▁evidence ▁of ▁horizontal ▁str esses . ▁ ▁Str at ig raph y ▁ ▁The ▁Sar ir ▁strat ig raph ic ▁column ▁generally ▁res emb les ▁succession ▁patterns ▁throughout ▁the ▁Sir te ▁Bas in , ▁with ▁some ▁variations . ▁In ▁the ▁early ▁re gress ive ▁phase , ▁bas al ▁sand st ones ▁were ▁depos ited ▁on ▁a ▁P rec amb rian ▁bas ement ▁of ▁ igne ous ▁and ▁met am orph ic ▁rocks . ▁Sand st ones ▁are ▁dated ▁on ▁ang ios perm ▁pol len ▁as ▁younger ▁than ▁Alb ian , ▁probably ▁from ▁the ▁Late ▁C ret ace ous . ▁After ▁a ▁length y ▁hi atus , ▁represented ▁by ▁un con form ity ▁and ▁sand stone ▁er os ion , ▁a ▁trans gress ive ▁sequence ▁of ▁red , ▁green , ▁and ▁pur ple ▁An h yd rite ▁sh ales ▁was ▁laid . ▁Var ieg ated ▁bed ▁rem n ants ▁occur ▁in ▁cr est al ▁sections ▁of ▁many ▁northern ▁structures , ▁such ▁as ▁in ▁well s ▁B - 1 - 6 5 ▁and ▁C - 1 - 8 0 . ▁ ▁A bove ▁the ▁trans gress ive ▁sequence ▁are ▁Late ▁C ret ace ous ▁sh ales ▁with ▁tight , ▁mic rit ic ▁carbon ate , ▁mark ing ▁the ▁top ▁of ▁the ▁Mes oz o ic . ▁These ▁sh ales ▁thick en ▁into ▁tr ough s , ▁providing ▁the ▁field ' s ▁sole ▁source ▁rock . ▁The ▁young est ▁fa una ▁are ▁Ma astr icht ian , ▁with ▁an ▁apparent ▁dis con form ity ▁between ▁the