Monday, November 25, 2013

Mine Creek Trail

The Mine Creek Trail begins at the Crabtree Creek Trail greenway, and runs north along Mine Creek, crossing North Hills Drive, then passing beneath Millbrook Road, and then following the east side of the Shelley Lake Loop.  From the northwest corner of the Shelley Lake Loop, it continues north, through a narrow tunnel under North Hills Drive, and then under Lynn Road.  A short distance north of Lynn Road, the paved greenway bends to the northeast and becomes the East Fork Mine Creek Trail, while the Mine Creek Trail bends toward the northwest, continuing as an unpaved and poorly marked trail north to its termination at Sawmill Road.  A portion of the Mine Creek Trail south of Shelley Lake is referred to as the Ironwood Trail, owing to the presence of ironwood trees.

Geologically, the Mine Creek Trail lies within various rock units of the Crabtree terrane.  These metamorphic rocks are schists and gneisses that were originally mainly sedimentary and volcanic rocks.  The rock layers along the trail lie on the east flank of a large fold structure, the Raleigh antiform.  The layers run in a north-northeast direction, and generally dip toward the east at a moderate to steep angle, and locally vertically.  Among the more distinctive rock types in the Crabtree terrane are mica schist containing garnet and other metamorphic minerals, and schist that is rich in graphite, from which Lead Mine Road gets its name.  See the descriptions of the Shelley Lake Loop and Lakepark trails for more information.

At the beginning of the Mine Creek Trail, rock exposures can be seen along the east bank of Mine Creek.  A very short distance ahead, a bridge on the trail crosses over the creek.  Beneath the south end of the bridge, there is a large exposure of schist (photo).  A more accessible example of this rock can be seen above the trail, behind the apartment complex here, where huge blocks were left during construction.  The schist here contains garnet, as well as staurolite and kyanite, indicating that medium to high metamorphic temperatures and pressures were achieved by these rocks during formation of the Appalachian Mountains.
Continue northward, crossing North Hills Drive carefully.  In a short distance, a ridge extends from the west, almost reaching to the greenway (photo).

The rock here has been blasted during excavation for the sewer line; drill holes are visible in the outcrop (photo).

Garnets and small folds are also visible (photos).

         Mica schist containing garnets (small reddish spots).  
               The schist had tiny folds called crenulations, 
                 which resemble corrugations in cardboard.

Tight complex folds highlighted by quartz vein.

About 1/4 mile north, the trail bends to the left (west), following a sharp bend in the creek.  At this point, there is a huge rock exposure of schist on the outside of the bend (photo).
The creek's erosive power is concentrated on the outside of
 the bend, creating steep cut banks, while low point bars on the 
opposite side of the creek are sites where sediment is deposited.

A short distance ahead, there is an intersection with two connecting spur trails near milepost 1.  On the spur to the right (toward North Hills Drive), there is a very nice rock ledge at the base of the slope (photo).
This is a fine-grained biotite gneiss with abundant feldspar and 
quartz, making it resistant to weathering.  The distinctive banded 
appearance of the rock is the primary characteristic of gneiss.  
The banding strikes north 15 degrees east and dips about 60 degrees 
toward the east - recall we are on the east limb of the Raleigh antiform.
A very short distance ahead, long rod-shaped outcrops can be seen on both sides of Mine Creek (photo).
The long dimension of these rock exposures indicates 
the strike of the rock layers, like the grain of wood.
From here, the trail continues north and passes under Millbrook Road.  The lower parking lot for the Shelley Lake Loop trail is on the left; go to the right to continue on the Mine Creek Trail.  From here the trail follows the east side of Shelley Lake; points of interest are described in the Shelley Lake entry.  Toward the north end of the lake, the trail intersects with the Snelling Branch Trail greenway, which bends off to the right and uphill toward North Hills Drive.  Immediately after crossing the bridge over the creek, the Mine Creek Trail diverges from the Shelley Lake Loop, continuing north.

After passing under North Hills Drive through a narrow tunnel, the greenway takes a wide bend to the left, leaving the creek and following the hill slope.  A narrow unpaved footpath goes to the right to follow the creek here, rejoining the greenway in a short distance.  If you follow the footpath, you can see two large cut bank outcrops where the creek bends (photo).  Opposite these cut banks, there is a well developed sandy point bar.

One of two cut bank exposures between North Hills Drive and Lynn Road.
About 1/4 mile past Lynn Road, the Mine Creek Trail splits off to the left, continuing as an unpaved footpath along the creek.  The stretch of unpaved greenway trail continues north to its termination at Sawmill Road.

Sawmill Segment of Mine Creek Trail

After leaving the paved greenway, this narrow footpath squeezes between the southern end of a rocky ridge and Mine Creek, then follows the western flank of the ridge northward along the creek.  The ridge owes its existence to a rock type that is very hard and resistant to weathering.  It is a fine-grained, light-colored gneiss rich in quartz and feldspar (felsic gneiss) that has a strong lineation and other evidence of having been deformed and stretched by fault movements.  One of the first exposures encountered is an elongate rock outcrop that partially blocks the trail (photo).
Outcrop of strongly lineated felsic gneiss on the trail.
The lineation is parallel to the pocketknife.

In a very short distance, the slope to your right is strewn with chunks of the felsic gneiss (photo).  This is the southern end of a ridge that parallels the NNE strike of the rock structure.  The ridge was cut through over time by the erosive force of Mine Creek.   
Rocky southern end of ridge.

The creek and trail then take a sharp right bend and begin to run parallel to the strike of the rocks.  Some of the rocks along the slope here have features indicative of strong deformation, such as very thin bands and abundant quartz veins (photo).
Loose block of thin-banded felsic gneiss along slope.  This
rock shows evidence of having been deformed in a fault zone.
Along the slope, there are lots of large chunks of quartz and gneiss with quartz veins (photo).
Rock chunks littering the slope that parallels the rock structure.

You quickly encounter a very large flat "pavement" outcrop of felsic gneiss (photos).  It sits along the steep creek bank, just below the trail.  The rock foliation strikes N15oE and dips 75toward the east.
Extensive pavement outcrop.  Trail is just above the steep bank;
view from across creek.  Note light-colored baseball cap for scale.
View from the trail of the same outcrop.  The nearly horizontal
lineation is visible.  Note this stretch of creek is roughly
parallel to the lineation.
The trail bends to the left, once again heading west across the strike of the rock structure.  Several sizable outcrops are visible in the creek and along the steep bank on the south side of the creek through this stretch (photo).
Outcrops of gneiss in and along creek.
From this point, the trail again takes a sharp bend and heads north-northeast, roughly paralleling the rock structure all the way to the trail end at Sawmill Road.  The terrain becomes flatter, and there are no more hard rocky stretches, because the trail has passed into a softer rock type - schist.

In about 1/4 mile, if the water is not high, you may be able to see a small elongate outcrop of weathered, moss-covered schist at a footbridge near some houses (photo).  The thin-layered, platy schist dips steeply toward the west.
View from footbridge, looking southwest, of schist outcrop.
In a couple hundred yards, there is a nice exposure of dark and light banded schist (photo).  Small folds are visible in this outcrop.
Outcrop of strongly banded schist; folds visible at right.

In a short distance, the trail runs along what appears to be an old dam.  Some of the rocks that were used to build the dam may be visible to the west.  The trail descends from the old dam and crosses a footbridge.  Here you may be able to see an example of the most distinctive rock type within the Crabtree terrane, graphite schist.  A sewer line crosses the creek just downstream from the bridge; a bit farther downstream, there is an excellent cut-bank exposure of vertically dipping white schist and black graphite schist (photo).

Eroded creek bank exposing black graphite schist just downstream
from sewer line (note pipe at left end of view).
If the water is not high, outcrops of steeply dipping schist are visible just downstream and upstream from the bridge (photos).
Outcrop of steeply dipping schist just downstream from bridge.

Outcrop of steeply dipping schist just upstream from the bridge.

Also, you may be able to explore the creek side just past (upstream from) bridge, and find loose pieces of garnet-bearing graphite schist (photo).  Graphite is soft enough to scratch with your fingernail, and it can mark paper - after all, it is pencil lead!.

Loose pieces of graphite-rich schist beside the creek, just
upstream from the footbridge.  Small dark spots are garnets.
In a short distance, the trail terminates at Sawmill Road.

Snelling Branch Trail

The Snelling Branch Trail greenway begins at the northeast corner of the Shelley Lake Loop, follows the creek valley eastward across North Hills Drive, and ends at Optimist Park and the athletic fields of Sanderson High School.

Just uphill from its junction with the Shelley Lake Loop, the trail parallels a steep stretch of Snelling Branch, and there is nearly continuous rock exposure in the creek.  These rocks lie on the eastern limb of the Raleigh antiform, a large arch-shaped fold.  A long rock outcrop features cascades and small waterfalls formed by Crabtree terrane gneiss dipping steeply toward the east (photos).
View from the foot of a long stretch of rock outcrop,
just uphill from the Shelley Lake Loop trail.

Detail of previous photo.
These rock layers dip east (right) at about 65 degrees.

A bit farther uphill, within sight of North Hills Drive, the creek is much closer to the trail.  Here, a very nice pavement exposure, and fin-shaped outcrops can be seen (photo).  These rocks are thinly banded fine-grained dark biotite gneiss.  The banding dips very steeply toward the east.

Another rocky stretch of creek.  Trail is just to the right.

The trail crosses North Hills Drive, then continues to follow the creek.  Here, there is lots of rock exposed along a steep cut bank; there are some small cascades as well (photo).  This section of the trail is within the Southwest Prong gneiss, a subunit within the Crabtree terrane.  This rock is rich in quartz and feldspar, and is more like granite than most other parts of the Crabtree terrane.  In some places the rock is highly weathered
to form saprolite, intermediate between hard rock and soil.

Hard Southwest Prong gneiss exposure above North Hills Drive.

Banding in the tan to orange gneiss here dips almost vertically, and the rock has a strong horizontal lineation, as if stretched like taffy (photo).
Partly weathered block of gneiss showing lineation.

After climbing this steep stretch, the terrain flattens out a bit.  The trail passes between athletic facilities of Sanderson High School and terminates at the parking area for Optimist Park.

Friday, November 1, 2013

Little Rock Trail

This trail begins across from the Walnut Creek Wetland Center, and connects to the Walnut Creek Trail.  After passing some apartments, houses, and other buildings on the right, the trail turns left and runs between houses on the right and the creek on the left.  Here a low stream outcrop, mostly covered by leaves, is visible of the opposite side of the creek (Photo).
Soon you come to a T intersection; turn right to stay on the trail.  You cross a street, then continue behind some apartment buildings.  Then there is a small bridge with a metal railing that crosses a tributary creek.  There is an outcrop of moss-covered Raleigh gneiss visible in this small creek.  Continuing on, just after the first picnic shelter, there is a much larger outcrop, forming cascades in the creek, visible through the trees to the right (Photo).
A short distance ahead you arrive at trail connection to Chavis Park.  If you go toward the park, the walkway passes over the creek on a bridge.  The rock wall on the sides of the bridge is entirely made of rounded spheroids of diabase (Photo).
These diabase boulders were likely brought in from elsewhere, because there is no diabase indicated near here on the geological map.

Walnut Creek Trail

The Walnut Creek Trail extends from Lake Dam Road, just east of Lake Johnson, through the Centennial Campus of NCSU, then through the southern parts of Raleigh all the way to the Neuse River.  Geologically, it begins in rocks of the Crabtree terrane, then passes through the Raleigh terrane, and then into granite of the Rolesville batholith.

