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  • 2016 Volume 36 Issue 3
    Published: 05 May 2016
      
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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 Zhuo，TANG Yongjie，ZHENG Yanwei，HUANG Kangyou，HAN Ziyun，ZONG Yongqiang，LI Pingri，TAN Huizhong．
    2016, 36(3): 313-325. https://doi.org/10.13284/j.cnki.rddl.002840
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    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.
  • Relationship between Late Quaternary Lithostratigraphy, Sea-level Change and Tectonics in the Pearl River Delta
    ZONG Yongqiang，HUANG Guangqing，XIONG Haixian，LI Xiaoyun，SUN Yiying．
    2016, 36(3): 326-333. https://doi.org/10.13284/j.cnki.rddl.002842
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    Based on a review of the lithostratigraphic data from the coastal area and the continental shelf of northern South China Sea, this paper has examined the Late Quaternary evolutionary history of the Pearl River Delta. Results show that: 1) the deltaic basin of the Pearl River contains two marine sequences, the upper (younger) one belongs to the present interglacial (the past 10.5 ka B.P.) deposit and the lower (older) one most likely is that of the high sea level period during the last interglacial (126–120 ka B.P.); 2) the burial depth of the older marine sequence within the deltaic basin is recorded at 10-15 m below present sea level, whilst the depth in the mouth region is found below 20 m, implying geological subsidence because the height of sea level during the last interglacial was close to that of the present; 3) within the tectonic framework of southeastward continental extension of the Eurasian Plate during the Cenozoic, the coast and continental shelf of northern South China Sea has experienced a continuous subsidence at a long-term average rate of 0.12 mm/a, which is similar to that measured by GPS at present; 4) on top of the continental subsidence, fault activity has enhanced the localized subsidence of the deltaic basin, which led to the creation of accommodation space for marine inundation during interglacial high sea levels.
  • Late Quaternary Tectonic Movements in the Pearl River Delta, China, Revealed from Stratigraphic Profiles
    YU Zhangxin，ZHANG Ke，LIANG Hao，LI Zhongyun．
    2016, 36(3): 334-342. https://doi.org/10.13284/j.cnki.rddl.002850
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    The Pearl River Delta is located at north margin of the South China Sea. Neotectonic movements play important role on the evolution of the delta featured as fault-blocks differential uplift and subsidence. Some critical topics, e.g. the active variation of different fault groups, the pattern of fault-blocks movements, are still debatable. Recently some Quaternary depositional terraces were discovered on Panyu Platform in the north Pearl River Delta. Those terraces can be identified into several stratigraphic layers: A. migmatite or granite bedrocks which have been deeply weathered into vermicular red soil, B. greyish white and yellow medium/coarse sand, cross-bedding structure, with weathering surfaces, C. dark grey to black silt with a few fine sand lense, wood fragments layer in the bottom, and D. dark grey silt, rhythmically intercalated by greyish white sand layers. Study on sedimentary facies of those layers shows that this sequence belongs to the Pearl River Delta lower marine transgressive cycle, which means the delta deposits was tilted after the 1st transgressive deposition, due to the NNW trending Hualong-Huangge fault zone. Other W-E and N-S trending terrace-borehole stratigraphic profiles in the Pearl River Delta area reveal the active variation of different fault groups. The W-E and NE-SW trending faults control the edge of the Pearl River Delta, while little influence on the pattern of delta deposition process and river channel distribution. The NNW-SSE and NEE-SWW trending faults are still active since the 1st marine transgression, making the delta deposits weekly tilt. The comparison of sedimentary sequence in the Pearl River Delta with continental shelf of the Northern South China Sea illustrates that besides the 2 cycles in the Pearl River Delta, there are much older cycles on the continental shelf due to intensive activities of the Littoral Fault Zone.
