. ▁▁ ▁Of ▁particular ▁significance ▁for ▁Som al il and , ▁rif ting ▁in ▁the ▁O lig oc ene ▁and ▁Mi oc ene ▁react iv ated ▁Mes oz o ic ▁normal ▁fault s , ▁forming ▁the ▁G ub an ▁Bas in . ▁The ▁bas in ▁is ▁situated ▁within ▁a ▁top ographic ▁high , ▁known ▁as ▁the ▁Som al il and ▁esc arp ment ▁and ▁is ▁filled ▁with ▁up ▁to ▁three ▁kilom eters ▁of ▁Late ▁C ret ace ous ▁and ▁C en oz o ic ▁sed iment ary ▁rocks . ▁In ▁places ▁within ▁the ▁bas in , ▁the ▁Late ▁C ret ace ous ▁Jes om ma ▁sand stone ▁is ▁over lain ▁by ▁the ▁er oded ▁rem n ants ▁of ▁the ▁E oc ene ▁T ale h ▁An h yd rite . ▁The ▁bas in ▁contains ▁sh ale , ▁lim estone , ▁mud stone , ▁sand stone ▁and ▁ev apor ite . ▁ ▁H ydro ge ology ▁Do z ens ▁of ▁spr ings ▁have ▁been ▁in ▁Som al il and , ▁where ▁they ▁are ▁more ▁common ▁in ▁kar st ▁aqu if ers . ▁Most ▁people ▁in ▁Som al il and ▁get ▁their ▁drink ing ▁water ▁from ▁aqu if ers , ▁although ▁poor ▁quality ▁water ▁often ▁means ▁that ▁bore hol es ▁go ▁abandoned . ▁▁ ▁The ▁E oc ene ▁K ark ar ▁Lim estone , ▁Aur adu ▁Lim estone ▁and ▁Ta ale x ▁Lim estone ▁are ▁important ▁kar st ic ▁aqu if ers ▁in ▁Som al il and ▁and ▁P unt land , ▁along ▁with ▁thick