Virginia Division of Mineral Resources Bulletin 86 Geology of the Shenandoah National Park, Virginia

ROAD LOG ALONG SKYLINE DRIVE

The following road log is a guide to important geologic features that can be seen from Skyline Drive in the Shenandoah National Park. The log is keyed to the numbered mileposts along Skyline Drive. It begins at the north entrance to the park, at the intersection of U. S. Highway 340 and Skyline Drive (mile 0.0) near the southern corporate limit of Front Royal, and continues to the south for 105.2 miles (169.3 km). Places of special interest geologically are marked with an asterisk.

Most of the geologic features can be seen from or near overlooks that provide room for safe parking, or are located in areas where Skyline Drive has wide shoulders on which parking is safe in dry weather. When parking along Skyline Drive, be sure to pull completely off the pavement and do not block fire roads or the entrance to overlooks or other facilities. Rock samples may not be collected or removed from Shenandoah National Park in accordance with National Park Service regulations.

Cumulative
miles	(km)	Explanation
0.0	(0.0)	Enter Skyline Drive from U. S. Highway 340 near southern corporate limit of Front Royal. At this location the drive is on Ordovician limestone and dolomite of the Rockdale Run Formation of the Beekmantown Group, which is obscured by rock debris from the Catoctin Formation.
0.5	(0.8)	Park Entrance Station. Skyline Drive crosses the Front Royal fault that separates the Rockdale Run and Catoctin formations.
1.4	(2.3)	Massive, purplish brown weathering, locally vesicular, northwestward-dipping basalt flow of the Catoctin Formation exposed along northbound lane. Brecciated basalt with epidote cement visible at north end of exposure.
2.0	(3.2)	Shenandoah Valley Overlook at milepost 2. View of the Front Royal area and the north end of Massanutten Mountain.
3.9	(6.3)	Basalt of the Catoctin Formation exposed by the northbound lane from this point to mileage 4.3 (km 6.9).
4.7	(7.6)	Entrance to Dickey Ridge Visitor Center and Picnic Grounds.
5.2	(8.4)	Parking overlook by southbound lane opposite locally epidotized basalt in roadcut. Zone of weathered-out vesicles visible near top of exposure.
*5.7	(9.2)	Signal Knob Overlook. To the west, meander loops of the South Fork of the Shenandoah River are visible near the west side of the valley. In the background is Massanutten Mountain on which several talus deposits have been formed from blocks of Silurian Massanutten Sandstone that have moved downslope from the mountain crest. In the roadcut to the east is one of the best exposures along Skyline Drive of a boundary between basalt flows and the sedimentary rocks commonly found in the Catoctin Formation (Figure 38).
Figure 38. Catoctin Formation at Signal Knob Overlook consisting of a thin, dark-red arkosic sandstone overlying a dark, dense, partially epidotized, vesicular basalt and underlying a lighter-hued basalt flow with columnar jointing. The dark iron-red coloration of the sedimentary layer is probably due to mineralization and "baking" by the overlying lava flow.
*6.9	(11.1)	Gooney Run Overlook. The boundary between the Catoctin and Pedlar formations, a profound unconformity between the late Precambrian volcanics and the porphyritic granodiorite of an earlier Precambrian pluton, passes beneath the parking area (not to the west of the overlook as is incorrectly shown on Plate 1). Purple pyroclastic phyllite and pale-green rhyolitic (?) tuffs of the basal Catoctin Formation are exposed between weathered basalt beds in the roadcut. A good exposure of the Pedlar granodiorite occurs 200 feet (61 m) west of the overlook at the end of the footpath.
7.3	(11.7)	Gooney Manor Overlook. Browntown Valley to the southwest and the low hills to the west are underlain entirely by rocks of the Pedlar Formation. The main body of the Blue Ridge encircles the valley to the north, east, and south, with most of the visible crest capped by Catoctin basalt.
9.2	(14.8)	Lands Run Gap. Here the road crosses a small concealed linear fault or flexure that separates the Catoctin Formation from granodiorite of the Pedlar Formation. Traces of rocks similar to those found in the Swift Run Formation and of epidotized granodiorite that commonly occur below the Catoctin Formation at the Precambrian unconformity are present along this linear depression. This association suggests that this boundary is an exposure of the unconformity along a vertical fold limb and probably not a fault as shown on Plate 1.
*9.5	(15.3)	Pull off on shoulder by southbound lane. Exposures 300 feet (91 m) upgrade to south are migmatitic, granitic gneiss of the Pedlar Formation (Figure 11). Light and dark layers in the gneiss define plunging folds. Massive hypersthene granodiorite is present on the crest of the ridge above the exposures, and it may have been intruded into the gneiss exposed here.
*10.1	(16.3)	For several hundred feet south and north of the sharp bend in Skyline Drive a series of near vertical diabasic dikes, each several tens of feet thick, extend across the road and are exposed in the roadcuts. These and similar dikes in the plutonic rocks of the Blue Ridge represent conduits through which the basaltic magmas of the Catoctin Formation were extruded. The dikes are very dark green, fine grained and porphyritic, and contain fragments and a few large blocks of epidotized granodiorite. Where contacts of dikes with the wall rock are visible, the Pedlar granodiorite is moderately epidotized or unakitic.
10.5	(16.9)	Pyroclastic mud flows at the base of the Catoctin Formation are exposed for several hundred feet up the slope above the southbound lane. These rocks are shown as the Swift Run Formation on Plate 1, but are not typical of that unit and possibly should be placed within the Catoctin Formation.
*10.7	(17.2)	Indian Run Overlook. The basal basalt flow of the Catoctin Formation is exposed in the roadcut by the overlook. The best display of columnar jointing along Skyline Drive can be seen at the north end of this exposure (Figure 39).