  • Major and Trace Elements Geochemistry and Paleoenvironmental Implications of Borehole ZK19 in the Lingdingyang Bay of the Pearl River Estuary
    WAXI Lali，WANG Jianhua，CHEN Huixian，WU Jiaxue，TAO Hui．
    2016, 36(3): 343-354. https://doi.org/10.13284/j.cnki.rddl.002841
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    The research on Late Quaternary sediments of borehole ZK19 in the Lingdingyang Bay of the Pearl River Estuary has shown that the formation of the borehole revealed mainly on the upper Pleistocene Series and Holocene Series. Bounded by the weathering layer formed during the last glacial period, it has demonstrated the two important transgressive events during the Late Pleistocene and Holocene respectively. The distribution of major, trace elements and their ratios (e.g. Al2O3/Na2O ratio, MgO/Al2O3 ratio, Sr/Ba ratio and V/Cr ratio), Chemical Index of Alteration (CIA) and Chemical Index of Weathering (CIW) were used to reconstruct the paleo-climate and environment changes. Paleo-environmental changes were reconstructed: 1) Middle Stage of Late Pleistocene MIS4-early MIS3: sedimentary facies changed from continental facies to coastal beach facies; gradually warming from cooler climate, sea level rose slowly; 2) MIS3 stage of Middle-late Stage of Late Pleistocene, sedimentary environment showed an estuarine facies, climate got warmer, sea level rose significantly; 3) Late Stage of Late Pleistocene MIS2 stage, during the Last Glacial Maximum the sea level dropped significantly, and the climate was cooler; 4) MIS1 (8-12 cal. ka B.P.), the climate was warmer, sea level rose fast, sedimentary environment consisted of fluvial facies-coastal tidal flat-estuarine shoal-estuarine facies; 5) The Middle Holocene sediment is lacked in the borehole, probably due to an underwater erosion of migration of estuarine shoal - channel; 6) Late Holocene (since 3 cal. ka B.P.) sedimentary environment was estuarine facies - delta front slope facies - delta front shoal facies, climate overall was relatively stable, and warmer than that in early Holocene.
  • Holocene Mollusc Records and Palaeoenvironmental Changes in the Pearl River Delta
    LIU Chunyao，YIN Jian，LIU Chunlian，HUANG Yi，WU Yueqin．
    2016, 36(3): 355-363. https://doi.org/10.13284/j.cnki.rddl.002830
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    A study has been carried out on the sediments and molluscs of core PRD11 drilled in the central Pearl River Delta plain. The results suggest that the sea level fluctuations, fluvial processes, and tectonic uplift and subsidence led to the environmental changes of the study area during the Holocene. Five environmental stages can be recognized: 1) Before 9 010 cal. a B.P., the sediments were subaerially exposed and experienced weathering process, which is indicated by the mottled clay in the lower part of core PRD11. 2) From 9 010 to 7 000 cal a. B.P.，an estuary environment began to develop at the site of core PRD11. 3) From 7 000 to 5 460 cal. a B.P., a decrease in water depth occured. 4) From 5 460 to 3 340 cal. a B.P., water depth increased again, with the largest water depth at around 4 546 cal. a B.P.. 5) Since 3 340 cal. a B.P., the environment gradually changed into an alluvial plain setting, with enhanced fluvial influence.
  • Holocene Paleoenvironment Reconstruction Based on Pollen Data in the Sanshui Basin, Northern Pearl River Delta
    HUANG Kangyou，HE Jiahui，ZONG Yongqiang，ZHENG Zhuo，ZHANG Guifang，CAO Linglong．
    2016, 36(3): 364-373. https://doi.org/10.13284/j.cnki.rddl.002849
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    Sanshui basin is located on the convergence of Xijiang and Beijiang Rivers of the northern Pearl River delta, where the sediment recorded the sea level changes during Holocene. Based on 12 AMS 14C dating results, pollen and diatom analyses were used to reconstruct paleoenvironment and seal level change during early Holocene. The results showed that because of the rapid sea-level rise Sanshui basin was inundated and the onset of rapid deltaic accumulation was at ~9 000 cal. a B.P. and 3 000 cal. a B.P. respectively. The environment varied as an evolution process of fluvial - river bay - estuarine - tidal-flat - estuarine- alluvial flat facieses. The sediment rate was at 1.6 cm/a in early Holocene, the sediment was mainly composed of fine silt. The marine transgression occurred at ~8 700 cal. a B.P., and reached the highest sea level stand at ~7 600 cal. a B.P. The mangrove forest was distributed around the seacoast, but the regional vegetations were characterized by subtropical evergreen forest which was dominated by Castanopsis and Quercus-evergreen type. The sediment consisted of silty peat at mid- and late Holocene (6 500-2 200 cal. a B.P.), with the sediment rate of 0.2-0.5 cm/a. The mangrove forest disappeared and the swamp developed, which was composed of Cyperaceae, Poaceae and spores. Since the age of ~2 200 cal. a B.P., the sediment rate has reached the highest value (1.7 cm/a) and the delta plain expended rapidly. Pollen evidence showed that the natural forest was likely disturbed by agricultural development during the late Holocene.
