Falls Lake Geology Location text:
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10000: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002). Virtual Field
Trip stop 10000 is located in the Trcs/si2 unit of Clark et al. (2001).
Unit description: Trcs/si2 - sandstone with interbedded siltstone: cyclical depositional sequences of
whitish-yellow to grayish-pink to pale red, coarse- to very coarse-grained, trough cross-bedded lithic
arkose that fines upward through yellow to reddish-brown, medium- to fine-grained sandstone, to
reddish-brown, burrowed and rooted siltstone. Bioturbation is usually surrounded by greenish-blue to
gray reduction halos. Coarse-grained portions contain abundant muscovite, and basal gravel lags consist
of clasts of quartz, crystalline rock clasts, and mudstone rip-ups. In the Falls Lake area, the majority of
the crystalline rock clasts are composed of diorite interpreted to have been sourced from the
Beaverdam diorite-gabbro complex (Virtual field trip stops 10007 and 10008).
10000: Rolling View State Recreation Area - View looking southwest toward shore showing outcrops of
Triassic sandstones and interbedded siltstones.
10000: Rolling View State Recreation Area - View looking south toward shore (farther down shore to
east from above) of Triassic sandstones with interbedded siltstones.
10000: Rolling View State Recreation Area - View looking toward south (farther down shore to east
from above) showing resistant sandstone interlayer weathering out of bank interlayered with siltstones.
10000: Rolling View State Recreation Area - View looking toward south showing relatively thick
sandstone layer in siltstones.
10001: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002). Virtual Field
Trip stop 10001 is located in the Trcs unit of Clark et al. (2001).
Unit description: Trcs - interbedded sandstone and pebbly sandstone: reddish-brown to dark brown,
irregularly bedded to massive, poorly to moderately sorted, medium- to coarse-grained, muddy lithic
arkoses, with occasional, matrix-supported granules and pebbles or as 1-5 cm thick basal layers.
Muscovite is common to absent. Occasional bioturbation is usually surrounded by greenish-blue to gray
reduction halos. Beds are tabular, 1-3 meters thick, with good lateral continuity. Unit becomes more
conglomeratic eastward as it grades into Trcs/c.
10001: Rolling View State Recreation Area - View looking south toward shore with sandstone outcrops.
10001: Rolling View State Recreation Area - View looking south toward shore with interlayered pebbly
sandstones and siltstones.
10001: Rolling View State Recreation Area - Close up of outcrop showing pebbly sandstone and
siltstone.
10001: Rolling View State Recreation Area - Outcrop area of columnar jointed diabase dike.
Unit description: Jd – Diabase: Dark green-black to gray-black, fine grained to locally plagioclase phyric
diabase, typically olivine-bearing. Weathers to brown to reddish brown, spheroidally rounded, dense
boulders and cobbles that can be traced along strike where outcrop is absent.
10001: Rolling View State Recreation Area - Close up of portion of outcrop area of columnar jointed
diabase dike.
10002 and 10003: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002).
Virtual Field Trip stops 10002 and 10003 are located in the Trcc unit of Clark et al. (2001).
Unit description: Trcc - conglomerate: reddish-brown to dark brown, irregularly bedded, poorly sorted,
cobble to boulder conglomerate. Muscovite is rare to absent in the very coarse-grained to gravelly
matrix. An arbitrary cut-off of greater than 50 percent conglomerate distinguishes this unit from the
Trcs/c facies. In the Falls Lake area, clasts are chiefly composed of diorite interpreted to have been
sourced from the Beaverdam diorite-gabbro complex (Virtual field trip stops 10007 and 10008).
Maximum clast diameters are in excess of 2 meters on an unnamed island in Falls Lake (Virtual field trip
stop 10006).
10002: Sandling Beach State Recreation Area - View looking east toward shore with outcrop of
conglomerate and sandstone interlayers.
10002: Sandling Beach State Recreation Area - View looking east toward shore (farther to the south
along shore than above) with outcrop of conglomerate and sandstone interlayers.
10002: Sandling Beach State Recreation Area - View looking east toward shore (farther to the south
along shore than above) with outcrop of conglomerate and sandstone interlayers.
10003: Sandling Beach State Recreation Area - View looking east toward shore with outcrop of
conglomerate and sandstone interlayers. Outcrop and boulders of diabase also present in right side of
photograph.
