ed ; ▁later ▁deeply ▁er oded ▁and ▁weather ed ▁sub a er ial ly ; ▁and ▁finally ▁buried ▁by ▁river ▁and ▁stream ▁sed iments . ▁ ▁Ex pos ures ▁of ▁the ▁un con form ity ▁at ▁Sic car ▁Point , ▁provided ▁James ▁H utton , ▁accompanied ▁by ▁John ▁Play f air ▁and ▁Sir ▁James ▁Hall , ▁the ▁clear est ▁example ▁of ▁an ▁un con form able ▁relationship ▁between ▁two ▁sets ▁of ▁sed iment ary ▁str ata ▁that ▁involved ▁a ▁complex ▁ge ological ▁history . ▁The ▁clear ▁trunc ation ▁of ▁near - vertical ▁Sil ur ian ▁sed iment ary ▁str ata ▁by ▁well - bed ded ▁con gl omer ates ▁and ▁sand st ones ▁belonging ▁to ▁the ▁Upper ▁Old ▁Red ▁Sand stone ▁allowed ▁H utton ▁to ▁demonstrate ▁the ▁existence ▁of ▁significant ▁breaks ▁in ▁the ▁ge ological ▁record , ▁in ▁this ▁case ▁a ▁break ▁separ ating ▁str ata ▁that ▁were ▁then ▁called ▁al pine ▁sch ist us ▁and ▁secondary ▁str ata . ▁This ▁and ▁other ▁un con form ites ▁provided ▁evidence ▁for ▁H utton ' s ▁ideas ▁about ▁the ▁rec y cling ▁of ▁ge ological ▁materials ▁and ▁for ▁un con form ities ▁representing ▁very ▁large ▁time ▁periods ▁He ▁argued ▁that ▁these ▁concepts ▁pointed ▁to ▁the ▁great ▁anti qu ity ▁of ▁the ▁Earth ▁and ▁the ▁vast ness ▁of ▁the ▁ge ological ▁time - scale . ▁ ▁Pow ell ’ s ▁Un con form ity , ▁Grand ▁C any on ▁The ▁Great ▁Un con form ity ▁of ▁Pow ell ▁in ▁the ▁Grand ▁C any on ▁was ▁first