Sr isotopic variations in Upper Proterozoic carbonates from Svalbard and East Greenland

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90355-4· OSTI ID:7266133

Derry, L A; Keto, L S; Jacobsen, S B; Knoll, A H ^[1]; Swett, K ^[2]

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1. Harvard Univ., Cambridge, MA (USA)
2. Univ. of Iowa, Iowa City (USA)

The authors report initial {sup 87}Sr/{sup 86}Sr values from an Upper Proterozoic carbonate succession from Svalbard and East Greenland. This succession, now tectonically separated into three sequences, is thick, relatively continuous, and well preserved. The relative ages of the samples from within the basin are well constrained by litho-, bio-, and chemostratigraphic techniques. The data from this study and related data from the literature are used to construct a curve of {sup 87}Sr/{sup 86}Sr for Upper Proterozoic seawater. The new data reported in this study substantially improve the isotopic record of Sr in seawater for the period between 650 and 800 Ma. The data indicate that {Delta}{sup 87}Sr values of seawater were variable but low ({Delta}{sup 87}Sr {approximately}{minus}500 to {minus}250) between 900 and 650 Ma, and rose rapidly to {approximately} +30 by 600 Ma. The range of variation of {Delta}{sup 87}Sr in seawater during the Riphean-Vendian exceeds the entire range of {Delta}{sup 87}Sr in seawater during the Phanerozoic. While variation in the average isotopic composition of Sr delivered to the oceans by rivers can account for some of the observed range, changes in the ratio of submarine hydrothermal flux to river water (continental) flux are responsible for the large variation in seawater Sr isotopic composition. Changes in the continental flux of Sr to the oceans can be related to tectonic factors. Large changes in the hydrothermal flux to river water flux ratio indicated by the data could have significant consequences for the chemistry of the ocean-atmosphere system.

• OSTI ID: 7266133
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:9; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALINE EARTH ISOTOPES
CARBONATE ROCKS
CHEMICAL COMPOSITION
CHEMISTRY
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GREENLAND
HYDROGEN COMPOUNDS
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
OXYGEN COMPOUNDS
PRECAMBRIAN ERA
ROCKS
SEAWATER
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
STRONTIUM ISOTOPES
TECTONICS
WATER
WATER CHEMISTRY