GSA Connects 2021 in Portland, Oregon

Paper No. 123-2
Presentation Time: 2:30 PM-6:30 PM


DONAHUE, Aaron and MACKENZIE, Lindsay, Geology, Eastern Washington University, 140 Science Building, Cheney, WA 99004

The Metaline Limestone is a middle Cambrian limestone unit containing an abundance of well-preserved trilobites and subordinate other fossil material. The fossils are often preserved as casts/molds and occasionally contain exoskeletal material. Although contemporaneous with the Burgess Shale Lagerstätte, the fossils within the Metaline Limestone do not exhibit the same fidelity of preservation. The goal of this study is to identify preliminary taphofacies within the Metaline Limestone to better understand the lack of exceptional preservation at this site.

A total of seven, previously-collected, blocks all containing trilobites from the Metaline Limestone were used in this study. The blocks were collected from both talus and in-situ; on the in-situ blocks both up-direction and direction North were noted. The taphofacies will be determined by sedimentological analyses and measuring different metrics including: concavity, degree of fragmentation and paleocurrent (alignment of fossils). The trilobites were also analyzed for deformation that occurred post fossilization.

The determined taphofacies for the trilobites of the Metaline Limestone will be compared to those of the Burgess Shale to identify differences in modes of preservation between the two sites.