The petroleum possibilities of a region depend on the presence of thick sections of sedimentary rock of favorable facies, preferably marine; on the conditions of sedimentation when the rocks were deposited; and on their subsequent structural history. In assessing the petroleum possibilities of South America these factors have been taken into account in so far as available data permit. The principal sedimentary basins are indicated on maps and the features of each discussed from the point of view of the petroleum geologist.

The survey indicates large areas that are potentially petroliferous, and an attempt has been made to classify them into three groups: (a) most favorable, (b) moderately favorable, and (c) possibly petroliferous but for various reasons less promising than the two preceding groups.

An unexpected result of the study was the suggestion that the eastern half of the great sub-Andean sedimentary trough may hold more accessible oil than the western half. Inaccessibility, unfavorable climate, and dense vegetation cover will retard exploration and development of the sub-Andean belt from northern Bolivia to central Colombia.

For a brief resume of the results of the study see the "Summary" at the end of the paper.