鄂尔多斯盆地延长期湖盆演化及其成因分析

Lake basin evolution of Ordos Basin during Middle-Late Triassic and its origin analysis

鄂尔多斯盆地中—上三叠统延长组沉积时期,湖盆中心存在向西南方向逐渐迁移的特征早期湖盆中心在吴旗—富县一带,中晚期向南迁移至华池—黄陵一带。受湖盆底形变化影响,延长组发育的西南沉积体系与东北沉积体系具有此强彼弱不对称发育的特点,即西南沉积体系在延长组沉积早期向盆内延伸距离远,长7期以后显著退缩,而东北沉积体系则反之。印支晚期西秦岭强烈的造山活动对盆地产生的自西南向北东方向的挤压力,以及阴山地区垂向构造隆升作用引起盆地东北部的翘升,可能是导致湖盆中心迁移及延长组南、北沉积体系不对称发育的根源。

Taking Chang 7 of the Triassic Yanchang age as the turning point, the depocenter of Yanchang Lake in Ordos Basin migrated southwestwardly from Wuqi-Fuxian area in Early Triassic to Huachi- Huangling area in Middle-Late Triassic. Affected by the migration, the southwest depositional system and the northeast depositional system developed unsymmetrically. The southwest system was more basinward- extending in Early Taiassic than in Late Triassic, however the northeast system has the opposition condition. The intensive orogenic movement of late Indo-Chinese epoch in western Qinling caused the SW to NE compressive force to Ordos Basin and the vertical uplift of Yinshan region caused the tilt of the northeast part of the Basin. The compressive force and the tilt may be the origin of the depocenter migration and the unsymmetrical development of the south and north depositional systems during Middle- Late Triassic in Ordos Basin.