Sanyitang profile, 43°30'N, 122°30'E, 9.2 m thick, was investigated in a brickyard in Sanyitang site,Horqin District of Inner Mongolia Autonomous Region,in extensively wide and shallow channel of the middle reach of Xiliaohe River. It is located less than 200 km west to the margin of East Asian Summer Monsoon front,and is therefore sensitive to climate changes. However, most previous studies were focused mainly on eolian dune or endorheic depression environments while shallow and wide flooding plains, with various types of sedimentation, were less selected for palaeoenvironmental reconstruction. In this study, depositional composition, facies, sequences and chronology (AMS ~(14)C dating and archaeology) of the Late Holocene sediments were preliminarily investigated in the major site, Sayitang profile, with 12 additional profiles in the surrounding areas. The study was conducted with multiple approaches including: (1) An estimated reservoir age, ca. 600 ~(14)C years, of the dated sedimentary organic materials. (2) A set of shards of pottery, found within the sequence, archaeologically determined around the late Neolithic. Consequently, ~(14)C dated 1203 cal. B.C., obtained from the exact same position, is tenable. Based on such a combination of archaeological and radiocarbon dating, a local chronological framework of the Late Holocene is preliminarily established. (3) Both chestnut and chernozem soils were distinguished clearly on their differentiated origins. The former was developed from its parent C Horizon of eolian fine sand and silt sediments while the latter was directly formed from lacustrine clay sediment. (4) The lacustrine sediment, being chernozem-pedogenetically, was abruptly terminated determined by a sharp contact boundary with the overlying sediments. Based on the aforementioned findings, the conclusions are drawn as follows. The local Late Holocene desertification, re-initiated slightly earlier than the first chestnut soil at ca. 1500 B.C. The dune reactivation was followed by the soil complex, consisting of several chestnut soil horizons, alternated frequently with fluvial and eolian sands till around 1250 cal. A. D. Then, a lake environment suddenly occurred at the late half of Medieval Warm Period around 12~(th) ~ 13(th) century. This lacustrine environment occurred and disappeared abruptly. These two events may indicate rapid alternation between humidity and aridity besides relatively mild and smooth transition determined by the chestnut pedogenetic processes in the area. Thus, a hypothesis of Hurried humidity and hurried aridity is proposed for further approaching. In the context of recent global warming and mid-latitude aridity,abrupt drought,as enlightened by the rapid termination of the lacustrine deposition in this study,is even much important to be better understood.