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==Example==
==Example==
Constructing depositional cycle charts for the GOM basin extends back to at least Kolb and Van Lopik<ref name=ch04r55>Kolb, C., R., Van Lopik, J., R., 1958, Geology of the Mississippi River deltaic plain, southeastern Louisiana: U., S. Army Engineer Waterway Experiment Station, Corps of Engineers, Vicksburg, MS, Technical Report 3-483, 120 p.</ref> and Frasier<ref name=ch04r33>Frasier, D., E., 1974, Depositional episodes: their relationship to the Quaternary stratigraphic framework in the north-western portion of the Gulf basin: University of Texas at Austin, Bureau of Economic Geology Circular 74-1.</ref> with Beard et al..<ref name=ch04r18>Beard, J., H., Sangree, J., B., Smith, L., A., 1982, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0066/0002/0150/0158.htm Quaternary chronology, paleoclimate, depositional sequences, and eustatic cycles]: AAPG Bulletin, vol. 66, p. 158–169.</ref> demonstrating the link between depositional sequences and glacial eustasy. The following figure is a composite chronostratigraphic chart that serves as an age model for the GOM basin Pliocene and Pleistocene, summarizing nine studies published between 1982 and 1993. The local cycle charts from each of these studies have been calibrated to the same time scale using the same bioevent marker taxa and are in turn correlated to the global foraminiferal zones and magnetostratigraphic polarity scale as defined by Berggren et al.<ref name=ch04r19>Berggren, W., A., Kent, D., V., Van Couvering, J., A., 1985, The Neogene: part 2. Neogene geochronology and chronostratigraphy in Snelling, N., J., ed., The Chronology of the Geologic Record: Blackwell Scientific Publishing and Geological Society of London Memoir 10, p. 211–260.</ref> and the oxygen isotope chronology of Joyce et al.<ref name=ch04r51>Joyce, J., E., Tjalsma, L., R., C., Prutzman, J., M., 1990, High-resolution planktic stable isotope record and spectral analysis for the last 5., 35 myr: ODP site 625 northeast Gulf of Mexico: Paleoceanography, vol. 5, p. 507–529.</ref> The resulting sum of the depositional sequences and their associated condensed sections (Schaffer, 1987a, b, .<ref name=ch04r72>Pacht, J., A., Bowen, B., E., Bearn, J., H., Schaffer, B., L., 1990, [[Sequence stratigraphy]] of Plio–Pleistocene depositional facies in the offshore Louisiana south additions: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 1–18.</ref> are illustrated.
Constructing depositional cycle charts for the GOM basin extends back to at least Kolb and Van Lopik<ref name=ch04r55>Kolb, C., R., Van Lopik, J., R., 1958, Geology of the Mississippi River deltaic plain, southeastern Louisiana: U., S. Army Engineer Waterway Experiment Station, Corps of Engineers, Vicksburg, MS, Technical Report 3-483, 120 p.</ref> and Frasier<ref name=ch04r33>Frasier, D., E., 1974, Depositional episodes: their relationship to the Quaternary stratigraphic framework in the north-western portion of the Gulf basin: University of Texas at Austin, Bureau of Economic Geology Circular 74-1.</ref> with Beard et al..<ref name=ch04r18>Beard, J., H., Sangree, J., B., Smith, L., A., 1982, [http://archives.datapages.com/data/bulletns/1982-83/data/pg/0066/0002/0150/0158.htm Quaternary chronology, paleoclimate, depositional sequences, and eustatic cycles]: AAPG Bulletin, vol. 66, p. 158–169.</ref> demonstrating the link between depositional sequences and glacial eustasy. The following figure is a composite chronostratigraphic chart that serves as an age model for the GOM basin Pliocene and Pleistocene, summarizing nine studies published between 1982 and 1993. The local cycle charts from each of these studies have been calibrated to the same time scale using the same bioevent marker taxa and are in turn correlated to the global foraminiferal zones and magnetostratigraphic polarity scale as defined by Berggren et al.<ref name=ch04r19>Berggren, W., A., Kent, D., V., Van Couvering, J., A., 1985, The Neogene: part 2. Neogene geochronology and chronostratigraphy in Snelling, N., J., ed., The Chronology of the Geologic Record: Blackwell Scientific Publishing and Geological Society of London Memoir 10, p. 211–260.</ref> and the oxygen isotope chronology of Joyce et al.<ref name=ch04r51>Joyce, J., E., Tjalsma, L., R., C., Prutzman, J., M., 1990, High-resolution planktic stable isotope record and spectral analysis for the last 5., 35 myr: ODP site 625 northeast Gulf of Mexico: Paleoceanography, vol. 5, p. 507–529.</ref> The resulting sum of the depositional sequences and their associated condensed sections (Schaffer, 1987a, b, .<ref name=ch04r72>Pacht, J., A., Bowen, B., E., Bearn, J., H., Schaffer, B., L., 1990, Sequence stratigraphy of Plio–Pleistocene depositional facies in the offshore Louisiana south additions: Gulf Coast Assoc. of Geological Societies Transactions, vol. 40, p. 1–18.</ref> are illustrated.
The composite of all the local studies appears under the column Sum of Sequences, three of which occur in only one or two studies and are considered to be local and possibly autocyclic events (locally forced redistribution of sediments). The youngest six cycles of the chart occur between the ''Pseudoemiliani lacunosa'' bioevent (0.8 Ma) and the sea floor (0.0 Ma) and average 130,000 years in duration. The ten older cycles were deposited between ''Globigerinoides mitra'' (4.15 Ma) and ''P. lacunosa'' (0.8 Ma) bioevents and average 330,000 years duration. These 16 cycles are interpreted as regionally significant and allocyclic (forced by changes external to the sedimentary unit). They are probably glacioeustatic cycles. (See Figure 4-25 and accompanying discussion.)
The composite of all the local studies appears under the column Sum of Sequences, three of which occur in only one or two studies and are considered to be local and possibly autocyclic events (locally forced redistribution of sediments). The youngest six cycles of the chart occur between the ''Pseudoemiliani lacunosa'' bioevent (0.8 Ma) and the sea floor (0.0 Ma) and average 130,000 years in duration. The ten older cycles were deposited between ''Globigerinoides mitra'' (4.15 Ma) and ''P. lacunosa'' (0.8 Ma) bioevents and average 330,000 years duration. These 16 cycles are interpreted as regionally significant and allocyclic (forced by changes external to the sedimentary unit). They are probably glacioeustatic cycles. (See Figure 4-25 and accompanying discussion.)