TROPICAL GEOGRAPHY ›› 2016, Vol. 36 ›› Issue (3): 313-325.doi: 10.13284/j.cnki.rddl.002840

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Environmental Changes Inferred from Spatial-temporal Distribution of Holocene Buried Peat Layers in Lower Reaches of the Xijiang and Beijiang and the River Confluence of Pearl River Delta

ZHENG Zhuo1,TANG Yongjie1,ZHENG Yanwei2,HUANG Kangyou1, HAN Ziyun1,ZONG Yongqiang3,LI Pingri2,TAN Huizhong2   

  1. (1.School of Earth Science and Geological Engineering,Sun Yat-sen University,Guangzhou 510275,China;2.Guangzhou Institute of Geography,Guangzhou 510070,China;3.Department of Earth Sciences,The University of Hong Kong,Hong Kong SAR,China)
  • Online:2016-05-05 Published:2016-05-05

Abstract: The buried peat and wood layers of Holocene are found widespread mainly in lower Xijiang and Beijiang Rivers, as well as in the confluence areas of northwestern part of Pearl River delta. In this paper, detailed studies of sedimentary facies, combined with radiocarbon dating, have enabled us to reconstruct the Holocene environment and evaluate the distribution of Holocene buried peat and wood layers in the study region. Four conclusions can be drawn as follows: 1) The terrestrial sedimentary sequences located in the northern boundary of Holocene Marine transgression and downstream areas of the Xijiang and Beijiang Rivers show the thick bedded peat which have the earliest age in the mid-late Holocene (7.5-1.5 cal. ka B.P.) and the main deposit period centered at 5.0-1.5 cal. ka B.P.; 2) In the marginal region of Pearl River Delta, terrestrial peat swamps emerged mainly due to the Holocene marine transgression, and the high sedimentation rate during the early Holocene (around 9-7 cal. ka B.P.) provided fertile mud for further development of brackish water swamp. In addition, the alluvial or flood deposits situated in downstream area of the Xijiang and Beijiang Rivers expanded after 8 cal. ka B.P., which also led to the prosperity of the Chinese cypress (Glyptostrobuspensilis) peat swamp; 3) The study area is considered to be a transitional region of ancient estuary and floodplain in the lower reaches of Xijiang and Beijiang Rivers during the mid-Holocene, that caused an emergence of peat swamp in a large scale, especially under its interaction between riverine and tidal currents; 4) The peatland was inundated by alluvial sediments at around 2-1.5 cal. ka B.P. under the process of aggradation in Pearl River Delta, that can be attributed to the destruction of tidal-fluvial balance, as well as the change in hydrological conditions. Moreover, the increasing human activity, deforestation and soil erosion should be also taken into consideration.

Key words: the Pearl River Delta, Xijiang, Beijiang, peat, Holocene, radiocarbon dating, sedimentation environment