Figure 39. Columnar basalt of the Catoctin Formation in the roadcut at the north end of Indian Run Overlook. Locally, the subparallel columns fan upward from high-temperature areas that existed in the flow during solidification.
		The terrane to the east and north is underlain by rocks of the Pedlar Formation capped, at the higher elevations, by thin remnants of the basal Catoctin basalt flows, possibly the same flows that are exposed in the roadcut.
11.2	(18.0)	Small exposures of the Swift Run Formation occur along the southbound lane of Skyline Drive. The road continues to the south on the Pedlar Formation for the next 3.1 miles (5.0 km).
12.4	(20.0)	Jenkins Gap Overlook. A view of the terrane developed on crystalline igneous rocks east of the Blue Ridge crest.
*13.8	(22.2)	Hogwallow Flats Overlook. This overlook provides a good view of the foothills formed by the plutonic rocks along the east side of the Blue Ridge mountains. Visible on very clear days, about 20 miles (32 km) to the east, are low ridges formed by rocks of the Catoctin Formation and the Chilhowee Group along the east flank of the Blue Ridge anticlinorium in Fauquier County.
14.3	(23.0)	The contact between the Pedlar and Catoctin formations extends across Skyline Drive just south of the Appalachian Trail crossing. The drive is on the Catoctin Formation for the next 6.7 miles (10.8 km).
14.9	(24.0)	Browntown Valley Overlook. At this overlook, and for nearly a mile to the south, Skyline Drive is constructed on a natural bench developed on the upper part of a Catoctin basalt flow, one of the 13 flow benches that can be seen along the west face of Mount Marshall (Figure 13). Across Browntown Valley and the low hills that separate it from the Shenandoah Valley, both crests of Massanutten Mountain are visible on clear days, as well as part of Great North Mountain, the next major ridge west of the Massanutten mountain range. These ridge crests mark the outcrop of steeply dipping quartzite beds of Silurian age.
*17.2	(27.7)	Range View Overlook. This overlook provides a rare, panoramic view of the Blue Ridge to the south and of the mountains and ridges to the east and west of it. From this location it can be seen that the shape, elevation, and linear extent of the ridges of the Piedmont province east of the Blue Ridge contrast strongly with those of the Valley and Ridge province to the west. The eastern ridges and hills of the Piedmont, formed on the massive plutonic rocks in the core of the Blue Ridge anticlinorium, vary in shape and elevation from ridge to ridge. These hills are of limited linear extent although they are generally aligned with their long axes parallel to the prevailing northeastward trend of the Blue Ridge mountains. The Massanutten mountain range and other ridges to the west in the Valley and Ridge are linear, and have relatively uniform shape and crestal elevations for long distances along their northeasterly trend. The differing morphology of the mountains in the Piedmont and Valley and Ridge is a reflection of the bedrock and structure. The hills to the east are formed by homogeneous intrusive and metamorphic rocks that are fractured and sheared along lines parallel to the Blue Ridge, and randomly crisscrossed by faults, joints, and dikes. In this area weathering and mass wasting is more rapid along the zones of fracture and the linear intrusive bodies, and has produced discontinuous linear lows that bound the irregularly shaped hills and ridges formed on the less intensely fractured plutonic rock.
		To the west the rocks of the Valley and Ridge are stratified, heterogeneous, and tilted with the thicker, inclined, resistant rocks forming the long, parallel, even crested ridges typified by Massanutten Mountain. Fault and joint systems also modify the rates of weathering and mass wasting of the stratified rocks producing gaps and saddles, but do not mask the dominating influence of the stratified sequence in controlling the characteristic shape and extent of the resistant ridges.
18.4	(29.6)	Gimlet Ridge Overlook. Another good view of Browntown Valley and the ridges to the northwest. Distant rock exposures on the steep slopes to the west are of the Pedlar Formation. The steep, narrow, closely spaced hollows along the escarpment are characteristically formed on the plutonic rocks on steep slopes below the contact with the Catoctin Formation.
19.0	(30.6)	Mount Marshall Overlook at milepost 19. A series of low gaps between the main Blue Ridge mass and the several southeastward-trending subsidiary ridges mark the location of a fault zone that separates the Catoctin Formation from the Pedlar Formation to the east. Massive basalts exposed north of the overlook have coarse columnar jointing.
19.3	(31.1)	Skyline Drive crosses a small vertical fault within the Catoctin Formation. Near the road the fault is not exposed, but a zone of angular basalt rubble appears to define its trace across the mountain crest.
19.7	(31.7)	Little Hog Back Overlook. To the west the very steep slope is underlain by the Pedlar Formation and is typical of slopes developed on this unit at higher elevations where the Catoctin Formation overlies it or has overlain it in the recent geologic past. The unconformity between the Catoctin and Pedlar formations passes beneath the eastern part of this overlook, with no evidence for the presence of the Swift Run Formation.
*20.1	(32.3)	Little Devil Stairs Overlook. The deep, steeply inclined gorge (Little Devil Stairs) to the south is formed in the Catoctin Formation along a northward-trending zone of fractures. Several northward-trending Catoctin feeder dikes at the head of the gorge are exposed in the roadcut at milepost 20 just north of the overlook, and may have influenced the development of Little Devil Stairs, if they penetrated the lower Catoctin basalt flows.
		Dark, coarse-grained granodiorite of the Pedlar Formation, much of which is unweathered, is well exposed adjacent to the overlook and to the north. Penetrating, dark-red iron stains, thought to be paleoweathering features preserved from late Precambrian time, are well displayed in both the fresh and weathered rock (see description for Hogback Overlook, milepost 21).
