Stratigraphy and Paleoenvironment of thong Pha Phum group in Kanchanaburi province

Abstract

The purposes of this study are to establish the detail lithology, stratigraphy, lithofacies and systematic paleontology of marine Silurian-Devonian sedimentary rocks of the Thong Pha Phum Group in Ban Tha Kraden, Si Sawat District, Kanchanaburi Province, and to interpret and reconstruct its depositional environment.

The Thong Pha Phum Group is well exposed in the study area. It consists mainly of shale, siltstone, sandstone, limestone, argillaceous limestone, calcareous shale, calcareous mudstone, and laminated mudstone with the many fossils such as graptolites, tentaculites, ostracods, brachiopods, nautiloids and trilobites. These strata are conformably underlain by the Thung Song Group (Ordovician age) and are conformably overlain by the Khuan Klang Formation (Early Carboniferous age). Abundant tentaculites were recognized and they consist of 7 species belonging to 3 genera: Nowakia acuaria, Nowakia (Cepanowakia) pumilio, Styliolina fissurella, Styliolina clavulus, Styliolina sp. A, Homoctenus tikhyi, and Homoctenus arctus indicating Early to Late Devonian age. In addition, graptolites (Monograptus sp. and Diplograptus sp.) were found in this area and they indicate probably Silurian? to Early Devonian. Based on the lithology, lithofacies, sedimentary structure, and fossils contains, they suggest that the Thong Pha Phum Group was deposited on the slope environment to deep marine basin in low energy conditions.