Abstract: The configuration of organic matter in marine carbonates has been studied with scanning electron microscope.The globules confirmed as carbon by electron probe are named globular organic matter,a marker of source rock.This study has shown that the kerogen in marine carbonates of sapropelis and mixed type has high hydrocarbon generation potential.Based on the souse and type of organic matter and exploration practice,marine carbonates should be taken as one of important souxce rocks.