  • Paleoenvironment Reconstruction and Sedimentary Record in the Wanqingsha Area of the Pearl River Estuary
    YU Shaohua，CHEN Fang，XIE Yecai，ZHOU Yang，WU Cong，CHEN Chixin，LONG Gui．
    2016, 36(3): 374-387. https://doi.org/10.13284/j.cnki.rddl.002844
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    In order to reconstruct the eustatic change and paleoenvironment of the estuary of Pearl River since the late Pleistocene, the Core ZK 316-2, which is located in the Wanqingsha district of the Pearl estuary, was chosen to carry on pollen analysis combining with diatom and lithological analyses. Results of diatom and pollen analyses as well as lithological analysis showed that the late Pleistocene experienced a large sea level transgression and regression and two smaller eustatic changes. During the transgression period in the late Pleistocene the pollen assemblages indicated warm and rainy climate, when vegetation was dominated by south sub-tropical Asian evergreen forest, including sub-tropic pollen types Cyclobalanopsis, Altingia, and Hamamelidaceae, etc. The appearing of Sonneratia in this period was deduced from the littoral face, and it represented the altitude of relative sea level. Although the dating year from 14C results in this oceanic layer was more than 30 ka, the regional pollen assemblages and diatom signals as well as the altitude of global sea level demonstrated that the deposition in the transgressive period during the late Pleistocene was more likely from MIS5, and the two shorter low sea level records probably corresponded to 5b and 5d. The upper layer of the core (less than 13.9 m in depth) was deposited since 2 232 cal. a B.P., and the pollen analysis demonstrated that the vegetation was still dominated by the subtropical evergreen forest, when the climate was colder and dryer during this period as compared with that in the transgressive period of the late Pleistocene. The flourishing of Poaceae, Pinus and Dicranopteris as well as fire records (charcoal) which indicated the anthropogenic disturbance during this period indicated that human activities and cultivated agriculture bloomed, almost synchronizing with the regression of sea level and deposition of the Pearl River delta.
  • Dating and Sedimentary Environment Reconstruction of Holocene Beach Profile in the Pearl River Estuary Islands
    WAN Yixing，ZHENG Zhuo，XIAO Yiting，TANG Yongjie，CHEN Cong．
    2016, 36(3): 388-398. https://doi.org/10.13284/j.cnki.rddl.002851
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    Holocene sand flat and sand dune deposits, which may be formed during the high sea level period in Holocene, are widely distributed in the coastal zone and islands of the Pearl River Estuary. These deposits contain rich information on Holocene marine transgression and environmental changes. Furthermore, rich Neolithic remains are found in these sediments in the islands around the Pearl River Estuary. Therefore, the coastal sandy marine deposits of Holocene, with evidences of both natural and cultural histories, have drawn great attention from scientists. In this paper, optical stimulated luminescence (OSL) dating and grain-size analysis were conducted. The results showed that the bottom of the coastal sandy marine deposits of Holocene might be formed more than 9 ka B.P. ago. Most of the OSL dating results showed that the Holocene sand flat and sandy eolian deposits were older than the Neolithic remains, which indicated that the former was formed before the latter. Another finding was that the overlying strata of the coastal sandy marine deposits often shifted rapidly to alluvial face of supratidal zone or dune at about 6.5 ka B.P., resulting in worsened grain-size sorting and great parameter fluctuations. The marine facies reached +4.8 m (modern elevation), which might be related to regional tectonic movement or the descending of sea level in Holocene. Combining grain-size analysis and archaeological excavation remains with other relevant records, the Holocene sedimentary environment was reconstructed; sea level change and differential tectonic movement, and relationship between man and nature in Holocene were revealed.
