Palaeontology and taphonomy of crinoid limestone in Amphoe Bugsamphan, Phetchabun

Abstract

Crinoid limestones are founded in Amphoe Bungsamphan,Phetchabun,contain not only abundant crinoids stems and also they associate with coral building animals, Brachiopods, Mollusca, Rugosa, Ammonoids, Calcareous sponges and Bryozoas. The longest chain stem is 78 cm. At first, I prepared the geologic map and classified geomorphic surface in study area and making the stratigraphical relationship between limestone and tuff. And the occurrence of crinoids fossils can be described the paleoenvironment are reconstructed. Crinoid stems are scattered in the layer parallel to bedding plane. Crinoids fossils are almost chained stems. The surface abrasion of stem is common. Unfortunately, all most of calyx are separated and lost, only one specimen of calyx is identified. Totally, 4 horizons are discriminated. Size frequency analysis of Crinoids diameter and length has been carried .Maximum and minimum length of chained stem is 104.0 mm and 0.3 mm. Maximum and minimum diameter of chained stem is 39.9 and 0.5 mm. Crinoids was the first invader as suspension feeder to the community. If the bottom conditions too soft, Crinoids cannot stand to get the foods. At first, lapilli tuff may be the last stage. In the final stage all most of the animals of the communities had been broken out and transported by the stronger current stem.