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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 conglomeraticeastward 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.

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).

10004: Sandling Beach State Recreation Area - View looking north toward shore with boulders of diabase.

10004: Sandling Beach State Recreation Area - View looking northeastat 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 Lake-Wake 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.