Changes

==Applying abundance patterns==

==Applying abundance patterns==

In the Texas offshore Pliocene and Pleistocene depocenter, patterns of fossil abundance are often the most widely applicable observational criteria for identifying the surfaces that define sequences.<ref name=ch04r6>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref><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><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> Sequence boundaries are associated with intervals of few or no in situ fossils and often abundance peaks of reworked fossils in the overlying lowstand systems tract. The transgressive surface is characterized by the stratigraphic upward change from decreasing fossil abundance to increasing abundance. The maximum flooding surface is marked by the maximum fossil abundance interval due to sediment starvation<ref name=ch04r59>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: SEPM Special Publication 42, p. 183–213.</ref><ref name=ch04r10 />

In the Texas offshore Pliocene and Pleistocene depocenter, patterns of fossil abundance are often the most widely applicable observational criteria for identifying the surfaces that define sequences.<ref name=ch04r6>Armentrout, J., M., 1987, Integration of biostratigraphy and seismic stratigraphy: Pliocene–Pleistocene, Gulf of Mexico: Proceedings, Gulf Coast Section SEPM 8th Annual Research Conference, p. 6–14.</ref><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><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> Sequence boundaries are associated with intervals of few or no in situ fossils and often abundance peaks of reworked fossils in the overlying lowstand systems tract. The transgressive surface is characterized by the stratigraphic upward change from decreasing fossil abundance to increasing abundance. The maximum flooding surface is marked by the maximum fossil abundance interval due to sediment starvation<ref name=ch04r59>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: SEPM Special Publication 42, p. 183–213.</ref><ref name=ch04r10 />

==Example abundance pattern==

==Example abundance pattern==

The figure below is an abundance histogram for the planktonic foraminiferal microfossils ''Globorotalia menardii'' (s = sinistral) and ''Globorotalia inflata'' from the MSC 160-1 core hole, East Breaks area (data provided by Gerry Ragan, Mobil Exploration and Producing US). The core hole is [[length::0.3 mi]] to the west of the seismic reflection profile shown in Figure 4-19. Data on sediment type and biostratigraphy from core hole MSC 160-1 permits geologic characterizations of both the regionally parallel and locally shingled-clinoform seismic facies.

The figure below is an abundance histogram for the planktonic foraminiferal microfossils ''Globorotalia menardii'' (s = sinistral) and ''Globorotalia inflata'' from the MSC 160-1 core hole, East Breaks area (data provided by Gerry Ragan, Mobil Exploration and Producing US). The core hole is [[length::0.3 mi]] to the west of the seismic reflection profile shown in [[:file:sedimentary-basin-analysis fig4-19.png|Figure 1]]. Data on sediment type and biostratigraphy from core hole MSC 160-1 permits geologic characterizations of both the regionally parallel and locally shingled-clinoform seismic facies.

The figure contrasts the abundance of sinistral (s) ''Globorotalia menardii (G. menardii)'' with that of ''Globorotalia inflata (G. inflata)'' in each sample. Note the alternating pattern of abundance.

The figure contrasts the abundance of sinistral (s) ''Globorotalia menardii (G. menardii)'' with that of ''Globorotalia inflata (G. inflata)'' in each sample. Note the alternating pattern of abundance.

==Pattern interpretation==

==Pattern interpretation==

[[file:sedimentary-basin-analysis_fig4-20.png|300px|thumb|{{figure number|1}}Comparison of the abundance of sinistral (s) ''Globoratalia menardii'' with that of ''Globorotalia inflata (G. inflata)'' in each sample. Note the alternating pattern of abundance. Copyright: Armentrout;<ref name=ch04r9 /> courtesy Gulf Coast SEPM and Geological Society of London.]]

[[file:sedimentary-basin-analysis_fig4-20.png|300px|thumb|{{figure number|2}}Comparison of the abundance of sinistral (s) ''Globoratalia menardii'' with that of ''Globorotalia inflata (G. inflata)'' in each sample. Note the alternating pattern of abundance. Copyright: Armentrout;<ref name=ch04r9 /> courtesy Gulf Coast SEPM and Geological Society of London.]]

The high abundance of ''G. menardii'' at depths of 0-20 ft (0-7 m) shown in [[:file:sedimentary-basin-analysis_fig4-20.png|Figure 1]] correlates with the interval at the sea floor that is part of the regionally extensive transgressive mud of the Holocene. The arrow on the seismic section, shown on Figure 4-19, at about 0.6 sec (two-way time) marks a trough between two high-amplitude continuous reflections that also correlate with the high-abundance interval of ''G. menardii'' between 190 and [[length::320 ft]] (58 and 98 m). In contrast, the stratigraphic intervals of ''G. menardii'' low abundance and ''G. inflata'' high abundance correlate with the shingled-clinoform seismic facies.

The high abundance of ''G. menardii'' at depths of 0-20 ft (0-7 m) shown in [[:file:sedimentary-basin-analysis_fig4-20.png|Figure 2]] correlates with the interval at the sea floor that is part of the regionally extensive transgressive mud of the Holocene. The arrow on the seismic section, shown on Figure 4-19, at about 0.6 sec (two-way time) marks a trough between two high-amplitude continuous reflections that also correlate with the high-abundance interval of ''G. menardii'' between 190 and [[length::320 ft]] (58 and 98 m). In contrast, the stratigraphic intervals of ''G. menardii'' low abundance and ''G. inflata'' high abundance correlate with the shingled-clinoform seismic facies.

Stratigraphic intervals with abundant ''G. menardii'' are interpreted to indicate warmwater interglacial conditions, and abundant ''G. inflata'' are interpreted as temperate-water glacial indicators.<ref name=ch04r52>Kennett, J., P., Elmstrom, K., Penrose, N., 1985, The last deglaciation in Orca basin, Gulf of Mexico: high-resolution planktonic foraminiferal changes: Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 50, p. 189–216.</ref><ref name=ch04r63>Martin, R., E., Neff, E., D., Johnson, G., W., Krantz, D., E., 1990, Biostratigraphic expression of sequence boundaries in the Pleistocene: the Ericson and Wollin zonation revisited: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 229–236.</ref> The correlation of abundant ''G. menardii'' with the regionally extensive transgressive mud of the Holocene provides local confirmation of the warm-water interglacial interpretation. The regionally continuous reflections at 0.6 sec also indicate a transgressive interglacial interval. The shingledclinoform facies correlates with the ''G. inflata'' abundance peak, suggesting deposition during temperate-water glacial conditions.

Stratigraphic intervals with abundant ''G. menardii'' are interpreted to indicate warmwater interglacial conditions, and abundant ''G. inflata'' are interpreted as temperate-water glacial indicators.<ref name=ch04r52>Kennett, J., P., Elmstrom, K., Penrose, N., 1985, The last deglaciation in Orca basin, Gulf of Mexico: high-resolution planktonic foraminiferal changes: Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 50, p. 189–216.</ref><ref name=ch04r63>Martin, R., E., Neff, E., D., Johnson, G., W., Krantz, D., E., 1990, Biostratigraphic expression of sequence boundaries in the Pleistocene: the Ericson and Wollin zonation revisited: Proceedings, Gulf Coast Section SEPM 11th Annual Research conference, p. 229–236.</ref> The correlation of abundant ''G. menardii'' with the regionally extensive transgressive mud of the Holocene provides local confirmation of the warm-water interglacial interpretation. The regionally continuous reflections at 0.6 sec also indicate a transgressive interglacial interval. The shingledclinoform facies correlates with the ''G. inflata'' abundance peak, suggesting deposition during temperate-water glacial conditions.