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PSStable Isotope Profiles in an Isolated Carbonate Platform: Implications for Stratigraphic Correlations*

Jean Hsieh1, David Katz1, Paul (Mitch) Harris1, Matt Buoniconti1, John Humphrey2, and Isabel Montanez3

 

Search and Discovery Article #50132 (2008)

Posted November 12, 2008

 

*Adapted from oral presentation at AAPG International Conference and Exhibition, Cape Town, South Africa, October 26-29, 2008.

Click to view list of articles adapted from presentations by P.M. (Mitch) Harris or by his co-workers and him at AAPG meetings from 2000 to 2008.

 

1 Chevron ETC - San Ramon, CA([email protected],[email protected], [email protected])  

2 Colorado School of Mines, Department of Geology, Golden, CO  

3 UC - Davis, Department of Geology, Davis, CA

 

Abstract

The δ13Ccarb values of biotically and abiotically precipitated marine carbonates display significant temporal variation that is well documented through the geological record (e.g., Popp et al., 1997). These variations have been attributed to changes in carbon cycling through changes in productivity and organic carbon burial rates, variations in carbon sources to the atmosphere and ocean, and shifts in weathering patterns and rates. The potential of secular variation in marine carbonate δ13Ccarb records as a chronostratigraphic correlation tool and paleoenvironmental proxy has been well established over the past two decades (e.g., Vahrenkamp, 1996; Montanez et al, 2000; Saltzman, 2002). However, carbonates are susceptible to diagenetic modification, particularly those deposited in shallow-water epeiric seas subjected to sea-level fluctuations. Thus, potential diagenetic influences on the δ13Ccarb values must be considered when interpreting measured values.

This study presents the results of measurements of the carbon and oxygen isotopic values from the late Visean through the Bashkirian for an isolated carbonate platform. We are examining the implications of the bulk rock stable isotope profiles for stratigraphic correlation in a reservoir. The δ13C stratigraphy shows trends to positive and negative δ13C values that can be correlated with sequence boundaries picked, using traditional facies variations based on core descriptions. Secular variability in the δ13C stratigraphy is also loosely correlated with changes in wireline log values. Several sequence boundaries could be modified and higher order cycle boundaries could be picked using the δ13C stratigraphy. These results suggest that stable isotope profiles can be used to help constrain the sequence stratigraphic framework of a carbonate reservoir.

 

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Isotopic Profiles and Their Use

  • Rises and falls in the Sr or C isotope data can correspond to eustatic sealevel changes.
  • An isotopic profile can be used to help to correlate sections, if original signals have not been reset at a later time.
  • Isotopic signals of whole rock samples may be affected by later formed cements. These signals may provide information about fluid movement or exposure events.
  • Can these signals be used to correlate in a Carboniferous isolated platform?

Summary and Conclusions

  • Trends to more negative carbon isotope values occur just below sequence boundaries, reflecting the incorporation of more depleted carbon from soil processes.
  • Trends to more positive carbon isotope values occur as the maximum flooding surface is approached, reflecting the burial of more depleted carbon and subsequent enrichment of remaining carbon in the water column.
  • More variations in the isotopic profiles occur where there are thinner beds reflecting more frequent changes in accommodation space or a decrease in accommodation.
  • Smaller changes in isotopic composition may reflect higher order variations that are not apparent in facies stacking patterns.
  • The frequency of sample analysis could be reduced. Further analysis of the data will provide an optimal sampling strategy.
  • These patterns in the platform support and add to the conclusions made using facies stacking patterns. But, in the slope, if there are similar isotopic variations as seen in the platform, this could be a powerful tool for correlating from platform to slope.
  • Comparison to worldwide outcrop data shows similar trends as found in ramp environments. This data supports the idea that the isotopic values and first order trends are likely to be a global signal rather than a result of local effects in shallow water environments.

Acknowledgments

Thanks to Jeroen Kenter, Ted Playton, and James Bishop for informative discussions.

Selected References

Bruckschen, P., S. Oesmann, and J. Veizer, 1999, Isotope stratigraphy of the European carboniferous; proxy signals for ocean chemistry, climate and tectonics: Chemical Geology, v. 161/1, p. 127-163.

Denison, R.E., R.B. Koepnick, W.H. Burke, E.A. Hetherington, and A. Fletcher, 1994, Construction of the Mississippian, Pennsylvanian and Permian seawater87Sr/86Sr curve: Chemical Geology, v. 112/1-2, p. 145-167.

Fielding, C.R., J. Whittaker, S.A. Henrys, T.J. Wilson, and T.R. Naish, 2008, Seismic facies and stratigraphy of the Cenozoic succession in McMurdo Sound, Antarctica; implications for tectonic, climatic and glacial history: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 260/1-2, p. 8-29.

Grossman, E.L., T.E. Yancey, T.E. Jones, P. Bruckschen, B. Chuvashov, S.J. Mazzullo and H. Mii, 2008, Glaciation, aridification, and carbon sequestration in the permo-carboniferous: the isotopic record from low latitudes: Palaeographhy, Palaeoclimatology, Palaeoecology, v. 268/3-4, p. 222-233.

Isbell, J.L., P.A. Lenaker, R.A. Askin, M.F. Miller, and L.E. Babcock, 2003, Reevaluation of the timing and extent of late Paleozoic glaciation in Gondwana; role of the transantarctic mountains: Geology, v. 31/11, p 997-980.

Katz, M.E., K.G. Miller, J.D. Wright, B.S. Wade, J.V. Browning, B.S. Cramer, and Y. Rosenthal, 2008, Stepwise transition from the Eocene greenhouse to the Oligocene icehouse: Nature Geoscience, v. 1, p. 329-334.

Kenter, J.A.M., and, P.M. Harris, 2006, Web-based outcrop digital analog database (WODAD); archiving and searching carbonate platform margins: AAPG Annual Convention, Houston, Texas, 9-12 April, 2006, AAPG Search and Discovery article #40300, web http://www.searchanddiscovery.net

Korte, C., T. Jasper, H.W. Kozur, and J. Veizer, 2005, δ18O and δ13C of Permian brachiopods; a record of seawater evolution and continental glaciation: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 224, p. 333-351.

Mii, H.S., E.L. Grossman, T.E. Yancey, B. Chuvashov, and A. Egorov, 2001, Isotopic records of brachiopod shells from the Russian platform; evidence for the onset of mid-Carboniferous glaciation: Chemical Geology, v. 175/1-2, p. 133-147.

Popp, B.N., E.A. Laws, R.R. Bidigare, J.E. Dore, K.L. Hanson, and S.G. Wakeham, 1998, Effect of Phytoplankton cell geometry on carbon isotopic fractionation: Geochimica et Cosmochimica Acta, v. 62/1, p. 69-77.

Saltzman, M.R., 2003, Late Paleozoic ice age; oceanic gateway or pCO2?: Geology, v. 31/2, p.151-154.

Veizer, J., et al., 1999, 87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater: Chemical Geology, v. 161/1-3, p. 59-88.

 

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