STRUCTURAL DEFORMATION CHARACTERISTICS OF THE KALPIN THRUST BELT ON THE NORTHWESTERN MARGIN OF THE TARIM BASIN

The Kalpin thrust belt,located at the NW margin of the Tarim basin,is a part of the southern South Tianshan marginal thrust system.On the basis of field investigation and seismic section interpretation,the Kalpin thrust belt has the following structural deformation characteristics: the thrust belt occurs in Paleozoic strata;the major detachment fault occurs in a Middle Cambrian gypsum-salt layer;the thrust sheets are imbricate;various thrust fronts are subaerially exposed;fault propagation folding and piggyback thrusting are found;and the thrust belt formed during the Pliocene-Holocene.According to the reconstructed balanced section,the minimal shortening rate of the thrust belt is 29.1%—40.7%.