Abstract:

Xinxiang is located between the mountainous region of northwest Henan and the plain of east Henan. Both the evolution of Yellow River alluvial fan and the Neotectonic movement have significant effect on the sedimentary process of the study area in Quaternary. This research dated core samples’ age and compared sedimentary facies of the stratigraphy in the study area according to the description of the core. The result implies that both the evolution of the Yellow River alluvial fan and the movement of the river channel from north to south play an important role in the sedimentation of the study area in Quaternary. Fluvial facies are the main sedimentary facies in this area. And all the drillholes reveal that the thickness of Holocene series is 10 m with the average age of about 9.5 ka, and the thickness of the Upper Pleistocene series is 69 m with the average age of 129 ka, and the thickness of the Middle Pleistocene series is 55 m with the average age less than 829 ka. This study didn’t find the bottom interface of the Lower Pleistocene series. In Early Quaternary, the Yellow River alluvial fan located at the west of the study area, and the river channel’s evolution had little effect on Xinxiang. The main sediments were of fine grained flood plain. As with the movement of the Yellow River from southwest to northeast, the main sediments were of the fluvial facies, and the sand became more than ever. In the Late Quaternary, the river channel moved to the south, thus the Yellow River alluvial fan had less impact on the study area than in the middle period of Quaternary, and the sand content decreased. In addition, this research suggests that the hiatus of the northeast of the study area and the differential subsidence in some region are the result of the Neotectonic movement in Early Quaternary. And the terrain in the northeast of the study area is higher than that in the southwest.

Key words: Quaternary, stratigraphic subdivision, sedimentary facies, sedimentary environment, Xinxiang of Henan Province