Changes

==Oxygen isotope model==

==Oxygen isotope model==

 

[[file:applied-paleontology_fig17-29.png|300px|thumb|{{figure number|1}}Typical oxygen isotope record for the middle Tertiary. Copyright: Wright and Miller, 1993;{{citation needed}} courtesy American Geophysical Union. Time scale adapted from Berggren et al.<ref name=ch17r12>Berggren, W., A., Kent, D., V., Flynn, J., J., 1985a, Paleogene geochronology and chronostratigraphy, in Snelling, N., J., ed., The Chronology of the Geological Record: Geological Society of London Memoir 10, p. 141–195.</ref><ref name=ch17r13>Berggren, W., A., Kent, D., and J.A. van Couvering, 1985b, Neogene geochronology and chronostratig- raphy, in N.J. Snelling, ed., The Chronology of the Geological Record: Geological Society of London Memoir 10, p. 211–260.</ref>]]

applied-paleontology_fig17-29.png|{{figure number|1}}Typical oxygen isotope record for the middle Tertiary. Copyright: Wright and Miller, 1993;{{citation needed}} courtesy American Geophysical Union. Time scale adapted from Berggren et al.<ref name=ch17r12>Berggren, W., A., Kent, D., V., Flynn, J., J., 1985a, Paleogene geochronology and chronostratigraphy, in Snelling, N., J., ed., The Chronology of the Geological Record: Geological Society of London Memoir 10, p. 141–195.</ref><ref name=ch17r13>Berggren, W., A., Kent, D., and J.A. van Couvering, 1985b, Neogene geochronology and chronostratig- raphy, in N.J. Snelling, ed., The Chronology of the Geological Record: Geological Society of London Memoir 10, p. 211–260.</ref>

Glacial-interglacial climatic fluctuations during the late Paleogene and Neogene have been causally related to Milankovitch orbital parameters (eccentricity, obliquity, and precession). During colder glacial climates the oceans become enriched in ¹⁸O relative to ¹⁶O because the lighter ¹⁶O molecule is more easily evaporated from seawater and becomes locked on land in the form of ice. During warmer intervals the reverse is true.

Glacial-interglacial climatic fluctuations during the late Paleogene and Neogene have been causally related to Milankovitch orbital parameters (eccentricity, obliquity, and precession). During colder glacial climates the oceans become enriched in ¹⁸O relative to ¹⁶O because the lighter ¹⁶O molecule is more easily evaporated from seawater and becomes locked on land in the form of ice. During warmer intervals the reverse is true.

==Oxygen isotope correlation==

==Oxygen isotope correlation==

Statistical stacking of detailed records of oceanic ¹⁸O/¹⁶O ratios, based primarily on the analysis of foraminifera from numerous deep-ocean cores and calibration to the geologic time scale, lets us construct standard oxygen isotope chronologies for the Pliocene-Pleistocene.<ref name=ch17r75>Ruddiman, W., F., Raymo, M., E., Martinson, D., G., Clement, B., M., Backman, J., 1989, Pleistocene evolution: Northern Hemisphere ice sheets and North Atlantic Ocean: Paleoceanography, vol. 4, p. 353–412., 10., 1029/PA004i004p00353</ref><ref name=ch17r77>Shackleton, N., J., Berger, A., Peltier, W., R., 1990, An alternate astronomical calibration of the lower Pleistocene time scale based on Ocean Drilling Program Site 677: Transactions of the Royal Society of Edinburgh, Earth Sciences, vol. 81, p. 251–261., 10., 1017/S0263593300020782</ref> and the Miocene and Oligocene<ref name=ch17r97>Wright, J., D., Miller, K., G., 1993, Southern Ocean influences on late Eocene to Miocene deep-water circulation: American Geophysical Union Antarctic Research Series, vol. 60, p. 1–25., 10., 1029/AR060</ref> Thus the oceanic ¹⁸O/¹⁶O record provides a precise correlative tool based on worldwide fluctuations in climate. Isotopic analysis of well-preserved foraminifera from core or outcrop samples or from well cuttings in areas of relatively high sedimentation rate may help us recognize worldwide oxygen isotope stages. Isotope studies can be useful locally in enhancing the stratigraphic resolution of existing biostratigraphy.

