A road guide to the Harpeth River and Stones River fault zones on the northwest flank of the Nashville Dome, central Tennessee

The authors use mesoscale structures and existing 1:24,000 scale geologic maps to infer the locations of four macroscale NNW-striking blind normal faults on the northwest flank of the Nashville dome approximately 30 km south of downtown Nashville. The Harpeth River fault zone has an across-strike width of approximately 6 km, and, from west to east, includes the Peytonsville, Arno, McClory Creek, and McDaniel fault zones. All of the fault zones are east-side-down except for the west-side-down Peytonsville fault zone. Mesoscale structures are exposed within each fault zone and are observed at three stops along Tennessee State Route (S.R.)-840 and at an additional stop 1.8 km south of the highway. These structures include minor normal faults (maximum dip separation 3.8 m), non-vertical joints, and mesoscale folds. No faults are depicted on existing geologic maps of the zone, but these maps reveal macroscale folding of the contact between the Ordovician Carters Formation and the overlying Hermitage Formation. The authors use the orientation and amplitude of these folds to constrain the orientation and length of the inferred blind fault zones and the amount of structural relief across the zones. The longest fault zones are the Arno (13.2 km long) and McDaniel (11.6 km) fault zones, and the amount of structural relief across these zones peaks at 27 m and 24 m, respectively. The authors also use existing geologic maps to hypothesize that a second east-side-down blind normal fault zone (Stones River fault zone) is located approximately 27 km northeast of the Harpeth River fault zone. The authors interpret non-vertical joints at one stop as fault-related, and they interpret joints at a second stop as related to a hanging wall syncline. Both of these stops are within 4 km of S.R.-840.