Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan)
The early Eocene is characterized by long-term global warming culminating in the Early Eocene Climatic Optimum (EECO). During this time interval, of which previously only the PETM was intensively studied, the Peri-Tethys was characterized by its position between north-south and east-west trending se...
Main Authors: | , , , , , , , |
---|---|
Format: | Conference Object |
Language: | English |
Published: |
2013
|
Subjects: | |
Online Access: | https://lirias.kuleuven.be/handle/123456789/574661 |
id |
ftunivleuven:oai:lirias.kuleuven.be:123456789/574661 |
---|---|
record_format |
openpolar |
spelling |
ftunivleuven:oai:lirias.kuleuven.be:123456789/574661 2023-05-15T15:19:03+02:00 Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) Deprez, Arne Tesseur, Steven Stassen, Peter D'haenens, Simon Steurbaut, Etienne King, Christopher Claeys, Philippe Speijer, Robert 2013-11-18 https://lirias.kuleuven.be/handle/123456789/574661 en eng The Micropalaeontological Society Annual General Meeting location:Natural History Museum, London, UK date:18-19 November 2013 https://lirias.kuleuven.be/handle/123456789/574661 Eocene benthic foraminifera Description (Metadata) only IMa conference_paper 2013 ftunivleuven 2017-06-02T19:48:35Z The early Eocene is characterized by long-term global warming culminating in the Early Eocene Climatic Optimum (EECO). During this time interval, of which previously only the PETM was intensively studied, the Peri-Tethys was characterized by its position between north-south and east-west trending seaways. The Aktulagay section in Kazakhstan provides an expanded record of the middle Ypresian (NP11-13, ~54-50 Ma), covering the lower part of the EECO. It features a series of sapropel beds, observed throughout the Peri-Tethys. In order to unravel paleoenvironmental changes, we carried out quantitative faunal studies and isotopic investigations on excellently preserved foraminiferal assemblages. The period from 54 to 52 Ma is characterized by a diverse assemblage of deep outer neritic benthic foraminifera, with common Pulsiphonina prima and Paralabamina lunata. Coupled negative carbon and oxygen isotope excursions point to hyperthermals occurring during this time interval, but these are not evident from the faunal or sedimentological record. The initially (54 Ma) well-ventilated oligo- to mesotrophic sea floor conditions gradually change to more eutrophic and oxygen-limited. This gradual onset culminates in permanent stratification in the sapropel-bearing unit around 52 Ma, with the dominance of Anomalinoides acutus and Bulimina aksuatica. The absence of ostracods and abundance of hematitic concretions are consistent with this interpretation. Rising δ13Cendobenthic indicate migration of endobenthic species to the sediment-water interface. Benthic foraminiferal assemblages dominated by Epistominella minuta at ~51-50 Ma indicate a highly seasonal food supply and episodic disruption of stratification. Dinoflagellate blooms and Acarinina isotope values at 20.25 m indicate lower salinity (lower δ18O) and higher productivity (higher δ13C), possibly due to riverine input. This coincides with the peak of the EECO, as indicated by its position close to the base of NP13 and rising δ13Cforam values. Although it is tempting to link the observed patterns to climate change, we can currently not exclude that changing paleogeography and variable connections to the Tethys, Atlantic and the Arctic ocean largely determined the long-term period of dysoxia and anoxia during deposition of the sapropel beds at the Peri-Tethyan seafloor. These rapid, small biofacies shifts observed in the Aktulagay section may reflect a stepwise transition in long-term re-shaping of benthic foraminiferal communities. status: published Conference Object Arctic Arctic Ocean Climate change Foraminifera* Global warming KU Leuven: Lirias Arctic Arctic Ocean |
institution |
Open Polar |
collection |
KU Leuven: Lirias |
op_collection_id |
ftunivleuven |
language |
English |
topic |
Eocene benthic foraminifera |
spellingShingle |
