MODERN BIOSTRATIGRAPHY OF THE TRENTON GROUP
INTRODUCTION
BIOSTRATIGRAPHY: A FEW CONSIDERATIONS
BIOSTRATIGRAPHY OF THE UPPER ORDOVICIAN
BIOSTRATIGRAPHY OF THE TRENTON GROUP
Graptolite and Conodont Biostratigraphy
Macrofaunal Biostratigraphy: Concepts of "BioZones"
Macrofaunal Biostratigraphy: Coenocorrelation and Gradient Analysis
Introduction:
Biostratigraphy is a sub-discipline of sedimentary geology that relies on the physical zonation of biota, both in time and space, in order to establish the relative stratigraphic position (i.e. older, younger, same age) of sedimentary rocks between different geographic localities. Although the basic rules of biostratigraphic zonation were established in the late 18th to early 19th centuries in Europe (ultimately resulting in the development of the Relative Geologic Time Scale), the implementation of biostratigraphic techniques was in use in the United States during the early to mid-1800's.
Some of the first geological surveys to be completed in the United States included those of the New York State Geological Survey. These surveys focused not only on New York's geological resources, but also emphasized the establishment of spatial and temporal relationships of stratigraphic units based on both lithologic and paleontologic composition. By the mid-1800's the New York Surveys had resulted in the development of a relative stratigraphic zonation based primarily on fossil distribution. New York localities are world famous for Cambrian through Devonian strata and fossils, but of particular importance to this website discussion is the contribution of the Ordovician rocks of central New York State to the establishment of a North American focused biochronology. The rocks found in the central New York Mohawk River Region, by definition of their fossil content, are now established as belonging to the Mohawkian Series of the Upper Ordovician Period