Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-26T17:05:14.120Z Has data issue: false hasContentIssue false
  • English
  • Français

Prograde Transitions of Corrensite and Chlorite in Low-Grade Pelitic Rocks from the Gaspé Peninsula, Quebec

Published online by Cambridge University Press:  28 February 2024

Wei-Teh Jiang  and
Donald R. Peacor
Wei-Teh Jiang*
Affiliation:
Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1063
Donald R. Peacor
Affiliation:
Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1063
*
2Present address: Department of Geology, Arizona State University, Tempe, Arizona 85287-1404.
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A prograde sequence of corrensite and chlorite in pelitic rocks of the diagenetic zone, anchizone, and epizone (illite crystallinity indices = 0.17–0.58°Δ2θ) of the Gaspé Peninsula, Quebec, was studied by analytical and transmission electron microscopy (AEM and TEM). The data collectively suggest that diagenesis/metamorphism of chlorite and corrensite follows a sequence of phase transitions, compositional homogenization, and recrystallization, approaching a state of equilibrium for which chlorite is the stable phase.

Corrensite occurs as coalescing, wavy packets of layers intergrown with chlorite and illite in the diagenetic and low-grade anchizonal rocks. Intergrowths of discrete chlorite and corrensite crystals, interstratified packets of chlorite and corrensite layers, terminations of smectite-like layers by chlorite layers, and 2–3 repeats of R2- and R3-ordered chlorite-smectite mixed layers occur. These materials are alteration products of detrital biotite or other precursor phases like trioctahedral smectite. The crystal size and proportion of corrensite decrease significantly from the diagenetic zone to the anchizone. Deformed corrensite is crosscut by straight packets of chlorite and corrensite in the diagenetic sample. Some chlorite occurs as discrete, euhedral to subhedral crystals intergrown with or enclosed by other phases in the absence of corrensite. The crystal size of chlorite and definition of crystal boundaries increase whereas density of crystal imperfections and randomness in orientation decrease with increase in grade of diagenesis/metamorphism. Crystals that are kinked or bent, or display gliding along (001) form low-angle boundaries with relatively defect-free crystals, implying deformation during crystal growth. Abundant well-defined low-angle boundaries associated with dislocations are observed in the higher grade rocks, consistent with a stage of readjustment of crystal boundaries during crystal growth. The AEM analyses show that the corrensite has lower Fe/(Mg + Fe) and Al/(Si + Al) than the coexisting chlorite in the diagenetic sample, and that the ranges of composition of chlorite of different grades overlap and become smaller with increasing grade, implying prograde homogenization.

The data imply that corrensite is a unique phase that is metastable relative to chlorite: its conversion to chlorite occurred at a grade as low as that of the high-grade diagenetic zone. The textural relations suggest that the metamorphic crystallization and recrystallization were coeval with deformation processes due to tectonism, partially modified by subsequent contact metamorphism. The data, combined with those of previous reports, suggest that the Gaspé Ordovician rocks constitute a part of a regional distribution of trioctahedral phyllosilicate-rich rocks in the northern Appalachians. The regional occurrence of abundant chloritic minerals is thus directly related to a specific tectonic regime with precursor sediments largely derived from an andesitic arc system(s).

Keywords

Analytical electron microscopyChloriteChlorite crystallinityCorrensiteDiagenesisGaspé PeninsulaSediment provenanceSyntectonic deformationTransmission electron microscopy
Type
Research Article
Information
Clays and Clay Minerals , Volume 42 , Issue 5 , October 1994 , pp. 497 - 517
Copyright
Copyright © 1994, Clay Minerals Society

Footnotes

1

Contribution No. XXX from the Mineralogical Laboratory, Department of Geological Sciences, The University of Michigan, Ann Arbor, Michigan 48109-1063.

