Holocene stratigraphic sequences in the northern Ordos Plateau and its implications for the disappearance of Huoluochaideng ancient city in the Han Dynasty, North China

Abstract

The Huoluochaideng ancient city, located in the northern Ordos Plateau, once was a prosperous metropolis in Han Dynasty. However, the city suddenly disappeared at ~2.0 ka and the reason for the disappearance is still a mystery. In this article, detailed analysis on the Holocene stratigraphic sequences and active tectonics in the area of northern Ordos Plateau are presented to reveal the reasons for the Huoluochaideng ancient city's disappearance. Our results show that the Huoluochaideng ancient cities were filled with the flood deposits and buried on a group scale. The Holocene flood deposits were widely distributed in the ancient city and adjacent areas. The 14C dating results of the flood deposits demonstrated the ancient city experienced at least three palaeoflood events (~2.05, ~1.99, and ~1.85 ka) during the Late Holocene, which are consistent with the occurrence time of the most recent palaeoearthquake events (~2.08–1.85 ka) on the Langshan Mountain piedmont fault. Therefore, it is suggested that the palaeoearthquake events and their secondary damages led to the outbreak of extensive floods in the northern Ordos Plateau. After the last flood event (~1.85 ka), the Huoluochaideng ancient city was buried again by the northward moving Kubuqi Desert due to the arid climate and desertification. In summary, the disappearance of Huoluochaideng ancient city is suggested to relate with the great flood events that was triggered by the palaeoearthquake on the Langshan Mountain piedmont fault, such as the levees break of the Yellow River.