As you pass the first apartment complex on the right, you are traveling over a layer of graphite schist, a distinctive unit within the Crabtree terrane.  In the brush to the right there may still be evidence of it, but watch out for poison ivy.  From here the trail follows a low-lying area that is very susceptible to flooding.  After crossing Trailwood Drive, the trail continues on Avent Ferry Road and then back to the right, following a tributary of Walnut Creek.  Next the trail passes into the Centennial Campus of North Carolina State University, traversing the north side of Lake Raleigh.

When you approach the north end of the Lake Raleigh dam, there is a small outcrop next to the trail.  This rock is an example of Falls leucogneiss, a distinctive, strongly lineated rock unit within the Raleigh terrane (photo).  For a better look at this leucogneiss, examine the large blocks in the median of Centennial Parkway.
The lineation here trends a few degrees to the west of north.  A better and bigger outcrop can be seen just off the trail at this point (photo).
A little farther along, just before a tunnel, there are several small flat (pavement) outcrops of Falls leucogneiss just to the right of the trail.

From this point, the trail passes under Lake Wheeler Road, through an industrial area, under a railroad trestle, and under South Saunders Street.  Then it passes the old city water filtration plant, and on a sidewalk passes the Eliza Pool Park.  The large rock chunks around the park are from the underlying Raleigh gneiss, and include some banded gneiss as well as granite.  The trail then turns north along Fayetteville Street.  In a few blocks, the trail takes a sharp right turn, then follows an unpaved path down a steep slope and across a footbridge.  Turn right here to stay on the Walnut Creek Trail (to the left is the start of the Rocky Branch Trail).

Soon you come to a road (Peterson Street) and turn right paralleling it.  Across from you is Carnage Middle School.  In a very short distance the trail turns right again to re-enter the woods.  The Walnut Creek Wetland Center is located just ahead at this point on Peterson Street, and the Little Rock Trail greenway begins across the street.

In a short distance, the trail runs on a long boardwalk across a wetland; there is an interpretive sign.  About three tenths of a mile onward, you will see a large pile of dark colored rocks next to the trail (photo).
This is near the spot where Grantland Drive ends, and these rocks are diabase boulders, piled here during construction.  Note the rounded shapes of some, the result of the spheroidal weathering process.  Diabase is an igneous rock that occurs as steeply dipping thin bands, called dikes.  These dikes formed from hot magma that intruded into cracks in the older (500 - 600 million year old) rock of the Raleigh terrane.  Diabase is 200 million years old, and records the breakup of the supercontinent Pangaea and the birth of the Atlantic Ocean.

Soon, the trail leaves the woods and follows Little John Road and then continues by Worthdale Park.  On a hill in this stretch, you pass a small road cut of weathered granite (photo).
 This is the first evidence that you have passed out of Raleigh gneiss and have entered the Rolesville batholith, a huge body of granite that is about 300 million years old, much younger than the metamorphic rocks into which this igneous mass intruded.  You will be in this body of granite for the reminder of the Walnut Creek Trail.

After passing through the Walnut Creek Softball Complex, you cross under Interstate 440.  The Walnut Creek Amphitheater is off to the right.  Continue straight on the Walnut Creek Trail, and the pavement soon gives way to a gravel surface for about a mile.  The trail takes a sharp right bend.  At the top of the next hill, you may see a small exposure of granite bedrock on the left (uphill) side of the path (Photo; pocket knife for scale).

The tiny black specks in the rock are crystals of black mica (biotite).  You may also notice several irregular long clots or strings of biotite.  Such features, known as schlieren, are common in igneous rocks and are probably related to flow of the hot magma during its cooling and solidification.

