A geometric model of faulted detachment folding with pure shear and its application in the Tarim Basin, NW China

We present an improved geometric model of faulted detachment folding with pure shear that is characterized by core thickening and a ramp-discordant backlimb. The model includes a two-stage evolution: 1) detachment folding involving pure shear with fixed hinges, and 2) faulted detachment folding, in which the core of anticline thrusts above a break-through fault in forelimb by limb rotation. The growth strata patterns of the model are also discussed with respect to factors such as limb rotation, tectonic uplift rate, and sedimentation rate. A thrust-related fold, called a TBE thrust fold, in the Tarim Basin in NW China, is analyzed as an example of the theoretical model. The result indicates that the TBE thrust fold has undergone a two-stage evolution with shortening of a few hundred meters. Both the theoretical model and the actual example indicate that the shortening in the detachment folding stage takes up a large proportion of the total shortening. The structural restoration of the TBE thrust fold also provides new evidence that the formation of a series of thin-skinned structures in the SE Tarim Basin initiated in the Late Ordovician. The model may be applicable to low-amplitude faulted detachment folds.