Evaluating Conceptual Plays
109
This play-level geological factor can be considered a parameter to be
estimated from data, or an expression of geological judgment.
White (1980) described a facies-cycle wedge (Fig. 5.1) as a body of
sedimentary rock bound above and below either by a regional unconformity or by the top of a major nonmarine tongue. The ideal wedge
represents a transgressive–regressive cycle of deposition, including,
from base to top, a vertical succession that varies from nonmarine to
coarse-textured marine, to fi ne-textured marine, to coarse-textured
marine, and back to nonmarine facies. Exploration plays located
Figure 5.1. (Continues)