A short distance ahead, the trail takes a sharp right and heads down a fairly steep slope.  Soon you pass beneath New Hope Road, and then beneath a power transmission line.  Next the trail passes through a large wetland area, and housing developments are seen on the left (north) side.  The blocks and boulders along this stretch are all granite belonging to the Rolesville batholith.  Many of them have been moved during construction activities.  Just beyond the 1 1/2 mile marker, in a curve, you will see a very rocky cut on the left side (Photo).
The rocks on this slope are part of the granite bedrock that underlies the ridge and is very well exposed at the surface.  Continue around the curve in the trail, and almost immediately you pass under another high power transmission line.  Here there is a flat pavement type outcrop of granite (Photo; hammer for scale.  Note poles for power line).
The trail continues through wetlands, with Walnut Creek to the right (south).  After a mile or so, you come to Barwell Road, where the trail crosses Walnut Creek on a trail bridge that parallels the highway bridge.  You may be able to see a large exposure of granite on the right side at the edge of the creek (Photo).

Then the trail follows a loop to pass under Barwell Road and continue along the south side of Walnut Creek.  If you have a clear view, you may notice two or three huge boulder outcrops down below you in the creek, beside a mobile home park.

In a short distance, the Walnut Creek ends at the Neuse River Trail.

Centennial Bikeway Connector

This short greenway segment extends from Western Boulevard, where it departs from the Rocky Branch Trail, crosses south to Centennial Parkway, then follows the sidewalk on the southwest side of the Parkway, almost to Lake Wheeler Road, where it follows a cutover downhill to the right, joining the Walnut Creek Trail.  Once arriving at the Walnut Creek Trail, go west (right) through the NCSU Centennial Campus and on the Lake Johnson, or east (left) toward southeast Raleigh and the Neuse River Trail.

After leaving the Rocky Branch Trail at Western Boulevard, you go uphill and to the left.  This long hill you climb, toward Centennial Parkway, owes its existence to the hardness and resistance to erosion of the underlying rock unit, Falls leucogneiss.

The Centennial Bikeway Connector contains some of the best examples of Falls leucogneiss in the greenway system.  After reaching Centennial Parkway, the bikeway continues on the other side of the road and heads downhill to the left.  If you want to see the best Falls leucogneiss, you my want to (carefully) visit the median, where huge blocks of leucogneiss were placed near where they were excavated for construction of Centennial Parkway (Photo).
If you examine some of these blocks, you can see the light pink or tan color of the fresh unweathered rock, and its other distinguishing characteristic, a strong lineation, composed of tiny dark minerals strung out in lines (not layers) through the rock (Photo).
The dark streaks contain the mineral magnetite, and as a result this rock will attract a sensitive magnet, such as a pivoting magnetic stud-finder.

The Falls leucogneiss is part of the Raleigh terrane, along with the Raleigh gneiss.  The leucogneiss is thought to be a body of granite that intruded into the Raleigh gneiss, and they were both later squeezed, stretched and heated together.  Some of the blocks on the Centennial Parkway median contain portions of Raleigh gneiss that were engulfed by the granite magma (Photo).  The dark portions of this rock are Raleigh gneiss, similar to an outcrop that may be seen on the Rocky Branch Trail greenway.
The Falls leucogneiss unit has been dated as about 540 million years old.  This would be the time when the granite intruded as a magma; the Raleigh gneiss must therefore be somewhat older than that.

As you continue along the Centennial Bikeway Connector sidewalk, after crossing the intersection with Blair Drive, you will see a green chain link fence to the right.  Beyond that, under the electrical transmission lines, is a series of excellent natural ledge outcrops of Falls leucogneiss (Photo).
If you go for a closer look, you will see that the rock is largely covered with lichen, but you can still see the lineation, which runs a little east of north.

Rocky Branch Trail

The Rocky Branch Trail begins at its intersection with the Walnut Creek Trail, just south of downtown Raleigh, between Fayetteville and S. Wilmington Streets.  It heads northwest, following Rocky Branch through the N.C State University campus, and is connected by a sidewalk along Gorman Street to the beginning of the Reedy Creek Trail at the southeast corner of the Meredith College campus at the intersection of Faircloth and Hillsborough Streets.