  • New Insight on the Marine Deposit in the Southern Hainan Island
    WANG Mengyuan，ZHENG Zhuo，HUANG Kangyou，ZHANG Yimeng．
    2016, 36(3): 399-405. https://doi.org/10.13284/j.cnki.rddl.002834
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    Based on AMS 14C and optical stimulated luminescence dating of core TLG01 from Tielu Harbor of Sanya in southern Hainan Island, this study comprehensively analyzes lithology, sediment grain size, color index, marine macrofossil and foraminifer indexes. The upper marine deposit belonging to the Holocene is thin that is interpreted as tidal sand flat. Whereas, the lower marine deposits, as thick as 38 m, are dated to MIS 5e and 5d according to optical stimulated luminescence dating. The late Pleistocene transgression-regression sequences are as follows: tidal sand flat-subtidal-tidal mud flat-tidal sand flat. The species of Mollusca living in deep-water condition are identified in late Pleistocene marine layer. The species identification and their related habitats make possible to restore the sedimentary facie. In MIS 5e, the content of silt and clay sharply increased followed by a decrease trend at MIS 5d. Sediment grain size, foraminifera abundance and sediment color index L* show that the highest sea level appeared at the beginning of MIS 5e, while from MIS 5e to MIS 5d, the sea level was lowered, accompanied by the increase in terrestrial coarse sand, indicating relative low sea level toward MIS 5d. The triangular plots of interglacial periods MIS 1 and MIS 5 are respectively consistent with modern surface sediments from the island intertidal zone of Zhanjiang and the South China Sea.
  • Late Quaternary Sediment Stratigraphy and Marine Cycles in the Pingtan Island, Fujian Province
    CHEN Cong，WAN Qiuchi，ZHENG Zhuo，YU Fengling，A Switzer，WAN Yixing．
    2016, 36(3): 406-416. https://doi.org/10.13284/j.cnki.rddl.002845
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    A 28.3 m long core, PT01, from the Pingtan Island, Southeast China, is selected to be studied. Radiocarbon dating (AMS 14C) and optical stimulated luminescene (OSL) are used for establishing chronology. Combining age-dating results with marine microfossil and color index, we classify the Late Quaternary sediment stratigraphy in the coastal region of Fujian Province. It is suggested that the late Pleistocene marine deposit, dated back to 124 ka, and abundant marine microfossil (e.g. foraminifer and ostracods), would belong to the Marine Isotope Stages 5(MIS 5). Moreover, the late Quaternary sediment could be divided into three units based on the analysis of lithology, microfossil, grain size and color index. Our results reveal that the sediment environment during the MIS 5 was significantly controlled by global sea level change which varied among coast, tidal flat, lagoon, and eolian sand, and probably there existed weathering process. A hiatus during the last glacial (MIS 2-4) was attributed to low relative sea level. And the Holocene deposit, as thick as 3.79 m, developed poorly and was mainly comprised of swamp facies and eolian dune.
  • Vegetation and Environmental Changes Inferred from a Holocene Pollen Spectrum in the Lower Reaches of Min River
    YUE Yuanfu，ZHENG Zhuo，Barry V ROLETT，HUANG Bojin，HUANG Kangyou，Rachid CHEDDADI．
    2016, 36(3): 417-426. https://doi.org/10.13284/j.cnki.rddl.002848
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    In order to reveal the Quaternary environment changes and human impact in Minhou area of the lower reaches of the Min River, Fujian Province, pollen and diatom analysis were carried out from the core FZ5 near Zhuangbianshan Neolithic site. The present result indicated that the Holocene marine transgression in Minhou began at about 9 000 cal. a B.P., and reached its maximum level at 7 500 cal. a B.P. Major marine regression occurred at about 1 900 cal. a B.P. Pollen analyses confirmed a dense evergreen broad-leaved forest during early and middle Holocene, indicating warm and humid climate condition. The optimal climate was relatively stable during the period between 7 500 and 1 900 cal. a B.P. The warm climate and local marine estuary environment were in favor of the development of the Neolithic culture (e.g. Tanshishan Culture) which was characterized with fishing and hunting economic lifestyles. Since 1 900 cal. a B.P., the pollen assemblages were mainly dominated by pioneer plants such as Dicranopteris, Poaceae and Pinus, suggesting a substantial change of the local vegetation. This forest alternation may be resulted from rapid development of human agriculture. High content of Poaceae pollen (including rice pollen type) was only found in the upper part of the profile, that confirmed the onset of large-scale development of rice cultivation at about 1 900 cal. a B.P.
