m NUREG/CR-1621 A Characterization of Faults in the Appalachian Foldbelt Prepared by A. L. Odom, R. D. Hatcher, Jr. Florida State University Prepared for U.S. Nuclear Regulatory Commission £CLos uRE I NOTICE This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, apparatus product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights. Available from GPO Sales Program Division of Technical Information and Document Control U. S. Nuclear Regulatory Commission Washington, D. C. 20555 and National Technical Information Service Springfield, Virginia 22161 NUREG/CR-1621 A Characterization of Faults in the Appalachian Foldbelt Manuscript Completed: July 1980 Date Published: September 1980 Prepared by A. L. Odom, R. D. Hatcher, Jr. Contributing Authors: D. E. Dunn - University of New Orleans T. J. Engelder - Lamont-Doherty Geologic Observatory P. A. Geiser - University of Connecticut S. A. Kish - University of North Carolina S. Schamel - Lafayette College D. U. Wise - University of Massachusetts Florida State University Tallahassee, FL 32306 Prepared for Division of Siting, Health and Safeguards Standards Office of Standards Development U.S. Nuclear Regulatory Commission Washington, D.C. 20555 NRC FIN No. B1053-8 ABSTRACT The characterization is a synthesis of available data on geologic faults in the Appalachian foldbelt regarding their description, generic implications, rate of movement, and potential as geologic-seismic hazards. It is intended to assist applicants and reviewers in evaluating faults at sites for nuclear facilities. Appalachian faults were found to fall into 13 groups which can be defined on either their temporal, generic, or descriptive properties. They are as follows: Group 1, faults with demonstrable Cenozoic movement; Group 2, Wildflysch type thrust sheets; Group 3, bedding plane thrusts - decollements; Group.4, pre- to synmetamorphic thrusts in medium to high grade terranes; Group 5, post-metamorphic thrusts in medium to high grade terranes; Group 6, thrusts rooted in low crystalline basement; Group 7, high angle reverse faults; Group 8, strike slip faults; Group 9, normal (block) faults; Group 10, compound faults; Group 11, structural lineaments; Group 12, faults associated with local centers; and Group 13, faults related to geomorphic phenomena. Unhealed faults (Groups 1, 6, 8, 9, and 12) must be considered candidates for reactivation. Heated brittle or ductile faults (Groups 4, 5, and 10) are not places of mechanical discontinuity and are unlikely candidates for reactivation. The remaining groups (2, 3, 7, 11, and 1:3) should be individually assessed as to their potential for reactivation. iii CONTENTS Page I. Introduction .................................................. I A. Purpose ....................... ......... ................... I B. Rationale ................................................. 2 II. Summary of Characteristics and Distribution of FaulTs in The Appalachian Foldbelt .......................................... 5 III. Fault Reactivation ............................................ 37 A. Fault classes most subject to reactivation ................ .37 B. Fault classes least subject to reactivation ............... 37 C. Successful techniques for dating last motion .............. 38 D. Relation of seismicity to surface breaks .................. 39 IV. Definition of Key Terms ....................................... 40 A. Fault ...................................................... 40 I. Ductile fault ......................................... 40 2. Brittle fault ......................................... 40 a. Unhealed .......................................... 40 b. Filled ............................................ 40 c. Healed ............................................ 40 B. Slip Versus Separation .................................... 42 C. Fault Zone Materials ...................................... 42 I. Products of cataclasis ................................ 42 2. Products of mylonitization .......................... 42 V. Faults With Demonstrable Cenozoic Movement (Group I) .......... 43 VI. Wlldflysche Type Sheets (Group 2) ............................. 59 VII. Bedding Plane Thrusts -- Decollements (Group 3) ............... 81 V VIII. Pre-to Synmetamorphic Faults in Medium to High Grade Terrane (Group 4) ........................................................... III IX. Postmetamorphic Thrusts In Medium to High Grade Terranes (Group 5) .................................. ... ...... 125 X. Thrusts Rooted in Low Grade To Unmetamorphosed Crystalline Basement (Group 6) .................................... ......... 