Hydrocarbon fingerprinting and palaeoenvironmental reconstruction of Cambrian-Ordovician sedimentary rocks, western Newfoundland, Canada

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dc.contributor.advisor Ventura, G. T. (G. Todd)
dc.creator Dooma, John
dc.date.accessioned 2020-05-27T17:25:11Z
dc.date.available 2020-05-27T17:25:11Z
dc.date.issued 2020
dc.identifier.uri http://library2.smu.ca/xmlui/handle/01/29356
dc.description 1 online resource (74 pages) : illustrations (chiefly colour), map
dc.description Includes abstract and appendix.
dc.description Includes bibliographical references (pages 62-74).
dc.description.abstract For this study, we have investigated marine carbonates and shales deposited as rhythmites from the lower Shallow Bay Formation and upper Green Point Formation of the Cow Head Group spanning the Cambrian-Ordovician boundary in western Newfoundland. Eighteen carbonate and shale samples were collected and processed for their hydrocarbon biomarkers. The resulting solvent extracts were analyzed using comprehensive two-dimensional gas chromatography-mass spectrometry (GC&times;GC-MS). Several petroleum biomarkers such as n-alkanes, acyclic isoprenoids, steranes, hopanes as well as various aromatic hydrocarbons were quantified. These compounds are used as parameters to reconstruct the paleodepositional conditions of the depositional environment, and the thermal maturation of the extractable hydrocarbons. Pristane/Phytane (Pr/Ph) ratios of the rock samples range from (~0.16 to ~3.1), indicating that the organic matter was deposited under anoxic to dysoxic and possibly oxic conditions. A comparison of the Ph/n-C<sub>18</sub> and Pr/n-C<sub>17</sub> suggests the organic matter is derived from mixed Type II/Type III kerogen. The rocks also contains C<sub>27</sub>, C<sub>28</sub>, C<sub>29</sub> &alpha;&beta;&beta;and &alpha;&alpha;&alpha;-steranes 24(S+R) and &alpha;&beta;- and &alpha;&beta;-diasteranes in which the C<sub>29</sub> stigmastanes dominate. Gammacerane, formed from the biological precursor, tetrahymanol found in ciliated detritivores that commonly thrive in marine stratified water columns was also detected. Gammacerane Index (GI) values are low, ranging from ~0.74 to ~3.5, indicating there is minimal stratification in the water column during sediment deposition. Maturation of source rocks was assessed by monitoring the ratio of trisnorneohopane (Ts) and trisnorhopane (Tm) as well as C<sub>31</sub> &alpha;&beta;-hopane 22S/C<sub>31</sub> &alpha;&beta;-hopane (22S+22R). Ts/(Ts+Tm) and C<sub>31</sub> ⍺𝛽 S/(S+R) values are 0 to ~0.68 and ~0.45 to ~0.54, respectively. These low values indicate the organic matter in most of the samples is early to moderately mature. Samples with the highest range of Ts/(Ts+Tm) from 0.57 to 0.62 likely experienced the main phase of oil generation. The &delta;<sup>13</sup>C profile across Shallow Bay Formation and Green Point Formation shows alternation of positive and negative &delta;<sup>13</sup>C excursions (SPICE event, post-SPICE event, and HERB or TOCE event). Changes in organic matter ratios are observed by using steranes/hopanes and Pr/Ph ratios. Distinct negative shifts of values for the two parameters correspond to negative &delta;<sup>13</sup>C<sub>carb</sub> excursions during SPICE, post-SPICE, and HERB events. At the Cambrian-Ordovician boundary, an inverse relationship between these two parameters (high steranes/hopanes percentage accompanied by low Pr/Ph ratios) exists that may be linked to oxygen drawdown from increased productivity in the water column that affected redox conditions at depth.
dc.description.provenance Submitted by Greg Hilliard (greg.hilliard@smu.ca) on 2020-05-27T17:25:11Z No. of bitstreams: 1 Dooma_John_Honours_2020.pdf: 2916414 bytes, checksum: 9a60d8813a785556f8ef3956020b2184 (MD5) en
dc.description.provenance Made available in DSpace on 2020-05-27T17:25:11Z (GMT). No. of bitstreams: 1 Dooma_John_Honours_2020.pdf: 2916414 bytes, checksum: 9a60d8813a785556f8ef3956020b2184 (MD5) Previous issue date: 2020-04-22 en
dc.language.iso en en_CA
dc.publisher Halifax, N.S. : Saint Mary's University
dc.title Hydrocarbon fingerprinting and palaeoenvironmental reconstruction of Cambrian-Ordovician sedimentary rocks, western Newfoundland, Canada en_CA
dc.type Text en_CA
thesis.degree.name Bachelor of Science (Honours Geology)
thesis.degree.level Undergraduate
thesis.degree.discipline Geology
thesis.degree.grantor Saint Mary's University (Halifax, N.S.)
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