PALEOSOLS IN THE LUOCHUAN LOESS SECTION : II. Degree of Weathering and Estimation of Paleoclimate

概要

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The degree of weathering varies from one paleosol to another and it reflects the paleoenvironment under which a paleosol was formed. Therefore, an attempt was made to estimate the degree of weathering of paleosols quantitatively, on the basis of the method proposed by ARAKI and KYUMA (1985). The data necessary for the use of the method (total contents of major elements, quartz and contents) were obtained and presented in this and previous papers. The results revealed that the degree of weathering of paleosols in terms of "Weathering Index" generally parallels the degree of pedogenetic development. A vertical plot of the Weathering Index for loess and paleosols along the Luochuan loess section was compared with the delta ^<18>O (oxygen isotropic ratio) plot for a deep sea core. The best matching attempted on the basis of certain assumptions yielded the following correlation: S1-stage 5, S2-stage 7, S3-stage 9, S4-stage 11, S5-stage 13-15, S6-stage 17, S6'-stage 18, S7-stage 19, and S8-stage 21. This correlation that places Brunhes/Matuyama polarity boundary just below S7 was supported by a paleomagnetic study conducted by geologists with the samples collected at the same location and at the same time. Conversely, the paleopedological study gave a supporting evidence to the geologists.
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