Lithostratigraphic division and correlation of Haojiatai NHA borehole from Nihewan Basin in Yangyuan, Heibei

Abstract: Nihewan Basin is situated in Sangan and Huliu river watershed, Hebei and Shanxi Province. It is well-known for its well-developed late Cenozoic strata and rich mammalian faunas and Paleolithic sites. Lithostratigraphic division of strata is critical for investigating region geology. In order to deeply know the stratum, a 365.82 m long core (N：40°13′0.4″，E：114°38′32.3″，H：938 m) was obtained by us at Haotjiatai in 2013, which is located in Huashaoyin town, eastern of Nihewan Basin. Based on the analyzing of lithostratigraphy, this long core could be divided into six formations downward. 1, Upper Pleistocene Malan Formation (9.64 m thick), which is eolian loess and shows depositional hiatus between it and underlying strata; 2, Upper Pleistocene Haojiatai Formation (23.46 m thick), which is shore-shallow lacustrine sediment; 3, middle-lower Pleistocene Xiaodukou Formation (36.08 m thick), which is delta to lakeshore sediment; 4, lower Pleistocene Nihewan Formation (87.92 m thick), which is shore-shallow lacustrine sediment; 5, Pliocene Daodi Formation (111.78 m thick), which is lake-marsh sediment; 6, Pliocene Huliuhe Formation (73.02 m thick), which is floodplain sediment. The strata in depth of 341.90—365.82 m is Cretaceous, whose bottom is undiscovered. The section is characterized by large thickness, good continuity and 100% coring rate. In the field, through checking depth against the drill footage the borehole was described and sampled in good continuity and high resolution. Our study show that, Nihewan stratum could not only correlate in the basin on Quaternary, but also with Loess Plateau, such as Haojiatai Formation with Salawusu Formation, Xiaodikou Formation with Lishi Loess and Nihewan Formation with Wucheng Loess. This profile could be used as one of stratotype about fluvio-lacustrine strata in North China region.