惠民凹陷中央隆起带沙四上亚段滩坝与风暴岩组合沉积

Composite Deposits of Beach Bar and Tempestite in the Upper Fourth Member of Shahejie Formation in the Central Uplift Belt of Huimin Depression

惠民凹陷沙四上亚段沉积时期,盆地边缘发育三角洲和扇三角洲沉积,受波浪和沿岸流的影响,在中央隆起带滨浅湖区形成了与岸线走向平行或斜交的滩坝砂体和风暴沉积。滩坝沉积成熟度较高,泥质含量少,岩性以中细砂岩和粉砂岩为主,也有少量砾石,砂岩中常见含双壳类化石、生物碎屑和炭屑。滩坝沉积可分为砂坝、砂滩和滩坝间微相,平面上该区滩坝砂体可分为近岸砂滩、近岸砂坝、坝间砂滩、远岸砂坝、远岸砂滩、水下隆起处砂坝和水下隆起处砂滩。此外,受风暴浪的影响,在浪基面和风暴浪基面之间的地带形成风暴沉积,主要由块状层理段、递变层理段、丘状交错层理段、平行层理段和块状泥岩段构成。该组合沉积体系的形成主要受古地形、物源性质、湖平面变化等方面的影响。

The delta and fan delta deposits developed in the period of the upper fourth member of Shahejie Formation in the edge Huimin depression. The beach bars and tempestite which parallel or diagonal to the praya developed in the meare area in central uplift belt on the effect of lake wave and coastal current. The maturity of beach bar is higher and the shale content is short. The lithologic characters are medium-fine sandstones and sihstones mainly, and light conglomerates exist too. The dissoconch fossil, biogenicdebris and charcoal debris are usually observed in the sandstones. The microfacies of beach bar are divided into sandy bar, sandy beach and inter beach bar. The sandstones include nearshore sandy beach, nearshore sandy bar, and sandy beach between bar, infralittoral sandy bar, infralittoral sandy beach, underwater uplift sandy bar and underwater sandy beach plain. The tempestites formed in the belt. of wave based surface and storm wave based surface. They are constituted of massive bedding section, graded bedding section, moundy cross bedding section, parallel bedding section and massive mud section. The formations of the mixed depositional systems are under the control of palaeotopography, provenance and change of lake surface, and so on.