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The Yuncheng salt lake has formed under the setting of stepped subsidence of fault-blocks from the north to the south in Yuncheng Basin. In the phase of red clay accumulation during 7.1-3.6 Ma, the size of palaeo-lake was larger than the present salt lake, and palaeo-monsoon had formed. At 3.6 Ma, the northern basement in the basin raised abruptly due to the radiative effect of Qinghai-Tibet Plateau uplifting, and palaeo-lake was contracting southwards. At ca. 2.6 Ma ancient river flowed into the northern part of the basin. During ca. 2.0-1.9 Ma aerolian effect strengthened and loess started to accumulate on the most part of the basin. Since ca. 1.8-1.0 Ma the subsidence of the lake fault-block has been speeding up abruptly. As under the natural hydrogradient the salt lake received enough groundwater supply, and the rate of loess accumulation in the lake area was lower than that of subsidence of the lake fault-block, the lake could be preserved and becomes the only modern lake on Chinese Loess Plateau. Four large strengthening change records of the monsoon were found in the lake sequence of 5.8-1.9 Ma B.P. 相似文献
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运城盐湖是在盆地内部断块自北向南阶梯性沉降背景下形成的． ７．１～３．６ Ｍａ红 土堆积期湖泊范围较今为大,古季风已形成; ３．６ Ｍａ因青藏高原隆升的辐射效应,盆地 北部基底突然抬升,湖泊向南退缩; ２．６ Ｍａ构造变动河流进入盆地北部, ２．０～１．９ Ｍａ间 风成作用增强,开始黄土堆积．由于湖区断块自 １．８～１．０ Ｍａ始加速沉降,在天然水力 梯度下有充足的地下水补给,黄土在湖泊中的堆积速率小于湖泊构造沉降速率,故形 成了黄土高原上惟一的现代湖泊． ５．８～１．９ Ｍａ间湖泊地层中有 ４次大的季风强度变化记 录． 相似文献
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