratigraphic interval) marks the turn-around point from an overall deepening to an overall shallowing trend. Associated with this horizon may be a major condensed section, marked by the lowest [http://www.thefreedictionary.com/terrigenous\ terrigenous] input, the greatest water depth (approximately), and organic enrichment. This condensed section can provide important fossil age data on [[continental margin]]s<ref name=ch17r60>Loutit, T., S., Hardenbol, J., Vail, P., R., Baum, G., R., 1988, Condensed sections: the key to age determination and correlation of continental margin sequences, in Wilgus, C., K., Hastings, B., S., Kendall, C., G. St. C., Posamentier, H., W., Ross, C., A., Van Wagoner, J., C., eds., Sea-Level Changes: An Integrated Approach: SEPM Special Publication 42, p. 183–213.</ref> because it usually contains the greatest abundance of microfossils and the highest concentration of pelagic forms, such as [[Microfossils_in_exploration#Principal_microfossils|planktonic foraminifera]] and [[Calcareous_microfossils#Calcareous_nannofossils|calcareous nannofossils]]. Other condensed sections are also (but less commonly) found (1) at the top of depositional cycles within the lowstand wedge and (2) overlying individual lowstand fans.

The [[Definitions_of_depositional_system_elements#Maximum_flooding_surface|maximum flooding surface]] (which may in fact be a thin stratigraphic interval) marks the turn-around point from an overall deepening to an overall shallowing trend. Associated with this horizon may be a major condensed section, marked by the lowest [http://www.thefreedictionary.com/terrigenous\ terrigenous] input, the greatest water depth (approximately), and organic enrichment. This condensed section can provide important fossil age data on [[continental margin]]s<ref name=ch17r60>Loutit, T. S., J. Hardenbol, P. R. Vail, and G. R. Baum, 1988, Condensed sections: the key to age determination and correlation of continental margin sequences, in C. K. Wilgus, B. S. Hastings, C., G. St. C. Kendall, H. W. Posamentier, C. A. Ross,and J. C. Van Wagoner, eds., Sea-Level Changes: An Integrated Approach: SEPM Special Publication 42, p. 183–213.</ref> because it usually contains the greatest abundance of microfossils and the highest concentration of pelagic forms, such as [[Microfossils_in_exploration#Principal_microfossils|planktonic foraminifera]] and [[Calcareous_microfossils#Calcareous_nannofossils|calcareous nannofossils]]. Other condensed sections are also (but less commonly) found (1) at the top of depositional cycles within the lowstand wedge and (2) overlying individual lowstand fans.

[[:file:applied-paleontology_fig17-26.png|Figure 4]] illustrates paleontologic and paleoenvironmental variables across a condensed section in the upper Eocene at St. Stephens Quarry, Alabama. The condensed section corresponds to the unnamed blue clay. Overlying Eocene [[Red Bluff]] and [[Bumpnose Formation]]s are [[Sea_level_cycle_phase_and_systems_tracts#Highstand_systems_tracts|highstand systems tract]] deposits; the [[Pachuta]] and [[Shubuta Formations]] represent shelf margin and [[Sea_level_cycle_phase_and_systems_tracts#Transgressive_systems_tracts|transgressive systems tracts]].

[[:file:applied-paleontology_fig17-26.png|Figure 4]] illustrates paleontologic and paleoenvironmental variables across a condensed section in the upper Eocene at St. Stephens Quarry, Alabama. The condensed section corresponds to the unnamed blue clay. Overlying Eocene [[Red Bluff]] and [[Bumpnose Formation]]s are [[Sea_level_cycle_phase_and_systems_tracts#Highstand_systems_tracts|highstand systems tract]] deposits; the [[Pachuta]] and [[Shubuta Formations]] represent shelf margin and [[Sea_level_cycle_phase_and_systems_tracts#Transgressive_systems_tracts|transgressive systems tracts]].

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]

[[Category:Sequence stratigraphy]]

[[Category:Sequence stratigraphy]]