275 Paleontology IX - Biostratigraphy and Ichnology

Wednesday, 3 November 2010
1:30 PM - 5:30 PM
Room 601

LOWER ORDOVICIAN INTERCONTINENTAL CORRELATION USING PELAGIC TRILOBITES

Paper number: 275-12
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

The potential of mesonektic trilobites of the Family Telephinidae for detailed correlation of Ordovician rocks has long been recognized. Species of Carolinites and Opipeuterella were capable of broad, in some cases apparently nearly global, adult dispersal, and they were not restricted in their ecological distribution to particular benthic habitats. Despite this potential, there has been only one detailed case study, of the species Carolinites genacinaca. There are have been two major impediments to the general utility of these trilobites. First, the quality of description has often been lacking, with only small photographs of a limited number of specimens available. Second, stratigraphic documentation has been somewhat piecemeal, as few continuous successions with multiple stratigraphically successive species have been documented.

New field collections from the Lower and lower Middle Ordovician of the Great Basin (Nevada, Utah, and Idaho) have yielded the most stratigraphically complete sequence known for species of either genus, in addition to those of their probable sister taxon, Goniophrys. Rocks of the Pogonip Group in eastern Nevada and western Utah, and the Garden City Formation of northern Utah and southeastern Idaho have yielded twelve distinct species of Carolinites and six of Opipeuterella, with a stratigraphic distribution from mid-Tulean (late Tremadocian) to early Whiterockian (Dapingian). All of the species are known from rich silicified collections, allowing nearly complete knowledge with multiple examples of all exoskeletal parts. Many species previously described from other regions and continents are represented, permitting detailed correlation of the famous shallow subtidal shelly fossil successions of western Laurentia with other tropical faunas from eastern Laurentia, Siberia, South China, and Australia.