Late early Oligocene deep-sea benthic Foraminifera and their faunal response to paleoceanographic changes in the eastern Equatorial Pacific

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doi: 10.1016/j.marmicro.2012.09.002
Author(s): Takata, Hiroyuki; Nomura, Ritsuo; Tsujimoto, Akira; Khim, Boo-Keun
Author Affiliation(s): Primary:
Shimane University, Research Center for Coastal Lagoon Environments, Matsue, Japan
Other:
Pusan National University, South Korea
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, Vol.96-97, p.123-132. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Supplemental information/data is available in the online version of this article; includes appendix. 56 refs.; illus., incl. 1 table, sketch map
Summary: We documented new data on the late early Oligocene benthic foraminifera and sediment geochemistry in the eastern Equatorial Pacific Ocean (EEP) from Integrated Ocean Drilling Program (Exp. 320) Site U1334 (paleo-water depth: ∼3650 to ∼3850 m) with some published data on those from Ocean Drilling Program (Leg 199) Sites 1218 (∼3850 to ∼4000 m) and 1219 (∼4270 to ∼4370 m) in order to understand the response of abyssal benthic foraminifera to paleoceanographic conditions during the interval ∼32-28 Ma. The relative abundances of Nuttallides umbonifer were distinctly different between Sites 1218 and 1219 during 31.0 to 29.9 Ma, although other major taxa (e.g., Globocassidulina subglobosa, Cibicidoides spp. and Oridorsalis umbonatus) showed no marked changes. The characteristics (e.g., Shannon-Wiener (H')) of the benthic foraminiferal fauna are affected by the abundance of a few dominant species rather than by the change in the number of species in the EEP. Based on multi-dimensional scaling (MDS), two MDS axes were recognized: MDS axis 1 (characteristic taxa: N. umbonifer and Cibicidoides sp. A) and MDS axis 2 (characteristic taxa: G. subglobosa and Bolivina huneri). The tendency of both MDS axes (1 and 2) showed a distinct depth gradient among the three sites after 28.6 Ma, whereas the tendency was different from 31.0 to 28.6 Ma, especially at Site 1218. Increased abundance of N. umbonifer in the EEP after ∼29 Ma was similar to that in the Atlantic Ocean after the expanded distribution of this species to shallower depths was finished. The faunal change at 28.6 Ma might be related to the change of deep water circulation, possibly with the influences of the Southern Component Water (SCW) and/or Northern Component Water in the South Atlantic Ocean. In contrast, the faunal change at 31.0 Ma might be related to the formation of the SCW and/or meridional overturning circulation in the Southern Ocean. In particular, MDS axis 1 exhibited the opposite tendency between Sites 1218 and 1219 around the Oi-2 event, whereas the depth gradient was clearly observed among the sites around the Oi-2* event. The opposite tendency of MDS axis 1 around the Oi-2 event might be explained by the varying influences of the SCW on different depths of the EEP, especially in terms of carbonate undersaturation. The influence of the SCW on benthic foraminifera in the EEP was different among the depths of the three sites in the Oi-2 event, however, the depth gradient of the SCW influence was gradually intensified in the Oi-2* event and the 28.6-28.0 Ma interval. Abstract Copyright (2012) Elsevier, B.V.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Assemblages; Benthic taxa; Cenozoic; Chemical composition; Deep-sea environment; East Pacific; Equatorial Pacific; Expedition 320; Expeditions 320/321; Foraminifera; IODP Site U1334; Integrated Ocean Drilling Program; Invertebrata; Leg 199; Lower Oligocene; Marine environment; Marine sediments; Microfossils; Morphology; North Pacific; Northeast Pacific; Nuttallides umbonifer; ODP Site 1218; ODP Site 1219; Ocean Drilling Program; Oligocene; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleoenvironment; Paleogene; Protista; SEM data; Sediments; Tertiary; Tests
Coordinates: N080000 N080000 W1315824 W1315824
N085300 N085300 W1352200 W1352200
N074800 N074800 W1420100 W1420100
Record ID: 2013033444
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands