云南东川地区层状地貌面的成因

在东川地区的山地及小江河谷的两侧山麓上部，分布着不同高度和不同规模的层状地貌面，对其成因仍有不同的认识。分歧主要表现在两个方面：一是高原隆升之前的初始地貌面是否是准平原型夷平面；二是山顶面之下的梯级层状地貌面的成因。本文从以下几个方面对上述问题进行讨论：(1)层状地貌面的地貌特征及其与侵蚀河谷体系的关系；(2)层状地貌面上堆积物的性质；(3)层状地貌面与断裂构造水平展布的关系；(4)相邻层状地貌面的空间过渡关系；(5)区域构造演化背景。作者认为在云贵高原抬升过程中，东川地区以挤压穹起隆升变形为主。不同海拔高度的层状地貌面具有多成因特性。山顶面及局部高原面是高原隆升之前古夷平面的残留。并遭到后期强烈的侵蚀改造。目前，尚缺乏足够证据证明高原隆升之前的古夷平面为准平原型夷平面。小江河谷两侧的梯级层状地貌面是侵蚀或剥蚀面，它们形成于高原隆升及初始地貌面解体之后，其梯级空间分布特征与区域性的阶段隆升有关。

Genesis of the Layered Landform Surfaces in Dongchuan, Yunnan Province

In the mountain and two slopes of Xiaojiang Valley, Dongchuang, Yun-Gui Plateau, the layered land-form surfaces with various altitude were developed and presented. But, the genesis or origin about the layered landform surfaces is still at issue. In this paper, this unresolved problem was discussed according to the following analysis: (1) the geomorphological characteristics of the layered landform surfaces; (2) the relationship between the layered landform surfaces and the erosion valley system; (3) the properties of depositions on the layered land-form surf aces, especially weathering mantles; (4) the relationship between the faults system and the layered landform surfaces; (5) the transition relationship between the neighboring layered landform surfaces with different altitude; (6) the background of regional tectonic evolution. The authors think that during uplift of Yunnan-Guizhou Plateau, the main deformation of Dongchuan area was in prominent compression and uplift. In research area, the layered landform surfaces with varying altitude were multi-genesis. The summit of mountain and partly plateau surface were the relicts of Neogene paleo-plana-tion surface. In addition, the relicts of paleo-planation surface were strongly eroded and reconstructed. Up to now, the information about paleo-planation surface formed before plateau uplift is still lack. So, the paleo-planation surface couldn' t be recognized as a peneplain. In the valley of Xiaojiang river, the layered landform surfaces were kinds of erosion surfaces or denudation surfaces. They formed after the disintegration of Neogene planation surface. The steplike distribution of landform surfaces indicated that the neotectonics was intermittent uplift in research region.