References

Ahn, J. H., and Peacor, D. R.. 1985 . Transmission electron microscopic study of diagenetic chlorite in Gulf Coast argillaceous sediments. Clays & Clay Miner. 33: 228–236.CrossRefGoogle Scholar
Ahn, J. H., and Peacor, D. R.. 1986 . Transmission and analytical electron microscopy of the smectite-to-illite transition. Clays & Clay Miner. 34: 165–179.Google Scholar
Alt, J. C., Anderson, T. F., Bonnell, L., and Muehlenbachs, K.. 1989 . Mineralogy, chemistry, and stable isotopic compositions of hydrothermally altered sheeted dikes: ODP Hole 504B, Leg 111. Proc. Ocean Drilling Prog., Sci. Res. 111: 27–39.Google Scholar
Alt, J. C., Honnorez, J., Laverne, C., and Emmermann, R.. 1986 . Hydrothermal alteration of a 1 km section through the upper oceanic crust, DSDP Hole 504B: Mineralogy, chemistry and evolution of seawater-basalt interactions. J. Geophys. Res. 91: 10309–10335.CrossRefGoogle Scholar
Anjos, S. C., 1986. Absence of clay diagenesis in Cretaceous-Tertiary marine shales, Campos basin, Brazil. Clays & Clay Miner. 34: 424–434.CrossRefGoogle Scholar
April, R. H., 1981. Trioctahedral smectite and interstratified chlorite/smectite in Jurassic strata of the Connecticut Valley. Clays & Clay Miner. 29: 31–39.CrossRefGoogle Scholar
Bailey, S. W., 1988. Chlorites: Structures and crystal chemistry. In Hydrous Phyllosilicates (Exclusive of Micas), Reviews in Mineralogy, Volume 19. Bailey, S. W., ed. Washington, D.C.: Mineralogical Society of America, 347–403.CrossRefGoogle Scholar
Banfield, J. F., and Eggleton, R. A.. 1988 . Transmission electron microscope study of biotite weathering. Clays & Clay Miner. 36: 47–60.CrossRefGoogle Scholar
Bettison, L. A., and Schiffman, P.. 1988 . Compositional and structural variations of phyllosilicates from the Point Sal ophiolite, California. Amer. Mineral. 73: 62–76.Google Scholar
Bettison-Varga, L., Mackinnon, I. D. R., and Schiffman, P.. 1991 . Integrated TEM, XRD, and electron microprobe investigation of mixed-layer chlorite-smectite from the Point Sal ophiolite, California. J. Metamorphic Geol. 9: 697–710.CrossRefGoogle Scholar
Björlykke, K., 1974. Geochemical and mineralogical influence of Ordovician island arcs on epicontinental clastic sedimentation. A study of Lower Palaeozoic sedimentation in the Oslo Region, Norway. Sedimentology 21: 251–272.CrossRefGoogle Scholar
Boles, J. R., and Franks, S. G.. 1979 . Clay diagenesis in Wilcox sandstones of southwest Texas: Implications of smectite diagenesis on sandstone cementation. J. Sediment. Petrol. 49: 55–70.Google Scholar
Brigatti, M. F., and Poppi, L.. 1984 . Crystal chemistry of corrensite: A review. Clays & Clay Miner. 32: 391–399.CrossRefGoogle Scholar
Brown, G., and Brindley, G. W.. X-ray diffraction procedures for clay mineral identification. In Crystal Structures of Clay Minerals and Their X-ray Identification. Brindley, G. W., and Brown, G., 1984 eds. London: Mineralogical Society, 305–360.Google Scholar
Burtner, R. L., and Warner, M. A.. 1986 . Relationship between illite/smectite diagenesis and hydrocarbon generation in Lower Cretaceous Mowry and Skull Creek shales of the northern Rocky Mountain area. Clays & Clay Miner. 34: 390–402.CrossRefGoogle Scholar
Cathelineau, M., 1988. Cation site occupancy in chlorites and illites as a function of temperature. Clay Miner. 23: 471–485.CrossRefGoogle Scholar
Cathelineau, M., and Nieva, D.. 1985 . A chlorite solid solution geothermometer. The Los Azufres (Mexico) geothermal system. Contrib. Mineral. Petrol. 91: 235–244.CrossRefGoogle Scholar
