Evidence for Cenozoic topographic rejuvenation associated with the Laurel Creek Lineament in the Spruce Pine 7.5-minute quadrangle, western North Carolina, USA

ABSTRACT Linear fracture systems that strike obliquely to rock units occur across western North Carolina and are associated with Cenozoic topographic rejuvenation of the region. A 2005 earthquake on fractures within one of these systems, the Laurel Creek Lineament, suggests it's an active system. Geologic mapping of the Spruce Pine 7.5-minute quadrangle was conducted to document fault kinematics on this lineament. Near-vertical joints and faults are exposed throughout the quadrangle and dominantly strike toward 080°/260°. Fault offsets were centimeter to meter in magnitude. Fault slip indicators suggest the north block moved up relative to the south block, supported by stream knickpoints that indicate disequilibrium on the northern block. Previous studies on the Boone Lineament, north of Spruce Pine, showed that fracture system moved with the south side up. These data indicate the block of crust between the Boone Lineament and the Laurel Creek Lineament has been uplifted by these fracture systems.


Introduction
Rocks exposed in the southern Appalachians record three mountain-building events associated with the assembly of Pangea, giving it a protracted and complicated tectonic history (e.g.Hatcher, 2010;Hibbard, 2000).The first event involved the accretion of an island chain onto Laurentia during the Ordovician Taconic orogeny (e.g.Abbott & Raymond, 1984).This was followed by the Silurian-Devonian Neoacadian orogeny during accretion of the Carolina terrane.The last was the Paleozoic Alleghanian orogeny, where Gondwana collided with North America culminating in the Pangea supercontinent.The Burnsville fault is an example of a Neoacadian fault in western North Carolina, known as a highgrade dextral strike-slip shear zone exposed between Burnsville and Waynesville, North Carolina (e.g.Trupe et al., 2003).This fault, and others that resulted from these orogenies, strike dominantly NE-SW.Rifting of Pangea during the Triassic left behind NE-SW oriented extensional faults and basins as the eastern margin of North America developed into a passive margin (e.g.Frizon de Lamotte et al., 2015).
Geomorphological and structural evidence suggests that topographic rejuvenation has occurred along the belt of high elevation within the Blue Ridge Mountains of western North Carolina and the Valley and Ridge of Virginia, USA (e.g.Hill, 2013Hill, , 2018;;Spotila & Prince, 2022) (Figure 1).In western North Carolina, there are various sets of linear topographic lows known as lineaments that have faults and fractures that strike obliquely to the NE-SW structures associated with the formation and rifting of Pangea, indicating that these lineaments are younger.Previous studies suggest that these fracture systems have accommodated topographic rejuvenation (Hill, 2013(Hill, , 2018) ) (Figure 1).Hill (2013) found that the Swannanoa Lineament (Figure 1), which is exposed from Fontana Lake, east through Asheville and Swannanoa, contains abundant joints and faults that strike E-W, oblique to the structures that are attributed to the assembly of Pangea, thus are considered to be unrelated.The Boone Lineament (Figure 1) contains a brittle fracture zone that overprints the older Linville Falls thrust fault (Hill, 2018).The brittle faults on this lineament are near vertical and exhibit normal and thrust motion, all with south side up fault motion.Stress tensors associated with these faults are oblique to the Paleozoic faults in this area implying that these brittle faults are younger.Hill (2018) argues that hook-shaped streams on the south block of the lineament show river capture associated with south side up motion and uplift.Hill (2013) used knickpoint data collected from stream profiles across western North Carolina to propose a relative chronology of uplift of the blocks bound by the lineaments (Figure 1).The study showed the block between the Swannanoa and Laurel Creek Lineaments had no preserved knickpoints, suggesting that it records the oldest uplift as they have eroded away.The block south of the Swannanoa and west of the Franklin Lineament uplifted next as the knickpoints are higher in elevation.Finally, the youngest two blocks, the block south of the Swannanoa Lineament and east of the Franklin Lineament (including the Cullasaja River basin from Gallen et al., 2011Gallen et al., , 2013)), and the block south of the Boone Lineament (north of the Laurel Creek Lineament), appear to have uplifted synchronously in the late Miocene, as evidence shows these blocks have higher elevations and knickpoints lower downstream.
These fracture zones appear to have some seismic activity (Hill, 2013) (Figure 1).In 2005, an earthquake occurred in Hot Springs, North Carolina, along the Laurel Creek Lineament which shows that this is an active system (Figures 1 and 2).In 2020, Sparta, North Carolina, faced a 5.1 magnitude earthquake that also occurred along an E-W oriented lineament system (e.g.Figueiredo et al., 2022) (Figure 1).
The Laurel Creek Lineament extends east from Hot Springs to Spruce Pine, North Carolina (Figure 1).Near Spruce Pine, it cuts through medium to high-grade metamorphic rocks of the Ashe Metamorphic Suite (AMS), which originated as sediment on the Iapetus ocean floor prior to the Taconic orogeny, and the Silurian-Devonian Spruce Pine Plutonic Suite.While the topography suggests that the lineament extends through Spruce Pine, it has not been previously mapped.This study was conducted to: (1) test the hypothesis that the Laurel Creek Lineament extends through Spruce Pine as suggested by the topography, (2) constrain the kinematics of fractures in the lineament, and (3) evaluate its role in topographic rejuvenation of this region.Geologic mapping in the field and from high resolution elevation models was used to constrain the locations of fractures and their kinematics.Fault kinematics were supported by identifying knickpoints along streams north and south of the lineament.Bedrock was mapped in addition to the fractures because lithology can control topographic relief and knickpoint development.

