泥河湾古湖的形成机制及其与早期古人类生存环境的关系

THE FORMATION MECHANISM OF THE NIHEWAN PALRO-LAKE AND ITS RELATIONSHIP WITH LIVING ENVIRONMENT FOR EARLY ANCIENT HUMEN

泥河湾盆地位于汾渭裂谷系的东北端，是裂谷系的重要组成部分。古近纪初恒山－大同一带发育软流圈上涌柱，导致岩浆喷发和地壳变薄，距今25～24Ma，阳原-石匣一带开始沉陷形成盆地，北侧出现伸展造山带。受到挤压作用使盆地内地壳缩短并在盆地南侧形成台地。上新世末至早更新世为盆地沉陷最盛时期，泥河湾古湖形成。距今2．0～0．8Ma，该地区为温和的温带气候环境，有的时段为亚热带气候，同时火山喷发的火山灰和风成沉积为盆地土壤提供了丰富矿物质养分，湖泊周边地区动植物繁盛，为早期古人类在此栖息提供了必要的条件。该裂谷型盆地是适于早期古人类生存和发展的地区，泥河湾盆地将是我国最有可能发现早期古人类化石的地点。

The Nihewan Basin is located at northeast end of the Fen-Wei rift valley system, and constitutes an important part of it. At the beginning of Eogene an upwelling plume of soft mantle was developed in Hengshan-Datong region. It caused thinning of the crust and magma eruption. During 25 24 Ma the crust began to subside along Yangyuan-Shixia area to form a basin, with an extensional orogen on its northern side. The compressional stress caused by shortening of the crust in the basin lead to the formation of terrace along its south side. The subsidence of the basin reached its acme during the terminal Pliocene to early Pleistocene when the Nihewan paleo-lake formed. During 2.0 - 0.8 Ma, the Nihewan paleo-lake saw a temperate climate intercalated with some subtropic intervals. The volcanic eruption and eolion deposits provided plentiful mineral nutrients necessary for living of animals and plants around the basin. These in turn offered the necessary living condition for early ancient humen. The Nihewan basin is a potential area to find the early ancient humen fossils.