湖盆无曝露缓坡带层序界面特征及成因——以松辽盆地他拉哈地区上白垩统为例

松辽盆地他拉哈地区在泉头组四段—嫩江组三段沉积时期为长期被湖水覆盖的缓坡带，层序地层学研究结果表明，层序界面在岩性—测井曲线特征上，有7种表现形式:(1)砂岩发育段内正反旋回的分界面；(2)砂岩发育段与含砂泥岩层（组）之间的正反旋回的分界面；(3)含砂泥岩层（组）与砂岩发育段之间的正反旋回的分界面；(4)钙质含量较高层段内正反旋回的分界面；(5)钙质含量较高的层（组）与含砂泥岩层（组）之间的正反旋回的分界面；(6)含砂泥岩层（组）与钙质含量较高的层（组）之间的正反旋回的分界面；(7)含砂泥岩层（组）内部的正反旋回的分界面。二级和三级层序界面以砂岩发育段内正反旋回的分界面为主，分别占92％和39％。四级层序，7种类型的界面出现的概率差别较小，表现形式具有真正的层序界面特征多样性。层序界面的特征取决于湖平面的升降、物源供应强度和蒸发作用的强度。

Characteristics and Genesis of Sequence Boundaries on Subaqueous Gentle Slope of Lacustrine Basin: a case study on Upper Cretaceous in Talaha region of Songliao Basin

Talaha region in Songliao Basin is the gentle slope which was covered with water in long term during the depositional periods of the Fourth Member of Quantou Formation to Third Member of Nenjinag Formation.On the basis of sequence stratigraphy studies,it is found that there are 7 types of sequence boundaries manifestation in the drilling well data,such as:(1)boundary between upper-coarsing cycle and upper-fining cycle within the sand-rich part of well profile;(2) boundary between upper-coarsing sand-rich cycle and upper-fining mud-rich cycle of well profile;(3) boundary between upper-coarsing mud-rich cycle and upper-fining sand-rich cycle of well profile;(4) boundary between upper-coarsing cycle and upper-fining cycle within carbonate-rich part of well profile;(5) boundary between upper-coarsing carbonate-rich cycle and upper-fining mud-rich cycle of well profile;(6) boundary between upper-coarsing mud-rich cycle and upper-fining carbonate-rich cycle of well profile;(7) boundary between upper-coarsing cycle and upper-fining cycle within mud-rich part of well profile.The second-order and third-order sequence boundaries dominated by the boundary between upper-coarsing cycle and upper-fining cycle within the sand-rich part of well profile,respectively is 92% and 39%.The fourth-order sequence boundaries are provided with diversity,there are near equal probability of 7 types of sequence boundaries.The characteristics of sequence boundaries are controlled by fluctuation of lake level,supply of source and intensity of evaporation.