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Publication Date

2012

Document Type

Honors Project

Department

Geosciences

Keywords

Cow Head Group (N.L.), Geochemistry-Newfoundland and Labrador-Cow Head Group, Geology-Newfoundland and Labrador-Cow Head Group, Carbon isotopes, Conglomerates, Excursion

Abstract

The causal mechanisms for the largely depauperate interval following the Cambrian Explosion and the GOBE are still poorly understood. The carbonate and shale of the Cambro- Ordovician Cow Head Group in Western Newfoundland, Canada, span this important interval in a deep-water slope setting. Similarities in the δ13Ccarb profile to other Cambro-Ordovician sections suggest that the Cambro-Ordovician Cow Head Peninsula may be accurately correlated with other profiles worldwide. Though the positive excursion of the later Cambrian (SPICE Event) was not recorded in this deep-water slope environment, the enriched δ13Ccarb values in beds correlated to the SPICE Event on the shelf suggest possible correlation between the strata. No trends between δ13Ccarb and δ18O values exist over time in a bed-by-bed analysis, suggesting that the δ13Ccarb profile was not significantly affected by meteoric diagenesis. To determine the influence of conglomerates on the overall profile, multiple matrix and clast values from the same sample were compared. The conglomerate study was consistent with the larger δ13Ccarb profile, and the vast majority of samples do not display a statistically significant difference between clast and matrix. The conglomerate study suggests that even when only clasts can be sampled, they may still be representative of the general trends in the δ13Ccarb profile. This, coupled with the correlation of the δ13Ccarb profile to three other Cambro-Ordovician profiles, indicates that the deep-water slope Cambro-Ordovician Cow Head Peninsula is an accurate record of the changes in seawater carbon isotope composition over this critical time in Earth history.

Language

English

Comments

v, 80 p. : col. ill. Honors project-Smith College, Northampton, Mass., 2012. Includes bibliographical references (p. 62-67)

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