CAMBRIAN TRACE FOSSILS FROM THE PARAIHO FORMATION (TETHYAN HIMALAYA) IN ITS TYPE SECTION AND ELSEWHERE

Trace fossils newly recovered in situ and from talus in sections of the Parahio Formation at its type location in Spiti and in Zanskar confirm the occurrence of ichnofossils at multiple horizons within the second and third Series of the Cambrian System. Their occurrence is consistent with other records in Cambrian rocks worldwide, and with the palaeoenvironmental interpretation for this formation based on physical sedimentology. The trace Ctenopholeus kutcheri is recorded for the first time in the Himalayan Cambrian. The occurrence of Psammichnites gigas in Zanskar constrains the lower part of the Parahio Formation in that region to be no older than late in the Terreneuvian (series 1) and no younger than series 2 of the Cambrian System, a result which is also consistent with the trace fossils and trilobites at the base of the Parahio Formation in the type section in the Parahio Valley. All body and trace fossils yet recorded from the Parahio Formation occur significantly above the Precambrian/ Cambrian boundary. With the exception of P. gigas and Astropolichnus, no Himalayan Cambrian trace fossil described to date aids in refining the Cambrian biostratigraphy of the Himalaya, because the stratigraphic ranges of these forms elsewhere extend beyond the Cambrian System. In fact, most trace fossils found in Cambrian rocks provide only coarse biostratigraphic resolution, indicating Phanerozoic or Palaeozoic age, and require other kinds of chronostratigraphic data to constrain their stratigraphic positions more exactly. The recent claim that trace fossils localize the position of the Precambrian/Cambrian boundary in the Parahio Valley is refuted.