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Abstract: Taphonomy and Microevolution of the Cape Phillips Formation Graptolite Fauna, Cornwallis Island, Northwest Territories

RUSSEL, JENNIFER C., Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia

Uncompressed graptolites from concretions of the Cape Phillips Formation, Cornwallis Island, NWT have the potential to yield valuable biostratinomic information unavailable in the study of flattened specimens. The method of layer-by-layer dissolution enables the examination of the orientation, preservational condition, and small-scale lateral and vertical heterogeneity in graptolite distribution within single bedding planes and through successive strata. With accompanying lithologic evidence it is possible to identify graptolite taphofacies that predict paleoecological and depositional conditions. The creation of a graptolite taphofacies model will have implications in graptolite paleoecology, graptolite biostratigraphy, and deepwater sedimentation.

With the completion of the taphonomic study, estimates of the stratigraphic completeness and the time interval between sampling horizons can be made in preparation for a microevolutionary study of two or more species prolific in the residues from the layer-by-layer dissolution. Graptolites are ideal subjects for a microevolutionary study: they are small in size, abundant in the fossil record, and because they lived in the planktonic realm, they are well distributed. Biometric analyses will permit comparison of rates of change between species and within species, which will identify modes of evolution and ranges in morphological variation. The uniquely preserved graptolites of the Cape Phillips Formation will aid in our understanding of inheritance and the development of evolutionary models for all organisms.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid