中国海南省中和镇古城墙砖的热释光测年研究

Thermoluminescence dating research of ancient wall bricks from Zhonghe Town,Hainan,China

采用热释光前剂量饱和指数法对海南省中和镇的8件古城门墙砖样品进行了年代测定研究。由于该地区离海近,粘土中的含沙量非常高,古人在烧制砖时,采用这种粘土作为制砖的原料。烧造时的温度相对高于其它地方烧制的砖。其中4件砖样内部呈灰色,3件砖样内部呈红色,其中1件砖样断面为外围灰色,内部红色。在应用高温细颗粒方法测定这批砖样的年代时,发现样品的高温热释光灵敏度非常差,且不规则,没有"坪曲线",因而无法得出这些古代城门墙砖的具体年代。后采用热释光前剂量饱和指数方法对古砖样品进行了古剂量测定,发现这些样品具有较好的热释光前剂量效应,且样品的热释光灵敏度较高,得到的古剂量具有很好的重复性。热释光测年结果表明,No.2、No.3、No.6、No.8样品的热释光年代分别为:距今590年、575年、530年和580年,为明代早期烧制;No.1、No.4、No.7样品的热释光年代分别为:距今410年、345年和375年,为明代中晚期烧制;No.5样品的年代为距今140年,为清代晚期。经考古人员现场考证,认为No.5样品所处位置存在火烧痕迹。这个火烧时间应该在中国清代晚期,即热释光测定年代。

This paper describes the use of the pre - dose ancient city wall brick samples from Zhonghe Town, Hainan quite high due to its proximity to the sea. When using this thermoluminescence （TL） dating technique on eight province. The sand content of the clay near this area is clay to produce wall bricks during ancient times, the firing temperature is much higher than used for making wall bricks in other areas. Of the eight specimens of wall brick, 4 are gray, 3 are red and 1 is gray outside and red inside. When measuring the paleodose of brick samples by the method of High Temperature All Grains, it is found that the luminescence sensitivity of samples is very poor and irregular, so it is very hard to find the plateau area in the plateau curve and impossible to determine the correct ages of these ancient wall brick samples by this method. Afterwards, regression method of saturation exponential in predose technique is adopted to date these ancient brick samples. It is found that these samples have a good pre - dose thermoluminescence effect and that the paleodose reproducibility of the samples is also good. Gray brick samples no. 2, 3, 6 and 8 are dated as A. D. 1424, A. D. 1439, A. D. 1484 and A.D. 1434, in the early Ming Dynasty （ 14th- 15th century） ; red brick samples no. 1,4 and 7 as A. D. 1604, A. D. 1669, A. D. 1639 in the late Ming Dynasty （16th- 17＇h century） and no. 5 is dated as A. D. 1874 in the late Qing dynasty （19th century）, respectively. The size and composition of sample no. 5 is very similar to those of samples no. l, 4 and 7. It is inferred that it has been produced at about the same time as no. 1, 4 and 7, but that the TL dating age of sample 5 is much younger. According to a fieldwork investigation by archaeologists, there was an accidental fire in the late Qing Dynasty where sample no. 5 was unearthed, which is in agreement with the TL dating age of sample no. 5 sample.