北黄海盆地东部坳陷侏罗纪古地形与沉积体系分布

北黄海盆地东部坳陷经历了多期复杂的构造演化,同沉积期盆地的古地形控制了物源区、沉积区及沉积物的搬运方向和方式。本文利用单井剥蚀量和原始沉积厚度计算、构造沉降量计算等方法,恢复了东部坳陷中侏罗世(J_2SQ1和J_2SQ2)和晚侏罗世(J_3SQ1和J_3SQ2)的古地形。J_2SQ1时期盆缘隆起连片,东部隆起已初具雏形,东部隆起两侧形成了两个凹陷区;J_2SQ2时期东部隆起扩大,成为坳中隆起,隆起两侧的凹陷区加深,北部的凹陷逐渐转变为主凹陷区;J_3SQ1时期东部隆起两侧凹陷继续加深;J_3SQ2凹陷区抬升,盆地整体沉积面积比前期略有减小。构造古地形控制了沉积物搬运和堆积。古隆起、古斜坡是沉积物通道,控制砂体的堆积和分布,其中陡坡带发育冲积扇和扇三角洲沉积,而缓坡带发育河流和三角洲沉积;古凹陷是沉积物的堆积场所,一般发育水下扇和湖泊沉积。东部隆起作为坳中隆起,不仅分隔了凹陷区,且成为重要的物源区。

Jurassic palaeotopography and sedimentary system distribution in eastern sag of North Yellow Sea Basin

The eastern sag of North Yellow Sea Basin experienced complicated multi-stage tectonic evolution, and the palaeotopography of the sedimentary basin controlled the provenance, sedimentary area, direction and mode of sediment transportation. The palaeotopography of Middle Jurassic and Late Jurassic in the eastern sag was reconstructed by the calculation of denudation, the original sediment thickness and tectonic subsidence of a single well. In the J2SQ1 period, the basin edge uplift became contiguous and the eastern uplift was emerging with two depressions formed on both sides of it. In the J2SQ2 period, the eastern uplift expanded and became a central uplift in the sag, with the depressions on both sides of the uplift deepened, and the depression in the north gradually became the main depression. During the J3SQ1 period, the depressions on both sides of the eastern uplift continued deepening. In the J3SQ2 period, the depressions were uplifted, and the depositional area of the whole basin slightly decreased. Tectonic topography controlled the sediment transportation and accumulation. The paleo-uplift and paleo-slope are the depositional passway, which controlled the accumulation and distribution of sand bodies. Alluvial fan and fan delta were developed in the steep slope, while the fluvial and delta deposits were developed in the gentle slope. The depression area was the accumulation site of sediments, with underwater fan and lake developed. The eastern uplift, which was an uplift in the central of the sag not only separated the depressions, but was also a provenance.