March 18 Field Trip to Examine Ancient Fault Zones Near Nashville, TN
Geoenvironmental Challenges first peer-reviewed publication is in press! The field guide paper is being published in conjunction with the 2015 Geological Society of America Southeastern Section Meeting. Geoenvironmental Challenges mentor Dr. Mark Abolins will lead a related one-day field trip on March 18, 2015.____________________________________________________________________________________________________________________________________________________________________________
A Road Guide to the Harpeth River and Stones River Fault Zones
on the Northwest Flank of the Nashville Dome, Central Tennessee
2015 Geological Society of America Southeastern Section Meeting
Pre-meeting field trip
One-day field trip: 18 March, 2015.
Early Registration Deadline: 17 February, 2015.
Mark Abolins1, Shaunna Young2, Joe Camacho3,**, Mark Trexler1,***, Alex Ward1,****, Matt Cooley1,****, and Albert Ogden1
1Department of Geosciences, Middle Tennessee State University, Murfreesboro, TN 37132
2Geology Department, Radford University, Radford, VA 24141
3Environmental Science and Management, Humboldt State University, Arcata, CA 95521
**Current address: IslandWood, 4450 Blakely Ave., NE, Bainbridge Island, WA 98110
***Current address: Environmental Sciences Corporation Lab Sciences, 12065 Lebanon Road, Mt. Juliet, Tennessee 37122
****Current address: Center for Earthquake Research and Information, University of Memphis, Memphis, Tennessee 38152
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 approx. 30 km south of downtown Nashville. The Harpeth River fault zone has an across-strike width of approx. 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-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 approx. 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 Tennessee-840.
Figure 1. Location of stops (numbered 1-6) and index of figures in relation to Tennessee 840, the Harpeth and Stones Rivers, hypothetical basement faults, the approximate axis of the Nashville Dome (Wilson and Stearns, 1963; Stearns and Reesman, 1986), and the epicenter of the 8 July, 2001 M2.6 earthquake. All faults are high-angle normal faults, and all are east-side-down except for the Peytonsville fault which is west-side-down. Inset shows location in relation to Nashville, Tennessee, and the rest of the eastern United States. PF-Peytonsville fault, AFZ-Arno fault zone, MFZ-McDaniel fault zone, and SRFZ-Stones River fault zone. The McClory Creek fault zone (MCFZ) is at Stop 3 and is too short to depict at this scale.
Figure 2. An east-side-down minor normal fault at Stop 2. See Figure 1 for location of Stop 2.
Figure 3. Groundwater dye traces near the hinge of the Stones River syncline (SRS) and the hypothetical Stones River fault zone (SRFZ). See Figure 1 for location.