Eocene benthic foraminifera Deprez, Arne Tesseur, Steven Stassen, Peter D'haenens, Simon Steurbaut, Etienne King, Christopher Claeys, Philippe Speijer, Robert Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
topic_facet |
Eocene benthic foraminifera |
description |
The early Eocene is characterized by long-term global warming culminating in the Early Eocene Climatic Optimum (EECO). During this time interval, of which previously only the PETM was intensively studied, the Peri-Tethys was characterized by its position between north-south and east-west trending seaways. The Aktulagay section in Kazakhstan provides an expanded record of the middle Ypresian (NP11-13, ~54-50 Ma), covering the lower part of the EECO. It features a series of sapropel beds, observed throughout the Peri-Tethys. In order to unravel paleoenvironmental changes, we carried out quantitative faunal studies and isotopic investigations on excellently preserved foraminiferal assemblages. The period from 54 to 52 Ma is characterized by a diverse assemblage of deep outer neritic benthic foraminifera, with common Pulsiphonina prima and Paralabamina lunata. Coupled negative carbon and oxygen isotope excursions point to hyperthermals occurring during this time interval, but these are not evident from the faunal or sedimentological record. The initially (54 Ma) well-ventilated oligo- to mesotrophic sea floor conditions gradually change to more eutrophic and oxygen-limited. This gradual onset culminates in permanent stratification in the sapropel-bearing unit around 52 Ma, with the dominance of Anomalinoides acutus and Bulimina aksuatica. The absence of ostracods and abundance of hematitic concretions are consistent with this interpretation. Rising δ13Cendobenthic indicate migration of endobenthic species to the sediment-water interface. Benthic foraminiferal assemblages dominated by Epistominella minuta at ~51-50 Ma indicate a highly seasonal food supply and episodic disruption of stratification. Dinoflagellate blooms and Acarinina isotope values at 20.25 m indicate lower salinity (lower δ18O) and higher productivity (higher δ13C), possibly due to riverine input. This coincides with the peak of the EECO, as indicated by its position close to the base of NP13 and rising δ13Cforam values. Although it is tempting to link the observed patterns to climate change, we can currently not exclude that changing paleogeography and variable connections to the Tethys, Atlantic and the Arctic ocean largely determined the long-term period of dysoxia and anoxia during deposition of the sapropel beds at the Peri-Tethyan seafloor. These rapid, small biofacies shifts observed in the Aktulagay section may reflect a stepwise transition in long-term re-shaping of benthic foraminiferal communities. status: published |
format |
Conference Object |
author |
Deprez, Arne Tesseur, Steven Stassen, Peter D'haenens, Simon Steurbaut, Etienne King, Christopher Claeys, Philippe Speijer, Robert |
author_facet |
Deprez, Arne Tesseur, Steven Stassen, Peter D'haenens, Simon Steurbaut, Etienne King, Christopher Claeys, Philippe Speijer, Robert |
author_sort |
Deprez, Arne |
title |
Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
title_short |
Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
title_full |
Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
title_fullStr |
Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
title_full_unstemmed |
Benthic foraminiferal and isotopic patterns during the Early Eocene Climatic Optimum (Aktulagay section, Kazakhstan) |
title_sort |
benthic foraminiferal and isotopic patterns during the early eocene climatic optimum (aktulagay section, kazakhstan) |
publishDate |
2013 |
url |
https://lirias.kuleuven.be/handle/123456789/574661 |
geographic |
Arctic Arctic Ocean |
geographic_facet |
Arctic Arctic Ocean |
genre |
Arctic Arctic Ocean Climate change Foraminifera* Global warming |
genre_facet |
Arctic Arctic Ocean Climate change Foraminifera* Global warming |
op_relation |
The Micropalaeontological Society Annual General Meeting location:Natural History Museum, London, UK date:18-19 November 2013 https://lirias.kuleuven.be/handle/123456789/574661 |
_version_ |
1766349245601808384 |