Chang, H. K., Mackenzie, F. T., and Schoonmaker, J.. 1986 . Comparisons between the diagenesis of dioctahedral and trioctahedral smectite, Brazilian offshore basins. Clays & Clay Miner. 34: 407–423.CrossRefGoogle Scholar
Conkin, J. E., 1986. Chattanooga Shale in the Tennessee Valley and Ridge of Hamilton and Bledsoe Counties. Louisville, Kentucky: Dept. Geol., Univ. Louisville, 11 pp.Google Scholar
Dean, R. S., 1962. A study of St. Lawrence Lowland shales. Ph.D. thesis, McGill University, Montreal, Canada, 236 pp.Google Scholar
de Caritat, P., Hutcheon, I., and Walshe, J. L.. 1993 . Chlorite geothermometry: A review. Clays & Clay Miner. 41: 219–239.CrossRefGoogle Scholar
Duba, D., and Williams-Jones, A. E.. 1983 . The application of illite crystallinity, organic matter reflectance, and isotopic techniques to mineral exploration: A case study in Southwestern Gaspé, Quebec. Econ. Geol. 78: 1350–1363.CrossRefGoogle Scholar
Enos, P., 1969. Cloridorme Formation, Middle Ordovician flysch, northern Gaspé Peninsula, Quebec. Geol. Soc. Amer. Spec. Pap. 117: 66 pp.Google Scholar
Eslinger, E., and Sellars, B.. 1981 . Evidence for the formation of illite from smectite during burial metamorphism in the Belt Supergroup, Clark Fork, Idaho. J. Sediment. Petrol. 51: 203–216.Google Scholar
Evarts, R. C., and Schiffman, P.. 1983 . Submarine hydrothermal metamorphism of the Del Puerto ophiolite, California. Amer. J. Sci. 283: 289–340.CrossRefGoogle Scholar
Faill, R. T., 1985. The Acadian orogeny and the Catskill Delta. In The Catskill Delta. Woodrow, D. L., and Sevon, W. D., eds. Geol. Soc. Amer. Spec. Pap. 201: 15–37.CrossRefGoogle Scholar
Frey, M., 1978. Progressive low-grade metamorphism of a black shale formation, central Swiss Alps, with special reference to pyrophyllite and margarite bearing assemblages. J. Petrol. 19: 95–135.CrossRefGoogle Scholar
Helmold, K. P., and van de Kamp, P.. Diagenetic mineralogy and controls on albitization and laumontite formation in Palaeogene arkoses, Santa Ynez Mountains, California. In Clastic Diagenesis. McDonald, D. A., and Surdam, R. C., 1984 eds. Amer. Assoc. Petroleum Geol. Mem. 37: 239–276.Google Scholar
Hesse, R., and Dalton, E.. 1991 . Diagenetic and low-grade metamorphic terrains of Gaspé-Peninsula related to geological structure of the Taconian and Acadian orogenic belts, Quebec Appalachians. J. Metamorphic Geol. 9: 775–790.CrossRefGoogle Scholar
Hillier, S., and Velde, B.. 1991 . Octahedral occupancy and the chemical composition of diagenetic (low-temperature) chlorites. Clay Miner. 26: 149–168.CrossRefGoogle Scholar
Hirsch, P., Howie, A., Nicholson, R. B., Pashley, D. W., and Whelan, M. J.. 1977 . Electron Microscopy of Thin Crystals. 2nd ed. Huntington, New York: Robert E. Krieger Publishing Co., 563 pp.Google Scholar
Hiscott, R. N., Pickering, K. T., and Beeden, D. R.. Progressive filling of a confined Middle Ordovician foreland basin associated with the Taconic Orogeny, Quebec, Canada. In Foreland Basins. Allen, P. A., and Homewood, P., 1986 eds. Int'l. Assoc. Sediment. Spec. Publ. 8: 309–325.Google Scholar
Hoffman, J., and Hower, J.. Clay mineral assemblages as low grade metamorphic geothermometers: Application to the thrust faulted disturbed belt of Montana, USA. In Aspects of Diagenesis. Scholle, P. A., and Schluger, P. R., 1979 eds. Soc. Econ. Paleontol. Mineral. Spec. Publ. 26: 55–79.CrossRefGoogle Scholar
Hower, J., Eslinger, E. V., Hower, M. E., and Perry, E. A. Jr. 1976 . Mechanism of burial metamorphism of argillaceous sediments: 1. Mineralogical and chemical evidence. Geol. Soc. Amer. Bull. 87: 725–737.2.0.CO;2>CrossRefGoogle Scholar