Topographic rejuvenation
There have been numerous hypotheses for the mechanisms that accommodated topographic rejuvenation within the Appalachians including: (1) isostatic uplift of a thick crustal root, (2) dynamic support from the mantle, and (3) delamination of the lower crust (Spotila & Prince, 2022 provide an extensive overview).Spotila and Prince (2022) point out that evidence for these mechanisms often overlap and our current tools cannot always distinguish which mechanism contributed to a particular structure.
Numerous studies have identified evidence for a crustal root below the Appalachian Mountains, necessary for a modern elevated landscape due to isostatic uplift (e.g.Spotila & Prince, 2022).Seismic and gravity studies suggest that a crustal root as thick as 57 km lies under the Blue Ridge Mountains (Biryol et al., 2016;Hawman et al., 2012;Hopper et al., 2016;Wagner et al., 2012Wagner et al., , 2018)).It is unclear if the crustal root has contributed to the elevated modern landscape of the Blue Ridge Mountains.This is because the root identified in these studies extends outside of the zone of high topography in this region and is not directly correlated with high topography.
As opposed to uplift that has occurred since the Paleozoic and Triassic tectonic events due to isostatic uplift, other studies suggest that the modern landscape is elevated due to Cenozoic uplift (e.g.Conrad et al., 2004;Liu, 2014Liu, , 2015;;Moucha et al., 2008;Rowley et al., 2013;Moucha & Ruetenik, 2017).One mechanism to accommodate this includes dynamic support from the mantle.Models for mantle convection under the southern Appalachians have been used to suggest up to 100 m of topographic uplift would have occurred during the Cenozoic (e.g.Moucha et al., 2008;Rowley et al., 2013;Moucha & Ruetenik, 2017).Other studies have suggested that lithospheric flexure of the Appalachians resulted from subsidence associated with the subduction of the Farallon slab (Conrad et al., 2004;Liu, 2014Liu, , 2015)).Much like the arguments for a crustal root cause, it is unclear if the mantle has contributed to the elevated modern landscape in the Blue Ridge Mountains because the structures identified in these studies do not directly correlate with the high elevation of the Blue Ridge.Regardless, Spotila and Prince (2022) do not rule out that any of these mechanisms could have contributed at least in part to the modern high relief and elevation.
Other models involve the mantle as well but invoke delamination of the lower crust.Biryol et al. (2016) modeled cold slabs at varying depths within the mantle under the Appalachians which they suggest could be lithospheric drips or delaminated lithospheric slabs.Detachment of a lithospheric slab would result in uplift of the crust above.Cold crust identified in this study overlaps with the higher elevations of the Blue Ridge Mountains but extends beyond, making this mechanism unclear.The most directly correlated mantle structure is from Hill (2018).This study shows a cold slab within the mantle that directly lies beneath the high elevations of the Blue Ridge at 240 km depth.While other mechanisms may be at play across the Appalachians, due to the proximity of the Blue Ridge Mountains above this slab, Hill (2018) argues that delamination of this slab at least in part contributed to the Cenozoic uplift of the mountains.
Evidence for Cenozoic topographic rejuvenation occurs throughout the Appalachians.Berti et al. (2015) document stream terrace and river channel patterns that record uplift consistent with the location and kinematics of the M w 5.8 2011 Mineral, Virginia, earthquake.There work suggests that there has been continued deformation in this region resulting in several meters of uplift over many millennia.Gallen et al. (2011Gallen et al. ( , 2013) ) constrained the elevations and locations of knickpoints on streams in the Cullasaja River basin, between the Franklin and Tuckasegee Lineaments (Figure 1), and showed that landslide frequency, channel steepness, and relief increase relative to the landscape above the highest knickpoints.They argue that this records landscape disequilibrium and erosional retreat during topographic rejuvenation, with relict landscapes preserved above the highest elevation knickpoints.Modeling of erosion rates indicates that relief has increased by >150% since at minimum 17.6-4.6Ma, incompatible with topographic rejuvenation associated with climate change alone (Gallen et al., 2013).They argue that their data supports a model of mantle driven regional uplift.Timing of uplift in the Cullasaja River basin is compatible with increased sedimentation rates and grain sizes from the Appalachians to the Atlantic margin and Gulf of Mexico at 16-12 Ma (e.g.Poag & Sevon, 1989;Galloway et al., 2011).These studies support a model of topographic rejuvenation that occurred within the Cenozoic, not associated with the Paleozoic and Triassic tectonic events.

