Evolution of Eastern Pacific Warm Pool and upwelling processes since the middle Miocene based on analysis of radiolarian assemblages: Response to Indonesian and Central American Seaways

Shin ichi Kamikuri, Isao Motoyama, Hiroshi Nishi, Masao Iwai

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)

Abstract

A quantitative radiolarian study at Ocean Drilling Program Site 1241 in the eastern tropical Pacific enables us to reconstruct paleoceanographic changes that occurred since the latest middle Miocene. Today, this site is located just under the Eastern Pacific Warm Pool (EPWP). Based on the abundance variations of radiolarian characteristic species which are indicators of upwelling and thermocline changes, it is suggested that three notable changes occurred at 10.6, 9.8, and 4.2 Ma in the region. Four distinct periods of oceanographic conditions bounded by these notable changes were characterized on the basis of the following: (1) stratified seawater (12.0 to 10.6 Ma); (2) a shallowing of the thermocline and an increasing of upwelling (10.6 to 9.8 Ma); (3) significant inflow of warm water to the eastern tropical Pacific caused by an intensified Northern Equatorial Countercurrent (NECC), resulting in the formation of EPWP (9.8 to 4.2 Ma); and (4) the reduction of the EPWP and the NECC, and an increase in upwelling (4.2 to 0 Ma). The timing of these paleoceanographic events indicated the strong relations with the opening and closing of the Indonesian and Central American (Panama) Seaways. The reduction of the EPWP (this study) and the deepening of the thermocline in western Pacific at about 4.2 Ma (Cannariato and Ravelo, 1997; Chaisson and Ravelo, 2000) indicated a change from a state resembling El Niño in the late Miocene and the early Pliocene time to a state resembling La Niña by the late Pliocene.

Original languageEnglish
Pages (from-to)469-479
Number of pages11
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume280
Issue number3-4
DOIs
Publication statusPublished - 2009 Sep 15
Externally publishedYes

Keywords

  • Eastern Pacific Warm Pool
  • Eastern equatorial Pacific
  • Indonesian and Central American Seaways
  • Northern Equatorial Countercurrent
  • Radiolarian assemblages

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

Fingerprint Dive into the research topics of 'Evolution of Eastern Pacific Warm Pool and upwelling processes since the middle Miocene based on analysis of radiolarian assemblages: Response to Indonesian and Central American Seaways'. Together they form a unique fingerprint.

Cite this