139 XI. High Angle Reverse Faults (Group 7) ............ 153 XII. Strike -slip Faults (Group 8) ....................... 162 XIII. Normal (Block) Faults (Group 9) ..................................... 190 XIV. Compound Faults With Long, Repeated Movement History (Group 10) .......................................................... 208 XV. Structural Lineaments (Group II) .................................... 233 XVI. Faults Associated With Local Centers (Group 12) ...................... 242 XVII. Geomorphic Faults (Group 13) ........................................ 252 XVIII. Glossary ............................................................ 261 XIX. Suggestions ......................................................... 270 XX. Appendices A. Critical need for in situ stress measurements ................... 275 B. Problems of DistinguishIng Between Seismic and Aseismic Faults i. 279 C. Cataclasis versus mylonitization ................................ 282 D. Linemanship ..................................................... 289 vi List of Illustrations Figure Page I-I Geotectonic map of the Appalachian Foldbelt ................ 6 11-2 Map Showing Distribution of Group I Faults ................. 7 11-3 I I 11 it i 2 It 8 11-4 i t if i W 3 I .99................. 11-5 If I I " It 4 ................. 10 11-6 I iI15 I. 5 ". II 12 11-7 W it WI ". 6 I. 11-8 I I i W W 8 ................. 13 . 14 11- 9 Wt WI I. 9 . ... ... 15 11-10 WI... W 10.WI10 12 ............. 16 WISW W" W" WI 13 WI" 17 1112 17 1 1 o .......... IV-I Relation Between Brittle and Ductile Faults ................ 41 V-I Recent Thrusting and Folding of a Syncline ................ 45 V-2 Map of Stafford and Brandywine Fault Systems .............. 48 V-3 Stratigrafic Variations across Stafford Fault Systems ...... 50 V-4 Geologic Cross Section in Area of Stafford ................ 51 Vl-I Schematic Representation of Three Types of Submarine Slides. 60 VI-2 Eastern North America During the Ordovician ................ 62 VI-3 Tectonic Units of the Taconic Allochthon ................... 63 VI-4 Cross Section of Central Taconic Range ..................... 63 VI-5 Map of Pennsylvania Great Valley and Allochthonous Rocks in Martinsburg Fm ....................................... 65 VI-6 Allochthons of Martinsburg Fm, Pennsylvania ................ 66 VI-7 Geologic Cross Section Along West Bank of Susquehanna River. 67 VI-8 Pre-Taconic and Taconian Evolution of North American in Western New England ....................... 71 VI-9 Model for the Evolution of the Appalachian Orogen ....... 72 VI-lO Diagram of Alternative Gravitational Emplacement Models .... 74 VI-II Schematic Section Showing Emplacement of Thrust Sheets ... 74 VII-I Ramping of Bedding Plane Fault ............................ 82 VII-2 Bedding Plane Fault Climbing Section by Decollement ..... 83 VII-3 Relationship Between Folding and Faulting .................. 84 VII-4 Apparent Violations of Dahlstroms Rules of Thrusting ...... 86 VI1-5 Thrust Fault Anatomy ...................................... 86 VII-6 Thrust Fault Terminology .................................. 87 VII-7 Complications of Thrust Faulting Geometry-Leading Edge ..... 8 VII-8 It it "I Wi "I -Trailing 8892 VI1-9 Bow Thrust ................................................ 92 V II-I 0 Rectangular Thrust ............... ........ ................ 92 Vi I-Il Secondary Transverse Tear Faults ........................... 93 VI1-12 Termination of Bedding Plane Thrust Into Folds ............. 93 VII-13 Terminations of Bedding Plane Thrust ..................... 94 VI 1-14 Relationship Between Detachment Surface and Silurian Salt Horizon ............................................ 100 VIl-15 Independence Between Paleo-isotherms and Detachment Surface ................................................. 103 VIII-I Folded, Imbricate Group 4 Thrusts of the Martic Region ..... 113 VIII-2 Major Structural Features of Eastern Connecticut ........... 114 Vii IX-I Typical Group 5 Thrust ....................................... 126 IX-2 Geologic Section of the Blue Ridge Province (N.C. - Tenn.) 129 IX-3 Cross Section of the Southern Appalachians ... 130 IX-4 Geologic Map of the Northeast End of the Alto AIlochthon ..... 131 X-1 Cross Section along the Valley and Ridge - Blue Ridge Boundary .................................................. 140 X-2 Section Acrossthe Reading Prong, Delaware Valley ............ 141 X-3 Map and Section of Little Stone Mountain (Tenn.) ............. 142 X-4 Map and Section of South Sandis field Quadrangle (Mass.) ..... 144 X-5 Geologic