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Detailed geologic mapping, U-Pb zircon geochronology and whole-rock geochemical analyses were conducted to test the hypothesis that the southwestern extent of the Cat Square terrane continues from the northern Inner Piedmont (western Carolinas) into central Georgia. Geologic mapping revealed the Jackson Lake fault, a ∼15 m-thick, steeply dipping sillimanite-grade fault zone that truncates lithologically distinct granitoids and metasedimentary units, and roughly corresponds with a prominent aeromagnetic lineament hypothesized to represent the southern continuation of the terrane-bounding Brindle Creek fault. Results of U-Pb SHRIMP geochronology indicate Late Ordovician to Silurian granitoids (444–439 Ma) occur exclusively northwest of the fault, whereas Devonian (404–371 Ma) granitoids only occur southeast of the fault. The relatively undeformed Indian Springs granodiorite (three individual bodies dated 317–298 Ma) crosscuts the fault and occurs on both sides, which indicates the Jackson Lake fault is a pre-Alleghanian structure. However, detrital zircon signatures from samples southeast of the Jackson Lake fault reveal dominant Grenville provenance, in contrast to Cat Square terrane detrital zircon samples from the northern Inner Piedmont, which include peri-Gondwanan (600–500 Ma) and a prominent Ordovician-Silurian (∼430 Ma) signature. We interpret the rocks southeast of the Jackson Lake fault to represent the southwestern extension of the Cat Square terrane primarily based on the partitioning of granitoid ages and lithologic distinctions similar to the northern Inner Piedmont. Data suggest Cat Square terrane metasedimentary rocks were initially deposited in a remnant ocean basin setting and developed into an accretionary prism in front of the approaching Carolina superterrane, ultimately overridden by it in Late Devonian to Early Mississippian time. Burial to >20 km resulted in migmatization of lower plate rocks, forming an infrastructure beneath the Carolina superterrane suprastructure. Provenance patterns support ∼250 km of Devonian dextral translation of the composite Inner Piedmont, which places the northern portion of the Inner Piedmont adjacent to a suite of ∼430 Ma plutons in the Virginia Blue Ridge during deposition. The megascopic thrust-nappe structural style of the northern Inner Piedmont, combined with southwest-directed lateral extrusion at mid-crustal depths, may reconcile differences in timing of metamorphism between the Carolina and central Georgia Inner Piedmont and structural contrasts between the Brindle Creek and Jackson Lake faults.

The conventional view that the basement of the southern and central Appalachians represents juvenile Mesoproterozoic crust, the final stage of growth of Laurentia prior to Grenville collision, has recently been challenged. New whole-rock Pb and Sm‑Nd isotopic data are presented from Mesoproterozoic basement in the southern and central Appalachians and the Granite-Rhyolite province, as well as one new U-Pb zircon age from the Granite-Rhyolite province. These data, combined with existing data from Mesoproterozoic terranes throughout southeastern Laurentia, further substantiate recent suggestions that the southern and central Appalachian basement is exotic with respect to Laurentia. Sm-Nd isotopic compositions of most rocks from the southern and central Appalachian basement are consistent with progressive growth through reworking of the adjacent Granite-Rhyolite province. However, Pb isotopic data, including new analyses from important regions not sampled in previous studies, do not correspond with Pb isotopic compositions of any adjacent crust. The most distinct ages and isotopic compositions in the southern and central Appalachian basement come from the Roan Mountain area, eastern Tennessee–western North Carolina. The data set indicates U-Pb zircon ages up to 1.8 Ga for igneous rocks, inherited and detrital zircon ages >2.0 Ga, Sm-Nd depleted mantle model (T DM ) ages >2.0 Ga, and the most elevated 207 Pb/ 204 Pb observed in southeastern Laurentia. The combined U-Pb geochronologic and Sm-Nd and Pb isotopic data preclude derivation of southern and central Appalachian basement from any nearby crustal material and demonstrate that Grenville age crust in southeastern Laurentia is exotic and probably was transferred during collision and assembly of Rodinia. These new data better define the boundary between the exotic southern and central Appalachian basement and adjacent Laurentian Granite-Rhyolite province.

