江苏三处旧石器遗址中发现的火山玻璃

火山灰年代学是判断第四纪沉积物年龄的有效手段。文章报告在江苏三处旧石器遗址（和尚墩、放牛山和将军崖）上部堆积中发现的火山玻璃及初步研究结果。和尚墩遗址的火山玻璃主要出现在两个层位: 上层距地表约45cm,火山玻璃的水合层很薄,年代有可能晚于K Ah火山（7.3ka）;  下层距地表约70cm,火山玻璃的水合过程已经完成,时代稍老,大致与日本晚更新世火山同期,至少相当于AT火山,年代等于/大于25ka。遗址中的火山玻璃分为pm型和bw型。形态、屈折率及微量包含物的研究表明,火山玻璃的来源可能与日本的火山喷发无关。江苏旧石器遗址中发现的火山玻璃对判断中国东部地区更新世沉积物时代以及埋藏其中的旧石器遗存年代具标志意义。

VOLCANIC GLASS DISCOVERVED FROM THREE PALEOLITHIC SITES,JIANGSU PROVINCE

Heshangdun,Fangniushan and Jiangjunya are three most typical Paleolithic sites in Jiangsu Province,South East China. These three sites were excavated six times during the past ten years,and several hundreds of stone artifacts were unearthed. This article reports the study on the volcanic glass discovered from the sites. There are 55 pieces of volcanic glass to has been discovered from 106 samples through treating by SPT(Sodium Polytungsteate)gravity separation solution(SG=2.42).They can be divided into the pm type and the bw type in terms of their shapes,refractive indexes,and micro inclusions. Some glass pieces were dated by AMS and TL. There are 40 pieces of volcanic glass from Heshangdun site. They mainly occur in two horizons. The upper horizon is near 45cm beneath the surface; the hydration shell of glass is very thin,only 2μm,suggesting an age later than eruption of Japanese K-Ah volcano(7.3ka). The lower horizon is near 70cm beneath the surface; the hydration process of glass had already completed,suggesting an age equal to the upper Pleistocene volcanic eruption in Japan or at least close to AT volcano eruption,around 25ka or older. AMS dating and TL dating of volcanic glass from Jiangjunya gave an age older than 10ka,probably 40～50ka. Our study indicates no relationship between the volcanic glass discovered in Heshangdun Paleolithic site and the volcanic glass discovered in Japanese volcanic ash and does not support a previous conclusion that volcanic glass came directly from the Shandong Peninsula and the Shengsi Islands and originally from Japan. If ignoring factors of second deposition,the volcanic glass found in Jiangsu Paleolithic sites highly likely came mostly from the Late Pleistocene volcanic eruption. Judged by hydration,however,the volcanic glass in the upper horizon may be of Holocene age. Importantly,the lower horizon with volcanic glass not only represents the Late Paleolithic culture,but also can be seen as a symbol of Late Pleistocene sediments in the east of China.