Petrography and origin of dolomite in carbonate deposits in various paleoclimates

In arid formations primary deposition of magnesium occurred in peritidal- a nd sabkha facies. In ancient sequences, the dolomite origin was primarily c hemogenic, biochemogenic, and biogenic and the textures formed were microgr anular. In younger sequences the dolomite had an early diagenetic origin an d magnesium deposition was chemogenic and biochemogenic; its texture is fin e-medium crystalline. In humid formations primary deposition of magnesium i n shallow waters is not significant. Comparatively high quantities of magne sium were deposited in relatively deep marine sediments in association with organic matter. Substantial quantities of dolomite were found only in reef s, the dolomitization being late diagenetic, metasomatism, the texture is m edium crystalline to macrocrystalline.