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 ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pufahl, P. K. Articles by Bone, Y. Search for Related Content GeoRef GeoRef Citation

Brachiopods in Epeiric Seas as Monitors of Secular Changes in Ocean Chemistry: A Miocene Example from the Murray Basin, South Australia

¹ Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada; present address: Department of Geology, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada; peir.pufahl{at}acadiau.ca
² Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada
³ Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada
⁴ Petro-Canada Oil and Gas, 150 6^th Avenue SW, Calgary, Alberta T2P 3E3, Canada
⁵ School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia, 5005, Australia

Early and middle Miocene cool-water carbonates from the Murray Basin, South Australia, preserve an excellent stable-isotope record of ocean-climate change. These variably fossiliferous heterozoan deposits accumulated on a low-energy, mesotrophic, centripetal epeiric ramp during a gradual shift in climate from cool, wet conditions and abundant continent-derived nutrients to a seasonal, arid climate with reduced delivery of trophic resources to the marine realm.

Temporal trends in ¹³C and ¹⁸O from unaltered brachiopods record an epeiric sea response to this warming. The globally recognized middle Miocene Monterey Event (~ 17 to 13.5 Ma) dominates the carbon isotope record, albeit with higher (~ 0.5) than open-ocean ¹³C values. Such higher ¹³C values are attributed to an increase in benthic carbonate production that accompanied climate change and the relatively short seawater mixing times characteristic of epeiric-sea systems. The Murray Basin oxygen isotope curve contains lower ¹⁸O values (~ 2.0 lower) than those of the deep-sea record. This difference is ascribed to the warmer seawater temperatures (~ 17 to 22°C) that prevailed across the Miocene Murray Basin.

These results show that the isotope chemistry of epeiric-sea brachiopods can be a reliable gauge of regional and global environmental evolution. Although diagenetic overprinting from meteoric cement-filled punctae and local forcing factors introduce "noise" that mutes isotopic signals, the open-ocean secular record is clearly discernible.