近50 ka以来雷州半岛北部泥炭序列~(87)Sr/~(86)Sr比值变化的环境意义研究
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摘要
通过测定雷州半岛北部湛江市屋山村和遂溪县下录村的2个泥炭序列锶同位素比值(~(87)Sr/~(86)Sr),探讨了晚更新世晚期以来我国北热带地区泥炭序列锶同位素的古环境指示意义.分析结果表明:(1)在过去近50 ka以来,泥炭序列中~(87)Sr/~(86)Sr比值变化于0.713～0.722之间,平均值为0.716.(2)通过与已发表的气候代用指标对比,发现在轨道尺度上~(87)Sr/~(86)Sr比值在暖湿期(如MIS 3阶段)呈现相对低值,而在相对凉(冷)期(如MIS 2阶段)则表现为高值;这种现象甚至在千年尺度上也有很好的体现.形成这种现象的主要原因可能是由于泥炭序列中~(87)Sr/~(86)Sr比值的变化与流域风化淋溶后残留的硅酸岩碎屑物质输入有关,且受到了因气候条件变化所导致的地表径流和植被繁茂程度变化影响.因此,本研究结果表明:雷州半岛北部地区泥炭序列~(87)Sr/~(86)Sr比值记录可以作为流域化学风化强度变化的有效指标.
The data of strontium isotope ratios(~(87)Sr/~(86)Sr) of two peat successions,which were obtained at Xialu Village in Suixi County and Wushan Village in Zhanjiang City on northern Leizhou Peninsula,are used to explore the paleoenvironmental significance of~(87)Sr/~(86)Sr of peat sequences in North Tropic China. The results show that values of~(87)Sr/~(86)Sr ratio in the peat sequences vary between 0. 713 and 0. 722 with a mean of 0. 716 in the past～ 50 000 years. Based on climatic variations reflected by multi-proxy records,on the orbit scale the~(87)Sr/~(86)Sr ratio exhibits relatively low values under wet and warm conditions( e.g.,in Marine isotopic stage 3,MIS 3),whereas in dry and cool periods such as MIS 2,~(87)Sr/~(86)Sr ratio shows relatively high values. This phenomenon is also reflected on millennial-scales climatic variations. The mechanism resulting in variations of~(87)Sr/~(86)Sr ratio in the peat successions may be related to the input of the residual silicate clastics,which have been weathered and leached in the catchment. On the other hand,changes in surface runoff as well as vegetation conditions may play a role in influencing input of strontium element. In this study,the~(87)Sr/~(86)Sr record in peat successions in North Tropic China is proved to be an effective proxy to indicate changes of chemical weathering intensity in the catchment,which are closely related to the evolution of Asian summer monsoon.
The data of strontium isotope ratios(~(87)Sr/~(86)Sr) of two peat successions,which were obtained at Xialu Village in Suixi County and Wushan Village in Zhanjiang City on northern Leizhou Peninsula,are used to explore the paleoenvironmental significance of~(87)Sr/~(86)Sr of peat sequences in North Tropic China. The results show that values of~(87)Sr/~(86)Sr ratio in the peat sequences vary between 0. 713 and 0. 722 with a mean of 0. 716 in the past～ 50 000 years. Based on climatic variations reflected by multi-proxy records,on the orbit scale the~(87)Sr/~(86)Sr ratio exhibits relatively low values under wet and warm conditions( e.g.,in Marine isotopic stage 3,MIS 3),whereas in dry and cool periods such as MIS 2,~(87)Sr/~(86)Sr ratio shows relatively high values. This phenomenon is also reflected on millennial-scales climatic variations. The mechanism resulting in variations of~(87)Sr/~(86)Sr ratio in the peat successions may be related to the input of the residual silicate clastics,which have been weathered and leached in the catchment. On the other hand,changes in surface runoff as well as vegetation conditions may play a role in influencing input of strontium element. In this study,the~(87)Sr/~(86)Sr record in peat successions in North Tropic China is proved to be an effective proxy to indicate changes of chemical weathering intensity in the catchment,which are closely related to the evolution of Asian summer monsoon.
引文
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[20]ZHONG W,CAO J Y,XUE J B,et al.Carbon isotope evidence of last glacial climate variations in the tropical NWLeizhou Peninsula,South China[J].Boreas,2012,41(1):102-112.
