Telescoping of isotherms beneath the South Tibetan Detachment System, Mount Everest Massif

► Deformation temperatures in the STDS footwall are estimated using quartz fabric opening angles. ► Results are described from three sampling transects on the north side of Mount Everest. ► Linear apparent thermal gradients of 370-420 °C per km are recorded at 0-500 m beneath the STDS. ► Models for this extreme telescoping of isotherms are discussed. ► Telescoping increases towards the south and may indicate dip-slip of 25-170 km on the STDS.