Evidence for eutrophication in the northwestern Pacific and eastern Indian Oceans during the Miocene to Pleistocene based on the nannofossil accumulation rate, Discoaster abundance, and coccolith size distribution of Reticulofenestra

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doi: 10.1016/j.marmicro.2015.01.001
Author(s): Imai, Ryo; Farida, Meutia; Sato, Tokiyuki; Iryu, Yasufumi
Author Affiliation(s): Primary:
Tohoku University, Institute of Geology and Paleontology, Sendai, Japan
Other:
Hasanuddin University, Indonesia
Akita University, Japan
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, Vol.116, p.15-27. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. 63 refs.; illus., incl. 1 plate, 2 tables, sketch map
Summary: To reconstruct the Cenozoic paleoceanographic evolution, in particular, temporal changes in nutrient levels, we studied calcareous nannofossil assemblages from Ocean Drilling Program holes 1210A, located in the northwestern Pacific Ocean, and 762B, situated in the eastern Indian Ocean. At each site we focused on the relationships among the nannofossil accumulation rate (NAR), relative abundance of Discoaster, and coccolith size of the genus Reticulofenestra. The co-occurrence of a low NAR, high Discoaster abundance and presence of large Reticulofenestra suggest a deep thermocline and nutricline, typical of oligotrophic conditions. Conversely, the co-occurrence of a high NAR, low Discoaster abundance and presence of small Reticulofenestra indicate a shallow thermocline and nutricline, typical of eutrophic conditions. The combination of these three parameters suggests that the gradual eutrophication and collapse of sea surface stratification occurred in the northwestern Pacific Ocean at 7.9, 6.4, and 5.0 Ma. In contrast, abrupt eutrophication is indicated at 8.8 Ma in the eastern Indian Ocean. Although the timing of eutrophication differs between the Pacific and Indian Ocean sites, it roughly coincides with tectonic and/or climatic events around the two oceans. This finding suggests that tectonic and climatic events are capable of causing an increase in the terrestrial input and/or coastal upwelling of nutrients that subsequently leads to the eutrophication of sea surface waters. Abstract Copyright (2015) Elsevier, B.V.
Year of Publication: 2015
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Assemblages; Biostratigraphy; Biozones; Cenozoic; Discoaster; Discoasteridae; Eutrophication; Exmouth Plateau; Floral list; Indian Ocean; Leg 122; Leg 198; Marine environment; Microfossils; Miocene; Morphology; Nannofossils; Neogene; North Pacific; Northwest Pacific; ODP Site 1210; ODP Site 762; Ocean Drilling Program; Pacific Ocean; Paleo-oceanography; Paleoecology; Paleoenvironment; Plantae; Pleistocene; Pliocene; Quantitative analysis; Quaternary; Reticulofenestra; Shatsky Rise; Size; Tertiary; West Pacific
Coordinates: N321300 N321300 E1581600 E1581600
S195315 S195314 E1121515 E1121514
Record ID: 2017014819
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands