uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Ocean productivity response to orbital forcing during the early Pliocene
(Paleobiology)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. (Paleobiology)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. (Paleobiology)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The early Pliocene was a warm period with increased ocean primary productivity, as part of a global paleoceanographic event called the late Miocene-early Pliocene biogenic bloom (~9-3.5 Ma). Many tectonic and paleoclimatic mechanisms, mainly linked to an increase and redistribution of nutrient supply in the ocean, have been proposed as driving forces for this event. However, the main phase of increased productivity and the termination of this event appear to be diachronous in different ocean basins. Here, we compiled proxy data for early Pliocene paleoproductivity from all major ocean basins, including both calcareous and siliceous plankton groups. After re-evaluating the age model resolution of the available paleo-records, we demonstrate that a main stage of decrease in primary productivity occurred during ~4.6-4.4 Ma. We then show that this productivity collapse coincided with an orbital configuration of long-term reduction in eccentricity amplitude and low amplitude obliquity. This combination of orbital parameters could have significantly affected seasonality and nutrient availability in the global ocean and suggests a previously undescribed paleoclimatic forcing that may have been a crucial step in contributing to the end of the biogenic bloom.

National Category
Natural Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
URN: urn:nbn:se:uu:diva-405369OAI: oai:DiVA.org:uu-405369DiVA, id: diva2:1398958
Note

Manuscript draft

Available from: 2020-02-27 Created: 2020-02-27 Last updated: 2020-02-27
In thesis
1. Latest Miocene – Early Pliocene Paleoclimate and Phytoplankton Productivity
Open this publication in new window or tab >>Latest Miocene – Early Pliocene Paleoclimate and Phytoplankton Productivity
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Paper I

Pre-Quaternary paleoclimate studies in Australia mainly focus on terrestrial records from the southeastern part of the continent. IODP Expedition 356 drilled on the northwestern Australian shelf, yielding Miocene-Pleistocene paleoclimate records in an area where climate archives are scarce. Post-expedition research revealed a dry-to–humid transition across the latest Miocene and early Pliocene (start of the “Humid Interval”). However, the complex tectonic history of the area makes these interpretations challenging. In this study, we investigate late Miocene to early Pliocene sediment cores from two sites that are only 100 km apart, but situated in two adjacent basins (Northern Carnarvon and Roebuck Basins). Combining lithofacies study, time-series analysis of potassium content (K wt%) and calcareous nannofossil abundance counts (N/g), this work disentangles the complex interplay between basin evolution and climate change between 6.1-4 million years ago (Ma). Overall, the investigated proxies show high correlation between both sites, except during 6.1-5.7 Ma. During this latest Miocene interval, Site U1463 records a gradual increase in K wt%, correlated with basin deepening, whereas Site U1464 records an abrupt rise in K wt% at ~6 Ma. We explain this diachronicity by differential basin subsidence. The tectonic interplay with our paleorecords makes it difficult to pinpoint the exact onset of the “Humid Interval”, but we conclude that high K wt% and coccolith abundances at Site U1464 indicate that humidity was already enhanced since at least 6 Ma. This age is consistent with data supporting a southward movement of the Intertropical Convergence Zone rain belt at ~7 Ma.

Paper II

The early Pliocene was a warm period with increased ocean primary productivity, as part of a global paleoceanographic event called the late Miocene-early Pliocene biogenic bloom (~9-3.5 Ma). Many tectonic and paleoclimatic mechanisms, mainly linked to an increase and redistribution of nutrient supply in the ocean, have been proposed as driving forces for this event. However, the main phase of increased productivity and the termination of this event appear to be diachronous in different ocean basins. Here, we compiled proxy data for early Pliocene paleoproductivity from all major ocean basins, including both calcareous and siliceous plankton groups. After re-evaluating the age model resolution of the available paleo-records, we demonstrate that a main stage of decrease in primary productivity occurred during ~4.6-4.4 Ma. We then show that this productivity collapse coincided with an orbital configuration of long-term reduction in eccentricity amplitude and low amplitude obliquity. This combination of orbital parameters could have significantly affected seasonality and nutrient availability in the global ocean and suggests a previously undescribed paleoclimatic forcing that may have been a crucial step in contributing to the end of the biogenic bloom

Place, publisher, year, edition, pages
Uppsala: Uppsala University, 2020. p. 32
Keywords
Late Miocene, early Pliocene, IODP, paleoclimate, basin evolution, phytoplankton, paleoproductivity, Milankovitch cycles
National Category
Natural Sciences
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-405370 (URN)
Presentation
2020-03-27, Småland lecture room (1st floor), University Earth Sciences Department (Geocentrum), Villavägen 16, Uppsala, 15:00 (English)
Opponent
Supervisors
Available from: 2020-03-19 Created: 2020-02-27 Last updated: 2020-03-19Bibliographically approved

Open Access in DiVA

No full text in DiVA

By organisation
Department of Earth Sciences
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 61 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf