The deep sea oxygen isotopic record: Significance for tertiary global ice volume history, with emphasis on the latest Miocene/early Pliocene
Planktonic and benthic isotopic records as well as carbonate sedimentation records extending from 6.1 to 4.1 Ma for eastern South Atlantic Holes 526A and 525B are presented. These data suggest ice volume variations about a constant mean sufficient to drive sea level between 10 m and 75 m below present. Isotopic records at the deeper (2500 m) site have been enriched by up to 0.5% by dissolution. Carbonate accumulation rates at both sites quadrupled at 4.6 Ma primarily because of increased production and, secondarily, decreased dissolution. The second part presents a Cenozoic-long composite {delta}{sup 18}O curve for tropical shallow-dwelling planktonic foraminifers and the benthic foraminifer Cibicides at 2-4 km depths. Surface {delta}{sup 18}O gradients between various low-and-mid latitude sites reflect: (1) widespread SST stability through the Cenozoic and (2) significant change in Tasman Sea SST through the Tertiary. Assuming average SST for tropical non-upwelling areas was constant, the planktonic composite suggest that global ice volume for the last 40 my has not been significantly less than today. Residual benthic {delta}{sup 18}O reflect relatively warm and saline deep water until the early Miocene after which time deep water progressively cooled. The third part presents {delta}{sup 18}O for Recent Orbulina universa from 44 core-tops distributed through the Atlantic and Indian Oceans. The purpose was to test the hypothesis that Orbulina calcifies at constant temperature and so records only ice volume changes. Orbulina commonly calcifies at intermediate depths over a wide range of temperatures salinities, and densities. These physical factors are not the primary controls on the spatial and vertical distribution of Orbulina.
- Research Organization:
- Brown Univ., Providence, RI (USA)
- OSTI ID:
- 7266142
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SEAWATER
ISOTOPE RATIO
AQUATIC ORGANISMS
ATLANTIC OCEAN
CARBONATE MINERALS
DENSITY
DEPTH
DISTRIBUTION
FLUCTUATIONS
GEOLOGIC HISTORY
GLACIERS
ICE
INDIAN OCEAN
OXYGEN 18
PALEOCLIMATOLOGY
SALINITY
SEA LEVEL
SEDIMENTARY ROCKS
SOUTHERN HEMISPHERE
TEMPERATURE DEPENDENCE
TERTIARY PERIOD
TROPICAL REGIONS
VOLUME
CENOZOIC ERA
DIMENSIONS
EARTH PLANET
EVEN-EVEN NUCLEI
GEOLOGIC AGES
HYDROGEN COMPOUNDS
ISOTOPES
LEVELS
LIGHT NUCLEI
MINERALS
NUCLEI
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PALEONTOLOGY
PHYSICAL PROPERTIES
PLANETS
ROCKS
SEAS
STABLE ISOTOPES
SURFACE WATERS
VARIATIONS
WATER
580000* - Geosciences