[21]XUE J B,ZHONG W,CAO J Y.Changes in C3and C4plant abundances reflect climate changes from 41,000 to10,000 yr ago in northern Leizhou Peninsula,South China[J].Palaeogeography,Palaeoclimatology,Palaeoecology,2014,396:173-182.
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[23]曹家元,钟巍,薛积彬,等.中国热带雷州半岛北部地区末次冰期气候变化的特征与机制[J].地质学报,2013,87(8):1179-1192.CAO J Y,ZHONG W,XUE J B,et al.Variation and mechanism of paleoclimate in the Last Glaciation in the tropic northern Leizhou Peninsular in South China[J].Acta Geologica Sinica,2013,87(8):1179-1192.
[24]肖仕鼎,黄其叙,陈红宏.湛江市水文特征[J].广东水利水电,2008(2):52-54.
[25]陈俊仁,姚伯初,吴能友.湛江田洋玛珥湖的形成与演化[J].广东地质,2002,17(1):12-18.CHEN J R,YAO B C,WU N Y.Formation and evolution of Maar Lake in Tianyang,Zhanjiang[J].Guangdong Geology,2002,17(1):12-18.
[26]蔡颖.雷州半岛西北部下录地区晚更新世晚期以来沉积环境演变的初步研究[D].广州:华南师范大学,2009.CAI Y.Preliminary research about evolution of sedimentary environment from Late Pleistocene of Xialu in the northwestern Leizhou Peninsular[D].Guangzhou:South China Normal University,2009.
[27]REIMER P J,BAILLIE M G L,BARD E,et al.Int Cal09and Marine09 radiocarbon age calibration curves,0-50,000 years cal BP[J].Radiocarbon,2009,51:1111-1150.
[28]GOLDSTEIN S L.Decoupled evolution of Nd and Sr isotopes in the continental crust and the mantle[J].Nature,1988,336:733-738.
[29]CHEN J,AN Z S,HEAD J.Variation of Rb/Sr ratios in the Loess-Paleosol sequences of central China during the last 130,000 years and their implications for monsoon paleoclimatology[J].Quaternary Research,1999,51(3):215-219.
[30]陈骏,安芷生,汪永进,等.最近800 ka洛川黄土剖面中Rb/Sr分布和古季风变迁[J].中国科学:D辑,1998,28(6):498-504.
[31]DEURER R,FORSTNER U,SCHMOLL G.Selective chemical extraction of carbonate-associated metals from recent lacustrine sediments[J].Geochimica et Cosmochimica Acta,1978,42(4):425-427.
[32]INGRAM B L,SLOAN D.Strontium isotopic composition of estuarine sediments as paleosalinity-paleoclimate indicator[J].Science,1992,255:68-72.
[33]陈骏,安芷生,刘连文,等.最近2.5 Ma以来黄土高原风尘化学组成的变化与亚洲内陆的化学风化[J].中国科学:D辑,2001,31(2):136-145.
[34]常凤琴.中国西部晚更新世中晚期古湖泊沉积锶同位素与环境变化[D].兰州:兰州大学,2008.CHANG F Q.The relationship between strontium isotope and environment variation in paleo-lake sediments during late period of Late Pleistocene in western China[D].Lanzhou:Lanzhou University,2008.
[35]李子岩,黄克兴.雷州半岛北部泥炭形成的时期、古气候和古地理[J].煤田地质与勘探,1989(1):12-16.
[36]万恩璞,王曼华,马学慧.广东下录埋藏泥炭的特征、成因及古地理环境探讨[J].地理科学,1987,7(4):338-347.WAN E P,WANG M H,MA X H.An approach to the characteristics,genesis and palaeogeographicl environment of Xialu buried peat in Guangdong Province[J].Scientia Geographica Sinica,1987,7(4):338-347.
[37]BERGER A,LOUTRE M F.Insolation values for the climate of the last 10 million years[J].Quaternary Science Reviews,1991,10(4):297-317.
[38]雷昉,鹿化煜,魏海珍,等.黄土高原南部黄土-古土壤酸溶相硼同位素组成(δ11B)及其对季风降水变化的指示[J].中国科学:地球科学,2014,44(7):1508-1518.LEI F,LU H Y,WEI H Z,et al.Variation of monsoon precipitation revealed by boron isotopic composition of the acid soluble in loess-paleosol sediment from southern Chinese Loess Plateau[J].Scientia Sinica Terrae,2014,44(7):1508-1518.
[2]FAURE G,POWELL J L.Strontium isotope geology[M].Berlin:Springer,1972.
