Identification of reef in Miocene, south of Qiongdongnan Basin

The southern part of the Qiongdongnan Basin was suitable for reef generation when the Meishan Formation deposited during Miocene.Seismic data collected in this region during the past few years have indicated that the Meishan Formation is characterized by typical mound reflection,mainly on ancient uplifts.The formation is flat at the bottom and convex at the top.There is clear boundary between top and bottom.The reflection is strong.Progradational or random reflection exists in the formation,while on the 2 flanks there is onlapping,and on the top there is drape.The wave impendence value is(8-10)×10⁶kg/(m²·s).The formation is regarded as reef according to present studies.Comparisons between reef and mud structure have been carried out based on the studies of regional sedimentary background,mound structure generation location and seismic reflection characteristics,indicating that it is impossible for shale diapire generation in the formation.