【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。更多还原

【Abstract】 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, the climatic conditions were dry and warm. Wet and cool climates occurred between 2 000 a and 1 000 a. The temperature variations reconstructed by our preliminary results of SFL on glacial-interglacial time scales agree very well with the marine oxygen isotopic stages (MOIS). During the interglacial of MOIS 9, climates were warm and wet, and the stalagmite grew very fast. During the glacial periods of MOIS 6 and 8, climates were cold and probably wet, and growth hiatus might have existed under the cold condition. The stalagmite grew very slowly during the interglacial of MOIS 7, resulting from very dry and warm climates reflected by the heavy δ 18O and δ 13C values. Within the last interglacial period (MOIS 5), warm-dry conditions prevailed during 5e, 5c and 5a and cold-wet conditions during 5d and 5b.更多还原