[3]刘东生.黄土与环境[M].北京:科学出版社,1985.
[4]KUKLA G,AN Z S.Loess stratigraphy in center China[J].Palaeogeography,Palaeoclimatology,Palaeoecology,1987,89:203-225.
[5]丁仲礼,刘东生,刘秀铭,等.250万年以来的37个气候旋迴[J].科学通报,1989,34(19):1494-1496.
[6]丁仲礼,孙继敏,余志伟,等.黄土高原过去130 ka来古气候事件年表[J].科学通报,1998,43(6):567-574.
[7]朱洪兵,杨杰东,陈骏.东亚夏季风变迁的灵敏的指标:黄土碳酸盐的87Sr/86Sr比值[J].南京大学学报(自然科学),1998,34(6):671-676.ZHU H B,YANG J D,CHEN J.Variations in87Sr/86Sr ratios of carbonates of Chinese loess-paleosol:a proxy index of the East Asian summer monsoon[J].Journal of Nanjing University(Natural Science Edition),1998,34(6):671-676.
[8]饶文波,杨杰东,陈骏,等.中国干旱-半干旱区风尘物质的Sr,Nd同位素地球化学:对黄土来源和季风演变的指示[J].科学通报,2006,51(4):378-386.
[9]BURKE W H,DENISON R E,HETHERMGTON E A,et al.Variation of seawater87Sr/86Sr throughout phanerozoic time[J].Geology,1982,10:516-519.
[10]MONTANEZ I P,BANNER J L,OSLCGER D A,et al.Integrated Sr isotope variations and sea-level history of Middle to Upper Cambrian platform carbonates:implications for the evolution of Cambrian seawater87Sr/86Sr[J].Geology,1996,24:917-920.
[11]JIN Z D,WANG S M,SHEN J,et al.Chemical weathering since the Little Ice Age recorded in lake sediments:a highresolution proxy of past climate[J].Earth Surface Processes and Landforms,2001,26:775-782.
[12]BICKLE M J,HARRIS N B W,BUNBURY J M,et al.Controls on the87Sr/86Sr ratio of carbonates in the Garhwal Himalaya,headwaters of the Ganges[J].Journal of Geology,2001,109(6):737-753.
[13]陈骏,汪永进,陈旸,等.中国黄土地层Rb和Sr地球化学特征及其古季风气候意义[J].地质学报,2001,75(2):259-266.CHEN J,WANG Y J,CHEN Y,et al.Rb and Sr Geochemical characterization of the Chinese loess and its implications for palaeomonsoon climate[J].Journal of Geological,2001,75(2):259-266.
[14]金章东,王苏民,沈吉,等.湖泊沉积物Sr同位素记录的小冰期[J].科学通报,2002,47(19):1512-1516.
[15]DASCH E J.Strontium isotopes in weathering profiles,deep-sea sediments,and sedimentary rocks[J].Geochimica et Cosmochimica Acta,1969,33(12):1521-1552.
[16]金章东,张恩楼.湖泊沉积物Rb/Sr比值的古气候含义[J].科学技术与工程,2002,2(3):20-22.JIN Z D,ZHANG E L.Paleoclimate implication of Rb/Sr ratios from lake sediments[J].Science Technology&Engineering,2002,2(3):20-22.
[17]金章东,王苏民,沈吉,等.小冰期弱化学风化的湖泊沉积记录[J].中国科学:D辑,2001,31(3):221-225.
[18]钟巍,薛积彬,甄治国,等.雷州半岛北部晚更新世晚期气候环境变化的泥炭沉积记录[J].海洋地质与第四纪地质,2007,27(6):97-104.ZHONG W,XUE J B,ZHEN Z G,et al.The climatic changes during last late-pleistocene indicated by peat deposit in the north Leizhou Peninsular[J].Marine Geology&Quaternary Geology,2007,27(6):97-104.
[19]ZHONG W,XUE J B,OUYANG J,et al.Last glacial climate variations on the tropical Leizhou Peninsula,South China[J].Journal of Paleolimnology,2010,44(3):777-788.
[20]ZHONG W,CAO J Y,XUE J B,et al.Carbon isotope evidence of last glacial climate variations in the tropical NWLeizhou Peninsula,South China[J].Boreas,2012,41(1):102-112.
[21]XUE J B,ZHONG W,CAO J Y.Changes in C3and C4plant abundances reflect climate changes from 41,000 to10,000 yr ago in northern Leizhou Peninsula,South China[J].Palaeogeography,Palaeoclimatology,Palaeoecology,2014,396:173-182.
