地理学报 ›› 1998, Vol. 65 ›› Issue (6): 537-544.doi: 10.11821/xb199806007

• 论文 • 上一篇    下一篇

阿拉斯加巴罗AB-67钻孔岩芯的沉积环境分析

王国, 张青松, 李元芳   

  1. 中国科学院地理研究所,北京100101
  • 收稿日期:1996-07-01 修回日期:1997-01-01 出版日期:1998-11-15 发布日期:1998-11-15
  • 基金资助:
    国家自然科学基金,(49571072)中国科学院资源与生态环境研究重大项目,(KZ951-A1-205)美国阿拉斯加北坡自治州野生生物管理部的资助

ANALYSIS OF SEDIMENTARY ENVIRONMENT OF AB 67 CORE AT BARROW, ALASKA

Wang Guo, Zhang Qingsong, Li Yuanfang   

  1. Institute of Geography, Chinese Academy of Science, Beijing 100101
  • Received:1996-07-01 Revised:1997-01-01 Online:1998-11-15 Published:1998-11-15
  • Supported by:
    Supported by National Natural Science Foundation of China, No 49571072, The Key Project of Resources and Eco-environmental Research in Chinese Academy of Sciences, No KZ951-A1-205, and Department of Wildlife Management, North Slope Borough, Alaska, USA

摘要: 巴罗AB-67钻孔岩芯的48个样品被进行了25个项目的粒度分析和44个项目的地球化学分析。本文对这些数据进行了Q型因子分析,并得到了4个主因子。研究表明,这4个因子分别代表了沉积环境的四项指标,它们分别为沉积速率、降水、海平面和温度。从岩芯顶部5个样品与巴罗气象台观测记录确定了古温度和古降水的转换函数,从210Pb测年和几个环境事件确定了沉积速率的转换函数。从沉积相的变化识别出了海平面因子。重建的温度和降水的曲线表明,16、17世纪巴罗地区的环境比现在更为寒冷、干旱。18、19世纪温度升高而降水变幅很大,20世纪的温度和降水波动都很剧烈,重建的温度曲线在岩芯的微体古生物变化组合上得到了很好的印证。

关键词: 巴罗, 钻孔岩芯, 沉积环境分析, Q型因子分析, 转换函数

Abstract: The purpose of this study is to reconstruct the record of recent environmental change at Barrow, Alaska through temporal inverse deduction using a sedimentary core. In this field of study, the traditional approach is qualitative, taking grain size, its statistical feature, geochemical composition and its combination as indexes of sedimentary environment to indicate environmental change. In recent years, the use of Q mode factor analysis and transfer function techniques has facilitated the quantification of paleoenvironment research. Q mode factor analysis has been used to study several undetermined factors, revealing certain results that are widely known. Changes of sea level, sedimentary rate, temperature and precipitation must cause changes in sedimentary grain size and chemical composition in the lagoon sedimentary environment. The causal relationship may not be strictly linear, but before nonlinear technique can be practically used, we will analyze grain size and geochemical composition by Q mode factor analysis to extract sedimentary environment factors. Factor identification is the key to Q mode factor analysis. Here, the identification was done according to: (1) the cause and effect relationship in sedimentary modeling; (2) the qualitative feature of environmental changes that are already known; (3) the degree of correlation between recent meteorological data and the factors identified. In this paper, we will identify temperature, precipitation, sedimentation speed and sea level as the major factors affecting environmental change. Defining transfer function is important in paleoenvironment quantitative research. The temperature and precipitation transfer function is obtained from linear transformation of these factors, and the two unknown constants are obtained by linear regression of 11 years of running mean climatic data from Barrow Meteorological Station. Determining sedimentary rate is very important for establishing sedimentary temporal model. The transfer function of sedimentary rate is from linear transformation of its factors, and the two constants needed are determined by 210 Pb timing and recognition of several environment events. The transfer function of sea level change is obtained from linear transformation of the sea level factor, and the two constants are determined by the time when marine sediment began and by the present ocean depth. Research on sea level change is only exploratory here because, first, there are no recent observed sea level data to compare with, and second, it remains to be further studied what effect sea level change had on shore zone sediment prior to marine transgression. Based on the analysis of the sedimentary environment of AB 67 core at Barrow, some conclusions are reached: 1) From the reconstructed sedimentary rate curve, we have determined the sedimentary period of each layer in the AB 67 core. Sedimentation in the bottom layer began in the latter half of the 16th century. 2) From our study of sea level change, we get the sea level change curve of Elson Lagoon. According to the grain size, geochemical composition and micropoleontology combination, marine deposit begins at the depth of 20 cm, which corresponds to the last half of the 18th century. This is earlier than the date estimated by 210 Pb. The mean uplift speed of sea level is 10 mm穉 1 over the last 200 years. 3) The trends of temperature and precipitation show that the environment in the 16th and the 17th centuries was colder and dryer than that of today, that temperature rose and precipitation fluctuated greatly in the 18th and the 19th centuries, and that both temperature and precipitation fluctuated greatly in the 20th century. The pattern of temperature fluctuation is well confirmed by the realignment of microponotoly in the AB 67 core.

Key words: Barrow, drilling core, sedimentary environment, Q mode factor analysis, transfer function

中图分类号: 

  • P531