GREATER HIMALAYAN GNEISS PRESERVES SEDIMENTARY STRUCTURES – PHENOMENON OR FANTASY?
The type Takhtsang Gneiss, within granulite facies, consists of alternating millimeter bands rich in quartz and biotite, interpreted as silt and clay interlaminations, respectively, in the protolith. This suggests possible tidal deposits or varves. This banding drapes around isolated “lenses” of contrasting and varied compositions, interpreted as dropstones. This combination suggests deposition in a glacial lake. Published comparisons of Takhtsang lithologies indicate a minimum dimension of 315 km for the postulated lake. These examples demonstrate the potential utility of relict sedimentary features in reconstructing geologic history, even in high-grade metamorphic terrains.