10003: Sandling Beach State Recreation Area - View looking east toward shore (farther to the south
along shore than above) with outcrop of conglomerate and sandstone interlayers.
10003: Sandling Beach State Recreation Area – Wide view of shore looking northeast (farther to the
south along shore than above) with outcrop of conglomerate and sandstone interlayers.
10004: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002). Virtual Field
Trip stop 10004 is located in the Trcc unit of Clark et al. (2001).
Unit description: Trcc - conglomerate: reddish-brown to dark brown, irregularly bedded, poorly sorted,
cobble to boulder conglomerate. Muscovite is rare to absent in the very coarse-grained to gravelly
matrix. An arbitrary cut-off of greater than 50 percent conglomerate distinguishes this unit from the
Trcs/c facies. In the Falls Lake area, clasts are chiefly composed of diorite interpreted to have been
sourced from the Beaverdam diorite-gabbro complex (Virtual field trip stops 10007 and 10008).
Maximum clast diameters are in excess of 2 meters on an unnamed island in Falls Lake (Virtual field trip
stop 10006).
10004: Sandling Beach State Recreation Area - View looking north toward shore with boulders of
diabase.
10004: Sandling Beach State Recreation Area - View looking northeast at outcrop of diabase (with yellow
fieldbook) intruding conglomerates.
10004: Sandling Beach State Recreation Area - View looking northeast at outcrop of diabase (hammer)
intruding conglomerates (maroon-colored outcrop in left side of photograph).
10004: Sandling Beach State Recreation Area – Boulder of diabase displaying typical spheroid shape and
brown-colored weathering rind. Soils derived from diabase is rich in iron and magnesium and is typically
a reddish color from iron-oxides as displayed in photograph (scale bar is 5 cm wide).
10004: Sandling Beach State Recreation Area – Spheroidally weathered boulders and cobbles in place in
outcrop of diabase (scale bar is in centimeters).
10004: Sandling Beach State Recreation Area – Conglomerates exposed along shore.
10004: Sandling Beach State Recreation Area – Conglomerates exposed along shore. In the Falls Lake
area, clasts are chiefly composed of diorite interpreted to have been sourced from the Beaverdam
diorite-gabbro complex (Virtual field trip stops 10007 and 10008).
10006: Wide view looking southeast at southwest end of island. Wave cut shore line exposes
conglomerates with clasts of Beaverdam diorite and gabbro clasts up to 6 feet diameter.
10006: View looking southeast at northwest side of island showing large sized clasts in conglomerates.
10007: View looking southeast at outcrop of diorite (light colored matrix) with enclaves of gabbro (dark
colored zones) within the Beaverdam diorite-gabbro complex of in the Carolina terrane. This rock type
is the intrusive breccia described by Wylie (1984).
Wylie, A.S., Jr., 1984, Structural and metamorphic geology of the Falls Lake area, Wake County, North Carolina [M.S.
thesis]:Raleigh, North Carolina State University, 79 p.
10008: View looking south at outcrop of gabbro of Beaverdam diorite-gabbro complex in Carolina
terrane.
10008: View looking northeast at outcrop face of gabbro.
10009: Boulder of meta-pyroxenite from meta-ultramafic pod within Beaverdam diorite-gabbro
complex.
Replace 10010 text on web page with below
10010: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002) and data from
the Bayleaf quadrangle (Horton et al., 1992). Virtual Field Trip stop 10010 is located in the CZfs unit of
Clark et al. (2002).
Unit description: CZfs- Falls Lake schist: Silvery-gray to black, fine- to medium-grained, well foliated,
white mica ± biotite ± garnet ± chlorite schist to gneiss.
Note: The generalized geologic map figure drafted using the 1985 Geologic Map of NC (NCGS, 1985) places
location 10010 within the Beaverdam diorite-gabbro complex. The generalized geologic map was based on
reconnaissance level mapping. Subsequent detailed mapping by Clark et al., 2002, indicated that the location is
underlain by schist assigned to the Falls Lake schist unit.
10011: Portion of detailed geologic map of the Creedmoor quadrangle (Clark et al., 2002) and data from
the Bayleaf quadrangle (Horton et al., 1992). Virtual Field Trip stop 10011 is located in the CZfs unit of
Horton et al. (1992).