*21.0	(33.8)	Hogback Overlook at milepost 21. Due to the removal of the Catoctin Formation by erosion in the recent geologic past, the crest of Hog Back Mountain is now underlain by the Pedlar Formation. The contact between the two rock units was little more than 100 foot (30 m) above the present crest, indicating that the rocks now exposed at the overlook were probably subjected to weathering prior to the extrusion of the Catoctin basalt flows in late Precambrian time. Dark-red iron stains that penetrate the granodiorite along incipient fractures are suggestive of ancient weathering features, as other generally open fractures in the same rock exhibit the typical brown iron-oxide-staining characteristics of recent weathering. These features can be seen in the rock exposures at the overlook near road level (Figure 40).
Figure 40. Granodiorite of the Pedlar Formation on the south side of Skyline Drive at Hogback Overlook, 0.2 mile (0.3 km) south of milepost 21 (Plate 1). The granodiorite is a light-gray, porphyritic, moderately foliated crystalline rock. The rocks exposed here were probably less than 100 feet (30 m) below the Precambrian erosion surface. The intersecting arm-like forms in the rock are purple, penetrative, iron-oxide stains along ancient healed fractures. The stains probably relate to mineralization during Catoctin volcanism or to weathering before the lavas covered the Precambrian surface.
		The view to the north from Hogback Overlook is the best in the northern section of the park. It encompasses much of the northernmost protuberance of the Blue Ridge into Shenandoah Valley. This area, underlain by Cambrian and Precambrian rocks, has been thrust several miles westward over the younger Cambrian and Ordovician carbonates. Browntown Valley, a portion of the protuberance is in the foreground with the Blue Ridge escarpment and Mount Marshall to the northeast.
21.3	(34.3)	The contact between the Catoctin and Pedlar formations extends across Skyline Drive at this point, but no evidence of the Swift Run Formation is visible.
21.8	(35.1)	Rattlesnake Point Overlook. A view of the eastern Blue Ridge mountains and the southeast foothills. Fine vesicular basalts are exposed in the roadcut at the north end of the overlook.
22.2	(35.7)	Entrance to Matthews Arm Campground.
24.0	(38.6)	Entrance to Elkwallow Wayside at milepost 24.
24.2	(39.0)	Entrance to Elkwallow Picnic Grounds.
25.0	(40.2)	The base of the Weverton Formation between mileposts 25 and 26 parallels Skyline Drive just above road level, and basalts or purple slate are exposed locally in the roadcut.
26.4	(42.5)	Jeremys Run Overlook. Jeremys Run drains a large, steep area underlain largely by the Catoctin Formation with caps of the Weverton and Hampton formations on the higher surrounding ridges. To the west, parts of Shenandoah Valley can be seen, with New Market Gap in the Massanutten Mountain area visible in the distance.
26.9	(43.3)	Jointed sandstone beds of the lower part of the Weverton Formation with well-developed spheriodal weathering are exposed by the southbound lane.
*27.1	(43.6)	Contact between the Catoctin and Weverton formations exposed above the southbound lane. Vesicular basalt of the Catoctin Formation is directly overlain by a conglomerate of angular basalt fragments and rounded quartz pebbles that comprise the base of the Weverton Formation at this location.
27.6	(44.4)	Thornton Hollow Overlook. A view to the east and north of the Blue Ridge foothills and the Elkwallow area, respectively. Massive basalts of the Catoctin Formation in the roadcut by the overlook are cut through with slickenside surfaces on which fibrous anthophyllite (a variety of asbestos) is preserved.
28.4	(45.7)	Beahms Gap Overlook on west side of Skyline drive, with a few large blocks of epidotized basalt breccia from the Catoctin Formation near the north entrance to the overlook.
29.5	(47.5)	On east side of Skyline Drive is an exposure of a massive, slightly vesicular purple basalt.
30.1	(48.4)	Pass Mountain Overlook. View of Luray area in Shenandoah Valley and New Market Gap in Massanutten Mountain to the west. The westernmost ridges of the Blue Ridge mountains are underlain by steeply dipping quartzite beds of the Chilhowee Group (the Weverton, Hampton, and Erwin formations).
31.4	(50.5)	Exit to U. S. Highway 211 at Thornton Gap.
31.5	(50.7)	Entrance to Panorama (restaurant and service station). A major geologic structure, the Stanley fault, passes from east to west through Thornton Gap and separates the Catoctin Formation (on the north) from the Pedlar Formation (on the south).
32.0	(51.5)	Exposures at milepost 32 of the Pedlar Formation occur intermittently along Skyline Drive for next 7.1 miles (11.4 km).
32.2	(51.8)	Marys Rock Tunnel. Excellent exposure of a Catoctin feeder dike on west side of north portal. Do not attempt to park here.
*32.4	(52.1)	Tunnel Parking Overlook. Park here and walk through tunnel to examine Catoctin feeder dike at mileage 32.2. View to the east of exposures of Old Rag Granite on Oventop Mountain in distance. Exposures on the west side of Skyline Drive are of very strongly foliated granodiorite typical of the Pedlar Formation in this part of the park. Foliation is so well developed that the rocks have a stratified appearance in these exposures.
*32.8	(52.8)	Buck Hollow Overlook. Excellent exposures in roadcut of strongly foliated Pedlar granodiorite with 2- to 3-inch (5- to 7-cm) long lenses of garnet-bearing felsic material. To the north in the extreme distance along the lower slopes of the Blue Ridge, two widely separated bedrock exposures visible on a clear day mark the locations of Little Devil Stairs to the west and Big Devil Stairs to the east, steep gorge-like features formed along northward-trending fracture zones in the Catoctin Formation.
33.1	(53.3)	Hazel Mountain Overlook. Additional exposures of the Pedlar granodiorite.
35.1	(56.5)	Pinnacles Overlook. View to the south of the north face of Old Rag Mountain with Corbin and Robertson mountains to the south and west, respectively, all areas underlain by the Old Rag Granite. Several exposures of the Pedlar Formation are present at the overlook.