The magnetic anomaly map of North America serves as a useful base from which to attempt palinspastic reconstruction of terranes accreted during the Elzevirian orogeny (1250–1200 Ma); the Shawinigan (1200–1150 Ma), Ottawan (1080–1020 Ma), and Rigolet (1020–1000 Ma) phases of the Grenvillian orogeny; and post-Grenvillian magmatism (760–600 Ma) and deformation prior to Iapetan rifting at 565 Ma. Accreted terranes had unique histories prior to amalgamation and share common tectonic events afterwards. Comparisons with magnetic signatures of the Paleozoic craton–craton suture, sutures of accreted terranes, and the Jurassic rifted-margin for the southern-central Appalachians provide a basis for discriminating among alternative Grenvillian sutures beneath the Appalachian orogen. The Elzevirian suture is partially preserved beneath the Appalachians where it separates the Reading Prong terrane from Laurentia (i.e., Adirondacks and composite-arc terrane and Canadian Grenville Province). The Shawinigan suture is partially preserved in the Llano area (Texas), but separated the now-fragmented and allochthonous Amazonian (as indicated from Pb-isotope data) blocks of the outboard Blue Ridge terrane from the Reading Prong terrane in the Appalachians. Isolated blocks of the Sauratown Mountains terrane are interpreted as outboard of the Blue Ridge terrane, but were also accreted during the Shawinigan phase. Within present-day Laurentia, the only fragment of a terrane believed to have been accreted during the main Ottawan phase is the Mars Hill terrane (North Carolina–Tennessee). This suggests that the outboard Ottawan suture may have served as the locus of Iapetan rifting along much of Laurentia. The Rigolet phase (1020–1000 Ma) is characterized by widespread “Basin and Range” type extension (NW–SE) associated with sinistral or dextral movement on the NY-AL lineament, mobilization of core-complexes (Adirondack Highlands), and AMCG magmatism along the outboard flank of the extensional region. Following the Rigolet phase, the Appalachian region continued to be characterized by NW–SE extension during the passage of a possible hotspot along a NE-track (760–600 Ma) across the Blue Ridge and other terranes, and during initial Iapetan rifting (565 Ma). The palinspastic rifted-margin of Laurentia crosses many of these terranes and sutures as well as the possible region of Rigolet extension and the possible hotspot track, thus providing many potential piercing points within the Grenville orogen for comparison with Paleozoic terranes like the Precordillera in South America.

Ion microprobe U–Pb analyses of zircons from basement units in the southern Appalachians, combined with supporting isotopic compositions and major and trace element geochemistry, have delineated a granitic magmatic pulse ∼1165–1150 Ma. The pulse is manifested by the Watauga River Gneiss (western Blue Ridge), Toxaway, Wiley, and Sutton Creek gneisses (eastern Blue Ridge), Pilot Mountain and Grassy Creek gneisses (Sauratown Mountains window), and possibly the Forbush gneiss (∼1140 Ma, Inner Piedmont or Sauratown Mountains window) and Cranberry-Mine Layered Gneiss (∼1190 Ma, western Blue Ridge). Additional samples analyzed include the Blowing Rock Gneiss (∼1080 Ma, Grandfather Mountain window), and the Carvers Gap Granulite Gneiss (∼1.8 Ga) and Cloudland Granulite Gneiss (detrital cores ∼1.2–1.8 Ga) from the Mars Hill terrane. Age data were evaluated by calculating concordia ages and concordia probability plots using 206Pb*/238U and 207Pb*/206Pb* data simultaneously. Rocks in the main magmatic pulse are granitic (63–72 wt.% SiO2), but elevated in K and incompatible trace elements compared to typical subduction-related magmas, and initial Nd ratios cluster tightly near CHUR. Mars Hill terrane samples are distinct in age, geochemistry (poorer in K and incompatible elements), and isotopic compositions (eNd−7.6 and −5 at 1.0 Ga). Zircons from almost all samples have metamorphic rims that yield ages ∼1030 Ma, with the exception of the Blowing Rock Gneiss. Ages of Grenvillian magmatism and metamorphism are similar to reported ages from the northern Blue Ridge of Virginia, the Adirondack Highlands, the Central Metasedimentary Belt (Canadian Grenville Province), and the Llano uplift of Texas. This suggests the entire southeastern margin of Laurentia has a similar history ∼1.2–1.0 Ga. Although consistent with known ages in Laurentia, the presence of ∼1.8 Ga rocks and TDM ages commonly >1.6 Ga is inconsistent with the inferred 1.6 Ga margin of Laurentia. This suggests either that the 1.4–1.5 Ga mid-continent terrane separates older portions of Laurentia, that this region was exotic, or that it was a rifted fragment of Laurentia reattached during Grenville orogeny. Surprisingly few Paleozoic metamorphic zircon rims have been identified, but the few analyses obtained from samples in the eastern Blue Ridge yield late Acadian ages (∼350 Ma). The similarity of basement units across the southern Appalachians suggests a relationship between these provinces and that the Piedmont terrane is not exotic to Laurentia during the Appalachian orogenic cycle.

