Publication Date:
2016-08-18
Description:
Two regional composite sections in the Frasnian, Upper Devonian, of New York State result from graphic correlation of conodont species. The first extends from Frasnian conodont zones 3 to 7, the second from Frasnian zones 11 to 13c (we prefer this terminology to "Montagne Noire" or "MN" zonation as the zone-defining species occur throughout the Devonian tropics). Key beds, widely traceable bases of prominent black shales, have been used with only a few exceptions to position the lines of correlation (LOC) in the graphs. Other key beds, not used for positioning, fall exactly on the LOC supporting the hypothesis of their synchrony. Fifty-five conodont species in the New York regional composites are compared with their ranges in the global Frasnian Composite Standard proving no major discrepancies. The taxonomy of Ancyrodella nodosa Ulrich and Bassler, widely misidentified in the past, has been clarified through restudy of the type specimens, resulting in its distinction from A . hamata Ulrich and Bassler (= A . buckeyensis Stauffer). A new species of Polygnathellus Bassler, which is restricted to Frasnian Zone 4, is kept in open nomenclature because the rarity of specimens is insufficient to determine the extent of intraspecifc variation and whether one or two species are represented in our New York and Western Australian collections.
Print ISSN:
0022-3360
Electronic ISSN:
1937-2337
Topics:
Geosciences
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