Early to late Pliocene calcareous nannnoplankton biostratigraphy and abundances from the NW Australian Shelf

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Author(s): Karatsolis, Boris Theofanis; Henderiks, Jorijntje
Author Affiliation(s): Primary:
Uppsala University, Uppsala University, Department of Earth Sciences, Sweden
Volume Title: European Geosciences Union general assembly 2018
Source: Geophysical Research Abstracts, Vol.20; European Geosciences Union general assembly 2018, Vienna, Austria, April 8-13, 2018. Publisher: Copernicus GmbH on behalf of the European Geosciences Union (EGU), Katlenburg-Lindau, Germany. ISSN: 1029-7006
Note: In English
Summary: The early to late Pliocene is considered a past analog for future warming on Earth with warmer sea surface temperatures and atmospheric CO2 levels similar to those already reached today (∼400ppm). Coccolithophores, marine calcifying haptophyte algae, are known to dominate the plankton community in warm and oligotrophic waters, and may therefore be better adapted to such conditions. IODP Expedition 356 Site U1464 is located on the NW Australian shelf, under the direct influence of the Indonesian Throughflow (ITF), which transports heat from the Pacific Warm Pool into the Indian Ocean. Here, we present the Pliocene nannofossil biostratigraphy of this site (145,15-286,67 m CSF-A; biozones NN12 to NN16) and use assemblage data to unravel past algal responses to temperature and other paleoceanographic variability in this tropical region. Nannofossils were identified using polarized light microscopy in slides that were prepared with an adaptation of the dilution technique (the "drop" technique). The top occurrence of Sphenolithus spp. is the most distinct biostratigraphic event (between 157,7-159,2 m CSF-A). Other biostratigraphic events are more difficult to constrain, such as the top occurrence of Reticulofenestra pseudoumbilicus (>7 m) and the base occurrence of Pseudoemiliania lacunosa. In addition, Discoaster species are rare and commonly overgrown and thus not as reliable as biostratigraphic markers compared to deeper marine settings. Reticulofenestrids (Reticulofenestra and Gephyrocapsa spp.) are dominant and occur in a variety of sizes and were thus grouped based on this parameter (<3 m, 3-5 m, >5 m). Out of these, the most abundant are the smaller than 5 m placoliths, which commonly exceed 70% of the total abundance, especially in the time interval after the top occurrence of Sphenolithus spp. The same top occurrence marks the onset of a decrease of Gephyrocapsa spp., which almost disappears in the top of our section (<2% of the total abundance at 149,6 m CSF-A). Other common species are Calcidiscus spp., Umbilicosphaera spp., Syracosphaera spp. and Pseudoemiliania lacunosa. At the fringes of the Indo-Pacific Warm Pool, this site documents distinct shifts in coccolithophore communities that reflect both evolutionary adaptations and ecological responses to changes in the predominant water masses. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Biostratigraphy; Cenozoic; Expedition 356; IODP Site U1464; Indian Ocean; International Ocean Discovery Program; Neogene; Pliocene; Tertiary; Upper Pliocene
Coordinates: S180355 S180355 E1183753 E1183753
Record ID: 2019014066
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from European Geosciences Union, Munich, Germany