长江三峡地区第四纪以来新构造上升速度和形式

NEOTECTONIC UPLIFT VELOCITY AND TYPE ALONG THE CHANGJIANG RIVER DURING QUATERNARY

本文以长江三峡地区各级夷平面和阶地作为重要标志,用地层学、古地磁测年、热释光测年和^(14)C测年等手段,确定了它们的时代,从而分别计算2Ma、0.73Ma和0.2Ma以来的新构造上升速度。本文还探讨了新构造上升的特征:(1)长江三峡是一个以巴东为中心的不对称的新构造穹形隆起区,宜昌以东和万县以西是相对坳陷区;(2)2Ma以来,新构造上升节奏为缓慢—较快—较慢;(3)0.73Ma以来,新构造上升中心有向东迁移的趋势。

In the Sanxia Gorge (the Three Gorges) area along the Changjiang (Yangtze) River, there are many steps of planation surface and river terrace (PS&RT), being the important marks of neotectonic uplift, the ages of which were determined by means of paleomagnetism dating, thermoluminescence dating and radio carbon-14 dating. According to the ages and appearance of PS&RT, the author calculates the neotectonic uplift velocity and represents its type in the Sanxia Gorge area during Quaternary. The main conclusions of this paper are as follows: 1. In the central zone of the Sanxia Gorge (Wushan to Zigui), the neotectonic uplift velocity was 0.37—0.47 mm/a during the last 2 Ma; 0.59—0.73 mm/a during the last 0.73 Ma; 0.38—0.43 mm/a during the last 0.20 Ma. In other words, average 0.28 mm/a during 2—0.73 Ma B.P.; 0.76mm/a during 0.73—0.20 Ma B.P.; 0.38—0.43mm/a during 0.20—0 MaB.P. 2. The Sanxia Gorge area is a unsymmetrical neotectonic uplift dome-zone, contrasting sharply with which, the sides to the east of Yichang County and to the west of Wanxian County are both relative depression zones. 3. During the last 2 Ma, the neotectonic uplift rhythm was slow, fast, rather slow. 4. During the last 0.73 Ma, the neotectonic uplift centre of the Sanxia Gorge area had been tending to move eastward.