  • Long Scale Climatic Drought Events in the Yangtze River Delta since the Late Pleistocene: Environmental Magnetic Records from the Sediment
    ZHOU Qixian，YANG Xiaoqiang，LI Jian，LIN Qinglong，PENG Jie，WENG Yuanzhong，DING Jieying，LIU Chunlian．
    2016, 36(3): 427-437. https://doi.org/10.13284/j.cnki.rddl.002852
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    Since the late Pleistocene, the Yangtze River Delta region affected by both the sea level and the East Asian monsoon, resulting in complex regional climate, has brought a lot of uncertainty for recovery of its long-term history and evaluation of future climate evolution. This article selected three long boreholes in the south Yangtze River Delta, CSB4, CSB6 and CSB8, to be studied. The analysis of environmental magnetism was for revealing the region's significant climate events recorded from the sediments since the late Pleistocene. The results showed that there were three significant low S300 areas in the three boreholes, when S300 was a low value, the magnetic susceptibility, ARM and SIRM values were low, and the ratio of IRMAF80mT/SIRM and that of ARM/ SIRM relatively were high, indicating that the concentration of magnetic minerals were reduced, particle size became small. Their sediments mainly were yellow silty clay containing ferromanganese tuberculosis. IRM acquisition curves and spectral quantitative analysis results revealed that the relative increase in the content of hematite high coercivity component in the sediments indicated that three significant dry events happened in the Yangtze River Delta. Based on the magnetic strata, AMS14C dating and optically stimulated luminescence dating, the three drought events happened in 163-121 ka B.P. (Event I), 57-42 ka B.P. (Event II) and 14-10 ka B.P. (event III), respectively. The three dry events were corresponding to a relatively low sea level, while the monsoon weakened, rainfall decreased, climate became dry, forming an oxidation-based environment.
  • Effect of Dehydration of Marine Sediments on Their Magnetic Properties
    LI Mingkun，OUYANG Tingping，TIAN Chengjing，ZHU Zhaoyu，TANG Zhihua，PENG Xuechao，QIU Yan，ZHONG Hexian．
    2016, 36(3): 438-447. https://doi.org/10.13284/j.cnki.rddl.002843
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    The technology of environmental magnetism has been increasingly widely applied in marine sediment research. Marine sediment contains a lot of water which is a kind of antimagnetic material. However, it’s not clear that loss of water during sample preparation and preservation is influential to its magnetic properties or not. Magnetic parameters were measured before and after drying for hundreds of marine sediment samples collected from the South China Sea. 685 samples were dried at room temperature, and their magnetic parameters κlf, κhf, SIRM, S-300 and κfd were measured every 40 days, totally 5 measurements. The other sixty samples were freeze dried and the same magnetic parameters were measured before and after drying. The results are shown as follows : 1) For samples dried at room temperature, κ decreased for most samples and increased for a few of samples while both S-300 and κfd decreased except the outliers; SIRM decreased at first 40 days and then increased, and it showed an increasing trend on the whole. 2) Magnetic parameters κ, S-300 and κfd showed an increasing trend and SIRM showed a trend of decrease for samples dried under freeze condition. 3) The variation trends of κ, SIRM and S-300 in profiles didn’t change during drying process. However, dehydration played a significant influence on profile variation of κfd. The variations of magnetic parameters may be due to comprehensive factors such as a weak oxidation during drying process, the reducing of “negative contribution” of water caused by water loss, the transition when fine magnetite and maghemite in wet state changed into paramagnetism and incomplete antiferromagnetism. Therefore, the same drying method must be used for the same batch of samples.
  • Paleoclimatic Interpretations of Speleothem δ18O Record in Monsoonal China: Controversies and Some Key Issues
    ZHOU Houyun，LIU Shuhua，PENG Xiaotao，DENG Xiaomin，CHEN Qiong，MI Xiaojian．
    2016, 36(3): 448-456. https://doi.org/10.13284/j.cnki.rddl.002835
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    The paleoclimatic interpretations of speleothem δ18O in the summer monsoon (SM) area of China are widely disputed in recent years. In this paper, we first simply introduce the major viewpoints about the paleoclimatic implications of speleothem δ18O in the SM area of China. Then we raised three key questions which may be crucial to the interpretations of speleothem δ18O record in the SM area of China, such as the test of calcite precipitation under isotope equilibrium conditions, the similarity and variability of different speleothem δ18O records, and the influence of cave ventilation on speleothem δ18O record. Those questions are closely related to the connecting mechanisms between speleothem δ18O records and climate environment in the SM area of China. Answer to those questions may be helpful to settling of the disputation on paleoclimatic interpretations of speleothem δ18O record in the SM area of China. Therefore, we suggest that more attention should be paid to those questions in future.
