The origin and accumulation of oil still remain among the many unsettled problems of the geology of petroleum. The theory that oil source material is sparsely and widely disseminated organic matter in shales and limestones, and that free oil migrates long distances to its final trap, fails to satisfy conditions of most oil pools.

It is suggested that oil source material is accumulations of rich organic matter deposited in restricted areas near to, indigenous to, or in contact with, the reservoir and trap of the present oil pools. It is probable that source material is more closely associated local conditions of sedimentation and environment than has been generally considered. The location of these deposits of rich organic matter is probably controlled by local favorable conditions of sedimentation on the floor of the epicontinental sea, by local favorable climatic conditions, by routes of travel of sea life, by food supply, and by shallow warm water, all these conditions being favorable for the growth, propagation, and accumulation of organic matter. The source material is probably minute organisms of a low or er and perhaps plant spores, all of which left few, if any, fossil remains. Several types of oil occurrences are cited in support of the theory that restricted accumulations of rich organic matter are the source of petroleum, which is in conflict with the theory that widely disseminated organic matter in lean shales and limestones is the source of oil, and with the theory that free oil migrates long distances from its source to the trap.