RALVAWNG PUK

Herbert Daniel Gebauer - 06/01/2018

A 110 m long rift in tectonically dislocated Tertiary (Oligocene to Pliocene) Surma Mudstone. SITUATION: The cave entrance lies at a linear distance of 4.5 km east-north-east of Biate (Inspection Bungalow: N23°14'32-: E93°07'20-: circa 1350 m) and below the abandoned Ralvawng village (N23°15'13-: E93°09'50-) on the north-eastern flank of a hill with the same name. CAVE DESCRIPTION: A flat and wide, almost rectangular entrance (5 by 1 m) lies a few metres up in a north-east facing cliff and gives access to a slightly ascending (+03°) rift cave passage (0.9 to 1.5 m wide, 0.4 to 2 m high) which is occasionally obliterated by collapse debris resulting in crawls or squeezes. At a distance 107 m from the entrance a fallen slab stands guard by a tight (0.2 m) gap which is perhaps penetrable by exceptionally flexible, slim and dedicated explorers. At some places separate wedged rocks and perched floors of compacted debris the solitary passage into two levels, each exactly above the oher and both flanked by the same rock faces. The cave floor is covered by loose sediment (sand, rocks) and the ceiling extends, occasionally bulging out, into the shale above or reveals the compact overlying band of mudstone which is not marked by a crack. Concretions (secondary calcite deposits) are completyly absent. The rock surfaces exposed in the cave are devoid of forms indicating erosion or corrosion. Neither abrasion by drainage nor corrosion (karst, solution and/or redeposition of calcitic matter) appears to have contributed to the cave development. Without any doubt the cave came into being when tectonical forces bent the 2 m thick and friable mudstone host rock which is sandwiched in between marly shales. The solitary and linear rift passage is probably aligned or parallel to the axis of an anticline or syncline. CAVE LIFE: Fungus gnats (Diptera: Mycetophilidae), about ten bats (Chiroptera: Microchiroptera: rhinolophus var.), traces of porcupine (Hystrix bengalensis Blyth?,in Mizo: sakuh) and fungi (clavicula type) on bat guano.