267 Paleontology V: Biostratigraphy and Taphonomy

Wednesday, 12 October 2011
1:30 PM - 5:30 PM
Room 205AB

NEW INTERPRETATIONS OF LATE CRETACEOUS SILICOFLAGELLATE EVOLUTION AND BIOSTRATIGRAPHY: RECENT DISCOVERIES FROM THE CANADIAN ARCTIC

Paper number: 267-5
Program: Technical Sessions
Time: 2:30 PM – 2:45 PM

Authors

Abstract

Unusual and well-preserved fossil silicoflagellates are described from marine sediments of the Kanguk formation on the northern Canada Arctic Margin and Archipelago. These include new taxa (two new genera and many new species) from Santonian and Campanian time intervals not previously studied for silicoflagellates. This work, combined with studies of the late Campanian silicoflagellates of DSDP Site 275 (southwest Pacific Ocean), Maastrichtian of DSDP Site 216 (northeast Indian Ocean) and Albian of ODP Site 693 (Weddell Sea, Antarctica), allow expansion of the Cretaceous silicoflagellate biostratigraphy to comprise seven zones that replaces the previous single Cretaceous zone. This also provides a more detailed interpretation of silicoflagellate evolution, including the timing of first appearances of important genera. The early Campanian record shows the evolution of Corbisema apical plates and unusual morphologies of Arctyocha. The important genus Lyramula makes its first appearance at the beginning of the Campanian.

Of particular interest are Santonian sediments preserved in down-faulted grabens on Devon Island. They were deposited in a shallow marine shelf setting that was never deeply buried. This preserved the fragile opal-A structure that is lost with deeper burial, while the footwalls protected the sediments from Late Cenozoic glacial erosion. This silicoflagellate flora is the second oldest report for this group and includes the previously enigmatic genera Cornua and Variramus, and new genera Schulzyocha and Umpiocha. These genera lack the basal rings associated with all Cenozoic silicoflagellate skeletal morphologies and require a new descriptive terminology. Discoveries of double skeletons for three genera show a morphological coupling different than known for Cenozoic silicoflagellates.