STUDY ON AN OSCILLATORY MICRO-LAMINATED DOLOMITE/LIMESTONE ROCK AND ITS IMPLICATION ON SEDIMENTARY DOLOMITE FORMATION
Ordovician micro-laminate carbonate rock from Southern Appalachian was selected for understanding the relationship between microbial mat and dolomite. In-situXRD, SEM and TEM results indicate that, the sample contains two distinctly different micro-laminae, dark layers with euhedral dolomite crystals, and bright layers dominated by calcite. Diffraction pattern from TEM and XRD shown clear (015) peak for dolomite within this sample, therefore the euhedral dolomite in this sample is ordered.
Our study show that since each laminae has an average width of ~0.2mm and darker layers are generally thinner than brighter layer. Higher porosity and less thickness indicate the dark layers were enrich in organic materials. Since the organic materials, which probably contains fair amount of microbial biomass during deposition, are concentrated in dark layers which catalyze dolomitization. The observed evidence in the natural sample supports preferred dolomitization and the relationship between organic material/ microbial biomass and dolomite micro-laminae.