By: A. L. Titus
One of the most important functions of paleontology in the earth sciences is time correlation of rock strata using taxonomic analysis of fossils in different regions. Comparisons of certain speciesâ€™ similarities between regions frequently allows for precise age dating and correlation of strata limited only by the presence/absence of species and the speed at which they evolved. Between their first appearance in the early/middle Devonian and their ultimate extinction at the K-T boundary, no other single taxonomic group is as precise or as widely useful for time correlation of strata as the ammonoid cephalopods, an extinct distant relative of the modern chambered nautilus. This is especially true for the Carboniferous Era, where ammonoid change was extremely rapid for reasons that are as yet not fully known, although global climate fluctuation is probably a key driving force.
During Mississippian time, a major island mountain range was thrust up in what is present-day central Nevada and eastern California. To the east of the mountain range lay a long, narrow, deep ocean basin that paralleled the mountain chain. Into this basin, known as the Antler foreland basin, untold millions of tons of sand, gravel, and mud were shed from the west creating thick deposits of marine sandstone, shale, and conglomerate. On the eastern edge of this seaway conditions were more conducive to carbonate deposition and many thick limestone deposits formed. Strata throughout this basin contain an abundant ammonoid fossil record. This record is rivaled by no other fossil group for intercontinental correlation, and yet is only just beginning to undergo intensive study. This paper is the very first of a series of comprehensive systematic studies on this extremely significant fauna which, when completed, will help to establish the Antler foreland in Utah, Nevada, and California as a global reference for Carboniferous research. Herein the paleogeographic ranges of many taxa are extended from Eurasia into North America and several new species and genera are named. This paper will serve as a benchmark work in Carboniferous ammonoid research and is an important source of information regarding this fascinating fossil group for both the public and professional geologists.
Pages: 109 p.
Media Type: Paper Publication