▁either ▁global ▁changes ▁in ▁e ust atic ▁sea ▁level ▁or ▁the ▁super cont inent ▁cycle , ▁the ▁periodic ▁mer ger ▁of ▁all ▁the ▁contin ents ▁into ▁one ▁approximately ▁every ▁ 5 0 0 ▁million ▁years . ▁ ▁H utton ' s ▁Un con form ity ▁H utton ' s ▁Un con form ity ▁at ▁Sic car ▁Point , ▁in ▁county ▁of ▁Ber wick shire ▁on ▁the ▁east ▁coast ▁of ▁Scotland , ▁is ▁an ▁angular ▁un con form ity ▁that ▁consists ▁of ▁g ently ▁di pping , ▁re dd ish , ▁Upper ▁Dev onian ▁and ▁Lower ▁Car bon ifer ous ▁bre c cias , ▁sand st ones , ▁and ▁con gl omer ates ▁of ▁the ▁Old ▁Red ▁Sand stone ▁over lying ▁deeply ▁er oded , ▁near - vertical , ▁grey ish , ▁Sil ur ian ▁( L land overy ) ▁gre yw ack es ▁and ▁sh ales . ▁The ▁L land overy ▁gre yw ack es ▁and ▁gra pt ol ite - b ear ing ▁sh ales ▁of ▁the ▁G ala ▁Group ▁were ▁depos ited ▁by ▁tur bid ity ▁curr ents ▁in ▁a ▁deep ▁sea ▁environment ▁about ▁ 4 2 5 ▁million ▁years ▁ago . ▁The ▁over lying ▁Dev onian ▁str ata ▁were ▁depos ited ▁by ▁rivers ▁and ▁streams ▁about ▁ 3 4 5 ▁million ▁years ▁ago . ▁Thus , ▁this ▁un con form ity ▁reflect s ▁a ▁gap ▁of ▁about ▁ 8 0 ▁million ▁years ▁during ▁which ▁deep ▁sea ▁sed iments ▁were ▁l ith ified , ▁fol ded , ▁and ▁u pl ift