▁Late ▁C ret ace ous ▁and ▁Pale oc ene , ▁marked ▁by ▁high ▁levels ▁of ▁g amma ▁radiation ▁on ▁logs . ▁ ▁The ▁Pale oc ene ▁is ▁also ▁a ▁carbon ate - sh ale ▁succession ▁with ▁carbon ate ▁build - ups ▁over ▁struct ural ▁high s , ▁forming ▁some ▁of ▁the ▁bas in ' s ▁best ▁res er voir s . ▁Although ▁thick ▁carbon ates ▁exist ▁over ▁the ▁field ▁and ▁other ▁high s ▁in ▁C - 6 5 ▁and ▁surrounding ▁areas , ▁no ▁hydro car b ons ▁were ▁found . ▁Res er voir ▁water ▁is ▁usually ▁fresh ▁or ▁bra ck ish , ▁suggesting ▁fl ushing . ▁Lim est ones ▁were ▁extens ively ▁dol om it ized , ▁resulting ▁in ▁large ▁cav ities ▁and ▁lost ▁circul ation ▁while ▁dr illing . ▁ ▁In ▁the ▁Lower ▁E oc ene , ▁Bas in ▁conditions ▁became ▁restricted , ▁producing ▁an ▁altern ating ▁dol om ite ▁and ▁an h yd rite ▁sequence ▁with ▁a ▁consistent ▁thick ness . ▁The ▁mid - E oc ene ▁saw ▁development ▁of ▁a ▁wide ▁carbon ate ▁platform , ▁rich ly ▁num mul it ic , ▁also ▁constant ▁in ▁thick ness . ▁There ▁are ▁arg il lace ous ▁lim estone ▁inter bed s , ▁mar l , ▁and ▁occas ional ▁cal care ous ▁sand st ones . ▁The ▁Late ▁E oc ene ▁reflect s ▁more ▁frequent ▁later al ▁variations ▁of ▁inter bed ded ▁lim est ones , ▁dol om ites , ▁mar ls , ▁and ▁sh ales . ▁ ▁Rec ent ▁to ▁O lig