[22]XUE J B,ZHONG W,XIE L C,et al.Vegetation responses to the last glacial and early Holocene environmental changes in the northern Leizhou Peninsular,South China[J].Quaternary Research,2015,84(2):223-231.
[23]曹家元,钟巍,薛积彬,等.中国热带雷州半岛北部地区末次冰期气候变化的特征与机制[J].地质学报,2013,87(8):1179-1192.CAO J Y,ZHONG W,XUE J B,et al.Variation and mechanism of paleoclimate in the Last Glaciation in the tropic northern Leizhou Peninsular in South China[J].Acta Geologica Sinica,2013,87(8):1179-1192.
[24]肖仕鼎,黄其叙,陈红宏.湛江市水文特征[J].广东水利水电,2008(2):52-54.
[25]陈俊仁,姚伯初,吴能友.湛江田洋玛珥湖的形成与演化[J].广东地质,2002,17(1):12-18.CHEN J R,YAO B C,WU N Y.Formation and evolution of Maar Lake in Tianyang,Zhanjiang[J].Guangdong Geology,2002,17(1):12-18.
[26]蔡颖.雷州半岛西北部下录地区晚更新世晚期以来沉积环境演变的初步研究[D].广州:华南师范大学,2009.CAI Y.Preliminary research about evolution of sedimentary environment from Late Pleistocene of Xialu in the northwestern Leizhou Peninsular[D].Guangzhou:South China Normal University,2009.
[27]REIMER P J,BAILLIE M G L,BARD E,et al.Int Cal09and Marine09 radiocarbon age calibration curves,0-50,000 years cal BP[J].Radiocarbon,2009,51:1111-1150.
[28]GOLDSTEIN S L.Decoupled evolution of Nd and Sr isotopes in the continental crust and the mantle[J].Nature,1988,336:733-738.
[29]CHEN J,AN Z S,HEAD J.Variation of Rb/Sr ratios in the Loess-Paleosol sequences of central China during the last 130,000 years and their implications for monsoon paleoclimatology[J].Quaternary Research,1999,51(3):215-219.
[30]陈骏,安芷生,汪永进,等.最近800 ka洛川黄土剖面中Rb/Sr分布和古季风变迁[J].中国科学:D辑,1998,28(6):498-504.
[31]DEURER R,FORSTNER U,SCHMOLL G.Selective chemical extraction of carbonate-associated metals from recent lacustrine sediments[J].Geochimica et Cosmochimica Acta,1978,42(4):425-427.
[32]INGRAM B L,SLOAN D.Strontium isotopic composition of estuarine sediments as paleosalinity-paleoclimate indicator[J].Science,1992,255:68-72.
[33]陈骏,安芷生,刘连文,等.最近2.5 Ma以来黄土高原风尘化学组成的变化与亚洲内陆的化学风化[J].中国科学:D辑,2001,31(2):136-145.
[34]常凤琴.中国西部晚更新世中晚期古湖泊沉积锶同位素与环境变化[D].兰州:兰州大学,2008.CHANG F Q.The relationship between strontium isotope and environment variation in paleo-lake sediments during late period of Late Pleistocene in western China[D].Lanzhou:Lanzhou University,2008.
[35]李子岩,黄克兴.雷州半岛北部泥炭形成的时期、古气候和古地理[J].煤田地质与勘探,1989(1):12-16.
[36]万恩璞,王曼华,马学慧.广东下录埋藏泥炭的特征、成因及古地理环境探讨[J].地理科学,1987,7(4):338-347.WAN E P,WANG M H,MA X H.An approach to the characteristics,genesis and palaeogeographicl environment of Xialu buried peat in Guangdong Province[J].Scientia Geographica Sinica,1987,7(4):338-347.
[37]BERGER A,LOUTRE M F.Insolation values for the climate of the last 10 million years[J].Quaternary Science Reviews,1991,10(4):297-317.
[38]雷昉,鹿化煜,魏海珍,等.黄土高原南部黄土-古土壤酸溶相硼同位素组成(δ11B)及其对季风降水变化的指示[J].中国科学:地球科学,2014,44(7):1508-1518.LEI F,LU H Y,WEI H Z,et al.Variation of monsoon precipitation revealed by boron isotopic composition of the acid soluble in loess-paleosol sediment from southern Chinese Loess Plateau[J].Scientia Sinica Terrae,2014,44(7):1508-1518.