The role of fossils in defining rock units with examples from the Devonian of western and Arctic Canada

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ID: 308328
1959
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Abstract
The formation is rightly considered the fundamental unit of rock classification. Definition must be broadly based if flexibility is to be maintained. Fossils as lithologic constituents are equal to any other physical constituent in defining rock units. Their use in this role must not be confused with their interpretive use in biostratigraphic correlation, for which biostratigraphic units are employed. These units are indistinguishable from time-stratigraphic units if the latter are redefined as practical working units; the hierarchy system, series, stage will serve for both. Three examples are given of the use of fossils in largely reconnaissance mapping of richly fossiliferous Devonian rocks: 1) On Ellesmere and Bathurst islands the correlation of roughly similar lithologic successions is supported by a sequence of faunas that allows recognition of the same 4 formations on the 2 islands, 200 mi. apart. 2) Near Kakisa River, upper Mackenzie Valley, where owing to poor outcrop, the upper boundary of a formation, that may be seen to correspond with a lithologic break only where the rocks are better exposed, is most conveniently defined by a marked faunal break. Structure was mapped by collecting fossils from small isolated outcrops in the area. 3) In the Alberta Rocky Mountains, difficulties experienced in choosing a consistent boundary between the Upper Devonian Fairholme group and the overlying Alexo formation may be solved in fossiliferous sections by using a marked faunal break that commonly corresponds to one of several possible boundaries, if lithology is considered exclusively. In these examples, the meaning of faunal changes or breaks is not relevant to formation definition. Thus no interpretation is involved, and the fossils are as much a physical character of the rocks as any other character.
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openalex_W2073998017 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors D. J. McLaren
Journal american journal of science
Year 1959
DOI
10.2475/ajs.257.10.734
URL
https://ajs.scholasticahq.com/article/58740.pdf
Keywords Keywords not found

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