In North America (say, Iowa) most Mesozoic and Cenozoic sediment deposited was (a) marine.
(most Mesozoic and Cenozoic sediment; deposited; ) (most Mesozoic and Cenozoic sediment; was (a); marine)
most Mesozoic and Cenozoic sediment most Mesozoic and Cenozoic sediment
deposited was (a)
marine