Fossil isotope records of seasonal climate and ecology: Straight from the horse's mouth

Research Article| March 01, 1998 Fossil isotope records of seasonal climate and ecology: Straight from the horse's mouth Z. D. Sharp; Z. D. Sharp 1Institut de Minéralogie, Université de Lausanne, BFSH-2, CH-1015 Lausanne, Switzerland Search for other works by this author on: GSW Google Scholar T. E. Cerling T. E. Cerling 2Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112-1183 Search for other works by this author on: GSW Google Scholar Author and Article Information Z. D. Sharp 1Institut de Minéralogie, Université de Lausanne, BFSH-2, CH-1015 Lausanne, Switzerland T. E. Cerling 2Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112-1183 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1998) 26 (3): 219–222. https://doi.org/10.1130/0091-7613(1998)026<0219:FIROSC>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Z. D. Sharp, T. E. Cerling; Fossil isotope records of seasonal climate and ecology: Straight from the horse's mouth. Geology 1998;; 26 (3): 219–222. doi: https://doi.org/10.1130/0091-7613(1998)026<0219:FIROSC>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Isotope analysis of a bulk fossil tooth gives a "snapshot" impression of paleoclimatic conditions—a single point in time. However, hypsodont teeth grow over a period of a year or more, so that stable carbon and oxygen isotope variations along their length are a "tape recorder" of short-term seasonal variations from the distant past. We have used a new in situ micro-laser sampling method to determine submillimeter carbon and oxygen isotope variations in the enamel of individual fossil horse teeth to assess ancient annual meteoric water variations and feeding patterns. The δ18O values from a 6.8 Ma fossil horse tooth (Astrohippus ansae) from Texas vary cyclically along the 6 cm length of the tooth with a smoothed amplitude of >4‰, similar to the monthly averaged amplitude measured in modern meteoric waters from the region. The seasonal δ18O values are ∼3‰ to 4‰ higher than those calculated from modern meteoric water data, suggesting either a higher local meteoric water value in the Miocene of Texas, or that the animal received a high proportion of its dietary water from plants or highly evaporated water. A Holocene horse tooth from the shores of Glacial Lake Agassiz, North Dakota (Equus sp.), also has isotopic variations with the same 35 mm periodicity, but a smoothed amplitude of only 2‰. This horse most likely had a buffered drinking supply. The calculated δ18O of the water in equilibrium with this tooth is the same as the modern measured annual average. The variations within a single tooth can be as large as those generally observed in entire stratigraphic sections of fossil teeth analyzed by bulk methods. The new method provides an important technique for evaluating fossil diagenesis; conventional bulk analyses of teeth fragments may not be representative of the whole tooth, thus explaining analytical scatter that has been previously attributed to diagenesis. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.