MAGNETOSTRATIGRAPHY OF A LOESS-SOIL SEQUENCE IN THE GARZE AREA, WESTERN SICHUAN
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摘要: 川西高原位于青藏高原的东南边缘, 气候主要受印度洋季风、高原季风的影响。广泛分布于川西高原的黄土-古土壤序列是高原周缘地区连续的古气候记录类型之一, 记录了上述环流系统的演化过程及其与青藏高原阶段性演化的关系, 对探讨高原隆升的环境响应具有重要意义。对川西甘孜地区甘孜-A剖面进行了系统的磁性地层学研究。结果表明, B/M界线出现在L7的底部, 并且在剖面下部出现了松山负向期的贾拉米洛正向极性亚带。以古地磁界限点作为时间控制点外推该剖面典型风尘沉积的底界年龄约为1.16 Ma BP。Abstract: The western Sichuan Plateau is located on the southeastern margin of the Qinghai-Tibet Plateau, and its climate is mainly controlled by the Indian monsoon and Plateau monsoon.The loesspaleosol sequence distributed widely on the western Sichuan Plateau is among the best continuous records of the Quaternary climate and environment on the margins of the plateau.It records the evolutionary process of the above-mentioned circulation system and its relation to the phased evolution of the QinghaiTibet Plateau and is crucial for understanding the regional environmental response to the uplift of the plateau.A systematic magnetostratigraphic study was conducted on the Garzê-A section in the Garzê area, western Sichuan.The results indicate that the B/M boundary appears at the top of L7 and that the Jaramillo normal polarity subzone of the Matuyama negative polarity zone appears in the lower part of the section.Extrapolation from the paleomagnetic boundary point yields a basal age of ～1.16 Ma for typical eolian deposits of the Garzê-A section.
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Key words:
- western Sichuan Plateau /
- Garzê /
- Garzê-A section /
- magnetostratigraphy
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图 2 甘孜-A剖面岩性地层及磁性地层
Figure 2. Lithostratigraphy and magnetostratigraphy of the Garzê-A section
图 3 甘孜-A剖面典型样品热退磁的剩磁矢量正交投影图
●为水平分量; ○为垂直分量
Figure 3. Orthogonal projection of vectors of remanent magnetism of thermal demagnetization of typical normal and reversed polarity samples from the Garzê-A section
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