Previous geologic mapping of the Spruce Pine quadrangle
The Spruce Pine quadrangle was by Brobst (1962).Their map incorporated field data from a previous study that mainly focused around the granodiorite and pegmatites of the plutonic suite (Olson, 1944).These studies mapped rocks of the AMS along with the Spruce Pine plutonic suite.Away from the intrusive units, structural data are sparse because mapping was not conducted at the 1:24,000 scale.
A more recent study mapped the Crabtree-Penland fault zone in the southwest portion of the quadrangle to document the cause of chloritized rocks of the AMS, which occur in mylonite (Borella, 2000).The mylonitic fault zone was constrained as late Alleghanian in age.They reported some NW-SE trending faults that all postdate folding and determined that the fractures were unrelated to the Alleghanian fault zone.These studies were foundational in documenting the Paleozoic geologic history but did not address the brittle faults and joints in this quadrangle, and thus their contributions to Cenozoic uplift is unclear.

Methodology
Rock type and structural data of foliations, joints, and faults in Spruce Pine quadrangle (Figure 1) were collected in the field with FieldMove on an iPad over the summer of 2021.Every road or trail accessible was traversed.Rock outcrops were found along the trails, roads, and on private property when granted access.The unmapped portion at the north of the quadrangle was inaccessible so was not mapped (supplementary map).To aid in identifying the location of rock outcrops or fractures, 1-m per pixel resolution LiDAR elevation data was used.This data is publicly available through the North Carolina Risk Management Offices Spatial Data Download portal at https://sdd.nc.gov/.At all outcrops that could be accessed, the rock type and orientations of the foliation, fractures, faults, and fault striations were documented where present using an iPAD equipped with FieldMOVE and GPS.GPS locations were logged for each location.Horizontal accuracies for the GPS coordinates were ∼3-5 m.
Rock contacts previously mapped by Brobst (1962) and Borella (2000) were remapped or more precisely constrained with the addition of more field data.These were used to construct a geologic map at a 1:24,000 scale (supplementary map).The map was overlain on a United States Geological Survey (USGS) topographic base map using the UTM Zone 17S projection and the NAD83 datum.Standard USGS geologic map colors, symbols, and designs were used.
The LiDAR data were also used to construct elevation profiles for streams that drain into the lineament.Flow accumulation and direction tools in ArcGIS Pro were used to distinguish stream locations.Stream profiles were created for Bear Creek, Beaver Creek, and Gouges Creek which all drain south into the lineament (refer to supplementary map for locations).Profiles were also constructed for Graveyard Creek, Rockhouse Creek, and Cathis Creek which drain north into the lineament (refer to supplementary map for locations).Stream profiles were created using ArcGIS Pro.Knickpoints were manually identified from the profiles and their elevations were extracted from the graphs.Knickpoints observed with proximity to lithologic contacts were removed from the data set.Those associated with anthropogenic processes such as dams and road crossings, identified from the LiDAR data or in the field, were also removed from the data set.