36.4	(58.6)	Jewell Hollow Overlook. View to the northwest of sharp-crested ridges formed on rocks of the Chilhowee Group near Shenandoah National Park Headquarters.
36.7	(59.1)	Entrance to Pinnacle Picnic Grounds.
38.6	(62.1)	Stony Man Overlook (Hughes River Gap). Exposures in roadcut of light-hued, fine-grained Pedlar granodiorite. The view to the west is of Luray and of Page Valley, that segment of Shenandoah Valley between Stanley and Luray which is underlain by Cambrain and Ordovician carbonates and shales. To the south, the profile of Stony Man is outlined in outcrops of columnar basalts of the Catoctin Formation.
39.1	(63.0)	Trail Parking Area. The concealed contact between the Pedlar and Catoctin formations is less than 100 feet (30 m) to the north. Excellent exposures of the Catoctin Formation along Stony Man Trail and for the next 0.7 mile (1.1 km) along Skyline Drive. Differentially epidotized columnar basalts are best displayed near the parking area along this section. To the north the Pedlar Formation exhibits the rectilinear, red iron stain patterns characteristically present in the plutonic rocks just below the Catoctin contact, and are thought to be the result of Precambrian weathering or the introduction of mineralizing fluids during Catoctin volcanism.
39.8	(64.0)	Hemlock Springs Overlook. A view to the north of the plutonic-rock terrane in the Pinnacles area. The hollow at the south end of the overlook is typical of the debris-filled hollows formed on the Catoctin Formation.
*40.6	(65.3)	Thorofare Mountain Overlook. The best view of Old Rag Mountain from Skyline Drive. Late afternoon lighting accentuates the northward-trending joint system visible on the north face of the mountain (Figure 41).
Figure 41. North face of Old Rag Mountain, with late afternoon light accentuating the north-trending fracture system in the granitic rocks. These joints roughly parallel the trend of the Catoctin feeder dikes exposed along the crest and may have formed during Catoctin volcanism.
41.1	(66.1)	Along the north side of Skyline Drive boulder fields and talus deposits of basalt debris lie on gently southeastward-dipping, differentially epidotized basalt flows of the Catoctin Formation for the next 0.4 mile (0.6 km).
41.7	(67.1)	North entrance to Skyland (highest elevation on Skyline Drive). In the Skyland area to the west more than 200 feet (61 m) of Swift Run sedimentary rocks separate Pedlar granodiorite from the lower basalt flows of the Catoctin Formation. The Swift Run Formation is exposed downslope (west) from Skyland restaurant and in a small quarry north of the stables. It is a stratified sequence of phyllite and coarse, pebbly sandstone of both pyroclastic and detrital origin. The restaurant and upper cabin area is on strongly cleaved basalts and the lower cabin area mostly on very dark-gray, gneissic granodiorite. All of Page Valley and most of Massanutten Mountain are visible from the Skyland area on clear days.
42.5	(68.4)	South entrance to Skyland. The contact between the Catoctin and Swift Run formations extends across Skyland Drive at this entrance and passes through the White Oak Canyon parking area to the east.
42.7	(68.7)	Approximate location of contact between the Swift Run and Pedlar formations.
*43.3	(69.7)	Timber Hollow Overlook. View to the west of Page Valley and of Hershberger Ridge beyond the small community of Ida at the west foot of the Blue Ridge. Hershberger Ridge is formed by rocks of the Erwin Formation and appears to be bounded by faults on the southeast and northwest. Just west of the overlook are exposures of Pedlar granodiorite cut by veins of epidote that may be the result of mineralization associated with the early Catoctin basalt flows.
43.8	(70.5)	Approximate location of the concealed Swift Run Formation. Skyline Drive passes onto the Catoctin Formation to the southeast.
44.3	(71.3)	Crescent Rock Overlook. View of Hawksbill Mountain to the southwest, the highest peak in the park, with several cliffs of columnar basalt visible on the northwest face (Figures 4, 42).
Figure 42. View from Crescent Rock Overlook west toward the small community of Ida at the mouth of Timber Hollow. The ridges just beyond the community mark the location of a narrow, folded belt of Catoctin and Chilhowee rocks that are apparently bounded by faults along the east and west foot of the ridges. Beyond these ridges is Page Valley, a segment of Shenandoah Valley that is floored by Cambrian and Ordovician carbonate rocks. Beyond the valley is the Massanutten mountain range and New Market Gap (upper left) that provides access between Page Valley and the northwestern part of Shenandoah Valley.
45.3	(72.9)	Exposures by southbound lane of gently southeastward dipping, amygduloidal basalt with veins of epidote and jasper. These rocks are characteristic of the upper few feet of many Catoctin basalt flows.
45.7	(73.5)	Hawksbill Trail parking area.
46.5	(74.8)	Old Rag View Overlook. Profile of the steep north face of Old Rag Mountain.
46.6	(75.0)	Upper Hawksbill parking area.
47.2	(76.0)	In curve on northeast side of Skyline Drive are exposures of Catoctin basalt in which small sedimentary dikes formed while the flow was cooling and possibly still mobile. The sediments are very fine-grained, yellow to purple, exhibit pseudo-bedding features, and were probably injected as a fluid mass into fractures at the base of the flow as it advanced across unconsolidated sediments.
47.8	(77.0)	Approximate location of the contact between the Catoctin and Pedlar formations; no evidence of the Swift Run Formation was found in this area.
