DEPOSITION AND ENVIRONMENTAL EVOLUTION OF LIAOHE RIVER DELTA SINCE LATE PLEISTOCENE

The 41.4 m deep coring hole of ZK2 was drilled at the Liaohe River Delta for the purpose to reveal the evolution of sedimentary environment. According to the depositional proxies, such as lithology, grain size, foraminifera and BIT, and the AMS¹⁴C dating data, the ZK2 core is divided into four depositional units. From bottom to top, the U1 is a river channel facies, the U2 a flood plain facies, the U3 a marine facies (Holocene transgression) and the U4 is an upper delta plain facies. Furthermore, the Unit U3, i.e. the marine segment of the sequence, could be divided into five layers, namely U3¹, U3², U3³, U3⁴, U3⁵ from bottom to top, corresponding to a sequence of estuarine facies-neritic facies-predelta facies-delta front facies-lower delta plain facies (tidal flat). All the indices of grain size, foraminifera and BIT indicate an obvious vertical change in depositional environments, resulted from the sea level change around the delta since 33 kyr BP.As a continuous sequence without interruption calibrated by reliable dating data, the U3 (15.75~2.65 m) may well reflect the Holocene transgression history of the Liaohe River Delta since 9 100 calyr BP.