Graphic Assembly of a Conodont-Based Composite Standard for the Ordovician System of North America
Published:January 01, 1995
Walter C. Sweet, 1995. "Graphic Assembly of a Conodont-Based Composite Standard for the Ordovician System of North America", Graphic Correlation, Keith Olin Mann, H. Richard Lane, Peter A. Scholle
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A composite standard (CS), assembled graphically through consideration of the ranges of more than 300 conodont species in measured sections at 127 localities, will apparently be adequate as the backbone for a conodont-based chronostratigraphic framework for the Ordovician System of North America. The SRS is a 374-m core through Middle and Upper Ordovician rocks drilled at a site in north-central Kentucky. Relations between the SRS and additional Ordovician sections have been determined graphically following a compilation strategy that involves extension of the network of correlated sections into older and younger rocks by use of overlapping control sections. The weakest link is currently between Ibexian and lower Whiterockian rocks and the well-controlled upper Whiterockian-Mohawkian-Cincinnatian part of the CS. An undescribed composite section through Whiterockian and lower Mohawkian rocks in east-central Nevada is cited as a promising bridge between these two parts of the Ordovician System. It is not certain if the CS extends to the top of the system, because it is not yet possible to add described North American sections through the Ordovician-Silurian boundary to the network of correlated sections anchored by the SRS described here.
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Graphic Correlation - An increasing number of geologists have begun to use graphic correlation because they find this robust technique provides finer stratigraphic resolution and better accuracy and precision than traditional zonations. This volume presents the graphic correlation method, recent methodological developments, and a number of technical papers exemplifying the technique. This collection of papers presents a summary of the technique as currently practiced and it should provide a starting point for those interested in high resolution stratigraphy through graphic correlation. Graphic correlation continues to develop and spread as more geologists use this important and innovative technique. Its potential is only beginning to become realized.