Changes in the depth habitat of the Oligocene planktic Foraminifera (Dentoglobigerina venezuelana) induced by thermocline deepening in the eastern Equatorial Pacific

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doi: 10.1002/2016PA002950
Author(s): Matsui, Hiroki; Nishi, Hiroshi; Takashima, Reishi; Kuroyanagi, Azumi; Ikehara, Minoru; Takayanagi, Hideko; Iryu, Yasufumi
Author Affiliation(s): Primary:
Tohoku University, Institute of Geology and Paleontology, Sendai, Japan
Other:
Kochi University, Japan
Volume Title: Paleoceanography
Source: Paleoceanography, 31(6), p.715-731. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 67 refs.; illus., incl. 1 plate, sketch map
Summary: Understanding planktic foraminiferal depth habitat along with consistent taxonomic concepts is key to accurate reconstruction of paleoceanographic records. The Oligocene-Pliocene long-ranging and widely distributed species Dentoglobigerina venezuelana lived in the mixed layer (shallower) during the early Oligocene, whereas the same species calcified at thermocline or subthermocline depths (deeper) during the late Oligocene and Miocene. The exact timing of the species' depth habitat change and its possible relationships with Oligocene climate dynamics remain unknown. Here we reveal isotopic records of D. venezuelana along with the Paragloborotalia siakensis group (a mixed-layer dweller) by using sediments at Integrated Ocean Drilling Program Site U1334 in the eastern equatorial Pacific throughout the Oligocene. A two-step depth habitat change of D. venezuelana is apparent: (1) from upper to lower mixed layer (∼27.4 Ma) and (2) from lower mixed layer to thermocline depth (∼26.3 Ma). In addition, the planktic foraminiferal faunal assemblage experienced a marked change from dominantly thermocline (deeper) species to abundant mixed-layer (shallower) species, suggesting that depth habitat shifts of D. venezuelana were clearly related to thermocline deepening in the eastern equatorial Pacific. Comparison of the first isotopic shift (∼27.4 Ma) at multiple sites (U1334, U1333, and 1218) revealed a southward depth habitat change of D. venezuelana within ∼200 kyr, implying overall thermocline deepening with reduced steepness in the eastern equatorial Pacific. We consider that global warming conditions during the late Oligocene likely caused thermocline deepening with upwelling decrease in the eastern equatorial Pacific, guiding D. venezuelana to adapt to greater depths in the water column. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Assemblages; C-13/C-12; Carbon; Cenozoic; Dentoglobigerina venezuelana; East Pacific; Equatorial Pacific; Expedition 320; Expeditions 320/321; Foraminifera; Habitat; IODP Site U1333; IODP Site U1334; Integrated Ocean Drilling Program; Invertebrata; Isotope ratios; Isotopes; Leg 199; Marine environment; Microfossils; Morphology; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1218; Ocean Drilling Program; Oligocene; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoenvironment; Paleogene; Planktonic taxa; Protista; Stable isotopes; Tertiary; Tests; Thermocline
Coordinates: N080000 N080000 W1315824 W1315824
N103100 N103100 W1382510 W1382510
N085300 N085300 W1352200 W1352200
Record ID: 2017045035
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom