Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past
Methane derived authigenic carbonate (MDAC) precipitation occurs within marine sediments as a byproduct of the microbial anaerobic oxidation of methane (AOM). While these carbonates form in chemical and isotopic equilibrium with the fluids from which they precipitate, burial diagenesis and recrystal...
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ftoregonstate:ir.library.oregonstate.edu:td96k5966 2024-09-15T18:18:42+00:00 Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past Joseph, Craig E. Torres, Marta Haley, Brian Rose, Kelly College of Oceanic and Atmospheric Sciences Oregon State University. Graduate School https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/td96k5966 English [eng] eng unknown Oregon State University https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/td96k5966 All rights reserved Methane -- Hydrate Ridge Carbonates Diagenesis -- Hydrate Ridge Paleoceanography -- Hydrate Ridge Masters Thesis ftoregonstate 2024-07-22T18:06:06Z Methane derived authigenic carbonate (MDAC) precipitation occurs within marine sediments as a byproduct of the microbial anaerobic oxidation of methane (AOM). While these carbonates form in chemical and isotopic equilibrium with the fluids from which they precipitate, burial diagenesis and recrystallization can overprint these signals. Plane polarized light (PPL) and cathodoluminescent (CL) petrography have allowed for detailed characterization of carbonate phases and their subsequent alteration. Modern MDACs sampled offshore in northern Cascadia (n =33) are compared with paleoseep carbonates (n =13) uplifted on the Olympic Peninsula in order to elucidate primary vs. secondary signals, with relevance to interpretations of the carbonate record. The modern offshore environment (S. Hydrate Ridge and Barkley Canyon) is dominated by metastable acicular and microcrystalline aragonite and hi-Mg calcite (HMC) that with time will recrystallize to low-Mg calcite (LMC). The diagenetic progression is accompanied by a decrease in Mg/Ca and Sr/Ca ratios while variation in Ba/Ca depends upon the Ba-concentration of fluids that spur recrystallization. CL images discern primary carbonates with high Mn/Ca from secondary phases that reflect the Mn- enrichment that characterizes deep sourced fluids venting at Barkley Canyon. Methane along the Cascadia continental margin is mainly of biogenic origin, where reported strontium isotopic values reflect a mixture of seawater with fluids modified by reactions with the incoming Juan de Fuca plate. In contrast, the Sr-isotopic composition of carbonates and fluids from Integrated Ocean Drilling Program (IODP) Site U1329 and nearby Barkley Canyon point to a distinct endmember (lowest ⁸⁷Sr/⁸⁶Sr = 0.70539). These carbonates also show elevated Mn/Ca and δ¹⁸O values as low as -12‰, consistent with a deep-source of fluids feeding thermogenic hydrocarbons to the Barkley Canyon seeps. Two paleoseep carbonates sampled from the uplifted Pysht/Sooke Fm. have ⁸⁷Sr/⁸⁶Sr values similar to those of the ... Master Thesis Methane hydrate ScholarsArchive@OSU (Oregon State University) |
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Open Polar |
collection |
ScholarsArchive@OSU (Oregon State University) |
op_collection_id |
ftoregonstate |
language |
English unknown |
topic |
Methane -- Hydrate Ridge Carbonates Diagenesis -- Hydrate Ridge Paleoceanography -- Hydrate Ridge |
spellingShingle |
Methane -- Hydrate Ridge Carbonates Diagenesis -- Hydrate Ridge Paleoceanography -- Hydrate Ridge Joseph, Craig E. Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
topic_facet |
Methane -- Hydrate Ridge Carbonates Diagenesis -- Hydrate Ridge Paleoceanography -- Hydrate Ridge |
description |
Methane derived authigenic carbonate (MDAC) precipitation occurs within marine sediments as a byproduct of the microbial anaerobic oxidation of methane (AOM). While these carbonates form in chemical and isotopic equilibrium with the fluids from which they precipitate, burial diagenesis and recrystallization can overprint these signals. Plane polarized light (PPL) and cathodoluminescent (CL) petrography have allowed for detailed characterization of carbonate phases and their subsequent alteration. Modern MDACs sampled offshore in northern Cascadia (n =33) are compared with paleoseep carbonates (n =13) uplifted on the Olympic Peninsula in order to elucidate primary vs. secondary signals, with relevance to interpretations of the carbonate record. The modern offshore environment (S. Hydrate Ridge and Barkley Canyon) is dominated by metastable acicular and microcrystalline aragonite and hi-Mg calcite (HMC) that with time will recrystallize to low-Mg calcite (LMC). The diagenetic progression is accompanied by a decrease in Mg/Ca and Sr/Ca ratios while variation in Ba/Ca depends upon the Ba-concentration of fluids that spur recrystallization. CL images discern primary carbonates with high Mn/Ca from secondary phases that reflect the Mn- enrichment that characterizes deep sourced fluids venting at Barkley Canyon. Methane along the Cascadia continental margin is mainly of biogenic origin, where reported strontium isotopic values reflect a mixture of seawater with fluids modified by reactions with the incoming Juan de Fuca plate. In contrast, the Sr-isotopic composition of carbonates and fluids from Integrated Ocean Drilling Program (IODP) Site U1329 and nearby Barkley Canyon point to a distinct endmember (lowest ⁸⁷Sr/⁸⁶Sr = 0.70539). These carbonates also show elevated Mn/Ca and δ¹⁸O values as low as -12‰, consistent with a deep-source of fluids feeding thermogenic hydrocarbons to the Barkley Canyon seeps. Two paleoseep carbonates sampled from the uplifted Pysht/Sooke Fm. have ⁸⁷Sr/⁸⁶Sr values similar to those of the ... |
author2 |
Torres, Marta Haley, Brian Rose, Kelly College of Oceanic and Atmospheric Sciences Oregon State University. Graduate School |
format |
Master Thesis |
author |
Joseph, Craig E. |
author_facet |
Joseph, Craig E. |
author_sort |
Joseph, Craig E. |
title |
Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
title_short |
Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
title_full |
Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
title_fullStr |
Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
title_full_unstemmed |
Methane sources, fluid flow, and diagenesis along the northern Cascadia Margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
title_sort |
methane sources, fluid flow, and diagenesis along the northern cascadia margin; using authigenic carbonates and pore waters to link modern fluid flow to the past |
publisher |
Oregon State University |
url |
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/td96k5966 |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/td96k5966 |
op_rights |
All rights reserved |
_version_ |
1810456786349588480 |