VIRGINIA DIVISION OF MINERAL RESOURCES PUBLICATION 35 GEOLOGY OF THE VILLAMONT AN D MONTVALE OUADRANGLES, VIRGINIA William S. Henika COMMONWEALTH OF VIRGINIA DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT DIVISION OF MINERAL RESOURCES Robert C. Milici, Commissioner of Mineral Resources and State Geologist CHARLOTTESVI LLE, VI RG IN IA 1 981 VIRGINIA DIVISION OF MINERAL RESOURCES PUBLICATION 35 GEOLOGY OF THE VILLAMONT AN D MONTVALE OUADRANG LES, VIRGINIA William S. Henika COMMONWEALTH OF VIRGINIA DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT DIVISION OF MINERAL RESOURCES Robert C. Milici, Commissioner of Mineral Resources and State Geologist CHARLOTTESVILLE, VIRGINIA 1 981 FRONT COVER: View of overturned beds in the Unicoi Formation near Bear Wallow Gap, Montvale quadrangle. Photo by T. M. Gathright, II. REFERENCE: Portions of this publication may be quoted if credit is given to the Virginia Division of Mineral Resources. It is recommended that refer- ence to this report be made in the following form: Henika, W. S., 1981, Geology of the Villamont and Montvale quadrangles, Virginia: Virginia Division of Mineral Resources Publication 3b. 18 p. VIRGINIA DIVISION OF MINERAL RESOURCES PUBLICATION 35 GEOLOGY OF THE VILLAMONT AN D MONTVALE OUADRANG LES, VIRGINIA William S. Henika COMMONWEALTH OF VIRGINIA DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT DIVISION OF MINERAL RESOURCES Robert C. Milici, Commissioner of Mineral Resources and State Geologist CHARLOTTESVILLE. VIRG I NIA 1 981 DEPARTMENT OF CONSERVATION AND ECONOMIC DEVELOPMENT Richmond, Virginia FRED W. WALKER, Director JERALD F. MOORE, Deputy Director BOARD ARTHUR P. FLIPPO. Doswell. Chairman HENRY T. N. GRAVES, Luray, Vice Chairman FRANK ARMSTRONG. III. Winchester WILBUR S. DOYLE, Martinsville ADOLF U. HONKALA, Midlothian MILDRE D LAYNE, Williamsburg FREDERIC S. REED, Manakin-Sabot GEORGE P. SHAFRAN, Arlington SHELTON H. SHORT, III, Richmond NICHOLAS D. STREET, Grundy E. FLOYD YATES, Powhatan COMMONWEALTH OF VIRGINIA Department of General t"J;"Tii;*li_ion of Purchases and Supply CONTENTS Pecn Abstract. I Introduction I Stratigraphy..... I Precambrian rocks 1 Strongly layered granulite gneiss. 1 Leucocratic granulite gneiss 2 Massive charnokite 2 Altered dikes. 2 Cambrian System 2 Unicoi Formation - lower member 2 Unicoi Formation - upper member 3 Harpers Formation 3 Antietam Formation 3 Shady Dolomite 4 Rome-Waynesboro unit . 4 Elbrook Formation 4 Conococheague Formation .. 4 Ordovician System 5 Stonehenge Limestone 5 Beekmantown Formation . 5 Lincolnshire Limestone and New Market Limestone 8 Paperville Shale and Liberty Hall Formation .. 8 Martinsburg Formation .... 8 Silurian-Ordovician rocks . 8 Tuscarora and Oswego sandstone 8 Devonian-Silurian rocks . 8 Lower Devonian-Upper Silurian sandstone. .. 8 Devonian System 8 Millboro Shale 8 Quaternary System 8 Talus 8 Fan deposits .. .. 8 Terrace deposits 9 Alluvium 9 Geologic structure I Pulaski thrust sheet. I Blue Ridge thrust sheet . 9 Folds in Blue Ridge thrust sheet. 9 Faults within the Blue Ridge thrust sheet. 10 Peaks of Otter fault . 10 Glade Creek fault . 10 Window south of Fincastle 11 Glade Creek window 11 Goose Creek window 11 Salem thrust sheet . 11 Coyner Mountain structure 11 Mineral Resources 12 Stone .......... t2 Shale and clay 13 Iron ore 13 Hematite 13 Limonite 13 Geologic and economic factors affecting land modification L4 Areas of floodplains, alluvial fans, and terrace deposits. l4 PRcp Areas of crystalline rocks t4 Areas of clastic rocks 15 Areas of Ordovician shale and Silurian-Devonian suartzite and shale 15 Areas of interlayered clastic and carbonate rocks 15 Areas of carbonate rocks t5 References 17 Index 18 ILLUSTRATIONS Pr-arn 1. Geologic map of Villamont and Montvale quadrangles, Virginia .... ....In pocket FrcuRn Pecn 1. Index map for Villamont and Montvale quadrangles . 1 2. Major fault and fault-related features in the Villamont and Montvale quadrangles . 6-7 3. Alternative cross section along the southeastern portion of A-A' (Plate 1) . 10 TABLES Pacn 1. Chemical composition of dolomite from Blue Ridge Stone Corporation quarry, Blue Ridge, Virginia 12 2. Highway aggregate test data, Blue Ridge Stone Corporation quarry, Blue Ridge, Virginia...... 12 o Analyses of hematite ore from the Harpers Formation . 13 4. Analyses of limonite ore from the Blue Ridge front . 