揽瓜阁阅读做题小分队 第133天 考古测试方法

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For absolute dating of archeological artifacts, the radiocarbon method emerged during the latter half of the twentieth century as the most reliable and precise method. The results of obsidian (volcanic glass) dating, a method based on the belief that newly exposed obsidian surfaces absorb moisture from the surrounding atmosphere at a constant rate, proved uneven. It was initially thought that the thickness of the hydration layer would provide a means of calculating the time elapsed since the fresh surface was made. But this method failed to account for the chemical variability in the physical and chemical mechanism of obsidian hydration. Moreover, each geographic source presented unique chemical characteristics, necessitating a trace element analysis for each such source. Yet, despite its limitations, obsidian dating helped archeologists identify the sources of many obsidian artifacts and to identify in turn ancient exchange networks for the flow of goods. Nor were ceramic studies and fluoride analysis supplanted entirely by the radiocarbon method, which in use allows for field labeling and laboratory errors, as well as sample contamination. In addition, in the 1970s dendrochronological (tree-ring) studies on the bristlecone pine showed that deviation from radiocarbon values increases as one moves back in time. Eventually calibration curves were developed to account for this phenomenon; but in the archeological literature we still find dual references to radiocarbon and sidereal, or calendar, time.

1. Based on the information in the passage, which of the following is LEAST likely to have been a means of dating archeological artifacts?
(A) Ceramics studies
(B) Radiocarbon dating
(C) Dendrochronological studies
(D) Fluoride analysis
(E) Obsidian hydration-layer analysis

2. In the passage, the author mentions all of the following as problems with radiocarbon dating EXCEPT:
(A) disparities with the calendar dating system.
(B) deterioration of samples.
(C) identification errors by archeological field workers.
(D) contamination of artifacts.
(E) mistakes by laboratory workers.

3. With which of the following statements would the passage’s author most likely agree?
(A) The greater the time that has elapsed since exposure of obsidian surface to moisture the less reliable the results of obsidian dating.
(B) The hydration layer accumulating through obsidian moisture absorption varies in thickness depending on the amount of surface area exposed to moisture.
(C) The unpredictability of the obsidian hydration process renders the obsidian dating method roblematic as a means of determining historical trade routes.
(D) The results of obsidian dating are as reliable and precise as those of fluoride analysis only if trace element analysis is performed for the geographic source of the obsidian.
(E) An obsidian artifact can be reliably dated using the obsidian method only if certain environmental conditions where the artifact was found are considered.

参考答案：

CBE

sudn

古董鉴定年代，radiocarbon法在20世纪后期出现了，被认为是精准可靠。
Obsidian 鉴定法，认为器物表面会从周围吸潮，被认为不可靠。
原本认为水层能提供器物从制作到现在所经历的时间。但是忽略了化学物质的变化。而且每个地理环境自带独特的化学特征，使得研究这些特征本来也是必要的。
然而，除却这些限制，obsidian 法让考古学家也能追溯货物的流通。
ceramic studies 和fluoride 定义法没有被 radiocarbon法完全取代。radiocarbon法有问题：现场鉴定，实验室错误和样品污染。
而且在1970年的 dendrochronological、年轮法显示，东西越古老，radiocarbon值的偏差越大。
甚至 calibration 曲线被用来研究这个现象。考古文献里我们仍然能发现双重radiocarbon 和sidereal， calendar 参考。

2021上北大

the radiocarbon method：the most reliable and precise method
obsidian (volcanic glass) dating：uneven
原理：
缺陷：
1、chemical variability
2、chemical mechanism
3、geographic source

优势：
1、Geographic source
2、identify in turn ancient exchange networks for the flow of goods

几种考古方法的比较：
radiocarbon method劣势：
相对于ceramic studies and fluoride analysis
1、field labeling and laboratory errors, as well as sample contamination
2、deviation from radiocarbon values increases as one moves back in time

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旧-radiocarbon method 被认为reliable/precise
新-举例obsidian dating有缺点: 无chemical variability, 要trace each source
     但是仍有帮助
最后一句没看懂
c
c(x dual references指同时使用) 定位-which in use allows for field labeling and laboratory errors, as well as sample contamination，把sample contamination和deterioration混了
e

Erebuslee

1 E
2 A 在末句出现calendar，找半天没找到AB，CDE都在同一个句子中
3 E

jiajiajiayi

CCC

KathyHHH

看一下！               

yu33

EBA

MollyWong

mark

ccccherry

EAC