Rock unit descriptions
The units in the field area include granodiorite and pegmatite of the Silurian-Devonian Spruce Pine plutonic suite and metagraywacke, schist, gneiss, amphibolite, and dunite of the Neoproterozoic AMS (refer to supplementary map).

Spruce pine plutonic suite
Pzg includes granodiorite which is medium to coarsegrained and dominantly composed of quartz, plagioclase feldspar, and muscovite.Less abundant are garnet, biotite, tourmaline, and REE minerals, although garnet is locally abundant in some outcrops.Earlier maps show this unit as alaskite but the composition of the unit is more accurately called granodiorite.Pzp consists of coarse to large-grained pegmatite dominantly made of quartz, plagioclase feldspar, and muscovite.Rare occurrences of thulite and phrenite were observed.Epidote was found mineralized within joints throughout Pzg and Pzp.
Zacs is a dark gray to green, medium to coarse grained, foliated biotite schist and gneiss.Much of the biotite is retrogressed to chlorite.um is a dunite with retrograde talc and serprentine.Zas is a light to dark gray, medium to coarse grained, foliated schist with muscovite, biotite, garnet, kyanite, and hornblende.Zsps is light to dark gray, coarse-grained schist with muscovite, biotite, quartz, feldspar, and garnet.Coarse grained micas and shear textures such as S-C fabrics and ∼1-5 cm rotated porphyroclasts are distinctive of this unit.Zmg contains biotite gneiss and mica gneiss.The biotite gneiss is dark gray, foliated, fine to medium grained with biotite, quartz, feldspar, and lesser garnet or hornblende.The mica gneiss is light to medium gray, fine to medium grained, foliated, and is composed of muscovite, biotite, quartz, feldspar, and garnet.Zaa is dark gray to black, fine to medium grained, foliated amphibolite composed of hornblende, quartz, plagioclase, with some garnet and epidote.
Zaa, Zsps, and Zmg are frequently interlayered together.Brobst (1962) mapped most of the rocks in the southeastern portion of the quadrangle as Spruce Pine schist and amphibolite.However, our observations are that the schist here is finer grained and more quartzofeldspathic than Zsps and were more like Zmg.

Structural observations
The Laurel Creek Lineament which crosses through Spruce Pine is an E-W trending lineament that can be seen throughout the quadrangle by joints and faults (Figures 3 and 4, supplementary map).Jointing was documented throughout the field area, but it was more pronounced in more competent units like Zaa, Zmg, and Pzg (e.g. Figure 3(a)).Fractures are dominantly oriented E-W.Five faults had evidence of north side up faulting and strike E-W (Figures 3(b,  c), and 4).While most of the fractures were near-vertical joints or dip-slip faults, one shallow thrust fault was identified with the hanging wall up toward the north (Figure 4(a, d)).This thrust fault cuts through E-W oriented joints and cataclasite that also exhibits north side up motion (Figure 4(b)), suggesting multiple episodes of north side up fault motion occurred.
Orientation measurements (n = 258) were taken from joints and faults in the quadrangle.Poles to the planes were plotted on a stereonet and represented on a rose diagram (Figure 5(a)).These data show that the dominant orientation of the joints and faults was toward 260°or 080°.Poles to the foliation planes were also plotted on a stereonet to interpret the dominant orientation (Figure 5(b)).The dominant foliation orientation is 043°with a dip of 11°toward the SE.

Stream knickpoints
Knickpoints discordant with lithologic contacts and anthropogenic disturbances (n = 24) were identified on streams flowing south into the lineament (Figures 6  (a) and 7).The elevations of these knickpoints ranged from 782 to 1071 m, with peak frequency at 867 m (s.d.70 m).A strong cluster (50%) of these knickpoints was found between 825 and 875 m.Streams on the south side of the lineament did not exhibit knickpoints associated with topographic disequilibrium (Figure 6(b)) and all were associated with anthropogenic disturbances or lithology.Lithology controls are most notable along Graveyard Creek where two knickpoints occur within Pzg, bounding a lens of weaker Zsps (Figure 6(b)).

