A Review of the Lithostratigraphy of the Early Cretaceous Sao Khua Formation, Khorat Group in Northeastern Thailand

Non-marine Cretaceous rocks are widespread in northeastern Thailand and is well known as “the red bed” Khorat Group. The Sao Khua Formation the upper half of Group which comprised six formations. This formation was named defined at type section for between restricted PhraWihan Phu Phan drainage area Huai Khua, an intermittent stream that flows westward parallel to highway Nong Bua Lamphu UdonThani Provinces. It contains richest most diverse vertebrate invertebrate Mesozoic fossils Thailand. characterized by sequence fining-upward successions least 4-5 megacycles throughout with total thickness ranging 400-700 meters. Each cycle starts a channel lag conglomerate clasts consist totally re-worked calcrete nodules. conglomerates were overlain fine-to medium-grained sandstones point bar deposit. Finally, top part each covered succession fine-grained floodplain deposit makes up 60%-70% formation. Paleosols commonly found within their geochemistry indicates semi-arid paleoclimate. Based on lithostratigraphy, interpreted have been deposited meandering river system under climate condition. age assigned Hauterivian-Late Barremian based bivalves fossils.