Wenlock (Silurian) graptolite biostratigraphy of the Cape Phillips Formation, Canadian Arctic Islands

Abstract

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.

Early Silurian (Wenlockian) δ13C profiles from the Cape Phillips Formation, Arctic Canada and their relation to biotic events

“…Approximately 50-100 mg of carbonate powder was reacted with three drops of anhydrous phosphoric acid at 70°C. Carbon isotope analyses are reported in the (Melchin 1989;Lenz and Melchin 1990;Lenz 1995). Dashed lines show positions of extinction and diversification events referred to in text.…”

Validity and composition of the Silurian trilobite genera Borealarges and Dicranogmus, with new species from the Canadian Arctic

“…Comprehensive locality information given by Adrain and Edgecombe (1997) is followed herein. Adrain (1994) cited the graptolite zonation of Lenz and Melchin (1990). Adrain and Edgecombe (1997) established a preliminary trilobite zonation calibrated against that for the graptolites.…”

The lichid trilobiteRadiolichasin the Silurian of Arctic Canada and Gotland, Sweden

“…In addition, they are precisely dated, as they occur interbedded with rich graptolite faunas. The graptolite zonation referred to is that established by Lenz & Melchin (1990;1991).…”