陕南石笋稳定同位素记录中的古气候和古季风信息  

PALEOCLIMATIC AND PALEOMONSOONAL VARIATIONS IN CENTRAL CHINA RECORDED BY STABLE ISOTOPIC RECORDS OF STALAGMITES FROM BUDDHA CAVE,SOUTH SHAANXI

作　　者：李红春[1] 顾德隆[1] Dorte Paulsen 王非[2] 陈文寄[2] 尹功明[2] 程海[3] R.L.Edwards 

机构地区：[1]美国南加州大学地球科学系,ca900890740 [2]中国地震局地质研究所,北京100029 [3]美国明尼苏达大学地质和地球物理系,mn55344

出　　处：《地震地质》2000年第B12期63-78,共16页Seismology and Geology

基　　金：美国自然科学基金!(NSFATM - 98184 0 7)

摘　　要：采自陕西省柞水县的石笋给出了过去 750a来的高分辨率气候记录以及全新世和80～ 330ka之间的低分辨率的气候变化。定年方法使用了石笋生长纹层计数法、2 10 Pb法和TIMS2 30 Th法。分析了石笋中δ18O和δ13C的气候含义 ,认为当δ18O和δ13C值变重时 ,指示干热的气候组合 ,当δ18O和δ13C值同时变轻时 ,指示湿冷的气候组合。在长时间尺度δ18O值的变化以反映温度变化为主 ,δ13C值的变化反映湿度变化为主。当δ18O变轻 ,而δ13C变重时 ,指示干冷气候。这时期的夏季风很弱而冬季风很强 ,相反 ,当δ18O变重 ,而δ13C变轻时 ,指示湿热气候 ,表明夏季风很强 ,冬季风很弱。过去 750a的记录中分为 :公元 12 50～ 152 0年的温暖中世纪 (MedievalWarmPeriod) ,公元 152 0～ 182 0年的湿冷小冰期 (LittleIceAge)和公元 182 0年以来的温热期。全新世的气候在 4 0 0 0a左右有一显著的变化。在此时之前的温度低于全新世的平均气温 ,而在此之后的温度高于全新世的平均气温。全新世气候记录可细分为 18个不同的时期。Two stalagmites were collected from Buddha Cave (109°10′E, 33°45′N), Zashui county of Shaanxi Province. The chronologies of these stalagmites were determined by lamination counting and by the 210Pb and 230Th (TIMS) methods. From the young stalagmite SF we have obtained a high-resolution δ 18O-δ 13C record spanning the past 750 years and a low-resolution record over the Holocene. The preliminary results of the old stalagmite SFL show the climatic variations between 80 ka and 330 ka. The δ 18O records of the stalagmites reflect changes in local precipitation on decadal or shorter scales, but register mainly air temperature variations on longer terms. The δ 13C variations in the stalagmites have recorded the long-term δ 13C variations of the local soil CO 2, which chiefly reflect changes in the C3 vs. C4 plant populations under climatic influences. When both the δ 18O and δ 13C increase, climatic conditions become warm and dry; and vice versa.But if the δ 18O increases and the δ 13C decreases, the climatic conditions may turn to warm and wet, indicating a prevailing of the summer monsoon in China. A combination of decreasing δ 18O and increasing δ 13C may represent cold and dry climatic condition that has characteristics of the winter monsoon. The high-resolution δ 18O-δ 13C record shows three major climatic intervals during the past 750 years: a warm-moderately dry between 1 250 and 1 510 AD, cold-wet between 1 520 and 1 820 AD, and warm since 1820 AD. They correspond to the Medieval Warm Period, the Little Ice Age, and the global warming trend, respectively. For the Holocene low-resolution record, we have identified 18 climatic divisions. Among them, a 1 000 yr wet-moderately warm period existed between 8 500 and 7 500 a, reflecting a strengthening of summer monsoon during early Holocene. Around 4 000 a, the climate shifted from lower-than-average temperature to higher-than-average temperature. Between 4 000 a and 3 000 a,

关 键 词：Δ^18O 全新世 Δ^13C 石笋 冬季风 古季风 夏季风 柞水县 记录 陕南 

分 类 号：P532[天文地球—古生物学与地层学] P467[天文地球—地质学]