A Test Comparison of Orientations of Interpreted Surface Drainage Lineaments and Deep-Subsurface Dipmeter Records in North-Central Louisiana
We examined the sixteen 7.5-minute topographic quadrangle sheets covering this area for straight drainage-course trends, interpreted them at 1:24,000 scale using a length cutoff of 300 m, and summed their measured orientations as a simple (nonlength-weighted) count for each 7.5-minute quadrangle and for all the quadrangles combined. This exercise resulted in an average of ~89 interpreted surface lineaments (range 63119) per individual 7.5-minute quadrangle, and a collective total of 1,422 lineaments for all 16 quadrangles. Rose plots of unaveraged counts prepared in 10° frequency classes for each 7.5-minute quadrangle and for the combined total data set show a very strong trend oriented NW-SE, a strong though weaker trend oriented NE-SW, and much weaker though discernible trends oriented ~N-S and ~E-W. These drainage-course trends show no statistically significant difference from the examined dipmeter subpopulation, except for the NW quadrant when the quadrants are considered separately.