Professor Birbal Sahni
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Some years later, B. Sahni, then a paleobotanist at the
University of Lucknow, reported the existence of numerous plant microfossils in
samples taken from the Salt Range Formation at the Khewra and Warcha salt
mines. Previously, doubt had been cast on plant fossils from the Salt Range
Formation. Critics, said Sahni, had pointed out that “in such a highly soluble
and plastic substance as the Salt Marl, extraneous material might have
penetrated through solution holes or have been enveloped during relatively
modern earth movements.”
But deep within the mines, Sahni found deposits
where such objections could not apply. The salt in these places ran in layers
separated by thin layers of saline earth, locally called “kallar.” Sahni noted
that “the kallar lies closely interlaminated with the salt, in beds which run continuously
for long distances and which, although visibly tilted, show no other visible
signs of disturbance.”
According
to Sahni,
the salt layers accumulated from evaporation of sea water in coastal
lagoons,
whereas the kallar represented dust and dirt blown on to the drying
salt by the
wind. Sahni guessed that the kallar might contain pollen and other
plant
microfossils. When he examined specimens, he found this to be so:
“Every single
piece has yielded microfossils…The great majority are indeterminable as
to
genus and species, being mainly shreds of angiosperm wood, but there
are also
gymnosperm tracheids with large round bordered pits, and at least one
good,
winged six-legged insect with compound eyes.” To Sahni this meant that
the Salt
Range Formation must be Eocene rather than Cambrian. Sahni later found
plant
fragments not only in the kallar, but in associated solid rock layers
composed
of dolomite and shale.
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