*48.1	(77.4)	Spitler Knoll Overlook on rocks of the Pedlar Formation. A view to the northwest of Page Valley, the town of Stanley, and New Market Gap in Massanutten Mountain. The sharp-crested peaks and ridges to the west comprise the northern part of an uplifted mass of Precambrian and Early Cambrian clastic rocks that extends lobe-like out into the valley. It is separated from later Cambrian and Ordovician carbonate rocks of Page Valley by the Stanley fault that passes between Stanley and the northern line of ridges.
48.3	(77.8)	Approximate location of the contact between the Pedlar and Catoctin formations, with the Catoctin present to the south.
49.0	(78.8)	Franklin Cliff Overlook at milepost 49. Several thick epidotized basalt flows form Franklin Cliffs, and remnants of an epidotized basalt breccia that marks the top of the upper flow are preserved in the wooded area between the cliffs and Skyline Drive at the north end of the overlook. To the west the low farmlands along the base of the Blue Ridge are covered by alluvial fans and terraces formed from resistant rock debris derived from the Blue Ridge and transported into the valley. These clay, sand, and boulder deposits conceal bedrock along a belt 1 to 3 miles (2 to 5 km) wide at the west foot of the Blue Ridge for many miles.
49.4	(79.5)	Fishers Gap Overlook.
50.6	(81.4)	Dark Hollow Falls parking area. The trail leads downhill for several thousand feet to Dark Hollow Falls (Frontispiece) where the surface drainage from much of the Big Meadows area tumbles over a series of small benches formed on a resistant basalt flow. Amygdaloidal and porphyritic basalts are well exposed along the stream above the falls (Figure 43).
Figure 43. Amygdaloidal metabasalt with the amygdules weathered out in relief along the trail to Dark Hollow Falls from Dark Hollow Falls parking area.
50.8	(81.7)	Entrance to Byrd Visitor Center.
51.0	(82.1)	Big Meadows marshy grassland at milepost 51 on south side of Skyline Drive.
*51.2	(82.4)	Entrance to Big Meadows lodge, restaurant, and camp grounds. The view from Blackrock of the trail west of Big Meadows Lodge is a panorama of Page Valley and the Blue Ridge escarpment north of Big Meadows. This is one of the few points from which many of the major structural elements of this area may be seen. The approximate trace of the Stanley fault can be followed to the east where it turns northeast through the valley at the foot of the Blue Ridge escarpment. Beyond the escarpment it turns to the east again, and extends across the Blue Ridge at Thornton Gap.
		To the west and north the straight, even crests of the paralleling ridges of Massanutten Mountain contrast sharply with the irregular, lobate front of the Blue Ridge, and attest to the greater structural complexity of the rock strata in the Blue Ridge.
*51.5	(82.9)	Tanners Ridge Overlook. The ridges bounding the westward bulge of the Blue Ridge on the northwest and southwest are formed by steeply tilted, resistant quartzites of the Erwin (Antietam) Formation.
53.4	(86.0)	Naked Creek Overlook. A westward view across Long Ridge capped by the Weverton Formation. Much of the mountainous area to the west is underlain by the Catoctin, Swift Run, and Pedlar formations except at the base of the western (Erwin) ridges where the Chilhowee Group lies directly on the Pedlar Formation.
*54.8	(88.2)	Hazeltop Ridge Overlook. A broad extension of Shenandoah National Park protrudes westward almost to the South Fork of the Shenandoah River. At milepost 55, just south of the overlook on the east side of Skyline Drive, are exposures of Catoctin basalts with epidosite lenses, wavy cleavage surfaces, and slickensides with chatter-marked surfaces.
55.6	(89.5)	The Point Overlook. Panorama from the western ridges to the southwest to Tanners Ridge and Blackrock to the north. Intensely sheared Catoctin basalt flows and volcanic tuff beds can be seen in the roadcut on the east side of Skyline Drive.
56.4	(90.8)	Bearfence Mountain Parking Area. Less than 200 feet (61 m) east along the trail to Bearfence Mountain, ledges of coarse-grained, very quartzose, cross-laminated sandstones of the Swift Run Formation are exposed in the nose of a northeastward-plunging, overturned anticline. These sandstones exhibit better sorting and rounding of the sand grains than most exposures of Swift Run clastics. Skyline Drive crisscrosses the thin, poorly exposed Swift Run Formation several times in the next 2 miles (3 km) to the south.
57.5	(92.5)	Entrance to Lewis Mountain Campground. Vertical sandstones of the Swift Run Formation are exposed in the northern part of the campground and to the north.
59.1	(95.1)	Oaks Overlook.
61.3	(98.6)	Baldface Mountain Overlook. The town in the distance is Shenandoah, built mostly on terrace-gravel deposits that cover Ordovician limestones and dolomites.
62.7	(100.9)	South River Overlook and entrance to South River picnic grounds. View down South River gorge between two mountains of Catoctin basalt.
*64.4	(103.6)	Hensley Hollow Overlook. Good exposures of the Swift Run Formation in the roadcut. The formation as exposed here is mostly phyllite with some beds containing dispersed pebbles and cobbles of granitic rock, vein quartz, and phyllite clasts. Skyline Drive crosses the contact between the Swift Run and Pedlar formations several times to the south between here and Swift Run Gap.
		Beyond Hensley Ridge to the northwest, Elkton is visible at the west end of a linear fault segment that separates quartzites and phyllites of the Chilhowee Group to the south from the Cambrian carbonates of the Shenandoah Valley to the north (Plate 2).
65.5	(105.4)	Swift Run Gap and junction of Skyline Drive with U. S. Highway 33. The Swift Run Formation was named and described from exposures about a mile east of Skyline Drive along an abandoned road above U. S. Highway 33. The gap is underlain by granodiorite of the Pedlar Formation, which is exposed intermittently along the drive for the next 4.5 miles (7.2 km).
67.2	(108.1)	Swift Run Overlook. Pedlar granodiorite exposed in the roadcut and overlook is porphyritic, coarse-grained, locally epidotized, and jointing is well developed. Exposures of Catoctin basalts can be seen high on the ridge to the east.
