Lithostratigraphy of a high terrace with petrified wood fossils in Northeastern Thailand: implication for the depositional environment and geologic setting of the Khon Kaen subbasin

Abstract

.Khon Kaen’s petrified wood fossil sites in northeastern Thailand, though less studied, hold significant paleontological value. These sites offer crucial insights into the region’s geology. The Quaternary gravel beds, which contain a diverse array of petrified wood, were deposited on elevated terraces along the western boundary of the Khon Kaen subbasin. Field investigations focused on collecting sedimentological data to analyze the stratigraphic sequence, identify lithofacies, and characterize architectural elements in the gravel pits. The unconsolidated units (Units I–IV) unconformably overlie the Khorat Group bedrock in the Ban Non Rang area (north) and the Ban Kean Phra Doo area (south). From bottom to top, these units are as follows: I) conglomeratic sand, II) lenticular gravel with sand, III) massive gravel, and IV) red sandy soil containing minor pebble clasts. The depositional environment is interpreted as a braided stream on an alluvial fan with some debris flow occurrences, influenced by medium- to high-energy gravity/debris flows (Units I–III). Unit IV is identified as having been influenced by bioturbation processes. The majority of clasts in Units II and III consist of quartz, likely originating from the mountain ranges to the north to northwest of the subbasin.