The Annapurna detachment is part of the orogen-parallel extensional South Tibetan detachment system, which extends along most of the length of the Himalaya. It crops out in the Kali Gandaki area of central Nepal, where it juxtaposes the Tethyan sedimentary sequence in the hanging wall with rocks of the Greater Himalayan metamorphic sequence in the footwall.

A five-stage structural evolution for the Tethyan sedimentary sequence is proposed. The first stage is characterized by southwest-verging isoclinal folds (D1). The second stage is represented by northeast-verging megascopic tight folds (D2). These first two stages are transposed in a 1,500-m-thick high strain zone (Dt) affecting the lowermost part of the Tethyan sedimentary sequence and the uppermost part of the Greater Himalayan metamorphic sequence. The high strain fabrics are associated with downto-the-northeast normal shear-sense indicators, which we link to initial ductile shearing along the Annapurna detachment. The fourth stage is postmetamorphic and marks a return to southwest-vergent thrusting and folding (D3). During this stage, parts of the high strain zone were reactivated as localized thrusts. The fifth stage is a brittle event associated with east-west extension along the Thakkhola graben structures. Late top-tothe-northeast brittle normal faults also disrupt rocks within the high strain zone during this stage and could mark the southern termination of the Thakkhola graben. The D2 northeast-verging folds, classically interpreted to be the result of gravitational sliding along the South Tibetan detachment system, clearly predate ductile extensional faulting. This folding phase, which thickened the Tethyan sedimentary sequence, is probably related to an older compressional event. The Annapurna detachment represents a zone of superposed shearing; both normal and thrust shear-sense indicators are preserved.