  • Process of Calcitization of Aragonite Altering δ18O Records of Aragonite Stalagmites
    ZHANG Huiling，YU Kefu，ZHAO Jianxin，FENG Yuexing，LIN Yushi，ZHOU Wei，LIU Guohui．
    2016, 36(3): 457-467. https://doi.org/10.13284/j.cnki.rddl.002854
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    The aragonite stalagmite has been used to be a new paleoclimate archive recently, but the problem of how the aragonite to calcite transition affects δ18O of aragonite stalagmites is still a puzzling problem. A stalagmite LH5, which was recovered from the Lianhua Cave, Central China, has been identified by XRD analyzing that its aragonite has partially inverted into calcite in the lower part in which the content of calcite ranges during 10%-27.5%. On the basis of 18 TIMS-U series ages and 311 δ18O measures of stalagmite LH5, this paper studied effects of aragonite to calcite transition on the aragonite stalagmite paleoclimate record. At first, uranium loss of aragonite in the process of aragonite-calcite transition results in radiometric ages deviating from real ages to form reversal ages. Although there are phenomena of aragonite to calcite transition in lower part of stalagmite LH5, low openness of uranium decay system (less than 10%) can’t change TIMS ages greatly which still can be used to set up time scale after eliminating abnormal ages. Secondly, through comparison of climate events during the last deglaciation，this paper revealed the aragonite to calcite transition resulting in abnormal δ18O signals which can’t record any climate events e.g. B?lling-Aller?d and Younger Dryas which have been recorded by the other stalagmites from Southern China. However, during the early Holonece, the aragonite segment of stalagmite LH5, δ18O fluctuations recorded climate change faithfully. Drip water is considered to be one of the main causes of the aragonite to calcite transition. As for stalagmite LH5, the splash erosion of cave water in collapse pit may play an important role in the process of aragonite to calcite transition. Because of intensity of penetrating and leaching of water in different part of aragonite stalagmites and heterogeneity of stalagmites, aragonite to calcite transition in aragonite stalagmite is not linear. It is the nonlinear transition of aragonite to calcite that leads to nonlinear change of δ18O, which results in δ18O signals of stalagmite in which aragonite to calcite transition occurred can’t reflect climate changes.
  • Carbon Isotope Compositions and Climate Changes of the Past 20,000 Years Inferred from a Mountainous Peat Bog of Northern Guangxi
    MAN Meiling，ZHENG Zhuo，LI Jie，WANG Mengyuan．
    2016, 36(3): 468-476. https://doi.org/10.13284/j.cnki.rddl.002839
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    This study concerns the organic carbon isotopes, TOC and C/N in a mountainous peat bog in northern Guangxi province. Result reveals the local vegetation variations and the climate changes since the LGM in subtropical China. Positive δ13Corg indicates vegetation types change due to the cold and dry climate during the LGM. However, cold and dry condition didn’t lead to vegetation degradation from forest to grassland even during the last glacial period, as δ13Corg shows the dominance of C3 plants around the mountains, which is also proved by pollen records. It can be inferred from the lithology and TOC that local peat-land began to accumulate during the period of 14-10 cal. ka B.P., which developed at fastest speed between 10 and 9 cal. ka B.P. Carbon isotope change towards negative values occurred slightly earlier than the formation of the swamp, indicating that strengthening of summer monsoon occurred at about 14 cal. ka B.P., which is basically concordant with the record from stalagmites. Obvious variation in carbon isotopes which occurred between 9-8 cal. ka B.P. may be relative to 8.2 ka cooling event or changes of organic matter sources. High input of organic matter and negative carbon isotopes in the period during 7.0-2.8 cal. ka B.P. corresponded to the wet and warm condition. Relatively positive change of δ13Corg at 1.7 cal. ka B.P. might be caused by prehistory human impact. The comparison between the δ13Corg data and those of the coastal lowland records from the Leizhou Peninsula shows that a big difference existed between plain and mountainous areas, probably because humidity didn’t reduce too much due to the effect of orographic precipitation in the mountains even during the LGM, while decrease in precipitation and high evaporation were apparently shown in the plains. It should be pointed out that the factors are quite complicated for the interpretation of δ13Corg values in the peat records. The changes in sediment environment, origin of the organic matter and geomorphologic conditions should be taken into consideration when using δ13Corg to reconstruct paleoclimate.