Statistical stacking of detailed records of oceanic ¹⁸O/¹⁶O ratios, based primarily on the analysis of foraminifera from numerous deep-ocean cores and calibration to the geologic time scale, lets us construct standard oxygen isotope chronologies for the Pliocene-Pleistocene.<ref name=ch17r75>Ruddiman, W., F., Raymo, M., E., Martinson, D., G., Clement, B., M., Backman, J., 1989, Pleistocene evolution: Northern Hemisphere ice sheets and North Atlantic Ocean: Paleoceanography, vol. 4, p. 353–412., 10., 1029/PA004i004p00353</ref><ref name=ch17r77>Shackleton, N., J., Berger, A., Peltier, W., R., 1990, An alternate astronomical calibration of the lower Pleistocene time scale based on Ocean Drilling Program Site 677: Transactions of the Royal Society of Edinburgh, Earth Sciences, vol. 81, p. 251–261., 10., 1017/S0263593300020782</ref> and the Miocene and Oligocene<ref name=ch17r97>Wright, J., D., Miller, K., G., 1993, Southern Ocean influences on late Eocene to Miocene deep-water circulation: American Geophysical Union Antarctic Research Series, vol. 60, p. 1–25., 10., 1029/AR060</ref> Thus the oceanic ¹⁸O/¹⁶O record provides a precise correlative tool based on worldwide fluctuations in climate. Isotopic analysis of well-preserved foraminifera from core or outcrop samples or from well cuttings in areas of relatively high sedimentation rate may help us recognize worldwide oxygen isotope stages. Isotope studies can be useful locally in enhancing the stratigraphic resolution of existing biostratigraphy.

==Strontium isotope stratigraphy==

==Strontium isotope stratigraphy==

 

[[file:applied-paleontology_fig17-31.png|thumb|{{figure number|3}}Evolution of the ⁸⁷Sr/⁸⁶Sr ratio in seawater through the Phanerozoic. After Burke et al.<ref name=ch17r23>Burke, W., R., Denison, R., E., Hetherington, E., A., Koepnick, R., B., Nelson, H., F., Otto, J., B., 1982, Variation of seawater 87Sr/86Sr throughout Phanerozoic time: Geology, vol. 10, p. 516–519., 10., 1130/0091-7613(1982)10<516:VOSSTP>2., 0., CO;2</ref> Copyright: Geology.]]

applied-paleontology_fig17-31.png|{{figure number|3}}Evolution of the ⁸⁷Sr/⁸⁶Sr ratio in seawater through the Phanerozoic. After Burke et al.<ref name=ch17r23>Burke, W., R., Denison, R., E., Hetherington, E., A., Koepnick, R., B., Nelson, H., F., Otto, J., B., 1982, Variation of seawater 87Sr/86Sr throughout Phanerozoic time: Geology, vol. 10, p. 516–519., 10., 1130/0091-7613(1982)10<516:VOSSTP>2., 0., CO;2</ref> Copyright: Geology.

An extensive database of ⁸⁷Sr/⁸⁶Sr measurements on marine carbonate, evaporite, and phosphate samples compiled at Mobil and elsewhere has permitted construction of a ⁸⁷Sr/⁸⁶Sr “curve” for the Phanerozoic (see illustration below). During intervals when the ⁸⁷Sr/⁸⁶Sr curve is relatively linear and steep with respect to time (e.g., during the Permian, Jurassic, Late Cretaceous, and several intervals within the Late Eocene to Holocene), the strontium curve can be used as a chronometer because any given ratio along the line can be associated with a unique numerical age. The accuracy of the resulting age estimates approaches ±1.0 m.y for the Cenozoic intervals.

An extensive database of ⁸⁷Sr/⁸⁶Sr measurements on marine carbonate, evaporite, and phosphate samples compiled at Mobil and elsewhere has permitted construction of a ⁸⁷Sr/⁸⁶Sr “curve” for the Phanerozoic (see illustration below). During intervals when the ⁸⁷Sr/⁸⁶Sr curve is relatively linear and steep with respect to time (e.g., during the Permian, Jurassic, Late Cretaceous, and several intervals within the Late Eocene to Holocene), the strontium curve can be used as a chronometer because any given ratio along the line can be associated with a unique numerical age. The accuracy of the resulting age estimates approaches ±1.0 m.y for the Cenozoic intervals.

==High-latitude example==

==High-latitude example==

The strontium isotope technique is especially useful in high-latitude and shallow-water marine sections of middle to late Tertiary age where biostratigraphic zones have relatively long durations and diagnostic calcareous taxa are often absent or difficult to identify.

The strontium isotope technique is especially useful in high-latitude and shallow-water marine sections of middle to late Tertiary age where biostratigraphic zones have relatively long durations and diagnostic calcareous taxa are often absent or difficult to identify.