Laurel Creek Lineament
The Laurel Creek Lineament is one within a group of lineaments in western North Carolina responsible for the Cenozoic rejuvenation of the Blue Ridge Mountains.The lineaments are perpendicular to the Appalachian Mountains with an approximate E-W orientation.Paleozoic and Triassic fault systems are generally NE-SW oriented, suggesting that the stresses that produced the lineament fractures are not the same stress that caused the faults during   the assembly and subsequent rifting of Pangea (Hill, 2013).
The rocks within the Spruce Pine quadrangle specifically contains various sets of joints and faults, more densely located around the lineament with a mean strike of 260°or 080°, parallel to the Laurel Creek Lineament (Figure 5).The dominant foliation orientation was 043°/11°dipping toward 133°(Figure 5).The fractures parallel to the Laurel Creek Lineament support that these are associated with the lineament.The orientations of the fractures are oblique to the foliation, supporting the interpretation that the fracturing is not associated with the older Paleozoic orogenies that produced the foliation and are younger, consistent with previous findings along the Boone fault (Hill, 2018).
Fault slip indicators including steps on the fracture face, offset rock units, and tension gashes all show north-side up fault motion on the faults (Figures 3  and 4).The presence of knickpoints that are not correlated to lithology occur only within the block north of the lineament, not the southern block, supporting north-side up fault motion.This combined with the fact that there are currently active retreating knickpoints supports Cenozoic motion on these faults.Callahan et al. (2019) shows that the lack of sediment supply can result in knickpoints that are in stasis and not retreating, even when topography is in disequilibrium.The consistency in knickpoint elevations across drainages here supports our interpretation of active retreat.
All knickpoints with proximity to lithologic heterogeneities were removed.This combined with the strong cluster in knickpoint elevations between 825 and 875 m supports our interpretation that the knickpoints are associated with a change in base level.Base level can be changed by uplift of the topography or river capture.Johnson (2020) documented stream pathways and paleo-river deposits that show capture of streams that previously flowed into the North Toe River by the Linville River in western North Carolina, southeast of the Spruce Pine quadrangle.This capture increased the flow into the Linville River, resulting in the downcutting within the Linville Gorge (Figure 1).This example shows the controls that river capture can have on the evolution of a river system.
To further support that knickpoints on the streams in the Spruce Pine quadrangle are not associated with river capture or lithologic heterogeneities, elevations of all land north and south of the lineament were compared.Pzg and the AMS occur both north and south of the lineament within the quadrangle.Pzg as a granodiorite is relatively more resistant to erosion that the AMS, creating knickpoints along streams where these heterogeneities occur, as expressed along Gouges Creek (Figure 6(a)).However, if lithology alone explained the erosional expression in the map area, then elevations north and south of the lineament should be similar.Figure 8(a) shows that the surface north of the lineament is on average 100 m higher than the surface south of the lineament.Within Pzg alone, the land north of the lineament is 70 m higher than south of the lineament (Figure 8(b)).Similarly, the surface composed of the AMS north of the lineament is 100 m higher than to the south (Figure 8(c)).This  demonstrates that lithology alone does not explain the elevation differences north and south of the lineament.
Additionally, if the knickpoints in this map area are associated with a river capture event we would expect to see erosional retreat of knickpoints on the north and south blocks as both drain into the same river system.This is not the case suggesting that a 70-100 m uplift of the north block best explains the topographic expression.

Lineament chronology
Topographic uplift throughout the Cenozoic occurred by shifting of crustal blocks bound by the lineaments (Hill, 2013) (Figure 1).Streams that flow north into the Laurel Creek Lineament do not exhibit disequilibrium while those on the north side of the lineament do.These data are consistent with previous research that suggests the block south of the Laurel Creek Lineament records an earlier uplift history than other blocks in western North Carolina (Hill, 2013(Hill, , 2018) ) (Figure 1).
The Boone fault, within the Boone Lineament, moved with the south side up (Hill, 2018).Findings from this study show that the Laurel Creek Lineament moved with the north side up.This suggests that the crust between this lineament and the Boone Lineament uplifted as a block by motion on these two lineaments.Major slope breaks along streams that drain into the Boone Lineament occur 200-400 m above the valley floor (Hill, 2018).The knickpoints in the Spruce Pine quadrangle are ∼30-300 m above the valley floor.The similarity in elevations of knickpoints on the south side of the Boone Lineament and the north side of the Laurel Creek lineament may indicate that they moved during a similar timeframe.However, this interpretation is based on similarity in elevations alone and more evidence is needed to understand the evolutionary history.Regardless, these data suggest that this block is likely the most recent to experience uplift.

