科尔沁沙地及其古水文网的演化变迁

在科尔沁，沙地的形成演化与古河流的变迁存在着密切的联系，本文通过对科尔沁沙地遥感图像的解析，全面分析了沙地与河流分布的宏观特征，结合野外考证资料，认为存在5期可辨认的河流发育阶段，每个阶段都有不同的河流展布特点，而风沙也存在至少4个活动期。古河道-Ⅴ形成于风沙-Ⅱ和Ⅲ期形成之前，可能是末次冰期之前，即中更新世或更早，这时河流能够进入古松辽大湖；  古河道-Ⅳ形成于风沙-Ⅱ和Ⅲ期形成之时，可能是末次冰期时期，这时河流与松辽大湖萎缩，规模减小，河流已不能进入松辽大湖，而是消失在沙地之中；  古河道-Ⅲ形成于风沙-Ⅱ和Ⅲ期形成之后，可能是末次冰期末期的冰消期，这时气温升高，大量的冰雪融水进入河流，促使河水漫流，流入沙垅垅间洼地，开始造成古西拉木伦河、古老哈河与教来河水文网之间的相互联系；  古河道-Ⅱ形成于全新世适宜期时期，统一的西辽河形成，伴随气候变化，出现多次风沙进退，对应于风沙-Ⅰ期；  河道-Ⅰ是现在，同属于风沙-Ⅰ期，活动沙地集中在翁牛特等地。

DEVELOPMENT AND EVOLUTION OF HORQIN SANDY LAND AND ANCIENT HYDROLOGICAL NETWORKS

In Horqin region,the formation and development of sandy land was closely related to the change and evolution of ancient rivers.In the paper,the macroscopic features of sandy land and drainage network were carefully analyzed according to remotely sensed images and field investigations.It was found that there were five identifiable stages of drainage network,codes as paleochannel-Ⅰ to -Ⅴ.The distribution characteristics of each drainage network stage were different from other's.There were at least four activation stages of desert.The paleochannel-Ⅴ might develop before the desert-Ⅱ and -Ⅲ and might form before the last glacial period,or an earlier period,such as midPleistocene.In the stage,rivers in Horqin areas flowed into the paleo-Songliao lake.The paleochannel-Ⅳ formed when the desert-Ⅱ and/or-Ⅲ developed.In the stage that might be the last glacial period,rivers in Horbin and the paleo-Songliao lake shrank and the rivers disappeared in deserts and did not flow into the paleo-Songliao lake.The paleochannel-Ⅲ developed after the desert-Ⅱ and -Ⅲ when may be the last deglaciation period.In the stage,temperature-rising result in a large amount of snow and ice melt-water to flow into rivers and overflow into lowlands between sand ridges to connect the ancient-Xilamulun river,the ancient-Laoha river and the ancient-Jiaolai river.The paleochannel-Ⅱ might form during the Holocene Optimal period.In the stage corresponding to the desert-Ⅰ stage,the uniform west-Liao river formed and there were several times of desert activation and dormancy.The river-Ⅰ developed at present and belong to the desert-Ⅰ stage.Most active deserts distributed in the Wengniute area.