  • Holocene Climate Records from a Mountain Wetland in Luoxiao Ranges
    HAN Aiyan，ZENG Lifeng，HUANG Kangyou，LIAO Wenbo，ZHENG Zhuo，CHEN Cong．
    2016, 36(3): 477-485. https://doi.org/10.13284/j.cnki.rddl.002855
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    A 150 cm core (JXA) was drilled from a mountain wetland in Jiangxi’ao, Jinggang Mountains in the southeast of mid-subtropical Luoxiao Ranges. Paleoenviromental proxies, such as loss-on-ignition (LOI), humification, organic carbon isotopic and grayscale were used to reconstruct the climatic evolution history in the study area. Based on 6 AMS 14C dating, the age of the sediment at the bottom of the core was ~11 cal. ka B.P.. The sedimentation process could be divided into four stages: 1) During the ages between 11 and 9.2 cal. ka B.P., the content of organic carbon was low and carbon isotopes were characteristic of C3 plants. The climate was relatively cool and dry; 2) in the period of 9.2–5.3 cal. ka B.P., the forest vegetation expanded according to carbon isotope, organic carbon and humification information. The peat land began to develop rapidly, and a warm and humid climate, which corresponded well to the Holocene optimum, was speculated; 3) at 5.3–2.2 cal. ka B.P., the carbon isotope curve showed changes in vegetation components between C3 and C4 plants. The climate was cool and dry; 4) during 2.2–0 cal. ka B.P., the monsoon activity tended to enhance, and the environment was possibly interfered by agricultural activities. The present study provides new paleoclimate evidence in subtropical regions, and indicated the Holocene optimum is between 9.2 and 5.3 cal. ka B.P.. The driving mechanism is mainly controlled by the insolation intensity in the northern hemisphere and summer monsoon variability.
  • Holocene Fire History in Relation to Climate Changes and Human Activities in Southern Subtropical China
    MA Ting，ZHENG Zhuo，MAN Meiling，LI Jie，PENG Huanhuan，HAN Aiyan，HUANG Kuangyou．
    2016, 36(3): 486-494. https://doi.org/10.13284/j.cnki.rddl.002853
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    Three cores at different elevations were collected from different geographical locations in the mountainous regions of the South China. Micro-charcoal and pollen analyses were conducted to examine regional Holocene fire history and discuss its possible relationship with both Asian monsoon variability and anthropogenic activities. Results showed extremely low micro-charcoal concentrations at the three cores at the period between 8.0 and 3.5 ka B.P., revealing low fire frequency. Meanwhile, high proportions of arboreal pollen demonstrated expansion of subtropical evergreen broadleaf forest. This phase is consistent with the Holocene moisture optimum and abundant precipitation. Furthermore, low population in the early-mid Holocene and no evidence of slash-and-burn cultivation during the Neolithic confirm the charcoal result. After 3.5 ka B.P., the abrupt increase in charcoal concentrations of the cores from lower elevation sites was closely related with a general drying trend towards the late Holocene, which might result from EASM weakening and decreased rainfall. This timing coincided with the Shang-Zhou Bronze period, reflecting also the impact of human activity. The notable decrease of arboreal pollen demonstrates severe damage of forest by fires. After 2.0 ka B.P., the high concentrations of micro-charcoal recorded in the cores of GY1 and LTY, as well as the rapid growth of Poaceae, Dicranopteris and Pinus, demonstrate agriculture development in low-altitude plains and hills, and this period is synchronous with the first population booming and spread of cow plough and iron farm implements. Micro-charcoal and pollen records of core GT-2 at higher elevation (>1 600 m) show a high fire frequency after 0.8 ka B.P., and this period saw severe disturbance of broadleaved forest by the expansion of anthropogenic activities and agriculture development to mountainous regions.
