Siam City Cement Public Company Limited area is located in Changwat Saraburi. The rock in this area belong to the Phu Phe Formation which is the oldest formation of the Saraburi Group. Characteristic of Phu Phe Formation is dark grey skeleton limestone interbedded with slaty shale and chert nodule. It has a complex geological structure. The detail study on lithology and paleontology may help to determine the geological structure and age of the rock in this study area. 27 samples were collected to study their petrography and carbonate classification by binocular microscope. Carbonate samples were classified into 3 types which is bioclastic packstone, crinoidal packstone to crinoidal rudstone and calcareous shale. Grains in carbonate rock contain several types of fossil such as crinoid, smaller foraminifera, bryozoan, algae and fusulinid. Based on field investigation, the fossil assemblage, and carbonate petrography in study area, they show that the depositional environment was in shallow seas where located between fair-weather wave base and storm-wave base. It might be in carbonate mid ramp. These data can be used for reconstructing geological map of the area.