Conclusions
This study within the 7.5-minute quadrangle of Spruce Pine, North Carolina determined that joints and faults associated with the Laurel Creek Lineament extend into this quadrangle.Joints and faults dominantly strike toward 080°/260°, parallel to the topographic lineament.Faults contained fault slicken lines that exhibited north side up motion with offsets ranging between cm to m scale.Elevation differences north of the lineament versus south suggests the north block uplifted by ∼70-100 m.These findings add to previous constraints on the Boone and Swannanoa Lineament and suggest lineaments are young fracture systems with fault motion contributing to topographic rejuvenation the region.Additional work to constrain timing and direction of fault motion on the other lineaments will provide a spatial and temporal history of the evolution of uplift in the Blue Ridge Mountains.

Software
Data was collected in the field using an iPad equipped with FieldMOVE by Petroleum Experts.All GIS data was processed and analyzes using ArcGIS Pro by ESRI.Final figures and products were assembled using Adobe Illustrator.Stereonet plots and rose diagrams were produced using Stereonet 11 (https:// www.rickallmendinger.net/stereonet).

Geolocation information
The main map is located in western North Carolina, USA.It contains the Spruce Pine quadrangle between latitude 36°N and 35°52 ′ 30 ′′ N and longitude 82°7 ′ 30 ′′ W and 82°W.

Figure 1 .
Figure 1.Lineaments and associated fractures in western North Carolina (red) with earthquakes from 1916 to 2023 (USGS).The black rectangle shows the Spruce Pine 7.5-minute quadrangle.SM, Smoky Mountains; BM, Black Mountains; BRE, Blue Ridge Escarpment; LR, Linville River.The inset map shows the location of western North Carolina within the lower U.S. and the elevated topography of the Blue Ridge (dotted line).Elevation data is from the USGS.

Figure 2 .
Figure 2. (a) Rose diagram of joints from the Laurel Creek Lineament from Hill (2013).(b) Focal mechanism of the 2005 3.7 M earthquake in Hot Springs, North Carolina from the USGS.
Figure 3(b) shows an example of one of the faults.It exhibits a 48 cm offset within semi-saprolitic Zsps.Offset rock units at this outcrop indicate the north block moved up along a high angle dip-slip fault.This fault strikes 270°.Tension gashes were also observed near the fault also indicating north side up (Figure 3(c)).

Figure 3 .
Figure 3. (a) Near vertical joints within Zaa that strike toward 260°.(b) Steep dip-slip fault with 48 cm of offset with north block up.The star is the location of (c).(c) Tension gashes, shear sense noted as black arrows.

Figure 4 .
Figure 4. (a) Near vertical joints, cataclasite, and faults indicating three brittle deformation events within Zaa, the first on the joints, second on the cataclasite (b and c), and third on a shallow thrust fault (d).The dashed line highlights foliation.(b) Fault striations on a fracture at the margin of the cataclasite (c) show steps indicating north side up slip.The inset stereonet shows the orientation of the fracture plane (black line) and the striation line (black dot).(d) Fault striations on two perpendicular fracture faces on a thrust fault that cuts through the cataclasite (c).The inset stereonet shows the orientation of the horizontal fault plane (black line) and the corresponding fault striation (black dot).

Figure 5 .
Figure 5. (a) Orientations of joints and faults plotted as poles on a stereonet and contoured, red with highest densities and blue with lowest densities.A maximum density shows a dominant strike of 080°/260°.The black bars are a rose diagram of the fracture strikes, also demonstrating this trend.(b) Orientation of foliations plotted as poles on a stereonet and contoured.The red shows where the points are densely concentrated, and the best-fit plane to that orientation is the yellow curved line.Refer to supplementary material for the geologic map.

Figure 6 .
Figure 6.(a) Profiles of south flowing stream systems north of the Laurel Creek Lineament.(b) Profiles of north flowing stream systems south of the lineament.

Figure 7 .
Figure 7. Histogram of knickpoint elevations, identified from the stream profiles.

Figure 8 .
Figure 8.(a) Elevation frequencies of pixels north vs. south of the Laurel Creek Lineament, (b) elevation frequencies of pixels within the granodiorite (Pzg) north vs. south of the lineament, and (c) elevation frequencies of pixels within the Spruce Pine schist (Zsps) north vs. south of the lineament.