Hyndman, D. W., 1985. Petrology of Igneous and Metamorphic Rocks. New York: McGraw-Hill, 786 pp.Google Scholar
Inoue, A., 1985. Chemistry of corrensite: A trend in composition of trioctahedral chlorite/smectite during diagenesis. J. Coll. Arts Sci., Chiba Univ. B–18: 69–82.Google Scholar
Inoue, A., 1987. Conversion of smectite to chlorite by hydrothermal and diagenetic alterations, Hokuroku Kuroko mineralization area, northeast Japan. In Proceedings of the International Clay Conference, Denver, 1985. Schultz, L. G., Olphen, H. van, and Mumpton, F. A., eds. Bloomington: The Clay Minerals Society, 158–164.Google Scholar
Inoue, A., and Utada, M.. 1991 . Smectite-to-chlorite transformation in thermally metamorphosed volcanoclastic rocks in the Kamikita area, northern Honshu, Japan. Amer. Mineral. 76: 628–640.Google Scholar
Inoue, A., Utada, M., Nagata, H., and Watanabe, T.. 1984 . Conversion of trioctahedral smectite to interstratified chlorite/smectite in Pliocene acidic pyroclastic sediments of the Ohyu district, Akita Prefecture, Japan. Clay Sci. 6: 103–116.Google Scholar
Islam, S., and Hesse, R.. 1983 . The P-T conditions of latestage diagenesis and low grade metamorphism in the Taconic belt of the Gaspé Peninsula from fluid inclusions: Preliminary results. Geol. Surv. Can., Curr. Res., Part B, Pap. 83–1B: 145–150.Google Scholar
Islam, S., Hesse, R., and Chagnon, A.. 1982 . Zonation of diagenesis and low-grade metamorphism in Cambro-Ordovician flysch of Gaspé Peninsula, Quebec Appalachians. Can. Mineral. 20: 155–167.Google Scholar
Jiang, W.-T., 1993. Diagenesis and Very Low-Grade Metamorphism of Pelitic Rocks from the Gaspé Peninsula, Quebec. Ph.D. dissertation, University of Michigan, Ann Arbor, Michigan, 269 pp.Google Scholar
Jiang, W.-T., and Peacor, D. R.. 1991 . Transmission electron microscopic study of the kaolinitization of muscovite. Clays & Clay Miner. 39: 1–13.CrossRefGoogle Scholar
Jiang, W.-T., and Peacor, D. R.. 1993 . Formation and modification of metastable intermediate sodium potassium mica, paragonite, and muscovite in hydrothermally altered metabasites from northern Wales. Amer. Mineral. 78: 782–793.Google Scholar
Jiang, W.-T., Essene, E. J., and Peacor, D. R.. 1990 . Transmission electron microscopic study of coexisting pyrophyllite and muscovite: Direct evidence for the metastability of illite. Clays & Clay Miner. 38: 225–240.CrossRefGoogle Scholar
Jiang, W.-T., Peacor, D. R., and Slack, J. F.. 1992 . Microstructures, mixed layering, and polymorphism of chlorite and retrograde berthierine in the Kidd Creek massive sulfide deposit, Ontario. Clays & Clay Miner. 40: 501–514.CrossRefGoogle Scholar
Kisch, H. J., 1987. Correlation between indicators of very low-grade metamorphism. In Low Temperature Metamorphism. Frey, M., ed. New York: Chapman and Hall, 227–300.Google Scholar
Kisch, H. J., 1990. Calibration of the anchizone: A critical comparison of illite ‘crystallinity’ scales used for definition. J. Metamorphic Geol. 8: 31–46.CrossRefGoogle Scholar
Knipe, R. J., 1979. Chemical changes during slate cleavage development. Bull. Minéral. 102: 206–209.CrossRefGoogle Scholar
Knipe, R. J., 1981. The interaction of deformation and metamorphism in slates. Tectonophys. 78: 249–272.CrossRefGoogle Scholar
Lee, J. H., Peacor, D. R., Lewis, D. D. and Wintsch, R. P.. 1986 . Evidence for syntectonic crystallization for the mudstone to slate transition at Lehigh Gap, Pennsylvania, U.S.A. J. Struct. Geol. 8: 767–780.CrossRefGoogle Scholar
