The Cenozoic Doi Ton Formation is outstanding for its leaf fossil deposited in sandstone of which the geologic age is still controversial. This research focuses on stratigraphy and sedimentary facies analyses in order to interpret the paleoenvironment, paleoclimate and identify the geologic age of the study area. Doi Ton Formation can be divided into upper and lower members. The upper Doi Ton member can be divided into five facies including, Sm, Sg, Sr, Sp, and Gm (Gm and Gmg). Furthermore, these facies make up two facies associations, which are (1) channel deposit (Gm, Gmg, Sg, Sr, Sp, and Sm), and (2) sandy bar (Sg, Sr, and Sp) indicating the braided river depositional environment. The lower member is mainly composed of mudstone that suggests the low energy environment. The mineral compositions and leaf fossils indicate the warm and humid climatic conditions during their deposition period.