Just after crossing Fayetteville Street, at the base of the Mt. Hope Cemetery hill, there is an excellent outcrop of Raleigh gneiss in the creek (Rocky Branch) on the right (Photo).
The banding typical of gneiss is well displayed as alternating dark and light-colored stripes.  In addition, you may see cross-cutting intrusions of light colored granitic rock and dark colored basaltic rock (Photo).
Small folds may also be visible, as well as pot holes scoured by stream erosion.  This outcrop is similar to several other exposures of Raleigh gneiss that can be seen in Pigeon House Branch, on either side of Capital Boulevard just north of downtown Raleigh between Wade Avenue and Wake Forest Road.

After you cross Lake Wheeler Road, the trail passes through grounds of Dorothea Dix Hospital.  There are more outcrops of Raleigh gneiss in the creek, but they are almost completely hidden by vegetation.  The trail passes under a railroad trestle across Western Boulevard from the entrance to Central Prison.  Here, Rocky Branch crosses to the other side of the road, in front of the prison.  There is a very good outcrop of gneiss in the tight bend of the creek over there, but the guards are generally not pleased if you try to look at it.  The outcrop actually has civil-war graffiti carved in it.

If you continue along the south side of Western Boulevard, you get views of Rocky Branch, which has cut a fairly deep valley here.  There are some large exposures of weathered gneiss on the opposite side of the creek, and then there are lots of discarded slabs of pavement obscuring the rocks.  (If you continue uphill and to the left, you can connect to the Walnut Creek Trail via the Centennial Bikeway Connector.  The long hill you climb in that direction, toward Centennial Parkway, testifies to the hardness and resistance to erosion of the next rock unit, Falls leucogneiss.)

Continuing on the Rocky Branch Trail on the north side of Western Boulevard, you pass Pullen Park.  Before reaching the tunnel under Pullen Road and entering the campus of North Carolina State University, you will pass a stream-gauging station operated by the U. S. Geological Survey (Photo).
This station is part of a nation-wide system of 1.5 million sites that measure surface water flow, depth, discharge and other parameters.  The data are collected and sent by satellite telemetry and posted in real time on the website <>.  Information regarding this particular station is located at

After passing through the Pullen Road tunnel, you will come to a large interpretive sign describing the portion of the Rocky Branch Trail that passes through North Carolina State University.  To the right of this sign, and across the trail, there are several ground-water monitoring wells (Photo).
Behind the sign and to the right back in the trees, there are large exposures of Falls leucogneiss, including this one which was the wall of a small quarry at one time (Photo).
 As you pass through the next tunnel (under Morrill Drive), you have crossed the Nutbush Creek fault, which separates the Raleigh terrane from the Crabtree terrane to the west.  This is a right-lateral strike slip fault, meaning that each side moved to the right relative to the other side (i.e. the east side moved south, the west north).  This is the same kind of fault as today's San Andreas in California, except that the Nutbush Creek fault stopped moving about 250 million years ago, while the San Andreas is still active.

As you traverse this portion of the greenway, you will see lots of interpretive markers describing features of streams such as Rocky Branch in a built-up environment.  The big blocks of rock in the creek along here were all hauled in from quarries as part of a stream restoration project.  There is one good place to see an exposure of the native rock, and it is at the intersection of Sullivan Drive and Varsity Drive, adjacent to the baseball stadium and tennis complex.  Here, there is a small waterfall outcrop of Southwest Prong gneiss, a unit within the Crabtree terrane (Photo).
This photo was taken from the culvert beneath the bridge.  To view the rock from above, you may have to lean over the railing along Varsity Drive and peer through the bushes.  Watch out for poison ivy!

Upon reaching Gorman Street, proceed right on the sidewalk to Hillsborough Street, which is the end of the Rocky Branch Trail greenway.  The Reedy Creek Trail greenway begins diagonally across this intersection at the corner of the campus of Meredith College.