*67.8	(109.1)	Sandy Bottom Overlook. Massive exposures of Pedlar granodiorite in the roadcut to the east. The panoramic view to the west includes sharp-crested phyllite and quartzite ridges of the western part of the Blue Ridge and the south peak of Massanutten Mountain in the distance. South of the overlook the park terrane west of Skyline Drive is dominated by ridges formed by rocks of the Chilhowee Group.
68.5	(110.2)	Smith Roach Gap. The Catoctin Formation caps the Pedlar granodiorite in the gap and on adjacent ridges.
*69.3	(111.5)	Bacon Hollow Overlook. The strongly foliated Pedlar granodiorite exposed in and near the overlook is typical of the rocks that underlie Bacon Hollow to the east. This spectacularly deep U-shaped hollow exemplifies the rapid weathering and disintegration of the Pedlar Formation that takes place after the removal of the protecting cap of resistant Catoctin basalt flows. Basalt cliffs rim the northern escarpment above cliffs developed in the granodiorite (Figure 2). The mountain to the south is capped by a much thicker remnant of the basalts, and the escarpment below them is not as well developed.
		Several small copper mines were opened in the lowest Catoctin basalt flow along the northern escarpment in the early twentieth century. Small quantities of native copper, malachite, cuprite, bornite, and chalcopyrite have been found in epidotized portions of the lower basalt flows.
*70.1	(112.8)	The Swift Run Formation, comprised of pebbly and sandy phyllites, is well exposed in the deep roadcut. The well-formed cleavage surfaces transverse to bedding have been flexed by a second cleavage parallel to the bedding, possibly indicating two periods of deformation.
70.6	(113.6)	Eaton Hollow Overlook. Good view 10 miles (16 km) to the north, where the lower Cambrian clastic rocks and Precambrian volcanic and plutonic rocks form a westward protuberence of ridges into the Shenandoah Valley.
71.2	(114.6)	Rocky Mount Overlook. A closer view of Rocky Mount, a ridge and talus deposit formed by the quartzites of the Erwin Formation (Figure 25). The low ridge and hollow east of Rocky Mount are underlain by phyllites and non-resistant metasandstones of the Harpers and Weverton formations. Strongly jointed basalt is exposed in the road cut opposite the overlook.
72.3	(116.3)	Beldore Hollow Overlook. View to the west of a broad expanse underlain by the Hampton Formation, the phyllitic middle portion of the Chilhowee Group. Massive epidotized basalts of the Catoctin Formation are exposed in the roadcut.
74.5	(119.9)	Loft Mountain Overlook. Dense, purple, slightly vesicular Catoctin basalts are exposed in the roadcut and on the overlook. Basalt-capped mountains to the east (Flat Top Mountain) and southwest (Loft Mountain) flank a boulder filled valley cut by Ivy Creek down into the Pedlar granodiorite.
75.3	(121.2)	Pinefield Gap. Approximate location of the contact between the Catoctin and Weverton formations, with the Weverton poorly exposed on the west.
75.4	(121.3)	Approximate location of the concealed contact between the Weverton and Hampton formations. Phyllites and metasandstones of the Hampton Formation are exposed intermittently from here to Twomile Run Overlook.
*76.2	(122.6)	Twomile Run Overlook. View to the west between Rocky Mountain and Rocky Mount, aptly named ridges capped by folded white Erwin quartzite strata and sheathed in quartzite talus. The sinuous, sharp-crested ridges and steep V-shaped hollows leading out from Skyline Drive to the north are typical landforms developed on incompetent metasandstone and phyllite of the Hampton Formation. To the northwest the resistant Erwin quartzite strata outline a syncline-anitcline fold-pair in the ridge top silhouetted against Shenandoah Valley and Massanutten Mountain (Figure 27).
76.9	(123.7)	Brown Mountain Overlook. View to the west into the Big Run drainage basin and southeast slope of Rocky Mountain. Folded, westward-dipping fine-grained metasandstone, phyllite, and coarse-grained quartzite of the Hampton Formation is exposed in the roadcut.
77.6	(124.9)	Ivy Creek Overlook. A view of Loft Mountain and the upper reaches of Ivy Creek gorge. In winter and early spring, quartzite ledges in the Weverton Formation are discernable along the low ridge east of Ivy Creek.
77.8	(125.2)	Good exposures of Hampton metasandstone and phyllite in the roadcut with well-defined bedding and cleavage. Cliffs of Weverton quartzite, in an overturned fold limb adjacent to its contact with the Catoctin Formation, are visible to the south in the upper (south) end of Ivy Creek gorge.
*78.1	(125.7)	Rocky Top Overlook. View to the west into the Big Run drainage basin, one of the largest drainage basins within the park. It is rimmed to the west and north by ridges capped by generally westward-dipping, but folded Erwin quartzite beds, and to the south and east by high Hampton and Catoctin ridges in the Loft Mountain area. Exposures of thick-bedded, phyllitic metasandstones and thin, interbedded shales of the Hampton Formation are exposed in a westward-dipping sequence in the roadcut by the overlook.
78.4	(126.1)	Cross-laminated, cross-grained quartzite of the Hampton Formation is exposed by the northbound lane adjacent to talus formed from the more common phyllites and metasandstones of that unit.
79.0	(127.1)	Exposure at milepost 79 of the lower phyllite member of the Hampton Formation along the southbound lane.
*79.4	(127.8)	Typical exposure of the lower Weverton Formation in the roadcut. Coarse, arkosic metasandstone, quartzites, and interbedded phyllite, all containing minor amounts of small quartz pebbles, are present in a westward-dipping sequence immediately above the purple slates that comprise the uppermost Catoctin Formation (not visible here). Park in the wayside to the south.
