Systematics and biostratigraphy of Lower Cambrian trilobites of western Laurentia
| dc.contributor.author | Bohach, Lisa Lynn | |
| dc.contributor.supervisor | Ludvigsen, Rolf | |
| dc.date.accessioned | 2018-07-20T18:21:26Z | |
| dc.date.available | 2018-07-20T18:21:26Z | |
| dc.date.copyright | 1997 | en_US |
| dc.date.issued | 2018-07-20 | |
| dc.degree.department | School of Earth and Ocean Sciences | en_US |
| dc.degree.level | Doctor of Philosophy Ph.D. | en_US |
| dc.description.abstract | Medial Lower Cambrian strata from continental shelf deposits of western Laurentia yield abundant, low diversity trilobite faunas. New faunas from the Cranbrook and Eager formations (southeastern British Columbia) and the upper Campito, Poleta, Harkless and Saline Valley formations (southwestern Great Basin, California and Nevada) have yielded: 33 species of Olenellina (20 new); 2 new species of Edelsteinaspidae (Redlichiina); 13 species of Corynexochida (5 new); 4 species of Ptychopariina (1 new); 1 new species of Eodiscina; 1 species of Oryctocephalidae; 1 new species of Protypidae; and 1 possible species of Cheiruroideidae. One new genus, Wannerellus, is established and tentatively assigned to the Wanneriidae. Systematic studies emphasize the importance of early ontogenetic features and ventral morphology in determining supraspecific relationships. Major changes are made to the suprageneric classification of the Olenelloidea: the Wanneriidae is recognized as a family separate from the Olenellidae; the Laudoniinae and Gabriellinae are abandoned and their type genera assigned to the Wanneriidae; the Mesonacinae is characterized as a peramorphic subfamily of the Olenellidae; and the Bristoliinae is synonymized with the Biceratopsinae (Olenellidae). The Corynexochidae is also changed in membership to include the Dorypyginae (=Ogygopsidae). Heterochrony is a major pattern of evolutionary change in Lower Cambrian trilobites. Biostratigraphic division of the medial lower Cambrian comprises 10 new subzones of 4 zones and is the first species-based trilobite zonation for Laurentia. It replaces previous genus-based zonations that are imprecise and questionable in recognition. In ascending order, the zonation includes: the Nevadia weeksi and Nevadia palmeri subzones of the Nevadia Zone; the Nevadella parvoconica and Nevadella eiicharis subzones of the Nevadella Zone; the Elliptocephala stewarti, Gabriellus poletensis and Wannerellus alcatrazensis subzones of the Elliptocephala Zone; and the Wanneria logani, Wanneria dunnae and Proliostracus buelnaensis subzones of the Olenellus transitans Zone. These zones and subzones can be correlated with other successions in western and eastern Laurentia. Biofacies differentiation of restricted shelf deposits is poorly developed in the Nevadella though Elliptocephala Zones. For this interval, the Nevadella and Wanneriid biofacies are successive biofacies of restricted shelf deposits and the Labradoria and Ekwipagetia biofacies are successive biofacies of open shelf deposits. Biofacies differentiation is well developed in the Olenellus transitans Zone, with an Olenellus Biofacies in elastics; a Wanneriid Biofacies in silty and oolitic carbonates; a Bonnia Biofacies in pure carbonates; and an Ogygopsis Biofacies in open shelf deposits. | en_US |
| dc.description.scholarlevel | Graduate | en_US |
| dc.identifier.uri | http://hdl.handle.net/1828/9754 | |
| dc.language | English | eng |
| dc.language.iso | en | en_US |
| dc.rights | Available to the World Wide Web | en_US |
| dc.subject | Paleontology | en_US |
| dc.subject | British Columbia | en_US |
| dc.subject | Cambrian | en_US |
| dc.subject | Trilobites | en_US |
| dc.title | Systematics and biostratigraphy of Lower Cambrian trilobites of western Laurentia | en_US |
| dc.type | Thesis | en_US |