Lake-level Variation Response to Tectonic Subsidence in a Second-Order Sequence of Continental Rift Basin
陆相断陷盆地二级层序时限构造沉降与

To pursue the lake-level variation response to tectonic subsidence in the continental rift basin, this paper introduced two parameters (subsidence flux and subsidence velocity flux) to show the whole characteristics of basement subsidence by using two-dimensional stripping-back analysis. In the Dongying Formation of the middle Huanghua depression, the delta depositional system is well developed. The Dongying Formation, as a second-order sequence, can be subdivided into four third-order sequences. Tectonic subsidence gradually weakened and subse-quently strengthened during the development of the Dongying Formation, characterized by intense rift faulting followed by later increasing down-warping. Combined with tectonic subsidence, depositional evolution and se-quence framework of the Dongying Formation, this paper holds that the fall of the lake-level and the flourishing of the delta depositional system were coupled with rapid tectonic subsidence, and the lake-level fall resulted from violent unbalanced tectonic subsidence, causing redistribution of lake-water towards main faults or down-warping centers. The lake-water supplement was insufficient compared with the newly increased accommodation space due to tectonic subsidence. As a result, the rise of the lake-level and the development of the deep lake corresponded to slow tectonic subsidence, and the lake-level variation had nothing to do with the gross of tectonic subsidence