HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by BASSETT, D. Articles by ETHINGTON, R. L. Search for Related Content GeoRef GeoRef Citation

OXYGEN ISOTOPIC COMPOSITION OF BIOGENIC PHOSPHATE AND THE TEMPERATURE OF EARLY ORDOVICIAN SEAWATER

¹ Department of Geological Sciences, University of Missouri, Columbia, Missouri 65211, USA;
² Department of Geography, Geology, and Planning, Missouri State University, Springfield, Missouri 65897, USAbassettd{at}missouri.edu

Stable isotopic values were measured on micrite, sparry calcite, dolomite, inarticulated brachiopods, and conodonts from the Lange Ranch section (central Texas) of the Lower Ordovician Tanyard Formation. The section spans the upper Cordylodus angulatus Zone through the lower Rossodus manitouensis Zone. An 2 negative ¹³C shift from >0 to <–1.5_VPDB through the section suggests the lower third of the Rossodus manitouensis Zone was sampled. Consistent with previous studies, the ¹⁸O values of carbonates are low, ranging from –3.3 to –8.1_VPDB. Phosphate ¹⁸O values range from 15.4 to 17.1_VSMOW. Paleotemperature estimates calculated from micrite ¹⁸O values assuming an ice-free seawater ¹⁸O value of –1_VSMOW indicate Early Ordovician tropical seawater temperatures averaged 42°C, whereas ¹⁸O values of co-occurring biogenic phosphate assuming the same seawater value yield paleotemperature estimates averaging 37°C. The phosphate values are interpreted as less affected by diagenesis than carbonate values and suggest Early Ordovician tropical paleotemperatures were not more than 10°C warmer or the oxygen isotopic composition of Early Ordovician hydrosphere was not more than 2 lower than present.

This article has been cited by other articles:

				J. A. Trotter, I. S. Williams, C. R. Barnes, C. Lecuyer, and R. S. Nicoll Did Cooling Oceans Trigger Ordovician Biodiversification? Evidence from Conodont Thermometry Science, July 25, 2008; 321(5888): 550 - 554. [Abstract] [Full Text] [PDF]