*80.9	(130.2)	Purple, porphyritic basalts of the Catoctin Formation crop out along the northbound lane in one of the best exposures of this rock type in the park (Figure 44). Park at Big Run Overlook to the south.
Figure 44. Porphyritic basalt beds on the south side of Skyline Drive. The dark, purplish-red metabasalts contain large crystals (phenocrysts) of red-stained feldspar and locally provide recognizable horizons in the metabasalt sequence.
79.5	(128.0)	Entrance to Loft Mountain Campground on the east, and wayside (service station and restaurant) on the west.
81.0	(130.3)	Exposures at milepost 81 along the northbound lane of purple slate and arkosic metasandstone of the Catoctin and Weverton formations, respectively, at the overturned contact between the units.
*81.2	(130.7)	Big Run Overlook. Northwest view of the Big Run drainage area and the gap between the Erwin quartzite ridges through which Big Run exits into Shenandoah Valley. Many of the better exposures of the Erwin and Hampton formations in Shenandoah National Park are present in this gap and upstream along Big Run. Pebbly, metasandstones of the Weverton Formation are exposed in the roadcuts to the east.
81.9	(131.8)	Doyles River Overlook. Eastward view of the Browns Cove drainage area formed on the Catoctin Formation and drained by Doyles River and Jones Run, along which several waterfalls may be seen from Falls Trail.
*82.3	(132.4)	Appalachian Trail crossing. From here to Browns Gap exposures along the southbound lane and along the Appalachian Trail to north (Figure 19) are representative of most lithologies in the Weverton Formation. Lenses of coarse grained, pebbly quartzite and laminated, silvery-green phyllite represent the range of clastic sedimentary strata exposed along Skyline Drive in this area. The lateral variation in bedding thickness and rock type is indicative of the probable fluvial origin of these sedimentary rocks. The Catoctin-Weverton contact, although not exposed, is at road level in Browns Gap.
83.7	(134.7)	Dundo Overlook and entrance to Dundo Campground. A broad expanse of gravel fans and terraces underlie the surface of the Shenandoah Valley visible to the west through the gap at the mouth of Dundo Hollow.
84.1	(135.3)	Falls Trail parking area on east.
*84.8	(136.4)	Gated fire road on west side of Skyline Drive provides hiking access to Blackrock, less than 0.5 mile (0.8 km) to the southwest. A large outcrop of bluish-gray, cross-laminated quartzite (Figure 21) within the Hampton Formation with an extensive talus deposit (Figure 26) forms Blackrock. The view to the west of Trayfoot Mountain includes several large but discontinuous talus deposits that were formed from equally discontinuous lenses of quartzite that appear to be lateral recurrences of the ledge-forming beds at Blackrock.
*86.8	(139.7)	Trayfoot Mountain Overlook. A broad view to the south of the crest of the Blue Ridge, with Trayfoot Mountain to the west and Pasture Fence Mountain to the east. From Dundo south to Jarman Gap, Skyline Drive follows the crest formed by rocks of the Hampton Formation. The paralleling ridge to the east is underlain by the Catoctin Formation that commonly forms higher crests than rocks of the Hampton Formation. In this area, however, the Hampton strata are gently inclined and only slightly folded, and include quartzite strata that make the unit more resistant to erosion and therefore capable of forming higher ridges. On and near Trayfoot Mountain the Hampton quartzites reach their maximum thickness and account for the still higher elevation of that ridge.
87.1	(140.1)	Appalachian Trail crosses Skyline Drive near exposure of ferruginous metasandstones of the Hampton Formation in the roadcut along the southbound lane.
87.6	(141.0)	Good view to northwest of the talus deposits formed by erosion of the Hampton quartzites on Trayfoot Mountain.
*88.7	(142.7)	Horsehead Overlook. View of Rocks Mountain to the southwest, an Erwin quartzite-capped ridge, and talus deposits of Hampton quartzite on the south end of Trayfoot Mountain. Exposures of interbedded metastandstone and phyllite of the Hampton Formation in the parking area have well-defined bedding and cleavage relationships that indicate these strata are overturned to the northwest (Figure 45).
Figure 45. Phyllite and thin interbedded metasandstone of the Hampton (Harpers) Formation in the overturned limb of a fold at Horsehead Mountain Overlook.
90.0	(144.8)	Calvary Rocks parking area. The trail west from Skyline Drive leads to Calvary Rocks, the nearest exposures of Erwin quartzites to Skyline Drive (Figure 24).
*9.14	(147.1)	Riprap Overlook. Turk Mountain, the high peak to the southwest, is capped by Erwin quartzite that has been preserved in the northeastern end of a southwestward-plunging syncline. To the west a broad expanse of farm land in the Shenandoah Valley may be seen. Low, forest-covered conical hills and linear, northeastward-trending ridges in the valley are formed where concentrations of chert or sandstone provide resistant zones in the Cambrian and Ordovician limestone and dolomite sequence.
*92.0	(148.0)	Moormans River Overlook. A view to the southeast through a major gap in the ridges formed by basalt flows of the Catoctin Formation. The lake, Moormans River Reservoir, a part of the Charlottesville water supply system, is impounded on granitic rocks of the Pedlar Formation where the Catoctin and Swift Run formations have been breached by Moormans River. The northeastward-trending segment of Moormans River occupies an extensive linear low within the Catoctin Formation, and may follow the trace of a reverse fault extending from the Loft Mountain area southwest through Jarman Gap. Additional evidence for such a fault may be the intensely sheared basalts locally exposed along this lineament.
92.1	(148.2)	Wildcat Ridge Overlook on west side of Skyline Drive.