Unit description: CZfs- Falls Lake schist: Silvery-gray to black, fine- to medium-grained, well foliated,
white mica ± biotite ± garnet ± chlorite schist to gneiss.
10011 and 10019 – Bayleaf Quad
10015, 10016, 10017, 10018 and 10020 – Wake Forest Quad
10020 –Horse Creek Schist outcrop– ref Stop 8 in Stoddard and Blake (1994)
Unit descriptions:
Czfa
CZfua
CZcwq
CZchc
CZflg
References:
Blake, D.E., Clark, T.W., and Heller, M.J., 2001, A temporal view of terranes and structures in the eastern
North Carolina Piedmont, in Hoffman, C.W., ed. Field Trip Guidebook for the 50th Annual Meeting of the
Southeastern Section, Geological Society of America, Raleigh, North Carolina, p. 149-180.
Clark, T.W., Gore, P.J., and Watson, M.E., 2001, Depositional and structural framework of the Deep River
Triassic basin, North Carolina, in Hoffman, C.W., ed. Field Trip Guidebook for the 50th Annual Meeting of
the Southeastern Section, Geological Society of America, Raleigh, North Carolina, p. 27-50.
Clark, T.W., Phillips, C.M., Blake, D.E., 2002, Manuscript geologic map of the Creedmoor 7.5-minute
quadrangle, North Carolina: North Carolina Geological Survey, scale 1:24,000.
Froelich, A. J., and Olsen, P. E., 1984, Newark Supergroup, a revision of the Newark Group in eastern
North America: U.S. Geological Survey Bulletin 1537-A, p. A55–A58.
Hibbard, J., Stoddard, E.F., Secor, D., Jr., and Dennis, A., 2002, The Carolina Zone: Overview of
Neoproterozoic to early Paleozoic peri-Gondwanan terranes along the eastern flank of the southern
Appalachians: Earth Science Reviews, v. 57, n. 3/4, p. 299-339.
Horton, J. W., Jr., Blake, D. E., Wylie, A. S., Jr., and Stoddard, E. F., 1994, Geologic map of the Falls Lake–
Wake Forest area, north-central North Carolina— a synopsis, in Stoddard, E., Blake, D. (eds.), Geology
and Field Trip Guide, Western Flank of the Raleigh Metamorphic Belt, North Carolina: Carolina
Geological Society Field Trip Guidebook, North Carolina Geological Survey, Raleigh, NC, p. 1–11.
Horton, J.W., Jr., Blake, D.E., Wylie, A.S., Jr., and Stoddard, E.F., 1992, Geologic map of the Falls LakeWake Forest area, northcentral North Carolina: U.S. Geological Survey Open File Report 92-269, scale
1:24,000.
North Carolina Geological Survey (NCGS), 1985, Geologic Map of North Carolina: Raleigh, North Carolina
Department of Natural Resources and Community Development, Geological Survey Section, scale
1:500,000.
Olsen, P.E., 1978, On the use of the term Newark for Triassic and Early Jurassic rocks in the eastern
North America, Newsletters on Stratigraphy, v. 7, no. 2, p. 90-95.
Parker, J. M., III, 1979, Geology and mineral resources of Wake County: North Carolina Geological
Survey Bulletin 86, 122 pp.
Stoddard, E.F. and Blake, D.E., eds., 1994, Geology and Field Trip Guide, Western Flank of the Raleigh
metamorphic belt, North Carolina, Raleigh, North Carolina Geological Survey, Carolina Geological Society
Guidebook for 1994, 110 p.
Stoddard, E.F., Blake, D.E., Horton, J.W., and Butler, J.R., 1994, The Falls Lake thrust: A pre-metamorphic
terrane-bounding fault in the eastern North Carolina Piedmont, in Stoddard, E.F. and Blake, D.E., eds.,
Geology and Field Trip Guide, Western Flank of the Raleigh metamorphic belt, North Carolina, Raleigh,
North Carolina Geological Survey, Carolina Geological Society Guidebook for 1994, p. 39-46.
Wylie, A.S., Jr., 1984, Structural and metamorphic geology of the Falls Lake area, Wake County, North
Carolina [M.S. thesis]:Raleigh, North Carolina State University, 79 p.