The sedimentary facies of Callovian-Oxfordian Stage in Amu Darya basin, Turkmenistan

Abstract：Based on core observations, identification of thin sections and paleontology, in combination with logging facies, seismic faces and regional depositional background, the authors have reached the conclusion that Callovian-Oxfordian carbonates in Amu Darya basin of Turkmenistan are carbonate platform deposits. Six types of sedimentary facies can be recognized, i.e., evaporative platform, restricted platform, open platform, platform-edge reef-shoal, platform fore-edge slope and platform basin facies. According to the facies correlation sections of the wells as well as the plane distribution and vertical evolution of sedimentary facies, the authors revealed the evolution characteristics of Callovian-Oxfordian sedimentary facies. The sedimentary environment changed from platform edge ramp, platform-edge reef-shoal, open platform and restricted platform into evaporative platform in turn, which constituted the multi-phase transgressive-regressive cycles. Finally, the depositional model of “platform with open, rimmed and gently dipping slope” has been established.