92.7	(149.2)	Crimora Lake Overlook. Westward view of an abandoned manganese-mining operation. The ore was concentrated in the sandy-clay residual material formed along the contact between the Erwin and overlying Shady formations.
93.7	(150.8)	Turk Mountain Overlook on west side of Skyline Drive.
94.6	(152.2)	Roadcut exposures of phyllite in the lower portion of the Hampton Formation for next 0.3 miles (0.5 km).
95.4	(153.5)	Sawmill Run Overlook. View to the south of the Blue Ridge crest formed by a folded sequence of basalts and interbedded sedimentary and tuffaceous rocks of the Catoctin Formation. Good exposures of folded quartzite beds in the Weverton Formation may be seen along the Appalachian Trail near the crest of the pine-covered ridge to the southeast.
95.6	(153.8)	Approximate contact between the Weverton and Hampton formations; Weverton to the southeast.
*95.9	(154.3)	Sawmill Ridge Overlook. Large lenses and discontinuous beds of Weverton metastandstone and quartzite interbedded with sericitic phyllite are displayed in roadcut. The upper part of an overturned anticline is visible at road level adjacent to the overlook (Figure 46).
Figure 46. Crestal portion of an overturned anticline in the Weverton Formation at Sawmill Ridge Overlook. Well-developed cleavage inclined to the right (southeast) tends to obscure bedding features even in the quartzites and competent metasandstones that are exposed here.
96.1	(154.6)	Sandy phyllite in the base of the Weverton Formation exposed along northbound lane.
96.2	(154.8)	Contact of the Weverton and Catoctin formations just north of gas pipeline in gap. In this area discordant attitudes of beds across the contact suggest the presence of a small fault, an angular unconformity, or fluvial channels cut in the surface of the Catoctin Formation and subsequently filled with cross-laminated sediments that now comprise the base of the Weverton Formation.
96.3	(154.9)	Epidotized metasandstones of Catoctin Formation along the northbound lane trend obliquely into the contact with sediments of the lower part of the Weverton Formation to the west.
96.9	(155.9)	Jarman Gap.
97.4	(156.8)	Massive basalts of the Catoctin Formation are exposed in roadcut below the power-transmission line.
97.6	(157.0)	Conglomerate, meta-arkose, and phyllite of the Catoctin Formation in roadcut by northbound lane. This sedimentary member is in contact with purple amygdaloidal slates below (exposed below road level to the north) and with epidotized basalt breccia above (exposed a few hundred feet along Skyline Drive to the south, at the intersection with an abandoned logging road). Traces of epidotized conglomerate rubble, characteristic of the top of sedimentary units overlain by basalts, are found near this contact. Interbedded basalt, arkosic metasandstone, and phyllite are intermittently exposed along the Skyline Drive from here south to Calf Mountain Overlook, approximately 1.3 miles (2.1 km).
98.2	(158.0)	Sedimentary member of the Catoctin Formation offset by high-angle fault (not exposed on Skyline Drive).
*98.9	(159.1)	Calf Mountain Overlook. View of the Waynesboro area to the west across a structurally complex terrane developed on rocks of the Chilhowee Group. South of Jarman Gap the trend of the rocks in the Blue Ridge shifts abruptly westward nearly 35 degrees. This shift in trend is accompanied by an increased number of overturned fold limbs and the appearance of thrust faults only rarely present northeast of Jarman Gap in the southern section of the park. To the north and west of the overlook are the crests of Turk and Ramsey mountains, formed by steeply dipping quartzite strata in the lower Erwin Formation. This rock unit is exposed here along the east limb of a plunging syncline that is overturned southwest of the gap separating the two mountains. The western escarpment of the Blue Ridge south of Jarman Gap has developed on basalts of the Catoctin Formation along its overturned contact with the Weverton Formation. Approximately 50 feet (15 m) west of the overlook are exposures of conglomeratic, arkosic metasandstone of the Catoctin Formation which contain clasts of volcanic rocks.
99.6	(160.3)	Beagle Gap. Typical mountain pasture land on the Catoctin Formation. Vesicular basalts and flow-top breccias are exposed to the south along the Appalachian Trail on private land.
*99.9	(160.7)	Beagle Gap Overlook. View to the east of the Ragged Mountains, a series of peaks and sharp-crested ridges developed on older Precambrian gneisses within the core of the Blue Ridge anticlinorium. The long, low mountain range on the horizon (Brown Mountain and Southwestern Mountain) marks the east flank of the Blue Ridge anticlinorium and the outcrop belt of the Catoctin Formation along it.
102.1	(164.3)	McCormick Gap. This gap, and the hollows leading into it from the north and south, are developed along the trace of an extensive Triassic diabase dike. The dike, which has weathered more rapidly than the Catoctin basalts, is well exposed where it traverses the Pedlar Formation south of the Blue Ridge and the Chilhowee rocks to the north, but is buried beneath Catoctin debris on the Blue Ridge proper.
102.4	(164.8)	McCormick Gap Overlook. View to the west of the Waynesboro area and the Shenandoah Valley. The low, linear, wooded ridges to the west and northwest are formed by resistant quartzites of the Erwin, Hampton, and Weverton formations.
104.7	(168.5)	South entrance station to Shenandoah National Park. In roadcut to the east is exposure of southeastward-dipping, overturned beds of conglomeratic, sandy phyllite within the upper Catoctin Formation. Granite pebbles in this portion of the formation attest to the presence of a mountainous granitic terrane protruding through the older basalt flows and acting as a local source for the clastic sediments after most of the Catoctin basalts had been deposited.
105.2	(169.3)	Leave Shenandoah National Park and Skyline Drive, begin Blue Ridge Parkway. Interchange immediately to the south with U. S. Highway 250 and Interstate Highway 64 at Rockfish Gap, between Waynesboro and Charlottesville.
		END OF ROAD LOG