Abstract
Age determinations by the C14 method have shown that dolomite in surficial sediments of Deep Spring Lake, California, is virtually recent. The dolomite crystals are generally less than 1 μ on the rhombohedral edge. The newly formed dolomite is calcium-rich, has a range of compositions, is very poorly ordered, and has weak basal reflections. A small amount of detrital dolomite is also present, which is compositionally and structurally distinct from the newly formed dolomite. The average growth rate of individual crystals is of the order of hundreds of angstroms per thousand years; the rate of growth of rhombohedral edges of the crystals has been roughly constant with time. Extreme slowness of growth of individual crystals seems essential for the formation of the ordered dolomite phase at low temperatures. A slow net rate of deposition appears essential to the development of the ordered phase before final burial. Ordering probably takes place near but slightly beneath the surface of the growing crystal. Conditions in Deep Spring Lake favorable for the formation of dolomite were initiated near the close of the pluvial period.
Published Version
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