Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Stanton, R. J. Articles by Ahr, W. M. Search for Related Content GeoRef GeoRef Citation

Early Mississippian climate based on oxygen isotope compositions of brachiopods, Alamogordo Member of the Lake Valley Formation, south-central New Mexico

¹ Department of Geology and Geophysics, Texas A&M University, College Station, Texas 77843, USA

Stable isotope compositions of brachiopod shells from the Alamogordo Member of the Lake Valley Formation (south-central New Mexico) provide information about Early Mississippian paleoclimate. The Alamogordo Member was deposited on a ramp at the southwestern edge of the North American craton, at lat 20°S. It consists of cherty lime-mudstone to lime-packstone (predominantly mudstone and wackestone) strata and scattered mud-cement (Waulsortian) mounds. The brachiopods analyzed lived at water depths estimated to have been between 100 and 300 m.

The ¹⁸O values of well-preserved shells of a single species of brachiopod average –2.3 relative to PDB (the Peedee belemnite isotope standard). This average represents a temperature of 21–26 °C if the isotopic composition of the seawater (¹⁸O_sw) was between 0 and –1, as inferred from Pleistocene and Holocene ¹⁸O_sw and other considerations. Sea-surface temperature would have been 26–31 °C (after we applied a +5 °C correction for water depth). This tropical climate for an Early Mississippian low-latitude site agrees with previous isotopic and climate-modeling results, but contrasts with a temperate climate inferred from comparison of the lithology and biota of the Alamogordo Member with those of modern temperate carbonates.

Key Words: Early Mississippian • New Mexico • oxygen isotopes • paleoclimate

This article has been cited by other articles:

				Elemental and Oxygen Isotope Composition of Early Jurassic Belemnites: Salinity vs. Temperature Signals Journal of Sedimentary Research, May 1, 2004; 74(3): 342 - 354.