Cretaceous environments of northeastern Thailand

摘要: The nonmarine Cretaceous rocks are widespread in the northeastern part of Thailand. They belong to Phra Wihan, Sao Khua, Phu Phan and Khok Kruat Formations Khorat Group overlying Maha Sarakham Formation. Reddish-brown light-gray sandstones, conglomeratic siltstones, claystones clongomerates main lithologies these rocks; calcrete nodules silcretes also present but salts gypsum found only interpreted as having been deposited by meandering braided rivers semi-arid arid conditions. Age determinations based mainly on vertebrates, bivalves palynomorphs, indicating that reassigned late Early Late Cretaceous. Previously known lime-nodule conglomerates silicified wood-like beds have re-interpreted paleosols silcretes, respectively. These maroon reddish-brown particularly Khua Petrographically geochemically, similar those climate South Africa, Canada other regions. As a result, may be used paleoclimate indicators for rocks, were fluvial system during paleoclimate. According physical, biological climatological changes Thailand, there repetitive from river systems corresponding paleoclimatological conditions Biological depending physical changes, which faunal abundance diversity confined