基于释光测年的福建晋江海岸沙丘粒度记录的风沙活动

采用OSL测年技术对福建晋江海岸沙丘剖面(SHA) 进行加密采样测年和粒度分析,初步确定了研究区近1000a 以来海岸沙丘发育的主要时段,以OSL测年值为基础,在统一时间标尺上综合对比东亚季风变化序列和福建沿海地区台风登陆记录,探讨了控制研究区海岸沙丘发育的主要因素.研究表明：(1) SHA沙丘表现为典型的海岸风成砂特征,海岸沙丘沉积后受风力侵蚀和后期化学风化作用的影响,粒径变粗,分选性变差,各粒级组分和粒度参数特征发生较大变化;(2) 近1000a 以来晋江海岸带海岸沙丘发育可划分为3 个时期,分别为AD1050~1300、AD1470~1600、AD1720~1950,尤其是小冰期(LIA),海岸风沙活动强烈,海岸沙丘发育盛行;(3) 近千年来区域降水量、海平面和台风强度变化与研究区海岸沙丘发育之间的关系尚不明确,而冬季风强度对海岸沙丘发育的影响明显,即海岸风沙活动期主要对应冬季风较强时期,但近50 年来海岸风沙活动较弱除了主要受冬季风减弱影响外,主要与人类经济活动所造成的地表覆被条件发生变化有关.

Coastal environment evolution record from Anshan coastal aeolian sand of Jinjiang,Fujian Province,based on the OSL dating

Grain size characteristics of the coastal aeolian sand and their chronology potential could greatly improve the interpretation of past environmental changes and provide valuable information on the past aeolian activities. However, lacking of direct dating methods, domestic scholars mainly focus on the distribution, grain size characteristics and geomophogensis to the coastal aeolian sand research. In this paper, quartz single aliquot regenerative optically-stimulated luminescence (OSL) dating with high resolution sampling was firstly applied to coastal aeolian sand in China for the Anshan (SHA) section (24°36′32.7″ N, 118° 39′ 20.3″ E) near the Anshan archaeological site along the Jinjiang coast, southeast Fujian. Through grain-size analysis, we assume that the SHA section demonstrates typical coastal aeolian sand characteristics, and affected by the blowout and chemical weathering after coastal sand deposited, the grain size parameter and content of different sizes of fraction have a large change, the grain size become coarser, the sorting for worse. The OSL ages of the 11 samples range from 839±132a to 108±21a show that SHA section formed in nearly 1000 years, and three periods of coastal aeolian sand activity can be divided, AD1050-1300, AD1470-1600 and AD1720-1950 respectively. Especially during the little ice age (LIA), coastal aeolian sand activity is strong, the development of coastal dunes sand is prevailing, and the OSL age shows that the coastal aeolian sand deposition represents a multiphase and episodic feature. We discuss the main controls of coastal aeolian sand development in the research area based on the OSL chronology. Compared with East Asian monsoon change sequence and the history of typhoon landfalls in Fujian, the result shows that the main control is the intensity of East Asian winter monsoon, but not the precipitation, typhoon landfalls and sea level change. The phase of aeolian activity mainly corresponds to the stronger East Asian winter monsoon period, but over the last half-century, the weakened aeolian activity may be due to human activities on a large amount of mining sand beside a weakened winter monsoon.