Late Holocene Origanism Records from Peat N-Alkanes of Xianshan Mountains in Fujian Province, Southeast China
详细信息   
摘要


     Sediment core from peatland is a well-established source of paleoenvironmental information. We discussed the regional climate change based on the analysis of n-alkanes from a 358cm-long peat core in Xianshan Mountain of Pingnan County （26°52.4＇N, 118°42.7＇E）, which is located in the central part of Fujian Province, Eastern Subtropical China. The elevation of the study site is 1303m a. s. 1., the mean annual temperature is about 13℃, maximum and minimum extreme temperature respectively 31.5℃ and -12.5℃. The climate exhibits a clear seasonal signal and the mean annual precipitation is ca. 2000mm. Using GC-MS techniques, a series of n-alkanes were identified in peat sediments with a total concentration ranging from 4.2μg/g to 43.2μg/g. The C,6 to C35 n-alkane homologues were detected in all samples and the n-alkane was found dominated by odd carbon chains,with a strong odd-over-even predominance. In typical peat layers,when the value of total organic carbon（TOC） is high, the long chain n-alkanes （C27, C29 or C31 ）were mostly abundant, indicating that the organic matter was mainly originated from trees and grasses and the local environment was dry. Whereas in other non-peat layers, when total organic carbon displays low value, n-alkanes C21 or C23 were abundant in the samples, together with the high contents of sand and gravel in the core, to some degree, indicate that the organic materials in those non-peat layers may have originated from some aquatic plants or sphagnums, and also suggests a wet or under water depositional environment. The ratio of C23/C27 in this core shows strong correlations with C23/C29 and Paq. proposed in previous research,and thus can be used in paleohydrological reconstruction from peat sediments. This peat records show strong agreements with dry-wet anomalies of Southern China, stalagmite δ18O record from Yuhua cave and Tian＇e cave,and also record of the saltwater species percentage in the Southern Okinawa Trough. Based on AMS14C dates, high-resolution peat records were used to reconstruct the past vegetation and climate changes over the past 1400 years. From 600A. D. to 910A. D. ,the organic matter was originated from grasses and aquatic plants or sphagnums, and the climate was dry. From 910A. D. to 1640A. D., the organic matter was primarily originated from aquatic plants or sphagnums, implying a wet climate condition. But this wet period was interrupted by two dry periods, 1270 - 1325A. D. and 1390 - 1450A. D. From 1640A. D. to present,the origin of organic matter was dominated by trees and grasses from water plants or sphagnums, and the climate was dry again. Studies on the characteristics and regularities of climate change in the past millennium have mostly emphasized on three important periods： the Medieval Warm Period （ MWP）, the Little Ice Age （LIA） and the Current Warm Period （CWP）. The n-alkane records in this study show the climate condition during MWP in study site was dry while during LIA was wet, indicating the climate in study area was primarily controlled by monsoons both on multi-decade and century timescales. This study can advanced the knowledge about transformation of historical monsoon changes in China.

© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号

地址：北京市海淀区学院路29号 邮编：100083

电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700