Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils
The Re-Os radiogenic isotope system has over the past three decades been successfully applied to organic-rich sedimentary rocks and oils as a geochronometer and geochemical tracer. The Re-Os geochronometer has provided a direct way of constraining the depositional age of organic-rich sediments as we...
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Victoria University of Wellington
2020
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ftvuwellington:oai:researcharchive.vuw.ac.nz:10063/9288 2023-08-15T12:42:33+02:00 Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils Rotich, Enock Handler, Monica Naeher, Sebastian 2020 http://researcharchive.vuw.ac.nz/handle/10063/9288 en_NZ eng Victoria University of Wellington http://researcharchive.vuw.ac.nz/handle/10063/9288 Author Retains Copyright Rhenium Osmium Source rocks Geochronology Oils Isotopes Taranaki Basin East Coast Basin Coals Text Doctoral 2020 ftvuwellington 2023-07-25T17:30:19Z The Re-Os radiogenic isotope system has over the past three decades been successfully applied to organic-rich sedimentary rocks and oils as a geochronometer and geochemical tracer. The Re-Os geochronometer has provided a direct way of constraining the depositional age of organic-rich sediments as well as the timing of oil generation events. Osmium isotopic compositions have further been utilised in understanding past climatic, oceanographic and geological events recorded in sediments, and in correlating oils to their source. Thus far, however, Re-Os studies of organic-rich sediments have mainly focused on marine black shales where Re and Os are primarily sourced from seawater. The work presented in this thesis seeks to investigate factors controlling Re-Os systematics and potential for geochronology in a range of fluvio-deltaic coaly rocks and terrestrial organic matter-dominated marine sediments, and associated oils from New Zealand’s Taranaki and East Coast basins. The Re-Os data presented here yield the first radiometric age for the late Paleocene Waipawa Formation (57.5 ± 3.5 Ma), a marine sedimentary unit that was formed by episodic input of large amounts of terrestrial woody plant matter resulting in high average sedimentation rates of up to ~10.6 cm/ky. This age is consistent with available biostratigraphic age determinations. The formation possesses Re (38.9 ± 17.6 ppb) and Os (526 ± 75.8 ppt) concentrations similar to those found in typical marine sediments containing amorphous organic matter deposited under much lower sedimentation rates. This indicates that organic matter type and sedimentation rate may not play a significant role in sequestration of these elements in organic-rich sediments. Unlike the Waipawa Formation, coals and coaly mudstones with varying degrees of marine influence (purely terrestrial to strongly marine-influenced) from the Rakopi, North Cape, Farewell and Mangahewa formations record low average Re (0.37 ± 0.25 ppb) and Os (24.5 ± 11.9 ppt) concentrations. These concentrations ... Doctoral or Postdoctoral Thesis North Cape Victoria University of Wellington: ResearchArchive New Zealand North Cape ENVELOPE(165.700,165.700,-70.650,-70.650) |
institution |
Open Polar |
collection |
Victoria University of Wellington: ResearchArchive |
op_collection_id |
ftvuwellington |
language |
English |
topic |
Rhenium Osmium Source rocks Geochronology Oils Isotopes Taranaki Basin East Coast Basin Coals |
spellingShingle |
Rhenium Osmium Source rocks Geochronology Oils Isotopes Taranaki Basin East Coast Basin Coals Rotich, Enock Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
topic_facet |
Rhenium Osmium Source rocks Geochronology Oils Isotopes Taranaki Basin East Coast Basin Coals |
description |
The Re-Os radiogenic isotope system has over the past three decades been successfully applied to organic-rich sedimentary rocks and oils as a geochronometer and geochemical tracer. The Re-Os geochronometer has provided a direct way of constraining the depositional age of organic-rich sediments as well as the timing of oil generation events. Osmium isotopic compositions have further been utilised in understanding past climatic, oceanographic and geological events recorded in sediments, and in correlating oils to their source. Thus far, however, Re-Os studies of organic-rich sediments have mainly focused on marine black shales where Re and Os are primarily sourced from seawater. The work presented in this thesis seeks to investigate factors controlling Re-Os systematics and potential for geochronology in a range of fluvio-deltaic coaly rocks and terrestrial organic matter-dominated marine sediments, and associated oils from New Zealand’s Taranaki and East Coast basins. The Re-Os data presented here yield the first radiometric age for the late Paleocene Waipawa Formation (57.5 ± 3.5 Ma), a marine sedimentary unit that was formed by episodic input of large amounts of terrestrial woody plant matter resulting in high average sedimentation rates of up to ~10.6 cm/ky. This age is consistent with available biostratigraphic age determinations. The formation possesses Re (38.9 ± 17.6 ppb) and Os (526 ± 75.8 ppt) concentrations similar to those found in typical marine sediments containing amorphous organic matter deposited under much lower sedimentation rates. This indicates that organic matter type and sedimentation rate may not play a significant role in sequestration of these elements in organic-rich sediments. Unlike the Waipawa Formation, coals and coaly mudstones with varying degrees of marine influence (purely terrestrial to strongly marine-influenced) from the Rakopi, North Cape, Farewell and Mangahewa formations record low average Re (0.37 ± 0.25 ppb) and Os (24.5 ± 11.9 ppt) concentrations. These concentrations ... |
author2 |
Handler, Monica Naeher, Sebastian |
format |
Doctoral or Postdoctoral Thesis |
author |
Rotich, Enock |
author_facet |
Rotich, Enock |
author_sort |
Rotich, Enock |
title |
Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
title_short |
Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
title_full |
Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
title_fullStr |
Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
title_full_unstemmed |
Rhenium-osmium geochronology and isotopic systematics in New Zealand source rocks and oils |
title_sort |
rhenium-osmium geochronology and isotopic systematics in new zealand source rocks and oils |
publisher |
Victoria University of Wellington |
publishDate |
2020 |
url |
http://researcharchive.vuw.ac.nz/handle/10063/9288 |
long_lat |
ENVELOPE(165.700,165.700,-70.650,-70.650) |
geographic |
New Zealand North Cape |
geographic_facet |
New Zealand North Cape |
genre |
North Cape |
genre_facet |
North Cape |
op_relation |
http://researcharchive.vuw.ac.nz/handle/10063/9288 |
op_rights |
Author Retains Copyright |
_version_ |
1774296656113565696 |