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SIGNS OF PHOTOSYNTHESIS ON A NEOPROTEROZOIC SNOWBALL
EARTH
by
Alison N. Olcott
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(GEOLOGY)
December 2006
Copyright 2006 Alison Olcott
Object Description
| Title | Signs of photosynthesis on a neoproterozoic snowball Earth |
| Author | Olcott, Alison Nicola |
| Author email | olcott@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2006-06-06 |
| Date submitted | 2006 |
| Restricted until | Unrestricted |
| Date published | 2006-10-02 |
| Advisor (committee chair) | Corsetti, Frank A. |
| Advisor (committee member) |
Sessions, Alex Berelson, Will Finkel, Steve Nealson, Kenneth H. |
| Abstract | Laterally extensive black shales were deposited on the São Francisco craton in southeastern Brazil during one of the low-latitude Neoproterozoic glaciations. The effect these glaciations had on the biosphere has long been controversial, but there has not been sufficient data to assess the impact. This study, the first organic geochemical investigation of synglacial sediments, synthesizes geological observations and biomarkers information from subsurface cores drilled through the glacial sediments. These rocks contain up to 3.0 wt.% organic carbon and pseudomorphs of the hydrated carbonate mineral ikaite, which are interpreted as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Furthermore, this environment is inconsistent with parts of the "Snowball Earth" hypothesis.; Additionally, the results of two other investigations into the Proterozoic biosphere are presented. The first is a re-analysis of stromatolite "diversity." Stromatolites are thought to be the preserved record of microbial mats, and their distribution through time is often interpreted as a proxy for phenomena as disparate as tectonic basin evolution, the carbonate saturation state of the Proterozoic ocean, and the evolution of metazoa. However, this reanalysis indicates that many of the previously interpreted "diversity" patterns are instead the result of data artifacts, and the true distribution of stromatolites through the Proterozoic may be less variable than previously thought.; The final project is the development of a method to measure the isotopic value of individual acritarchs, organic-walled microfossils with a robust record through the Proterozoic. The hope is that the 13C/12C |
| Keyword | biomarker; snowball Earth; neoproterozoic; glaciation |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Type | texts |
| Legacy record ID | usctheses-m60 |
| Rights | Olcott, Alison Nicola |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | http://www.usc.edu/isd/libraries/services/ask_a_librarian/email/ |
| Filename | etd-Olcott-20061002 |
| Archival file | uscthesesreloadpub_Volume4/etd-Olcott-20061002.pdf |
Description
| Title | Page 1 |
| Full text | SIGNS OF PHOTOSYNTHESIS ON A NEOPROTEROZOIC SNOWBALL EARTH by Alison N. Olcott A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (GEOLOGY) December 2006 Copyright 2006 Alison Olcott |
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