Evaluating the Ca isotope proxy

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doi: 10.2475/03.2010.03
Author(s): Fantle, Matthew S.
Author Affiliation(s): Primary:
Pennsylvania State University, Geosciences Department, University Park, PA, United States
Volume Title: American Journal of Science
Source: American Journal of Science, 310(3), p.194-230. Publisher: Yale University, Kline Geology Laboratory, New Haven, CT, United States. ISSN: 0002-9599 CODEN: AJSCAP
Note: In English. 120 refs.; illus., incl. sketch map
Summary: The use of Ca isotopes as a proxy for mass flux imbalances in the Ca cycle is evaluated critically. A compiled Ca isotope record for the last 45 Ma, derived from bulk nannofossil ooze and with a temporal resolution of ∼0.5 Ma, and an interpretation of the record are presented in the context of the global Ca cycle. This analysis, which assumes that nannofossil ooze records isotopic variations in seawater, indicates a dynamic Ca cycle in the Cenozoic. Such dynamic behavior has serious implications for the C cycle and suggests feedbacks between the Ca and C cycles to stabilize, or buffer, the oceanic carbon reservoir. Alternative applications of the Ca isotope proxy are investigated, using numerical models to determine the extent to which Ca isotopes are sensitive to other aspects of the Ca cycle; the results of the simulations are applied to specific cases in the Cenozoic. The simulations illustrate how variations in the global fractionation factor between calcium carbonate and seawater can produce trends similar to those observed when comparing previously published Ca isotopic compositions of marine barite to the nannofossil ooze record. The large drop in the δ44Ca value of bulk nannofossil ooze near the Eocene-Oligocene boundary can be reconciled in two ways, either as a substantial increase in weathering relative to sedimentation or as an indicator of changing depositional mode within the ocean. Though the preferred interpretation is not clear at present, it is evident that Ca isotopes stand to be a unique proxy for Ca cycling once the isotope systematics are elucidated.
Year of Publication: 2010
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; Alkaline earth metals; Angola Basin; Atlantic Ocean; Bioclastic sedimentation; Ca-44; Calcium; Carbonate sediments; Cenozoic; Clastic sediments; Coccolithophoraceae; DSDP Site 167; DSDP Site 214; DSDP Site 400; DSDP Site 522; DSDP Site 590; Data bases; Data processing; Deep Sea Drilling Project; Digital simulation; East Pacific; Eocene; Equatorial Pacific; Geochemical cycle; Geochemistry; Global; IPOD; Indian Ocean; Integrated Ocean Drilling Program; Isotopes; Leg 130; Leg 17; Leg 22; Leg 48; Leg 73; Leg 90; Lord Howe Rise; Marine sediments; Metals; Microfossils; Monte Carlo analysis; Nannofossils; Ninetyeast Ridge; North Atlantic; North Pacific; Northeast Pacific; Northwest Pacific; Numerical models; ODP Site 807; Ocean Drilling Program; Oligocene; Ontong Java Plateau; Ooze; Pacific Ocean; Paleo-oceanography; Paleogene; Plantae; Quaternary; STELLA; Sedimentation; Sediments; South Atlantic; South Pacific; Southwest Pacific; Stable isotopes; Statistical analysis; Tertiary; West Pacific
Coordinates: N001906 N033626 E1613538 E1563728
S200000 N090000 E1030000 E0860000
N470000 N570000 W0080000 W0240000
S293000 S253000 E0034000 W0114000
S453129 S211153 E1745653 E1611336
Record ID: 2010059202
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from the American Journal of Science, Yale University, Kline Geology Laboratory, New Haven, CT, United States