▁sea ▁environment , ▁followed ▁by ▁sh ales ▁and ▁be lem n ite ▁foss ils ▁from ▁an ▁ep ic ont inental ▁sea . ▁ ▁C en oz o ic ▁( 6 6 ▁million ▁years ▁ago - present ) ▁Sed iment ation ▁continued ▁in ▁the ▁C en oz o ic . ▁De position ▁of ▁the ▁Yes om ma ▁Sand stone ▁continued ▁until ▁another ▁regional ▁marine ▁trans gression ▁in ▁the ▁Middle ▁E oc ene . ▁The ▁opening ▁of ▁the ▁G ulf ▁of ▁A den ▁created ▁bra ck ish ▁bas ins , ▁which ▁filled ▁with ▁marine ▁depos its ▁in ▁the ▁Mi oc ene ▁and ▁O lig oc ene . ▁Out cro ps ▁of ▁these ▁rock ▁units ▁are ▁limited ▁to ▁a ▁few ▁coast al ▁areas ▁in ▁Som al il and , ▁but ▁rapid ▁fault ing ▁created ▁off sh ore ▁bas ins ▁with ▁up ▁to ▁two ▁kilom eters ▁of ▁sed iments ▁from ▁the ▁late ▁C en oz o ic . ▁In ▁fact , ▁C en oz o ic ▁sed iments ▁cover ▁much ▁of ▁Som al il and . ▁▁ ▁The ▁formation ▁of ▁the ▁Som ali ▁Pl ate ▁began ▁ 6 0 ▁million ▁years ▁ago ▁and ▁acceler ated ▁at ▁the ▁end ▁of ▁the ▁O lig oc ene , ▁approximately ▁ 2 3 ▁million ▁years ▁ago . ▁As ▁the ▁Arab ian ▁Pl ate ▁and ▁Som ali ▁Pl ate ▁r ift ed ▁apart , ▁forming ▁the ▁G ulf ▁of ▁A den ▁through ▁sea ▁floor ▁spread ing ▁in ▁the ▁Late ▁Mi oc ene ▁mag ma ▁intr ud ed ▁between ▁the ▁two ▁pl ates