Nd and Sr isotopic evolution of the oceans of the past 800 million years

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6145025

Keto, L S

This thesis comprises four related studies on the Nd and Sr isotopic composition of oceans through time. The first study uses Lower Paleozoic fossil samples of Europe and North America to establish that phosphatic fossils retain the distinct Nd isotopic signatures of paleoceans. These signatures may be used as tracers of paleoceanic water masses through time and consequently as tracers of paleogeography. The second study provides a framework for understanding and interpreting the Nd isotopic record of individual oceans as well as for determination of the mean oceanic isotopic compositions of Nd. Variations in individual ocean Nd isotopic compositions through time have implications for regional geology and paleoceanic circulation whereas the mean oceanic Nd isotopic compositions have implications for the global inputs to the oceans from the continents. The third study extends the record of well-defined /sup 87/Sr//sup 86/Sr values for seawater into the Late Proterozoic using carbonate samples of East Greenland and Svalbard. A thermal subsidence model is used to quantify the ages of these samples. Criterion for recognizing samples which have preserved /sup 87/Sr//sup 86/Sr seawater primary values are developed and the Sr and C isotopic records for paleoseawater of the past 1000 Ma are compared. The fourth study integrates the paleocean Nd and Sr isotopic records, as developed in the first parts of the thesis, into a model of the changing chemical and mass inputs to the oceans of the past 800 Ma.

• Research Organization: Harvard Univ., Boston, MA (USA)
• OSTI ID: 6145025
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
580400 -- Geochemistry-- (-1989)
580500 -- Oceanography-- (1980-1989)
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
ATLANTIC OCEAN
BETA DECAY RADIOISOTOPES
CARBON ISOTOPES
CHEMISTRY
ELECTRON CAPTURE RADIOISOTOPES
ELEMENTS
EUROPE
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FOSSILS
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGIC MODELS
GREENLAND
HOURS LIVING RADIOISOTOPES
HYDROGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE RATIO
ISOTOPES
METALS
NEODYMIUM
NORTH AMERICA
NUCLEI
OXYGEN COMPOUNDS
RADIOISOTOPES
RARE EARTHS
SEAS
SEAWATER
STABLE ISOTOPES
STRONTIUM 86
STRONTIUM 87
STRONTIUM ISOTOPES
SURFACE WATERS
WATER