Abstract:

Pingliang Formation of Middle Ordovician developed only in west and south margins of Ordos Basin in North China Platform.Two kinds of gravity flow deposits,carbonate and elastic rocks developed in the formation.The carbonate gravity flow deposits include debris flow deposits (mainly breccialimestone),turbidites(mainly calcarenite) and grain flow deposits(echinoderm-elastic grainlimestone).Clastic gravity flow deposits are mainly turbidity flow deposits,consisting of conglomerate and sandstone.The formation and distribution of the gravity flow deposits were governed by simultaneous faulting and sedimentary framework.The latter includes four types:1.fracture-grabon; 2.fracture-slope; 3.platform-slope;4.platform-graben.The simultaneous fault is both an important factor in the formation of slopes and the source province of the gravity flow.Down along the slopes,collapse,slump,debris flow(and gravity flow), high and low density turbidity flow deposits occur sequentially.There are different complexes of simultaneous faults,and in turn differentia of gravity flow deposits and various sedimentary frameworks in the region.The gravity flow deposits are potential important hydrocarbon reservoirs.