Microstructural and geochemical investigation of North American lower-middle Paleozoic trilobites and recent arthropods

• Main Author: McAllister, John E.
• Other Authors: Department of Earth Sciences
• Format: Thesis
• Language: English
• Published: Brock University 2009
• Subjects: Trilobites; Arthropoda > North America; Paleontology|yPaleozoic; Paleontology > North America; Geochemistry; Microstructure; Beale; Cape Beale; Pacific; Severn River
• Online Access: http://hdl.handle.net/10464/1959

Trilobites ¥tere collected from Ordovician and Devonian formations of Ontario} New York} Ohio} Oklahoma} and Indiana. Diversity was generally low} but 19.?telllS and Ph.~tY>ps ¥tere the most abundant species from the Ordovician and Devonian} respectively. Recent marine arthropods ¥tere collected from the Atlantic shore of the middle Florida Keys} and from the Pacific and lagoonal waters at Cape Beale} B. C. Fresh-water arthropods were collected along the shore of the Severn River in northcentral Ontario. Cuticles ¥tere analyzed for major} minor and trace elements, 180 and 13C isotopes, as ¥tell as examined by scanning electron micr?scope to identify original and diagenetic fabrics. Examination of trilobite cuticles by scanning electron microscope revealed several microstructures consistent with those observed in Recent arthropods. Microstructures} such as setae and tegumental gland duct openings} in like sized Lim/IllS and Isoteline trilobites may indicate common ancestral origins for these organisms, or simply parallel cuticle evolutions. The dendritic microstructure, originally' thought to be a diagenetic indicator, was found in Recent specimens and therefore its presence in trilobites may be suggestive of the delicate nature of diagenesis in trilobites. The absence of other primary microstructures in trilobites may indicate alteration, taxonomic control} or that there is some inherent feature of S EM examination which may' not allow detection of some features} while others are apparently visit·le onl~1 under SH.·1. The region of the cuticle sampled for examination is also a major influence in detecting pristine microstructures, as not all areas of trilobite and Recent arthropod cuticles will have microstructures identifiable in a SEM study. Subtleties in the process of alteration, however} ma~·· leave pristine microstructures in cuticles that are partial~/ silicified or do 10m itized, and degree and type of alteration may vary stratigraphically and longitudinally within a unit. The presence of fused ...