Mesoscale structures in Paleozoic strata of the Tennessee western Highland Rim: Insights into distant orogenic events

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ABSTRACT Geologic structures in generally flat-lying strata overlying intracratonic regions commonly reveal relationships to distal stress fields created by orogenic events and clarify continental-scale deformation. Here, mesoscale structures in exposed Paleozoic strata and Precambrian through Paleozoic strata in cores are described in the western Highland Rim, Tennessee, USA, along the Tennessee River. An analysis of linear stream segments was also completed to investigate broad changes in structural grain in the northern part of the study area. The structures range from pervasive systematic fractures to meter-scale folds and faults. The mesoscale structures and the Clifton saddle, a low arch between the regional Pascola Arch and Nashville Dome, are interpreted with regard to stress fields created by Appalachian and Ouachita orogenic events. In most cases, the timing recorded by fracture relationships is ambiguous, but fracture timing at key locations supports the prevailing view that Ouachita far-field stress led to SW-NE fracture initiation and associated folding prior to structure development connected to the Alleghanian (Appalachian) events. Similarly, Mississippian uplift along the Clifton saddle likely represents forebulge development during initiation of the Ouachita foreland basin. Several examples of SE-NW fracture development prior to that of Ouachita deformation argue for lithologic complexities with regard to timing of fracture development as well as potential overlap in timing of the Ouachita and Alleghanian stress fields. Several N-S to SSW-NNE up-to-the-west faults along the Tennessee River are inconsistent with Appalachian and Ouachita events and likely relate to continental-scale propagation of Paleozoic or Mesozoic stress during Rocky Mountain events. Linear stream segment orientations roughly follow fracture trends in the northern part of the study area but commonly are collinear with the axis of the Clifton saddle in the southern part of the study area. The results of the study emphasize the subtle variations in fracture and other mesoscale structure development and the complexities of interpreting their development with regard to distal orogenic events.

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