四千年前北越Đầu Rằm遺址貝類殼體 穩定碳氧同位素所反映之環境意義
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2012
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Abstract
本研究分析並比較下龍灣現生及Đầu Rằm考古遺址之貝類殼體同位素組成，以了解四千年前北越之古環境變遷。
現生殼體之氧同位素數據皆可反映年際之循環變化，其極大值可對應至冬季低溫，極小值可對應至夏季高溫。將此生長模式應用於遺址殼體以判斷其死亡季節，推測居住於Đầu Rằm遺址之人類可能主要於春夏之交採集血蚶，於夏季與冬季採集珠螺、瘤珠螺、草蓆鐘螺。
比較遺址與現生殼體數值顯示遺址螺類殼體氧同位素極小值之平均較現生螺類殼體大0.36‰，極大值之平均則二者無顯著差異；遺址血蚶殼體氧同位素極大值之平均較現生血蚶殼體大1.31‰，極小值之平均則二者無顯著差異。結果顯示四千年前之夏季海溫約較現今低1.5°C，且冬季之淡水影響與現今截然不同。
To understand the paleoenvironment of northern Vietnam in c. 4000 B.P, we analysed the isotope compositions of modern mollusk shells collected from Ha Long Bay and compared their oxygen isotope records to those of mollusk shells collected from Đầu Rằm archaeological site. The oxygen isotope data of individual modern mollusk shells reveals annual cycles with the maximum values corresponding to low temperatures in winter, and with the minimum values corresponding to high temperatures in summer. Thus, seasonal pattern can be recognized in modern mollusk shells and can be applied to mollusk shells collected from archaeological site. The Đầu Rằm ancient inhabitants might mainly collect Tegillarca granosa shellfishs between late spring to early summer and might collect Lunella coronata, Lunella granulate and Monodonta labio shellfishs in summer and winter. The average minimum d18O values of archaeological gastropod shells is 0.36‰ greater than that of the modern gastropod shells, while the average maximum d18O values do not show the difference significantly. The average maximum d18O values of archaeological Tegillarca granosa shells is 1.31‰ greater than that of the modern Tegillarca granosa shells, while the average minimum d18O values do not show the difference significantly. The results of this study indicate that the summer sea surface temperature (SST) in c. 4000 B.P. is approximately 1.5°C lower than modern SST. Moreover, the effects of freshwater in the winter in c. 4000 B.P. are much different from the effects of freshwater today.
To understand the paleoenvironment of northern Vietnam in c. 4000 B.P, we analysed the isotope compositions of modern mollusk shells collected from Ha Long Bay and compared their oxygen isotope records to those of mollusk shells collected from Đầu Rằm archaeological site. The oxygen isotope data of individual modern mollusk shells reveals annual cycles with the maximum values corresponding to low temperatures in winter, and with the minimum values corresponding to high temperatures in summer. Thus, seasonal pattern can be recognized in modern mollusk shells and can be applied to mollusk shells collected from archaeological site. The Đầu Rằm ancient inhabitants might mainly collect Tegillarca granosa shellfishs between late spring to early summer and might collect Lunella coronata, Lunella granulate and Monodonta labio shellfishs in summer and winter. The average minimum d18O values of archaeological gastropod shells is 0.36‰ greater than that of the modern gastropod shells, while the average maximum d18O values do not show the difference significantly. The average maximum d18O values of archaeological Tegillarca granosa shells is 1.31‰ greater than that of the modern Tegillarca granosa shells, while the average minimum d18O values do not show the difference significantly. The results of this study indicate that the summer sea surface temperature (SST) in c. 4000 B.P. is approximately 1.5°C lower than modern SST. Moreover, the effects of freshwater in the winter in c. 4000 B.P. are much different from the effects of freshwater today.
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穩定同位素, 越南, Đầu Rằm遺址, 貝類殼體, 古氣候, stable isotope, Vietnam, Đầu Rằm archaeological site, mollusk shell, paleoclimate