Abstract: Stable Isotopic Composition of a Late Eocene Archeocete Whale, Basilosaurus cetoides, from Wayne County, Mississippi

Edwin W. Emmer, Dean A. Dunn

An exposed Late Eocene Archeocete whale near Matherville, Wayne County, Mississippi was discovered in Spring 1993. Although this specimen consisted mainly of marginally-preserved thoracic and cervical vertebra, with a few rib fragments, a premolar tooth with intact enamel was recovered from an indurated block of the Pachuta Marl Member, Yazoo Formation.

Although paleotemperature analyses of Tertiary strata have been routinely made using calcareous microfossils, this specimen represents one of the few isotopic measurements of a homeothermic animal. Stable-isotopic analysis has been made of phosphate tooth enamel of this specimen, and when combined with isotopic analysis of carbonate and phosphate of bone (rib fragments and the cervical vertebra) from the same animal, provides the opportunity to assess previously-published Late Eocene paleotemperature estimates.

Estimates of isotopic fractionation of this Late Eocene whale from local seawater are complicated by the fact that there is no modern analog of this fossil whale. As a modern analog, isotopic analyses have been made of cetacean teeth, using specimens of bottle-nosed dolphins obtained from the Southeastern Marine Mammal Stranding Network. Comparison of isotopic ratios of modern cetaceans to the water temperature structure of the Gulf of Mexico should allow us to assess the isotopic paleotemperature estimates of the Eocene Archeocete.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas