Carbon and oxygen isotopes of bulk carbonate in sediment deposited beneath the eastern Equatorial Pacific over the last 8 million years

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doi: 10.1002/2015PA002825
Author(s): Reghellin, Daniele; Coxall, Helen K.; Dickens, Gerald R.; Backman, Jan
Author Affiliation(s): Primary:
Stockholm University, Department of Geological Sciences, Stockholm, Sweden
Volume Title: Paleoceanography
Source: Paleoceanography, 30(10), p.1261-1286. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 148 refs.; illus., incl. strat. cols., 4 tables, sketch map
Summary: To improve the understanding and utility of bulk carbonate stable carbon and oxygen isotope measurements, we examine sediment from cores in the eastern equatorial Pacific that span the last 8 Ma. We measured δ13C and δ18O in 791 samples from Integrated Ocean Drilling Program Site U1338 and Deep Sea Drilling Project Site 573, both located close to the Pacific equator. In 100 samples, we measured δ13C and δ18O on isolated <63 µm and <38 µm fractions, which concentrates calcareous nannofossil carbonate and progressively excludes foraminiferal carbonate. Bulk carbonate δ13C and δ18O records are similar to published records from other sites drilled near the equator and seem to reflect mixed layer conditions, albeit with some important caveats involving the precipitation of calcite by coccolithophores. The comparatively lower δ13C and δ18O of the <63 µm and <38 µm fractions in sediments younger than 4.4 Ma is attributed to an increase in deep-dwelling planktic foraminifera material in bulk carbonate, shifting the bulk isotopic signals toward higher values. Bulk carbonate δ13C is similar over 2500 km along the Pacific equator, suggesting covarying concentrations and δ13C of dissolved inorganic carbon within surface waters since 8 Ma. Greater bulk sediment δ13C and δ18O, higher sedimentation rates, and low content of coarse material suggest intensified wind-driven upwelling and enhanced primary productivity along the Pacific equator between 8.0 and 4.4 Ma, although a full understanding of bulk carbonate records will require extensive future work. Abstract Copyright (2015), American Geophysical Union. All Rights Reserved.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 12 Stratigraphy, Historical Geology and Paleoecology; Algae; C-13/C-12; Carbon; Carbonates; Cenozoic; DSDP Site 573; Deep Sea Drilling Project; East Pacific; Electron microscopy data; Equatorial Pacific; Expedition 321; Expeditions 320/321; Grain size; IODP Site U1338; IPOD; Integrated Ocean Drilling Program; Isotope ratios; Isotopes; Leg 138; Leg 85; Lithostratigraphy; Marine environment; Marine sedimentation; Marine sediments; Microfossils; Miocene; Nannofossils; Neogene; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 850; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleo-oceanography; Paleoenvironment; Plantae; Pleistocene; Pliocene; Quaternary; SEM data; Sedimentation; Sedimentation rates; Sediments; Stable isotopes; Tertiary; Upper Miocene
Coordinates: N023028 N023028 W1175811 W1175811
N002954 N002955 W1331834 W1331835
N011749 N011751 W1103116 W1103118
Record ID: 2016042274
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom