Review of paleoceanographic transition during the Oligocene in the eastern Equatorial Pacific Ocean

Author(s): Takata, Hiroyuki; Nomura, Ritsuo; Seto, Koji
Author Affiliation(s): Primary:
Shimane University, Research Center for Coastal Lagoon Environments, Matsue, Japan
Volume Title: Kaseki Fossils
Source: Tokyo [Kaseki = Fossils, Vol.81, p.5-14. Publisher: Palaeontological Society of Japan,], Japan. ISSN: 0022-9202
Note: In Japanese with English summary. 34 refs.; illus., incl. sketch maps
Summary: Paleoceanographic condition in the deep-sea ocean during the Eocene-Oligocene transition is affected by change in ice volume in the Antarctic region and deep-water formation in the Southern Ocean. ODP Leg 199 in the eastern equatorial Pacific Ocean recovered continuous sections containing well-preserved microfossils during the Eocene-Oligocene interval, and provides an opportunity to study this transition. In this paper, we review recent results of the Oligocene paleoceanography and outlines of faunal change in benthic foraminifers in the eastern equatorial Pacific Ocean. Sedimentary records from ODP Leg 199 represent a deepening of calcite compensation depth (CCD) more than 1 km near the Eocene/Oligocene boundary in the eastern equatorial Pacific Ocean. Around the interval of CCD change, two-step positive sifts of oxygen isotope occurred in benthic foraminifers within ∼300 kyrs. The glaciation events marked by the Oil isotope event coincide with the intervals of low eccentricity and low obliquity amplitude variations, due to absence of warm summer. Other three glacial events of 29.16, 27.91 and 26.76 Ma during the Oligocene are probably related to low obliquity amplitude variation fluctuating with about a 1200 kyr.-cycle. Abyssal benthic foraminifers show an increase in Antarctic-bottom water fauna (Nuttallides umbonifer) around the Early/Late Oligocene boundary in the eastern equatorial Pacific Ocean. The short-term abundance peaks of Nuttalides umbonifer are correlative with the Oi event, suggesting that this species could be useful as a proxy of the Antarctic ice-sheet expansions.
Year of Publication: 2007
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctica; Assemblages; Atlantic Ocean; Bay of Biscay; Benthic taxa; Cantabria Seamount; Cenozoic; DSDP Site 119; DSDP Site 317; DSDP Site 526; DSDP Site 558; DSDP Site 563; Deep Sea Drilling Project; Deep-sea environment; East Pacific; Equatorial Pacific; Foraminifera; Glaciation; IPOD; Invertebrata; Leg 12; Leg 199; Leg 33; Leg 74; Leg 82; Manihiki Plateau; Marine environment; Microfossils; Mid-Atlantic Ridge; North Atlantic; North Pacific; Northeast Pacific; ODP Site 1218; ODP Site 1219; Ocean Drilling Program; Oligocene; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Paleogene; Protista; South Atlantic; South Pacific; Southeast Pacific; Southern Ocean; Tertiary; Walvis Ridge
Coordinates: N333831 N374615 W0372036 W0434603
S300724 S300724 E0030818 E0030818
S110006 S110005 W1621546 W1621547
N074800 N085300 W1352200 W1420100
Record ID: 2012019576
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute.