T7 Cenozoic Ostracode Research: Developments in Paleoclimatology, Paleohydrology, Paleoecology, and Phylogenetics

Sunday, 4 November 2012
8:00 AM - 12:00 PM
203B

PALEOBIOGEOGRAPHY OF CYTHERISSA LACUSTRIS (OSTRACODA) IN NORTH AMERICA

Paper number: T7-6
Program: Technical Sessions
Time: 9:10 AM – 9:25 AM

Authors

Abstract

The ostracode Cytherissa lacustris (Sars, 1863) is a well-known bioindicator species with a circumpolar, Holarctic distribution. Its heavy and distinctive calcite carapace has made it an easily identifiable and useful source of environmental and isotopic (del 18O and del 13C) information in paleolimnologic records throughout mid and high latitudes of the northern hemisphere (Danielopol et al., 1990). It is possible to trace the paleobiogeography of this species through time in North America by examining its Cenozoic fossil records. The earliest known record of the genus Cytherissa occurs in the early Paleocene continental deposits of northern Alaska, (Brouwers & DeDeckker, 1993) suggesting that C. lacustris arose in high latitudes in Paleogene time and spread southward. The oldest occurrence of the genus in Eurasia occurs in Eocene aged continental deposits in Mongolia (Su, 1984).

In North America, the first appearance of the species C. lacustris occurs in syngamic form in Pliocene aged ancient lake deposits in Butte Valley, California (Carter, 1994; Mathias, 2012), and as a parthenogen in the Plio-Pleistocene Lake Idaho deposits of Hagerman, Idaho (Forester, 1991 ). The Butte Valley record is slightly older than the Lake Idaho record, and in Butte Valley C. lacustris is very similar to C. lacustris baikalensis, an extant syngamic form from Lake Baikal (Bronshtein, 1947). All other records of this species in North America are of the parthenogenetic form. C. lacustris appears in numerous Pleistocene lake deposits of the U.S., as far south as Pleistocene Lake Estancia, New Mexico (Allen & Anderson, 1993) and northward to Beringia sites (now submerged) (Wells, 2011). Holocene records indicate that the species retreated to Canada and the Great Lakes by about 8,000 calendar years ago. Cytherissa lacustris distributions appear to trace the approximate summer position of the polar front in North America, and may have additional value as a tracer of the polar front in northern hemisphere records of Pliocene through Holocene age.