Origin and Sedimentary Features of Two Kinds of Lake Deltas in the Shrinkage Phase of A Half-braben-like Basin

Key words: 
• half-braben-like basin /
• shrinkage phase of lake /
• river-mouth-dam-lake delta /
• Gilbert lake delta

Abstract: Taking the Pingzhuang and Tiefa basins as an example, the authors proposed that the river-mouth-dam lake delta developed in the along-lake belt where the river, locating in one side of the basin boundary fault and in front of the fan, flew into the lake in the shrinkage phase of a versiera shape lake basin . It had similar sedimentary features to the delta controlled by the river of sea-bank. The Gilbert lake delta developed in the along-lake belt where the river, locating in one side of the sediment-erosion basin, flew into the lake. It had vertical-sequences strata composed of bottom-set bed, foreset bed and topset bed, with sand lobe shape. It had no relationship with fan in the origin space. Based on this, the authors discussed geologic setting of two kinds of lake deltas, and, moreover, investigated the origin of their developing conditions and progradational patterns.