陆相断陷盆地可容空间转换特征

The Accommodation Transition in Faulted Lake Basin

陆相断陷盆地具有构造活动影响大、沉积物供给不均衡、湖盆范围小、物源多等特点。由于自身的局限性,这些因素对层序发育的控制作用更加明显,而直接影响湖盆可容空间的因素为构造沉降、沉积物供给和湖盆水体,三者的相互关系不仅使湖盆在演化过程中可容空间、水深和相对湖平面具有一致的变化,同时其变化又存在非统一性。构造沉降和水体为主控因素时,往往形成欠补偿沉积,相对湖平面和可容空间统一增加;构造沉降和沉积物供给为主控因素时,相对湖平面增加,可容空间在盆地的不同部位其变化不一致,在盆地中心可容空间增加,边缘可容空间减小,而在其间存在一个稳定区,即可容空间转换带。东营凹陷古近系沙河街组三段中亚段层序由湖进体系域和湖退体系域组成,湖进体系域为构造主控,相对湖平面和可容空间在盆地统一增加;湖退体系域沉积物供给的影响比较明显,可容空间在盆地缓坡中部和陡坡中部不变,形成可容空间转换带,该带外侧可容空间减小,内侧可容空间增加。

The faulted basin has the characteristics of the extensive influence of tectonic subsiding, the abundant and unbalanced sediment supply, limited water area and multi-material sources. Those lead to the difference between the marine basin and the faulted lake basin. The style of the parasequence sets differs with the position in the faulted lake. In some period, the change of the relative lake level has difference in the different place. At the lake marginal area, the accommodation becomes less and, in the mid part, the accommodation becomes larger, between those are- as, there is an accommodation transition zone. The accommodation transition is predominated by the tectonic subsiding, sediment supply and water body. Tectonic subsiding and sediment supplying make the re-distribution of the water body and the change of the relative lake level with the same water volume. Only under the situation of the water volume changing, the relative lake level has the accordant changing.