Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia
Multiple stable isotope investigations from upper Eocene to lower Oligocene deep-water marine sequences record the transition from global greenhouse to the icehouse conditions (Oi-1 glacial). While Southern Ocean high latitude deep sea records of this transition are well known, their shallow marine...
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ftucl:oai:eprints.ucl.ac.uk.OAI2:10097293 2023-12-24T10:09:31+01:00 Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia Gallagher, SJ Wade, B Qianyu, L Holdgate, GR Bown, P Korasidis, VA Scher, H Houben, AJP McGowran, B Allan, T 2020-08 text https://discovery.ucl.ac.uk/id/eprint/10097293/7/Wade_Gallagher%20et%20al%202020.pdf https://discovery.ucl.ac.uk/id/eprint/10097293/ eng eng Elsevier https://discovery.ucl.ac.uk/id/eprint/10097293/7/Wade_Gallagher%20et%20al%202020.pdf https://discovery.ucl.ac.uk/id/eprint/10097293/ open Global and Planetary Change , 191 , Article 103218. (2020) Eocene Oligocene Oi-1 EOT-1 Greenhouse Icehouse Southeast Australia Article 2020 ftucl 2023-11-27T13:07:34Z Multiple stable isotope investigations from upper Eocene to lower Oligocene deep-water marine sequences record the transition from global greenhouse to the icehouse conditions (Oi-1 glacial). While Southern Ocean high latitude deep sea records of this transition are well known, their shallow marine equivalents are rare and have the potential to record the eustatic and oceanic consequences of Paleogene glacial variability. The well-known high paleolatitude (~55°S) neritic carbonate sequence at Browns Creek and Castle Cove in the Otway Basin in southeast Australia spans the Eocene-Oligocene boundary. During this time the area lay on the northeastern margin of the Australo-Antarctic Gulf facing the evolving Southern Ocean. The importance of this record has been hampered by a lack of a consistent stratigraphy and contradictory microfossil interpretations. To reconcile these issues we combine new bio-, chemo- and lithostratigraphic analyses of the outcrops and a new core (Colac-2) with pre-existing data to revise the stratigraphy. This confirms the middle/upper Eocene boundary is near the base of the section. The overlying upper Eocene siliciclastic strata are truncated by an unconformity (of ~0.8 Ma in duration) and overlain by glauconitic sand (the Notrostrea greensand) deposited after ~35.9 Ma. Subsequently deepening to middle to outer neritic depths deposited cyclic carbonates. Shallowing after ~35 Ma deposited laterally variable calcareous siliciclastic facies. These strata were tilted and eroded prior to 34 Ma leading to shallow water facies that may have been subaerially exposed during uplift. Brachiopod strontium isotope dates and an 0.5‰ carbon isotope excursion above this unconformity suggests the top of the Browns Creek and the base of the Castle Cove section correlate to Eocene-Oligocene transition (EOT-1) at ~34 Ma. The subsequent persistence of positive C/O isotope values above this level records the transition to the Oi-1 glaciation at ~33.7 Ma. Strong cyclicity in the inner shelf Castle Cove limestone ... Article in Journal/Newspaper Antarc* Antarctic Southern Ocean University College London: UCL Discovery Antarctic Southern Ocean Browns ENVELOPE(-44.583,-44.583,-60.700,-60.700) |
institution |
Open Polar |
collection |
University College London: UCL Discovery |
op_collection_id |
ftucl |
language |
English |
topic |
Eocene Oligocene Oi-1 EOT-1 Greenhouse Icehouse Southeast Australia |
spellingShingle |
Eocene Oligocene Oi-1 EOT-1 Greenhouse Icehouse Southeast Australia Gallagher, SJ Wade, B Qianyu, L Holdgate, GR Bown, P Korasidis, VA Scher, H Houben, AJP McGowran, B Allan, T Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
topic_facet |
Eocene Oligocene Oi-1 EOT-1 Greenhouse Icehouse Southeast Australia |
description |
Multiple stable isotope investigations from upper Eocene to lower Oligocene deep-water marine sequences record the transition from global greenhouse to the icehouse conditions (Oi-1 glacial). While Southern Ocean high latitude deep sea records of this transition are well known, their shallow marine equivalents are rare and have the potential to record the eustatic and oceanic consequences of Paleogene glacial variability. The well-known high paleolatitude (~55°S) neritic carbonate sequence at Browns Creek and Castle Cove in the Otway Basin in southeast Australia spans the Eocene-Oligocene boundary. During this time the area lay on the northeastern margin of the Australo-Antarctic Gulf facing the evolving Southern Ocean. The importance of this record has been hampered by a lack of a consistent stratigraphy and contradictory microfossil interpretations. To reconcile these issues we combine new bio-, chemo- and lithostratigraphic analyses of the outcrops and a new core (Colac-2) with pre-existing data to revise the stratigraphy. This confirms the middle/upper Eocene boundary is near the base of the section. The overlying upper Eocene siliciclastic strata are truncated by an unconformity (of ~0.8 Ma in duration) and overlain by glauconitic sand (the Notrostrea greensand) deposited after ~35.9 Ma. Subsequently deepening to middle to outer neritic depths deposited cyclic carbonates. Shallowing after ~35 Ma deposited laterally variable calcareous siliciclastic facies. These strata were tilted and eroded prior to 34 Ma leading to shallow water facies that may have been subaerially exposed during uplift. Brachiopod strontium isotope dates and an 0.5‰ carbon isotope excursion above this unconformity suggests the top of the Browns Creek and the base of the Castle Cove section correlate to Eocene-Oligocene transition (EOT-1) at ~34 Ma. The subsequent persistence of positive C/O isotope values above this level records the transition to the Oi-1 glaciation at ~33.7 Ma. Strong cyclicity in the inner shelf Castle Cove limestone ... |
format |
Article in Journal/Newspaper |
author |
Gallagher, SJ Wade, B Qianyu, L Holdgate, GR Bown, P Korasidis, VA Scher, H Houben, AJP McGowran, B Allan, T |
author_facet |
Gallagher, SJ Wade, B Qianyu, L Holdgate, GR Bown, P Korasidis, VA Scher, H Houben, AJP McGowran, B Allan, T |
author_sort |
Gallagher, SJ |
title |
Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
title_short |
Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
title_full |
Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
title_fullStr |
Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
title_full_unstemmed |
Eocene to Oligocene high paleolatitude neritic record of Oi-1 glaciation in the Otway Basin southeast Australia |
title_sort |
eocene to oligocene high paleolatitude neritic record of oi-1 glaciation in the otway basin southeast australia |
publisher |
Elsevier |
publishDate |
2020 |
url |
https://discovery.ucl.ac.uk/id/eprint/10097293/7/Wade_Gallagher%20et%20al%202020.pdf https://discovery.ucl.ac.uk/id/eprint/10097293/ |
long_lat |
ENVELOPE(-44.583,-44.583,-60.700,-60.700) |
geographic |
Antarctic Southern Ocean Browns |
geographic_facet |
Antarctic Southern Ocean Browns |
genre |
Antarc* Antarctic Southern Ocean |
genre_facet |
Antarc* Antarctic Southern Ocean |
op_source |
Global and Planetary Change , 191 , Article 103218. (2020) |
op_relation |
https://discovery.ucl.ac.uk/id/eprint/10097293/7/Wade_Gallagher%20et%20al%202020.pdf https://discovery.ucl.ac.uk/id/eprint/10097293/ |
op_rights |
open |
_version_ |
1786208707787358208 |