  • Rainfall Erosivity in the Lianjiang Watershed in Karst Areas of Northern Guangdong, China
    WANG Mingchong，ZHANG Xinchang，WANG Xizhi，WEI Xinghu，LI Huixia．
    2016, 36(3): 495-502. https://doi.org/10.13284/j.cnki.rddl.002832
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    One of the main ecological environment problems is soil erosion for the Lianjiang Watershed. Rainfall erosivity reflects potential ability of soil erosion caused by rainfall. Therefore it is of great significance for valuing consequences of regional soil loss caused by regional rainfall erosivity precisely and formulating measures to maintain soil and water. We arranged the data of daily precipitation from 1980 to 2013 at 35 meteorological stations along the Lianjiang river basin. Based on the data above, we got RA, RB and RC, which were calculated from daily precipitation, monthly precipitation and annually precipitation. We got the optimum R through the test of effective coefficient M accordingly. Next, we used the Inverse Distance Weighted (IDW), Spline with Tension and Ordinary Kniging for spatial interpolation and test to ensure the most accurate interpolation method, and then made interpolation analysis. The result showed that: the IDW and monthly precipitation was more suitable for the calculation and valuation of rainfall erosivity in the Lianjiang Watershed. The spatial-temporal variation of rainfall erosivity in the Lianjiang Watershed was evident. The spatial distribution of rainfall erosivity was similar to that of precipitation year-by-year. In the middle-upper reaches of the Lianjiang River, the average annual rainfall erosivity was found significantly higher in high and large mountain areas than in other places. There was more plentiful precipitation in the lower reaches of the Lianjiang River, and also the average annual rainfall erosivity in the areas was relatively high.
  • Progress in Western Rurality Research in China
    FAN Xuegang，ZHU Hong．
    2016, 36(3): 503-512. https://doi.org/10.13284/j.cnki.rddl.002847
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    Rurality is the core concept of Western multi-disciplinary rural studies, especially rural geography. The combination and conflict among rural sociology, agrarian political economy, rural geography saw the diversity and abundance of rurality topics. The evolution of academic trends in social science and the transformation of rural society respectively in the terms of theory and practice pushed the development of rurality studies. In popular discourse, rurality simply represents different features, which distinguish the rural from the urban, like lifestyle, economy structure, land use and so on. The ways of ‘knowing’ rurality are under the constantly fluid condition: from the ontology of rurality and the macro social economic structures at the early stage to the existence of rural ‘others’ finally to the hybrid complexity of modernized rurality. With the deepening of rurality studies, a series of hot topics came into being one after another: rurality index, discourse of rurality, social difference, daily performance. Though approaches to rurality are various, the power relations and social differentiation rather than the social spatial features became main research directions with the influence of cultural turn and rocketing-up of post-modernism in rural studies. In another word, against the background of the multi rural interests, the representation and reproduction of rurality rather than ‘objective’ rural index have a great importance to understand the representative and material production and reproduction of rurality and politics of rural change under the context of modern capitalism. This review, based on social and academic background of rurality studies, focuses on the social construction of rurality and its burgeoning trends in Chinese rurality studies. The social constructionist treats rurality as the process and product of social, cultural construction not the existed reality, stresses on power relations and otherness. The transition from the former approaches to the social constructionist could be viewed as the transformation from materiality of rurality to its representation, from the rurality itself and macro structural dynamics to the ‘knowing’ means of rurality. The present China rurality study focuses on rurality index and its quantitative models, the concerned researches contain important practical meanings for governmental departments to understand rural problems and make the reasonable solutions for rural planning and rural regeneration. In western rural studies, due to its indication of linear development view and lack of interpretive potential for rural change, rurality index is criticized greatly. In nowadays rural China, the modernization discourse of rural development dominates, while the unequal power relations and ‘othering’ of disadvantaged peasants are overlooked at some degree. Under such social, academic context, social construction of rurality could provide alternative and critical lens to deconstruct dominant discourses of rurality and discover power relations and interest conflict among different social groups.
  • Distribution and Cause of Celebrities in Jiangxi Province since the Qin and Han Dynasties
    LI Bo，LIU Ying，FENG Xinghua．
    2016, 36(3): 513-520. https://doi.org/10.13284/j.cnki.rddl.002831
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    Based on related researches in the past, this paper mainly studies the number of Jiangxi’s celebrities，the characteristics of their geographical distribution and its causes by the research methods of GIS graphics technology, mathematical statistics and historical documents. The results show that: since Qing and Han dynasties, the geographical distribution of Jiangxi’s celebrities has been imbalanced. The majority of celebrities’ lived in the middle and northeast of Jiangxi Province while only a few in the North and South. Therefore, it can be seen that the quantity of celebrities varied greatly in different periods．As time went by, the type of celebrities gradually became rich. The focus of the distribution of celebrities transferred from the North to the Middle, then to the South. The imbalanced regional distribution and development of Jiangxi’s celebrities resulted from the combined effects of a series of factors such as natural environment, economic conditions, traffic conditions, education level, population migration and so on．