孢粉资料定量重建泥河湾盆地侯家窑遗址时期的古气候

泥河湾盆地侯家窑遗址在中国旧石器文化及古人类演化进程中占有十分重要的地位, 但前人研究多集中在古人类及哺乳动物化石及其地层年代方面, 对古人类生存时的古气候、古环境研究较少, 更未见定量研究。本文利用最终筛选后的420个表土和83个地层样品的孢粉数据, 采用MAT(modern analogue technique)方法定量重建了泥河湾盆地侯家窑遗址220~85ka B.P. 的年均温和年均降水序列。依据孢粉定量重建的气候变化序列与大西洋-太平洋深海氧同位素和南极冰芯记录的MIS 5、MIS 6和MIS 7阶段有较好对应。冰期时, 泥河湾盆地的年平均气温比现在低2~4℃, 年均降水量比现在多200~400mm; 间冰期时, 年均气温比现在高约1℃, 或与现在相近, 年均降水量也与现在相近。冰期时, 泥河湾盆地的古气候相对稳定, 间冰期时波动频繁。侯家窑古人类生活在大理冰期(MIS 6阶段), 气候寒冷湿润, 丰富的动植物资源成为侯家窑人的主要食物来源, 侯家窑人已学会适应和抵御严寒的气候环境。

POLLEN-BASED QUANTITATIVE RECONSTRUCTION OF THE PALEOCLIMATE DURING THE FORMATION PROCESS OF HOUJIAYAO RELIC SITE IN NIHEWAN BASIN OF CHINA

Nihewan Basin is one of the ideal regions to study the climate and environment changes as well as the mutual relations between human activities to the climate and environment, and become a hot area of many disciplines studies of archeology, palaeoenvironment, paleoclimatology, paleontology, chronology and stratigraphy etc.Houjiayao Relic Site(40°06'2.26"N, 113°58'42.50"E) is located at the west furrow bank of Liyigou Stream, a small branch of Sanggan River in the west of Nihewan Basin, with an altitude of 980m, where is adjacent to Dageda Mountain in the north, against Liuleng Mountain in the south, about 1500m away from the southwest of Houjiayao Village, Dongjingji Town, Yangyuan County, Hebei Province.Houjiayao Relic Site plays a significant role in the Paleolithic culture of China and in the stages of Paleolithic human evolution.Previous studies have primarily concentrated on ancient human and mammal fossils and their chronostratigraphy.Studies on the relevance of paleoclimate and paleoenvironment for the survivals of ancient mankind in the site are limited, and we are unaware of any quantitative investigation of this topic.Based on the stratum and geomorphic position and its output stratum, we used the idea of Li Zhengtao and suggested that Houjiayao Relic Site and its buried stratum were formed in 220~85ka B.P.Then in this paper, on the basis of numerous research results regarding quantitative reconstruction of the paleoclimate, we finally used 420 screened surface pollen data from the East Asia surface database and meteorological observation data from sampling sites in the research area, and applied the MAT(Modern Analogue Technique)method to quantitatively reconstruct the sequences of annual average temperature and annual average precipitation of Houjiayao Relic Site.The reconstructed result shows that the temperature and precipitation during 220~85ka B.P.varied over three main stages and seven sub-stages.At the 1st stage, the annual average temperature was 6.5~8.5℃, and the average temperature of the hottest month was 21.5~23.0℃.The annual average precipitation was 240~480mm.The climate was temperate and dry.At the 2nd stage, the annual average temperature decreased rapidly to 4~6℃, and the annual average precipitation significantly increased and was approximately in the range of 600~800mm.The climate was cold and humid.At the 3rd stage, the annual average temperature was generally 5~9℃, and the annual average precipitation was in the range of 240~600mm.The reconstructed curves of temperature and precipitation variation of Houjiayao Relic Site during 220~85ka B.P.correspond closely with the Atlantic-Pacific marine oxygen isotope and Antarctic ice-core records.The reconstructed three main stages correspond respectively to the 5th, 6th and 7th stages(stages MIS 5, MIS 6 and MIS 7)determined from the marine oxygen isotope.On the basis of above reconstructed result, we arrived at the conclusions: the annual average temperature in the Nihewan Basin during the glacial period was approximately 2~4℃ less than the present, and the annual average precipitation was approximately 200~400mm greater than the present.The annual average temperature during the inter-glacial period was approximately 1℃ higher than the present, or it was close to the current value, and the annual average precipitation was also similar to the current value.The paleoclimate in Nihewan Basin was relatively stable in the glacial period, whereas frequently fluctuated during the inter-glacial period.Houjiayao Man lived in Dali glacial period(MIS 6), and rich animals and plants were their main source of food.Houjiayao Man had learned to adapt to and withstand the cold climate.