Khao Noi Rock Succession

The site is a small hill on the east of the route no. 416. It is an abandon quarry as a type area for the Pa Kae Formation and Wang Tong Formation. The Pa Kae Formation is 66 meters thick with a red thin-bedded limestone characterized as a mud crack-like stromatolitic structure consisting of 10 – 15 centimeter-thick beds. The cracks are filled with higher resistant dark brown material. Fragmentary fossils found from this rock formation are Late Ordovician trilobites, nautiloids, crinoids, and brachiopods.

The Pa Kae Formation is conformably overlain by the Wang Tong Formation. The Wang Tong Formation is a succession of black shale with graptolites and trilobites and intercalation of chert in the upper part. The fossils indicate Late Ordovician – Early Silurian in ages.

Graptolites are extinct marine animals that lived in the seas about 370 million years ago. Like corals they were colonial – each graptolite was made up of many tiny individual animals which linked together into a single colony. As fossil, they have a shiny look as though they had been drawn onto the rock with a pencil.