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Book Chapter

Descriptions of Individual Stratigraphic Units

January 01, 1975


The youngest unit studied in this area is he Cramer (fomerly Trivoli) Member. Its high stratigraphic position dictates that it will be preserved only on the geographically restricted, topographically high rldgeline running froa Faralngton eastward toward Peoria (Fig. 1 ). Only two Cramer localities within the study area were saapled for conodonts. The two are HLithically dissimilar and not faunally hoaogeneous. The type locality (Wanless, 1957, p. 193) has a aasslve fairly pure limestone and an overlying nodular, argillaceous, packed mixed biomicrite, obviously weathering out of a shale. At locality 3 (Wanless, 1958, locality 169) nodular, pagked Derbya biomicrites alterna te, with shale Interbeds below the aaln limestone member (member 152). The high degrees of lithologic and faunal difference between the two successions may represent distinct stratigraphic units.

Faunally, locality 1 is an offshore Aethotaxis-blofacies (1A) to Idioprioniodus-biofacies (IB) unit dominated by platform elements transitional between Idiognathodus and Streptognathodus. Locality 3 is so heavily dominated by elements of the Carusgnathus-biofacies that little else of a diagnostic nature is present. Neither locality has produced unquestioned specimens of Neognathodus or Gondotella. Absence of Neognathodus and domination by Streptognathodus canoellosus are compatible with an early Missourian assignment and suggest its (nearest correlatives to be the Lower Brush Creek .In Ohio and the Bertha in Kansas-Missouri, although aore data are needed for substantiation.. Absences are unsafe criteria for age determinations, and Wanless (1956, p. 50-51) has reported “Metalonchodina”, an element that is a component of Idioprioniodus and supposedly restricted to pre-Missourian nocks, to

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Pennsylvanian Conodont Biostratigraphy and Paleoecology of Northwestern Illinois

Glen K. Merrill
Glen K. Merrill
Department of Geology College of Charleston Charleston, South Carlina
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January 01, 1975




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