Liou, J. G., Seki, Y., Guillemette, R. N., and Sakai, H.. 1985 . Compositions and parageneses of secondary minerals in the Onikobe geothermal system, Japan. Chem. Geol. 49: 1–20.CrossRefGoogle Scholar
Meunier, A., Clement, J.-Y., Bouchet, A., and Beaufort, D.. 1988 . Chlorite-calcite and corrensite-dolomite crystallization during two superimposed events of hydrothermal alteration in “Les Crêtes” granite, Vosges, France. Can. Mineral. 26: 413–422.Google Scholar
Mexias, A., Formoso, M., Meunier, A., and Beaufort, D.. Composition and crystallization of corrensite in volcanic and pyroclastic rocks of Hilário Formation, (RS) Brazil. In Proceedings of the 9th International Clay Conference, Strasbourg, 1989. Farmer, V. C., and Tardy, Y., 1990 eds. Sci. Géol., Mém. 88: 135–143.Google Scholar
Moore, D. M., and Reynolds, R. C. Jr. 1989 . X-ray Diffraction and the Identification and Analysis of Clay Minerals. New York: Oxford University Press, 332 pp.Google Scholar
Peacor, D. R., 1992. Diagenesis and low-grade metamorphism of shales and slates. In Minerals and Reactions at the Atomic Scale: Transmission Electron Microscopy, Reviews in Mineralogy, Vol. 27. Buseck, P. R., ed. Washington, D.C.: Mineralogical Society of America, 335–380.CrossRefGoogle Scholar
Pickering, K. T., 1987. Deep-marine foreland basin and fore-arc sedimentation: A comparative study from the Lower Palaeozoic northern Appalachians, Quebec and Newfoundland. In Marine Clastic Sedimentology. Leggett, J. K., and Zuffa, G. G., eds. London: Graham and Trotman, 190–211.CrossRefGoogle Scholar
Pickering, K. T., and Hiscott, R. N.. 1985 . Contained (reflected) turbidity currents from the Middle Ordovician Cloridorme Formation, Quebec, Canada: An alternative to the antidune hypothesis. Sedimentology 32: 373–394.CrossRefGoogle Scholar
Pollastro, R. M., and Barker, C. E.. Application of clay-mineral, vitrinite reflectance, and fluid inclusion studies to the thermal and burial history of the Pinedale anticline, Green River basin, Wyoming. In Roles of Organic Matter in Sediment Diagenesis. Gautier, D. L., 1986 ed. Soc. Econ. Paleont. Mineral. Spec. Publ. 38: 73–83.CrossRefGoogle Scholar
Quinlan, G. M., and Beaumont, C.. 1984 . Appalachian thrusting, lithospheric flexture, and the Palaeozoic stratigraphy of the Eastern Interior of North America. Can. J. Earth Sci. 21: 973–996.CrossRefGoogle Scholar
Reynolds, R. C. Jr. . Interstratified clay minerals. In Crystal Structures of Clay Minerals and Their X-ray Identification. Brindley, G. W., and Brown, G., 1984 eds. London, U.K.: Mineralogical Society, 249–303.Google Scholar
Reynolds, R. C. Jr. . Mixed layer chlorite minerals. In Hydrous Phyllosilicates (Exclusive of Micas), Reviews in Mineralogy, Vol. 19. Bailey, S. W., 1988 ed. Washington D.C.: Mineralogical Society of America, 601–629.CrossRefGoogle Scholar
Rheams, K. F., and Thornton, L. N.. 1988 . Characterization and geochemistry of Devonian oil shale, north Alabama, northwest Georgia, and south-central Tennessee: A resource evaluation. Geol. Surv. Alabama Bull. 128: 1–214.Google Scholar
Roberson, H. E., 1988. Random mixed-layer chlorite-smectite: Does it exist? In Abstracts, 25th Clay Minerals Society Annual Meeting, Grand Rapids, Michigan, p. 98.Google Scholar
Roberson, H. E., 1989. Corrensite in hydrothermally altered oceanic rocks. In Abstracts, 26th Clay Minerals Society Annual Meeting, Sacramento, California, p. 59.Google Scholar
Roberts, B., and Merriman, R. J.. 1990 . Cambrian and Ordovician metabentonites and relevance to the origins of associated mudrocks in the northern sector of the Lower Palaeozoic Welsh marginal basin. Geological Magazine 127: 31–43.CrossRefGoogle Scholar
