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

Key words: 
• Huimin depression /
• central uplift belt /
• beach bar /
• tempestite /
• depositional model

Abstract: 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 siltstones 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.