Small 660‐km seismic discontinuity beneath Tibet implies resting ground for detached lithosphere

Using seismic profiles comprising of high‐resolution, triplicate waveforms across apertures of over 1,000 km, we show that because of high P wave speed ( V P ) near the bottom of the mantle transition zone, the contrast in V P across the 660‐km discontinuity beneath central Tibet is small: only about 70% of that beneath the northern Indian shield. This subhorizontal anomaly of high V P is most likely a remnant of detached mantle lithosphere that recently sank to depth, thus providing key evidence for a direct connection between continental collision near the surface and deep‐seated dynamics in the mantle.