REGIONAL FRACTURE PATTERNS IN EOCENE STRATA OF NORTHERN LOUISIANA: CORRELATIONS WITH NEOTECTONIC FEATURES

Three pairs of systematic plateau-style joints have been identified in Eocene-age strata in northern Louisiana. These same patterns are also apparent in stream valley patterns developed within the outcrop area of these strata. Geomorphic evidence of neotectonic activity, including tilted alluvial systems, reversal of alluvial plain slopes, impounded streams, domed peneplains, and recently reactivated river incision, abound. The orientations of neotectonic features identified by river valley deformation, as well as the orientations of large, enigmatic, regional escarpments, correlate with two of these joint pattern trends (005/085 & 025/280). Outcrop relations suggest that the third joint pair (060/325) appears to predate the two neotectonic trends. Thus, the neotectonic activity was apparently preceded by another post-Eocene tectonic event with a distinct stress field.