Dolomites petrography diagenesis analysis, probable Shahbazn-Asmari formations boundary and facies based on dolomicrite geochemistry, petrogaphic evidences a nd statistic methods in Darabi section (Southwest Iran)

The Shahbazan Formation with the age of Middle Eocene to Late Eocene consists of dolomite, dolomitic limestone and marl sequence. The study area is located in the southwest of Iran in the Lorestan province. Based on field observations and petrographic studies (grain size and fabric), five different dolomite types are recognized. In the dolomicrite (dolomite I) due to the presence of evaporite mold, peloid grain and algal laminates, it has been concluded that dolomicrites were deposited in a tidal flat environment and secondary dolomite (II, III, IV and V) formed during shallow to deep burial diagenesis. In diagenetic environments, by increasing diagenetic processes, in dolomicrite, Mg, Fe and Mn value have been increased while the contents of Ca, Sr and Na decreased. According to change in mineralogy component and dissolution prossess in probable boundary between the Shahbazan and the Asmari Formations, the contents of Ca, Sr and Na have been increased and the value of Mg, Mn and Mn/Ca decreased. On the basis of cluster analysis, geochemical results of analyzed samples divided into four different groups that indicate different characters of sedimentary environment.