Thousands of Potholes in the Mekong River and Giant Pedestal Rock from North-eastern Thailand: Introduction to a Future Geological Heritage Site

Abstract

A site with thousands of potholes, locally named “Samphunbok (SPB),” and a giant pedestal (mushroom) rock possess a very high geological value. The potholes are being formed on the riverbed of the Mekong River; whereas the giant pedestal rock is the largest on the Khorat Plateau, and is located in Ubon Ratchathani province, north-eastern Thailand. Based on detailed geological, geomorphological, and sedimentological perspectives, this paper presents the geological history of both erosional features for the future promotion of the Global Geopark Network. The giant pedestal rock is likely to be a remnant of degradation and weathering after a regional tectonic event. It is sculptured in the fracture zone of thick sandstone beds after uplifting and folding. No evidence of abrasion by wind was found. The formation of potholes is limited inside the Mekong River bankfull elevation. The appearance of potholes in different levels of the sandstone beds infers their formation in relation to the vertical evolution of the Mekong River. All geological data shown in this paper confirm the rareness of potholes and the giant pedestal rock in terms of how they were sculptured and preserved through time. These erosional features at SPB are discussed and introduced in this paper as a global geological heritage site.