Figure 7: Bug Field, Paradox Basin, San Juan County, Utah, showing correlation between a producing Pennsylvanian algal mound and a basement block boundary. Red contour lines are Pennsylvanian Desert Creek structure; blue lines are profile residual magnetic contours at 0.5 nT interval. The basement block corresponding to the magnetic high ("H") would have tilted to the south with its north edge (red) upthrown, localizing the algal mound. Structure contours from Krivanek (1981).