Figure 18. Thickness and distribution of Manning Canyon Shale, Doughnut Formation, and Chainman Shale (modified from Moyle, 1958). The Doughnut Shale is the principal source rock for this time slice; however, the Manning Canyon Shale could be a significant source rock if it is preserved in a subthrust position along the edge of the Oquirrh Basin where much thinner Oquirrh Formation would have been deposited.