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Bed Rock Geology of the East Barre Area, Vermont

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Bed Rock Geology of the East Barre Area, Vermont BED ROCK GEOLOGY OF THE EAST BARRE AREA, VERMONT By VARANASI RAMA MURTHY VERMONT GEOLOGICAL SURVEY CHARLES G. DOLL, State Geologist Published by VERMONT DEVELOPMENT COMMISSION MONTPELIER, VERMONT BULLETIN NO. 10 1957 dm I '- S ' - S '5 i . Rock of Ages Ouariv seen from its southwestern end. Prominent joint surfaces and a dark dike cutting the Barre granite are seen in the left side of the photograph. Grout piles in the background. CONTENTS PAGE ABSTRACT 11 INTRODUCTION ....................... 12 Location and Area .................... 12 Regional Geologic Setting . . . . . . . . . . . . . . . 12 Previous Work ..................... 14 Present Study ..................... 15 Method of Work . . . . . . . . . . . . . . . . . . . 16 Acknowledgments ................... 16 Topography and Drainage ................ 17 Climate and Water Supply ................ 18 Industries and Access to the Area ............. 19 STRATIGRAPRY . . . . . . . . . . . . . . . . . . . . . . 19 General Statement ................... 19 Stratigraphic Units . . . . . . . . . . . . . . . . . . 20 Stratigraphic Relations .................. 21 Definitions of Formations ................ 22 Westmore Formation . . . . . . . . . . . . . . . . 22 Barton River Formation ................ 22 Waits River Formation ................ 24 Barton River Formation ................. 24 Distribution . . . . . . . . . . . . . . . . . . . . 24 Lithology ...................... 24 Thickness . . . . . . . . . . . . . . . . . . . . . 25 Correlation ...................... 25 Age ......................... 26 Westmore Formation . . . . . . . . . . . . . . . . . 27 Distribution . . . . . . . . . . . . . . . . . . . . 27 Lithology ...................... 28 Thickness........................ 31 Correlation ...................... 31 Age......................... 32 Waits River Formation ................. 35 General Statement .................. 35 History of the Name .................. 35 Lithology ...................... 36 Thickness . . . . . . . . . . . . . . . . . . . . . 37 PAGE Correlation ...................... 38 Age ......................... 38 Standing Pond Member of the Waits River Formation . . 39 General Statement .................. 39 Lithology ...................... 40 Thickness . . . . . . . . . . . . . . . . . . . . . . 41 Gile Mountain Formation . . . . . . . . . . . . . . . . 41 History of the Name .................. 41 Distribution . . . . . . . . . . . . . . . . . . . . . 42 Lithology ...................... 42 Thickness . . . . . . . . . . . . . . . . . . . . . . 44 Correlation ...................... 44 Age ......................... 44 Relationship between the Westmore and the Gile Mountain formation ...................... 44 STRUCTURE ........................ 46 General Statement ................... 46 Terminology ...................... 47 Bedding ....................... 47 Schistosity ...................... 47 Cleavage ....................... 47 Syncline and Anticline ................. 47 Trend of Bedding ................... 47 Dextral and Sinistral Patterns of Folds .......... 48 Structural Features ................... 48 Early Structures ....................SO Early Schistosity .................. 50 Early Folds ......................SI Later Structures ....................S6 General Statement ..................S6 Field Data ..................... 57 Origin of the Structures . . . . . . . . . . . . . . . . . 59 Structure of the Westmore Formation ........... 66 Structural Synthesis ................... 68 PLUTONIC ROCKS ..................... 69 General Statement ................... 69 Early Work ...................... 70 The Bane granite .................... 70 PAGE Petrography . . . . . . . . . . . . . . . . . . . . 71 Modal Analysis of the Bane Granite ........... 73 Relationship between Muscovite and Biotite ....... 76 Relationship between Muscovite and Plagioclase . . . . 76 The Knox Mountain Granite ............... 79 Petrography ..................... 79 Qualitative Spectrographic Analysis of the Granites ..... 81 Relation of the Granites with the host rocks . . . . . . . 82 Internal Structural Features of the Granites . . . . . . . 86 Flow Structures .................... 86 Joints ........................ 86 Longitudinal Joints ................. 87 Cross Joints..................... 87 Flat-lying Joints .................. 88 Origin of the Bane Granite ................ 88 Petrologic Evidence .................. 89 Structural Evidence .................. 92 Mode of Emplacement .................. 