江西中部玉华山沼泽泥炭记录的过去两千年气候变化初步研究

A PRELIMINARY STUDY OF THE CLIMATE CHANGE SINCE 2ka ARCHIVED BY A PEAT CORE FROM YUHUA MOUNTAIN IN THE MIDDLE JIANGXI PROVINCE

过去2ka是研究气候变化的重要时间段，其中中世纪暖期、小冰期和现代暖期备受关注，但气候阶段的起止时间、温湿配置等还存在争议。本文选取赣中玉华山沼泽泥炭钻孔进行孢粉、粒度、腐殖化度、烧失量、Rb/Sr、Zr/Rb等多指标分析研究过去2ka来气候变化。结果揭示过去2ka研究区域的气候变化可以分为5个阶段：1）0～600A.D.期间该地区主要表现为较为冷湿的气候；2）600～850A.D.进入隋唐暖期，气候转暖干；3）850～1400A.D.对应中世纪暖期，中间存在次级波动，整体上表现为湿润气候；4）1400～1900A.D.进入小冰期，处于冷干环境，但是中间存在一些次级波动；5）1900～2000A.D.进入现代暖期，气候较为湿润。对比分析表明，该研究区域的气候变化响应了东部季风区过去2ka的气候变化趋势。

The past 2ka was an important period for studying climate change. The study of the Medieval Warm Period, the Little Ice Age and the Modern Warm Period have attracted much attention. However, many studies disagree on the climate conditions that prevailed during the key phases. Yuhua Mountain（27°50＇27″～27°50＇33.51″N, 115°38＇51.22″～115°38＇57.84″E） is a part of the warm and humid subtropical monsoon climate region. The annual average temperature is 18℃, with the maximum temperature（39.5℃）in summer and the lowest temperature（-9.2℃）in winter. The annual precipitation is 1500～2000mm, with 3～6 months of rainy season. Two peat cores, 210-cm-long peat core YHS1（27°50＇30.27″N, 115°38＇54.23″E） and 350-cm-long peat core YHS2（27°50＇29.44″N, 115°38＇54.98″E）, were drilled from Yuhua Mountain at the middle of Jiangxi Province in 2014. We used multi-proxies including grain-size, humification, loss on ignition（LOI）, Rb/Sr, Zr/Rb, Concentricystes and the pollen percentage of the trees and upland herbs.18 samples were selected for AMS 14C dating. The age-depth model in this paper was established by Bayesian Analysis. The deposition rate of the core above 312cm was very fast, but took a big drop when it went deeper. Here we only studied the climate changes in the past 2000 years. Combining with Concentricystes changes, we analyzed the grain-size composition. The results showed that the grain sizes were coarse during 0～600A.D. and 1400～1900A.D., while those of 600～1400A.D. and 1900～2000A. D.were fine comparatively, indicating a change from an active lacustrine environment to stagnant marsh condition. Combining with the multi-proxies of pollen, grain-size, humification, LOI, Rb/Sr and Zr/Rb, we found there were five climate phases during the past 2000 years：（1）during 0～600A.D., cold and wet climate was characterized by high values of humification, LOI, Zr/Rb, pollen percentage of trees, coarse grain sizes and low values of Rb/Sr, pollen percentage of upland herbs; （2）during 600～850A.D., which is the Sui and Tang dynasties with warm climate. Low humification, LOI, Zr/Rb, fine sediment sizes and a little lower percentage of trees than period 1 indicated a warm and dry climate in this period; （3）during 850～1400A.D.（MWP）, the climate fluctuated, but as a whole it was warmer than the phase 2; （4）during 1400～1900A.D.（LIA）, the whole climate tendency was dry and cold by high values of humification, LOI, Zr/Rb, grain sizes, percentage of upland herbs pollen and low values of Rb/Sr, percentage of trees pollen. （5）during 1900～2000A.D., low humification, LOI, Zr/Rb, high Rb/Sr, fine grain sizes, high percentage of trees pollen and low percentage of upland herbs pollen indicated a warm and wet climate（the Modern Warm Period）. The comparative analysis shows that the climate change of the study area respond to the eastern monsoon region climate trends in the past 2ka.