摘要
湖光岩玛珥湖HUG B孔岩心记录了62kaBP以来的古气候、古环境变化信息。全岩有机碳同位素组成(δ13CTOC)分析表明,62kaBP以来δ13CTOC值变化比较明显,其变化范围为-28.5‰～-15.5‰。结合孢粉和有机地球化学指标进行综合分析,湖光岩玛珥湖δ13CTOC变化曲线可划分为6个演化阶段:62～58和48～40.5kaBP两个时段的δ13CTOC值偏负,沉积物中有机质主要来源于热带—亚热带地区的陆生C3森林植被,反映了温暖潮湿的气候环境;58～48和40.5～17.2kaBP期间δ13CTOC值明显偏正,沉积物中有机质主要源自C4草本植物,反映了湖光岩地区有效降水量减少、干旱程度增加导致湖光岩玛珥湖湖面下降,大量C4草本植物生长在暴露的湖滨岸;17.2～4kaBP时段内δ13CTOC值尽管存在更加频繁的波动,但总体呈现逐渐偏负的趋势,反映了暖湿和冷干气候多次交替但总体上逐渐变暖、变湿的气候环境;4kaBP以来δ13CTOC值存在逐渐偏正的趋势,虽然不排除人类活动的影响,但很可能反映了干旱程度的再次增加。综合分析表明,有效降水量(降水量-蒸发量)是控制湖光岩玛珥湖地区C3/C4植物相对生物量变化的主导因素。湖光岩玛珥湖有机碳同位素的研究结果支持区域气候环境而不是大气CO2浓度变化是末期冰期以来热带低纬度地区C3/C4植被相对生物量变化的主要原因。
Core HUG-B of Huguangyan Maar Lake recorded paleoclimatic and paleoenvironmental changes since 62 kaBP. Bulk organic carbon isotopic composition (δ^(13)C_(TOC)) of HUG-B core is analyzed. The variation range of δ^(13)C_(TOC) values is from -28.5‰ to -15.5‰. Combined with pollen and organic geochemistry results, the δ^(13)C_(TOC) curve of Huguangyan Maar Lake since 62 kaBP can be divided into six stages. During 62~58 and 48~40.5 kaBP, the δ^(13)C_(TOC) values were much more negative, the organic components of sediments were mainly from terrestrial C_3 plants of tropical and subtropical forest, indicating two warm and humid periods. In contrast, during 58~48 and 40.5~17.2 kaBP, the paleoclimatic conditions became much drier and colder, with significantly heavier δ^(13)C_(TOC) values. The organic components of these two periods were of dominant C_4 herbaceous plants, suggesting that the open grassland landscape dominated in the lake shore of Huguangyan Maar Lake when the lake level dropped because of serious dryness around Huguangyan Maar Lake area. Since 17.2 kaBP, there is the tendency of gradual lighter δ^(13)C_(TOC) values in spite of much high frequency oscillations, which indicates the tendency to warmer and more humid condition superimposed by many alternations of warm, humid condition with cold and dry climate. After 4 kaBP, (δ(^(13)C_(TOC))) values became heavier, which may indicate increased drought, but it is most likely the distortion caused by human activity. Based on comprehensive analysis, the virtual precipitation (i.e. precipitation minus evaporation) is the key factor that controls the C_3/C_4 relative plants biomass around Huguangyan area. This result supports the fact that regional climate change rather than atmospheric CO_2 acted as the dominant control factor on glacial-interglacial variations in C_3 and C_4 plant relative abundance in tropical low latitude area such as around Huguangyan Maar Lake.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2005年第2期115-126,共12页
Marine Geology & Quaternary Geology
基金
中国科学院知识创新工程重要方向性项目(KZCX3SW145
KZCX2SW118)
国家自然科学基金项目(40302023)
国家重点基础研究发展规划"973"项目(2004CB720207)
