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Unlithified to lithified beds of dolomicrite, 1-3 cm thick, have been cored from the muds of Baffin Bay from depths greater than 350 cm below the water-sediment interface. From a consideration of the 7 m and greater depth of these dolomicrites below present sea level, the relative stability of this part of the Texas coast, and comparison with accepted sea-level curves, it has been demonstrated that these dolomicrites must be of subtidal origin. C14 dates on the dolomicrites indicate that they formed 2,000-4,000 years B.P.
The ^dgr O18 values of Baffin Bay surface waters reflect the salinity conditions of the waters. With salinity ranges of 5^pmil to 60^pmil, the corresponding ^dgr O18 values are -3.4^pmil to +3.3^pmil. Intermediate salinities have intermediate ^dgr O18 values.
The ^dgr O18 ranges for the dolomicrite sediments are +4.8^pmil to +5.4^pmil relative to PDB. These values indicate that the dolomicrites precipitated from hypersaline waters. ^dgr C13 ranges for the dolomicrite sediments range from -1.6^pmil to -7.5^pmil relative to PDB. These values indicate a considerable influence of metabolic carbon during the precipitation of the dolomicrites.
Lack of textural or isotopic evidence of a carbonate precursor to the dolomicrite, as well as the observed isotopic ranges of the dolomicrites and their position in the sedimentary column, lead to the belief that the dolomicrites from Baffin Bay, Texas, are of a primary, subtidal origin.
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