Robinson, D., and Bevins, R. E.. 1986 . Incipient metamorphism in the Lower Palaeozoic marginal basin of Wales. J. Metamorphic Geol. 4: 101–113.CrossRefGoogle Scholar
Schiffman, P., and Fridleifsson, G. O.. 1991 . The smectitechlorite transition in drillhole NJ-15, Nesjavellir geothermal field, Iceland: XRD, BSE and electron microprobe investigations. J. Metamorphic Geol. 9: 679–696.CrossRefGoogle Scholar
Shau, Y.-H., and Peacor, D. R.. 1992 . Phyllosilicates in hydrothermally altered basalts from DSDP hole 504B, leg 83—A TEM and AEM study. Contrib. Mineral. Petrol. 112: 119–133.CrossRefGoogle Scholar
Shau, Y.-H., Peacor, D. R., and Essene, E. J.. 1990 . Corrensite and mixed-layer chlorite/corrensite in metabasalt from northern Taiwan: TEM/AEM, EPMA, XRD, and optical studies. Contrib. Mineral. Petrol. 105: 123–142.CrossRefGoogle Scholar
Slack, J. F., Jiang, W.-T., Peacor, D. R., and Okita, P. M.. 1992 . Hydrothermal and metamorphic berthierine from the Kidd Creek volcanogenic massive sulfide deposit, Timmins, Ontario. Can. Mineral. 30: 1127–1142.Google Scholar
Šrodo$na, J., 1984. X-ray powder diffraction identification of illitic materials. Clays & Clay Miner. 32: 337–349.CrossRefGoogle Scholar
St. Julien, P., and Hubert, C.. 1975 . Evolution of the Taconian orogen in the Quebec Appalachians. Amer. J. Sci. 275–A: 337–362.Google Scholar
Suchecki, R. K., Perry, E. A. Jr., and Hubert, J. F.. 1977 . Clay petrology of Cambro-Ordovician continental margin, Cow Head klippe, western Newfoundland. Clays & Clay Miner. 25: 163–170.CrossRefGoogle Scholar
Tomita, K., Takahashi, H., and Watanabe, T.. 1988 . Quantitative curves for mica/smectite interstratifications by X-ray powder diffraction. Clays & Clay Miner. 36: 258–262.CrossRefGoogle Scholar
Velde, B., and Medhioub, M.. 1988 . Approach to chemical equilibrium in diagenetic chlorites. Contrib. Mineral. Petrol. 98: 122–127.CrossRefGoogle Scholar
Vergo, N., and April, R. H.. 1982 . Interstratified clay minerals in contact aureoles, West Rock, Connecticut. Clays & Clay Miner. 30: 237–240.CrossRefGoogle Scholar
Walker, J. R., and Thompson, G. R.. 1990 . Structural variations in chlorite and illite in a diagenetic sequence from the Imperial Valley, California. Clays & Clay Miner. 38: 315–321.CrossRefGoogle Scholar
Weaver, C. E., 1989. Clays, Muds, and Shales. Amsterdam: Elsevier, 819 pp.Google Scholar
Weaver, C. E., Highsmith, P. B., and Wampler, J. M.. 1984 . Chlorite. In Shale-Slate Metamorphism in Southern Appalachians. Amsterdam: C. E. Weaver and Associates, Elsevier, 99–139.CrossRefGoogle Scholar
Weber, K., 1981. Kinematic and metamorphic aspects of cleavage formation in very low-grade metamorphic slates. Tectonophys. 78: 291–306.CrossRefGoogle Scholar
Whalen, J. B., 1985. The McGerrigle plutonic complex, Gaspé, Quebec: Evidence of magma mixing and hybridization. Geol. Surv. Can., Curr. Res., Part A, Pap. 85–1A: 795–800.Google Scholar
White, S. H., and Johnston, D. C.. 1981 . A microstructural and microchemical study of cleavage lamellae in a slate. J. Struct. Geol. 3: 279–290.CrossRefGoogle Scholar
White, S. H., and Knipe, R. J.. 1978 . Microstructural variation of an axial plane cleavage around a fold—A H.V.E.M. study. Tectonophys. 39: 355–381.Google Scholar
Williams, H., and Hatcher, R. D.. Appalachian suspect terranes. In Contributions to the Tectonics and Geophysics of Mountain Chains. Hatcher, R. D., Williams, H., and Zietz, I., 1983 eds. Geol. Soc. Amer. Mem. 158: 33–53.CrossRefGoogle Scholar