洞庭湖现代构造与湖盆演变

DONGTINGHU MODERN TECTONICS AND ITS BASIN EVOLUTION

洞庭湖区是东南地洼区北段和华中地洼区交接处的一个地洼盆地。自白垩纪形成以来，经历次构造运动，沧桑更替。第四纪全新世早期曾为河网化平原。至１９世纪后期，主要因为断裂构造活动，使长江向南分流注入洞庭，低处盈水成湖，洞庭湖进入新的盛衰演变阶段。 根据不同年代的卫星遥感图象解译与历史资料对比分析，现代洞庭湖区的构造运动是块断差异升降运动。该区在先期多次构造运动中形成的断裂，在现阶段活动多转化为具张性特征的断裂。其中北北东向、北西西向和北西向３组断裂控制湖盆的基本格局，而北东向、近东西向和南北向断裂则制约湖盆内部的隆坳分布。不同方向断裂构造复合对盆内隆坳的控制尤其明显：东部北北东向断陷带与南部近东西向断陷带复合控制南洞庭横岭湖深坳陷；中部掀斜坳陷区与南部近东西向断陷带复合控制南洞庭万子湖深坳陷；东部北北东向断陷带与北东向断裂复合，于其复合断裂下降盘控制东洞庭湖中深坳槽；西部块断隆起带与南部近东西向断陷带复合使西洞庭目平湖萎缩。

Dongtinghu is a geodepression basin which locates in northern part of southeastern Diwa and associates with the central-China Diwa. It has developed since the Cretaceous period through,all of the tectonic movements and land changes. Early in stage of the Quuaternary Holocene epoch, Dongtinghu area was a channelization plain. Later in 19 century, as mainly the activities of tectonic movement, Yangtz river was split off to immit floods into Dongtinghu areas, which the lower areas changed into lakes. At that time, Dongtinghu went into a new stage of development. In accordance with the contrast analysis between different years of satellite image interpretation and geologic data, the modern tectonics in Dongtinghu are mainly block-faulting movements of discrepancy up-and-down. Most of the faults formed in advance tectonic movements are translating into extensional characteristics. The main three group of faults are striking NE, NWW and NW, which are the fundamentally pattern of basic structures in the Dongtinghu basin. And the three group of faults striking NE, near EW and NS are controlling ridgys and troughs distributing inside the Dongtinghu basin. It is especially distinctness that the structure composites of in different directions are controlling ridgys and troughs distributing inside Dongtinghu basin. The composites of eastern taphrogenic zone of striking NE and southern near striking EW are controlling the Hunlinghu deep trough in southern Dongtinghu. The composites of central taphrogenic area and southern near striking EW are controlling the Wanzihu deep trough in southern Dongtinghu. The composites of eastern taphrogenic zone of striking NE and faults of striking NE are controlling the mid-lake deep trough in eastern Dongtinghu. And the composites of western block-faulting uplift zone and southern taphrogenic zone of near striking EW are controlling the shrink of Mopenghu in western Dongtinghu.