We don't have synonyms for marinite yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are marine, marinate and maritime.
(n) :
(geology) A gray to black oil shale of marine origin in which the chiefmain organic components are lamalginite and bituminite derived from marine phytoplankton, with varied admixtures of bitumen, telalginite and vitrinite
(n) :
(geology) A gray to black oil shale of marine origin in which the chiefmain organic components are lamalginite and bituminite derived from marine phytoplankton, with varied admixtures of bitumen, telalginite and vitrinite