93 Age of the Bane Granite ................. 95 Dike Rocks ....................... 95 Granitic Dikes . . . . . . . . . . . . . . . . . . . 95 Structural Trends .................. 96 Mineralogy of the Pegmatites ............. 97 Basic Dikes ...................... 97 Mineralogy ..................... 97 METAMORPHISM ...................... 98 General Statement ................... 98 Argillaceous Rocks .................. 99 Green-Schist Facies ................. 99 Albite-Epidote-Amphibolite Facies .......... 100 Amphibolite Facies . . . . . . . . . . . . . . . . 101 Calcareous and Impure Calcareous Rocks ........ 101 Green-Schist Facies ................. 101 Albite-Epidote-Amphibolite Facies .......... 102 Amphibolite Facies . . . . . . . . . . . . . . . . 102 Metavolcanics .................... 103 Contact Metamorphism ................ 104 Amphibolite Facies . . . . . . . . . . . . . . . . 104 PAGE Distribution and Mode of Occurrence of Important Minerals . 105 Chlorite ...................... 105 Calcite ....................... 105 Biotite ....................... 108 Garnet ....................... 108 Actinolite ..................... 108 Hornblende ..................... 110 Diopside ...................... 110 Sillimanite ..................... 110 Cordierite...................... 110 Plagioclase Feldspar ................. 110 Relation between Deformation and Metamorphism...... 111 Cause of Metamorphism ................. 112 ECONOMIC GEOLOGY .................... 113 Granite ......................... 113 Factors Affecting the Value of Granite .......... 113 Economic Classification of Granite ........... 114 Copper Deposits .................... 114 History of the Mines ................. 114 Geology of the Mines Region .............. 115 Mineralogy of the Ore ................. 115 Origin of the Ore ................... 116 Gravel Deposits ..................... 117 BIBLIOGRAPHY ...................... 118 Illustrations PLATES PAGE Frontis piece. Rock of Ages Quarry, seen from its southwestern 2 end. Prominent joint surface and a dark dike cutting the Barre granite are seen in the left side of the photograph. Grout piles in the background. PLATE 1. Geological Map of the East Bane quadrangle. Scale 1:62,500 . (in pocket) 2. Structural Map of the East Bane quadrangle . Scale 1:62,500 . (in pocket) 3. Regional geologic map and probable structure sections ...................(in pocket) PLATES PAGE 4. Bedding in the Westmore formation. Outcrop about lz miles N25°E of Cobble Hill School. Alternation of argil- laceous and arenaceous Iithology. Thicker beds are more quartzose. Schistosity parallel to bedding . . . . . . . 29 5. Sinistral folds shown by deformed quartz veins in the West- more formation on top of Mt. Pleasant ........ 52 6. Sinistral minor folds in the bedding, on the eastern flank of Mt. Pleasant, 150 yds. NE of the summit. Outcrops of the Westmore formation ...............S2 7. Early stage sinistral folds in calcareous schist of the Waits River formation. Size of the minor folds varies from a few inches to a few feet. Outcrop I Y2 miles south of Pike Hill School ...................... 55 8. Slip cleavage parallel to axial planes of small chevron folds in the Standing Pond amphibolite. Outcrop IY4 miles N70°E of Eaton School .................. 55 9. Completely recumbent acute fold in a limestone bed of the Waits River formation. Outcrop 1Y2 miles S20°E of South Washington village ................ 58 10. Acute recumbent fold in limestone beds of the Waits River formation. Picture taken obliquely to include the cross- section and the longitudinal section. Axial plane dips 20° due north. Outcrop 1V2 miles south of South Washington village ...................... 58 11. Sinistral recumbent folds in limestone beds of the Waits River formation. Outcrop back of a farm house IY6, miles S10°E of South Washington village .......... 59 12. Plastic deformation in calcareous beds of the Waits River formation. Folds plunge west, and the axial planes of folds dip 35° due NW. Outcrop 1Y2 miles N45°W of South Washington village ................. 60 13. Rotated sinistral folds of the early stage, on the crestal part of the cleavage arch. Outcrop of calcareous schist of the Waits River formation IY2 miles southeast of South Washington village ................. 60 14. Sinistral folds of the early stage deformation in the Waits River formation. Outcrop I mile SE of Waits River village 61 15. Sinistral folds in limestone bed of the Waits River formation. PLATES PAGE Outcrop in road-cut on Rte. 302, mile NW of Fuller Hill ........................ 61 16. Sharp contact between 'dark' and 'light' granite. Faint banding observable
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