176-3 Elemental and Petrographic Methods for Trilobite Cuticular Analysis

Session: Laws of the Grave: Advances in Taphonomy Across the Paleontologic Record

Presenting Author:

Authors:

Abstract:

Trilobites are an extinct group of arthropods that are often preserved into the modern day through the fossilization of their cuticle, or exoskeleton, which can hold a wealth of information about their biology and environment. An understanding of the original and diagenetic structures of the trilobite cuticle is necessary to derive information about their exoskeletal morphology, as well as the chemistry of their depositional environment. Here, methods for analyzing trilobite cuticle have been refined, utilizing different techniques to gain a full picture of their structure and taphonomy. Petrographic thin sections were cut from two Kaskia sp. pygidia from different localities to better understand how original structures may be altered post deposition. These thin sections were observed at three thicknesses, to see if sections thinner than the standard 30 μm revealed more information. The trilobites from one locality were found to be recrystallized, while those from the other preserved much of the original cuticle. The evidence for this was best observed using the standard 30 μm thin sections. SEM analysis of the surface cuticle was also performed, reconsidering previous notions about original and diagenetic surface structures. Previous claims about surface taphonomy were called into question, as marks left by a bamboo dowel, not visible to the naked eye, appeared similar under SEM to textures previously described as original. Dendritic structures were also determined to be unreliable for determining the extent to which a trilobite cuticle has been altered. After observing physical changes that occur with diagenesis, two non destructive elemental mapping techniques, μ-XRF and FESEM-EDS, were compared in trilobites from both localities, to determine which method can most efficiently detect trace elements, and to see if differences in elemental composition were observable between well preserved and recrystallized cuticles. μ-XRF detected trace elements more effectively than FESEM-EDS, though no difference was observed between well preserved and altered cuticles when using either method. More work needs to be done on trilobite cuticles from other sites, as different depositional and diagenetic environments will likely impact the visible structure of the cuticles in different ways. Different species of trilobites from different time periods and paleoenvironments may also differ from those studied here, requiring further analysis.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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