Wenlock (Silurian) graptolite biostratigraphy of the Cape Phillips Formation, Canadian Arctic Islands
The Canadian Arctic Islands Wenlock is represented by a diverse assemblage of graptolites from the Cape Phillips Formation. Cyrtograptids are continuously present throughout all but the uppermost Wenlock. Species of Cyrtograptus constitute the main basis for biostratigraphic zonation, supported to a...
| Published in: | Canadian Journal of Earth Sciences |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Canadian Science Publishing
1990
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1139/e90-001 http://www.nrcresearchpress.com/doi/pdf/10.1139/e90-001 |
| Summary: | The Canadian Arctic Islands Wenlock is represented by a diverse assemblage of graptolites from the Cape Phillips Formation. Cyrtograptids are continuously present throughout all but the uppermost Wenlock. Species of Cyrtograptus constitute the main basis for biostratigraphic zonation, supported to a much lesser degree by Monograptus, Monoclimacis, and Pristiograptus through most of the series. The uppermost Wenlock is dominated by Pristiograptus in association with rare Gothograptus.The following biostratigraphic zones and their correlations are proposed: (1) Cyrtograptus centrifugus – Cyrtograptus insectus Zone (earliest Wenlock); (2) Cyrtograptus aff. rigidus – Monograptus aff. riccartonensis Zone (late early Wenlock); (3) Cyrtograptus perneri – Monograptus cf. munchi Zone, in which Cyrtograptus multiramis is a particularly common element (mid-Wenlock age); (4) Cyrtograptus lundgreni – Monograptus testis Zone, divisible into a lower Monograptus testis n.ssp. and an upper Monograptus testis testis Subzone (late Wenlock); and (5) Pristiograptus ludensis Zone (latest Wenlock). The second and third zones are also possibly divisible into lower and upper subzones, but with less certainty.The degree of zonal subdivision in the Cape Phillips is lower than in Europe. It was observed locally that a number of the key species showed a high degree of overlap and some inconsistencies in their ranges from section to section.Paleoecologically, a few species, particularly Cyrtograptus preclarus, Cyrtograptus cf. malgusaricus, and Pristiograptus meneghini, appear to have preferred basin-margin regions. |
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