Biogenic silica diagenesis under early burial in hemipelagic marine sediments
Four aspects of biogenic silica diagenesis are researched under this project: signatures of ongoing silica diagenesis in pore water, drivers leading to anomalous compaction (abrupt petrophysical changes), bottom-water temperature controls on silica dissolution and recycling, and temperature-time rel...
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ftuloxford:oai:ora.ox.ac.uk:uuid:c7d3f4d9-0b43-41f6-9ce4-626aa27320bb 2023-05-15T13:54:35+02:00 Biogenic silica diagenesis under early burial in hemipelagic marine sediments Varkouhi, S Tosca, N Cartwright, J 2018-10-01 https://ora.ox.ac.uk/objects/uuid:c7d3f4d9-0b43-41f6-9ce4-626aa27320bb unknown https://ora.ox.ac.uk/objects/uuid:c7d3f4d9-0b43-41f6-9ce4-626aa27320bb info:eu-repo/semantics/openAccess Thesis 2018 ftuloxford 2022-06-28T20:23:39Z Four aspects of biogenic silica diagenesis are researched under this project: signatures of ongoing silica diagenesis in pore water, drivers leading to anomalous compaction (abrupt petrophysical changes), bottom-water temperature controls on silica dissolution and recycling, and temperature-time relationships in silica later diagenesis. Results of this project are discussed in Chapters 4–7. Chapter 4 demonstrates, based on pore chemistry, mineralogy, and thermodynamic analyses, that solubility equilibrium is reached for diagenetic silica in pore water at opal-A to opal-CT transition zone captured by Ocean Drilling Program Sites 794 and 795 in Japan Sea; thus opal-CT is precipitating across the transition. It is also argued that ion transport mechanisms have failed to erase signatures of ongoing diagenesis. Chapter 5 utilises texture and mineralogical analyses of hemipelagic sediments from Sites 794 and 795 to place anomalous compaction across the transition zone in a diagenetic context. A sharp decrease in opal-A content in the transition under dissolution causes a significant decrease in sediment stability which results in a porosity drop and other petrophysical variations. Subsequent precipitation of opal- CT has, however, had far less effects on porosity. Chapter 6 models variations in silica dissolution and recycling with bottom-water temperatures using data from 22 representative Ocean Drilling Program sites. Though model expression of early diagenesis confirms a relationship between temperature and opal-CT formation in young sediments (< 4 Ma) near the seabed in the Antarctic, the established inverse temperature-time correlation in silica diagenesis contradicts main controls from low bottom temperature over a short geological time. Chapter 7 investigates temperature-time relationships in silica diagenesis by examining 67 scientific drill sites where the opal-A to opal-CT transition zone lies in Cenozoic sediments. Based on these constraints, the reference opal-CT stability field is modified. The ... Thesis Antarc* Antarctic ORA - Oxford University Research Archive Antarctic The Antarctic |
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ORA - Oxford University Research Archive |
op_collection_id |
ftuloxford |
language |
unknown |
description |
Four aspects of biogenic silica diagenesis are researched under this project: signatures of ongoing silica diagenesis in pore water, drivers leading to anomalous compaction (abrupt petrophysical changes), bottom-water temperature controls on silica dissolution and recycling, and temperature-time relationships in silica later diagenesis. Results of this project are discussed in Chapters 4–7. Chapter 4 demonstrates, based on pore chemistry, mineralogy, and thermodynamic analyses, that solubility equilibrium is reached for diagenetic silica in pore water at opal-A to opal-CT transition zone captured by Ocean Drilling Program Sites 794 and 795 in Japan Sea; thus opal-CT is precipitating across the transition. It is also argued that ion transport mechanisms have failed to erase signatures of ongoing diagenesis. Chapter 5 utilises texture and mineralogical analyses of hemipelagic sediments from Sites 794 and 795 to place anomalous compaction across the transition zone in a diagenetic context. A sharp decrease in opal-A content in the transition under dissolution causes a significant decrease in sediment stability which results in a porosity drop and other petrophysical variations. Subsequent precipitation of opal- CT has, however, had far less effects on porosity. Chapter 6 models variations in silica dissolution and recycling with bottom-water temperatures using data from 22 representative Ocean Drilling Program sites. Though model expression of early diagenesis confirms a relationship between temperature and opal-CT formation in young sediments (< 4 Ma) near the seabed in the Antarctic, the established inverse temperature-time correlation in silica diagenesis contradicts main controls from low bottom temperature over a short geological time. Chapter 7 investigates temperature-time relationships in silica diagenesis by examining 67 scientific drill sites where the opal-A to opal-CT transition zone lies in Cenozoic sediments. Based on these constraints, the reference opal-CT stability field is modified. The ... |
author2 |
Tosca, N Cartwright, J |
format |
Thesis |
author |
Varkouhi, S |
spellingShingle |
Varkouhi, S Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
author_facet |
Varkouhi, S |
author_sort |
Varkouhi, S |
title |
Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
title_short |
Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
title_full |
Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
title_fullStr |
Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
title_full_unstemmed |
Biogenic silica diagenesis under early burial in hemipelagic marine sediments |
title_sort |
biogenic silica diagenesis under early burial in hemipelagic marine sediments |
publishDate |
2018 |
url |
https://ora.ox.ac.uk/objects/uuid:c7d3f4d9-0b43-41f6-9ce4-626aa27320bb |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
https://ora.ox.ac.uk/objects/uuid:c7d3f4d9-0b43-41f6-9ce4-626aa27320bb |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1766260579777904640 |