Lake Johnson Geology

The Lake Johnson Greenway is divided in two by the causeway of Avent Ferry Road.  The western portion is a mostly unpaved hiking trail, while the eastern portion is paved and suitable for biking.  All rock exposures around Lake Johnson belong to various rock units within the Crabtree terrane.  The axis of a large fold, the Raleigh antiform, passes from north to south through the eastern half of the lake.

Lake Johnson West

From the parking lot at the north end of the causeway, proceed west along the northwestern edge of the lake.  The terrain is very flat here, but you should be able to see a more rugged shoreline on the other side to the south.  The western end of Lake Johnson is where Walnut Creek enters, and has deposited considerable sediment, forming a small delta that constitutes a nice wetland.  As you proceed along the unpaved path on the southwestern portion of the lake, you will encounter spots where the uphill side of the trail was cut and some low portions have been filled in, to make the trail more level.

If you look closely, you can see a small cut exposing weathered granitic gneiss, showing banding, under a pine tree.  A short distance ahead, you encounter a better outcrop of orange-colored granitic gneiss (Photo).
The banding, or foliation, of the gneiss dips moderately toward the west (in the uphill direction).

There is a short spur trail leading to a steep bluff where there is a bench and a nice overlook providing a lake vista.  Here there is an excellent outcrop of very light colored (leucocratic) gneiss (Photo).
The foliation strikes about north-south and dips about 20o toward the east.  There is also a strong lineation, plunging about 13o to the north.  This rock unit is called the Southwest Prong gneiss.

Ahead in a tributary creek, you will get a view of a big cut bank outcrop of fine-grained mica-rich gneiss or schist.

After reaching Avent Ferry Road, cross and walk north toward the causeway.  You will encounter a nice roadcut exposure at the south end of the causeway.  This rock is a mica-rich gneiss or schist that weathers into thin platy slabs (Photo).
The foliation strikes north-northwest and dips toward the southwest, and there is a lineation plunging south.

Lake Johnson East

Note:  From the parking lot along Avent Ferry Road south of the lake, this description follows the greenway trail counterclockwise.  Also, be forewarned that this section of trail has more steep hills than other trails and is usually very busy, especially if the weather is nice.

According to the geological map, the low point following the first steep hill is where the axial trace of the Raleigh antiform passes through.  This would mean that foliation (layering) in rock outcrops here should be nearly horizontal, whereas it dips away from this trace on either side.  Unfortunately, there are no outcrops visible from the trail at this point.  However, as you climb the second steep hill, you may be able to see a rock exposure in a small creek down to your left (Photo).
The foliation dips about 25 or 30 degrees toward the east.  Recall the outcrop near the south end of the causeway dips west, so we have indeed crossed the axis of the antiform (an arch-shaped fold).  A bit farther along the trail, just beyond the 2-mile marker, there is an outcrop to the right up on the hillslope and ridge. The rocks here also dip gently toward the east (Photo).
Continue along the trail until just before the dam.  There is a very large exposure of rock just below the spillway (Photo).
To see it, take the trail spur to the right toward Lake Dam Road, then walk up a small unmarked trail below the dam.  This outcrop consists of mica schist containing the metamorphic minerals garnet and staurolite. Elsewhere near Lake Johnson the mineral kyanite may also be found; together, these metamorphic minerals tell geologists that the rocks were buried to a depth of about 15 miles and reached temperatures of about 650oC.  The foliation of the schist here dips eastward very steeply, around 80o.  This rapid steepening on the east flank of the Raleigh antiform may also be seen at the greenways around Shelley Lake and along Crabtree Creek.  This indicates that the Raleigh antiform is asymmetric, more steeply dipping on the east than on the west.

You may choose to continue the Lake Johnson East Loop Trail, proceeding across the dam and then west toward the north shore of the lake.  Alternatively, the Walnut Creek Trail begins immediately across Lake Dam Road from the dam.