Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan
The upper Ordovician succession of Jordan was located ~60°S, less than 100 km from the Hirnantian ice sheet margin. New graptolite dates indicate glaciation ended in Jordan in the late Hirnantian (persculptus Biozone). The succession records two glacial advances within the Ammar Formation and the su...
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Online Access: | http://nora.nerc.ac.uk/id/eprint/1616/ https://doi.org/10.1016/j.palaeo.2005.01.007 |
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ftnerc:oai:nora.nerc.ac.uk:1616 2024-06-09T07:46:50+00:00 Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan Armstrong, Howard A. Turner, Brian R. Makhlouf, Issa M. Weedon, Graham P. Williams, Mark Al Smadi, Ahmad Abu Salah, Abdulfattah 2005 http://nora.nerc.ac.uk/id/eprint/1616/ https://doi.org/10.1016/j.palaeo.2005.01.007 unknown Elsevier Armstrong, Howard A.; Turner, Brian R.; Makhlouf, Issa M.; Weedon, Graham P.; Williams, Mark; Al Smadi, Ahmad; Abu Salah, Abdulfattah. 2005 Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan. Palaeogeography, Palaeoclimatology, Palaeoecology, 220 (3-4). 273-289. https://doi.org/10.1016/j.palaeo.2005.01.007 <https://doi.org/10.1016/j.palaeo.2005.01.007> Earth Sciences Publication - Article PeerReviewed 2005 ftnerc https://doi.org/10.1016/j.palaeo.2005.01.007 2024-05-15T08:42:16Z The upper Ordovician succession of Jordan was located ~60°S, less than 100 km from the Hirnantian ice sheet margin. New graptolite dates indicate glaciation ended in Jordan in the late Hirnantian (persculptus Biozone). The succession records two glacial advances within the Ammar Formation and the subsequent deglaciations. Organic-rich black shales (Batra Formation) form part of the final deglacial transgressive succession that in-filled an existing low stand glacial continental shelf topography. The base of the black shale is coincident with the maximum flooding surface. During transgression, interfluves and sub-basin margins were breached and black shale deposition expanded rapidly across the region. The top of the black shales coincides with peak highstand. The “expanding puddle model” (sensu Wignall) for black shale deposition, adapted for the peri-glacial setting, provides the best explanation for this sequence of events. We propose a hypothesis in which anoxic conditions were initiated beneath the halocline in a salinity stratified water column; a fresher surface layer resulted from ice meltwater generated during early deglaciation. During the initial stages of marine incursion, nutrients in the monimolimnion were isolated from the euphotic zone by the halocline. Increasing total organic carbon (TOC) and δ13Corg up section indicates the organic carbon content of the shales was controlled mainly by increasing bioproductivity in the mixolimnion (the Strakhov model). Mixolimnion nutrient levels were sustained by a continual and increasing supply of meltwater-derived nutrients, modulated by obliquity changes in high latitude insolation. Anoxia was sustained over tens to hundreds of thousands of years. The formation of black shales on the north Gondwana shelf was little different to those observed in modern black shale environments, suggesting that it was the nature of the Ordovician seas that pre-disposed them to anoxia. Article in Journal/Newspaper Ice Sheet Natural Environment Research Council: NERC Open Research Archive Palaeogeography, Palaeoclimatology, Palaeoecology 220 3-4 273 289 |
institution |
Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
unknown |
topic |
Earth Sciences |
spellingShingle |
Earth Sciences Armstrong, Howard A. Turner, Brian R. Makhlouf, Issa M. Weedon, Graham P. Williams, Mark Al Smadi, Ahmad Abu Salah, Abdulfattah Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
topic_facet |
Earth Sciences |
description |
The upper Ordovician succession of Jordan was located ~60°S, less than 100 km from the Hirnantian ice sheet margin. New graptolite dates indicate glaciation ended in Jordan in the late Hirnantian (persculptus Biozone). The succession records two glacial advances within the Ammar Formation and the subsequent deglaciations. Organic-rich black shales (Batra Formation) form part of the final deglacial transgressive succession that in-filled an existing low stand glacial continental shelf topography. The base of the black shale is coincident with the maximum flooding surface. During transgression, interfluves and sub-basin margins were breached and black shale deposition expanded rapidly across the region. The top of the black shales coincides with peak highstand. The “expanding puddle model” (sensu Wignall) for black shale deposition, adapted for the peri-glacial setting, provides the best explanation for this sequence of events. We propose a hypothesis in which anoxic conditions were initiated beneath the halocline in a salinity stratified water column; a fresher surface layer resulted from ice meltwater generated during early deglaciation. During the initial stages of marine incursion, nutrients in the monimolimnion were isolated from the euphotic zone by the halocline. Increasing total organic carbon (TOC) and δ13Corg up section indicates the organic carbon content of the shales was controlled mainly by increasing bioproductivity in the mixolimnion (the Strakhov model). Mixolimnion nutrient levels were sustained by a continual and increasing supply of meltwater-derived nutrients, modulated by obliquity changes in high latitude insolation. Anoxia was sustained over tens to hundreds of thousands of years. The formation of black shales on the north Gondwana shelf was little different to those observed in modern black shale environments, suggesting that it was the nature of the Ordovician seas that pre-disposed them to anoxia. |
format |
Article in Journal/Newspaper |
author |
Armstrong, Howard A. Turner, Brian R. Makhlouf, Issa M. Weedon, Graham P. Williams, Mark Al Smadi, Ahmad Abu Salah, Abdulfattah |
author_facet |
Armstrong, Howard A. Turner, Brian R. Makhlouf, Issa M. Weedon, Graham P. Williams, Mark Al Smadi, Ahmad Abu Salah, Abdulfattah |
author_sort |
Armstrong, Howard A. |
title |
Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
title_short |
Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
title_full |
Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
title_fullStr |
Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
title_full_unstemmed |
Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan |
title_sort |
origin, sequence stratigraphy and depositional environment of an upper ordovician (hirnantian) deglacial black shale, jordan |
publisher |
Elsevier |
publishDate |
2005 |
url |
http://nora.nerc.ac.uk/id/eprint/1616/ https://doi.org/10.1016/j.palaeo.2005.01.007 |
genre |
Ice Sheet |
genre_facet |
Ice Sheet |
op_relation |
Armstrong, Howard A.; Turner, Brian R.; Makhlouf, Issa M.; Weedon, Graham P.; Williams, Mark; Al Smadi, Ahmad; Abu Salah, Abdulfattah. 2005 Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan. Palaeogeography, Palaeoclimatology, Palaeoecology, 220 (3-4). 273-289. https://doi.org/10.1016/j.palaeo.2005.01.007 <https://doi.org/10.1016/j.palaeo.2005.01.007> |
op_doi |
https://doi.org/10.1016/j.palaeo.2005.01.007 |
container_title |
Palaeogeography, Palaeoclimatology, Palaeoecology |
container_volume |
220 |
container_issue |
3-4 |
container_start_page |
273 |
op_container_end_page |
289 |
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1801376837155160064 |