14 GEOLOGY OF THE VILLAMONT AND MONTVALE QUADRANGLES, VIRGINIA By William S. Henika ABSTRACT border of area), and the minimum elevation of The Villamont and Montvale quadrangles are approximately 890 feet occurs along Goose Creek. located approximately 10 miles southeast of Roa- noke, Virginia in western Bedford and eastern Botetourt counties. The quadrangles include por- tions of the Appalachian Valley and Ridge, BIue Ridge and the western Piedmont geological prov- inces. The portion of the area in the western Piedmont and the eastern part of the Blue Ridge is underlain by Precambrian metamorphic rocks which have been thrust northwestward over the Paleozoic sed- imentary formations which underlie the Appala- chian Valley. Large, folded thrust systems mapped in the area Figure 1. Index map for Villamont (V) and Montvale (M) include the Blue Ridge thrust system, the Salem quadrangles. thrust sheet and the Pulaski thrust system. Win- dows, tectonic slices and folds occur within each Much of the region was studied by Woodward sheet. A sequence of thrusting events, beginning (1932) and by Butts (1941). Several excellent doc- with the emplacement of the Pulaski sheet and end- toral dissertations of the area were used as guides to ing with subthrust splay faulting and folding in the my own mapping program. Studies include ones by younger Blue Ridge thrust sheet, is described. Andrews (1952), Chen (1960), Hamilton (1964) and Hematite was extensively mined from Cambrian Hazlett (1968). The field survey began in 1977 in the sandstones in the Blue Ridge, and limonite was Villamont quadrangle and was completed in the mined from secondary deposits along the Blue Montvale quadrangle in 1980. Ridge front during the last century. Agricultural I wish to acknowledge Dr. Bruce Hobbs who as lime and crushed stone for aggregate are produced acting State Geologist initiated and supported the from Cambrian dolomite and were formerly pro- mapping project in the Roanoke area. Dr. Robert C. duced from several now abandoned quarries; high- Milici, who became State Geologist in 1979, not only calcium limestone, dolomite, shale and clay are provided guidance on the complex structures in the potential mineral resources in the area. area, but also assisted our mapping parties during several field visits. INTRODUCTION Numbers preceded by "R" or "F" in parentheses correspond to rock The Villamont and Montvale Z.b-minute quad- and fossil sample localities; sam- ples are on file at the Division of Mineral Resources. rangles are located approximately 10 miles north- eastof Roanoke, Virginia in western Bedford County and eastern Botetourt County. Together the quad- rangles comprise an area of approxim ately ll7 STRATIGRAPHY square miles, bounded by north latitudes 97"22,90,, PnocenasnlAN RoCKS and 37"30' and by west longitudes T9o3Z'30" and (Strongly) T,ayered Granulite Gneiss 79"52'30" . The quadrangles (Figure 1) include por- tions of the Appalachian Valley, the Blue Ridge and Strongly layered granulite gneiss is the oldest the Piedmont provinces. The Blue Ridge is a major unit recognized in the area. The rock in fresh expo- peninsular ridge that bisects the area diagonally sures (REFERENCE LOCALITY l, R-742L; R- from the northeast to the southwest. It is separated 7559-R7563) consists of dark-gray to grayish- from the high mountains in the southeastern portion green, garnet-othopyroxene granulite gneiss inter- of the area by the broad valley of the North Fork layered with garnet-qttartz bearing leucocratic Goose Creek, which lies in a window through the granulite gneiss layers 5 to 50 feet (1.5-15 m) thick. upper levels of the Blue Ridge thrust sheet. The A segregation layering is defined by lenticular maximum elevation of approximately 2,810 feet masses of bluish qtartz or quartz, orthoclase and occurs on the peak of McFalls Mountain (eastern andesine separated by lenticular segregations of VrRcrlre DrvrsroN op MtNpRel RESOURCES orthopyroxene (uralitized), garnet and opaque min- The unit is exposed along State Road 692 in the erals (1-3 mm thick). Feldspathic layers weather southeastern portion of the Montvale quadrangle light- to yellowish-gray to pinkish whereas the (REFERENCE LOCALITY 4). The massive igne- mafic minerals weather to moderate browns. ous rock is also well-exposed along the Blue Ridge Weathering accentuates the aspect of layering in Parkway just east of the quadrangle boundary in the rock. The high embankment on the north side of the Peaks of Otter National Recreation area, where the Blue Ridge Parkway at the Five Oaks Overlook it typically forms high mountains such as Harken- (REFERENCE LOCALITY 2) shows such well- ing Hill and Sharp Top. The charnokite contact is developed layering. In addition, at that exposure the sharply discordantwith the strongly layered granu- granulite gneiss is cut by well-defined, leucocratic lite gneiss on the slopes of Harkening Hill. stringers that increase in abundance in the unit Where the charnokite pluton is narrow, the con- towards the southwest and seem to be related to the tact appears more or less coneordant, but it is leucogranulite gneiss mapped separately on Wild- sheared; exposures