High-resolution ion microprobe analysis of zircon has provided ages for previously undated plutons of the high-grade eastern Blue Ridge of northeastern Georgia and southwestern North Carolina. These data, together with backscattered electron imaging, reveal the presence of nearly ubiquitous inherited cores of highly variable age and magmatic rims that have experienced variable Pb loss, thus making interpretation of conventional U-Pb analyses very difficult. Ion probe rim analyses indicate that the plutons were emplaced during both the mid-Ordovician (Taconian orogeny; Whiteside pluton, 465 Ma; Persim- mon Creek Gneiss, 480 Ma) and mid-Devonian (Acadian orogeny; Rabun pluton, 375 Ma; Pink Beds pluton, 390 Ma; Looking Glass pluton, 380 Ma). A large trondhjemite dike north of Asheville is less confidently assigned an age of 415 Ma. Zircons from all intrusions have predominantly 1.0 to 1.25 Ga cores (Grenvillian). In addition, both Devonian and Ordovician plutons have smaller populations of Late Proterozoic-early Paleozoic (0.5-0.75 Ga), Middle Proterozoic (1.4 Ga), and Late Archean (2.6-2.9 Ga) cores. The ubiquitous, round cores and thick magmatic rims suggest significant resorption and then protracted growth within the melts. Zircon saturation tem- peratures based on whole-rock (melt) Zr concentrations are lower than ex- pected for magma generation (710°-760°C). Zirconium concentrations may not reflect saturation at maximum temperature, if melting was very rapid (10 5 yrs), or if zircon cores represent grains that were shielded from melt inside host grains for much of the magmatic history. The Late Proterozoic-early Paleozoic and Grenvillian inheritance is similar to documented ages of basement exposed in the eastern Blue Ridge. No expo- sures of 1.4 Ga rocks are known in the southern Appalachians, but detrital and inherited zircons of this age have been reported, and 1.4 Ga granites are widespread in the craton to the northwest. However, the combination of absence of Early Proterozoic zircon and presence of Late Archean zircon is inconsistent with the known distribution of basement rocks in southeastern North America. No Archean rocks or inherited zircons have been reported from the southern and central Appalachians; the nearest Archean exposures are 1000 km north, across a dominantly Early Proterozoic terrane. This suggests either that the Laurentian configuration of Archean basement was very complex or that the crust that underlay the plutons at the time of their emplacement included a far-travelled terrane (emplaced during Grenvillian or early Paleozoic orogeny?). Ages of magmatic and inherited zones of zircon from the plutons demon- strate that similar crust underlay the eastern Blue Ridge during both Taconian and Acadian orogenies, that there was no single episode of voluminous magma- tism, and that metamorphism and deformation began before 470 Ma and contin- ued after 370 Ma. These plutons do not constitute a significant convergence- related arc, though it is possible that they represent a displaced part of an arc that lies primarily to the east (in the Inner Piedmont?). Previous geochemical studies have demonstrated that the eastern Blue Ridge intrusions include both a very primitive component, either mafic magma or relatively young mafic source rock, and a component derived from more mature

Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and filtered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York–Alabama lineament (dextral fault). Toward the east and south, high-angle discordance between the northeast-trending Appalachians and the east-west–trending wedge of overlapping Mesozoic and Cenozoic Gulf Coastal Plain sediments reveals how bedrock geophysical signatures progressively change with deeper burial. High-frequency magnetic anomalies in the Appalachian deformed domain (ADD) correspond to amphibolites and mylonites outlining terranes, while broader, lower-amplitude domains include Paleozoic intrusive bodies and Grenville basement gneiss. Fundamental ADD structures (e.g., the Alexander City, Towaliga, and Goat Rock–Bartletts Ferry faults) can be traced southward beneath the Gulf Coastal Plain to the suture with Gondwanan crust of the Suwannee terrane. Within the ADD, there is clear magnetic distinction between Laurentian crust and the strongly linear, high-frequency magnetic highs of peri-Gondwanan (Carolina-Uchee) arc terranes. The contact (Central Piedmont suture) corresponds to surface exposures of the Bartletts Ferry fault. ADD magnetic and gravity signatures are truncated by the east-west–trending Altamaha magnetic low associated with the Suwannee suture. Arcuate northeast-trending magnetic linears of the Suwannee terrane reflect internal structure and Mesozoic failed-rift trends. Geophysical data can be used to make inferences on surface and subsurface geology and vice versa, which has applicability anywhere that bedrock is exposed or concealed beneath essentially non-magnetic sedimentary cover.

The Pine Mountain terrane, the southernmost basement massif in the southern Appalachians, comprises a Grenville age basement complex and Paleozoic(?) cover sequence, now exposed in a complex window within the Piedmont terrane. The window is framed at its eastern end by three faults, all of demonstrably different ages.

The southern Appalachian Pine Mountain window exposes 1.1 Ga Grenvillian basement and its metasedimentary Paleozoic(?) cover through the allochthonous Inner Piedmont. The issue of whether the crustal block inside the window was either transported above the master Appalachian (late Alleghanian) decollement or is an autochthonous block that was overridden by the decollement has been debated for some time. New detrital zircon geochronologic data from the cover rocks inside the window suggest this crustal block was derived from Gondwana but docked with Laurentia before the Alleghanian event. Reprocessed deep seismic reflection data from west-central Georgia (pr- and poststack noise reduction, amplitude variation analysis, and prestack depth migration) indicate that a significant band of subhorizontal reflections occurs almost continuously beneath the window collinear with the originally recognized decollement reflections north of the window. A marked variation in the decollement image, from strong and coherent north of the window to more diffuse directly beneath the window, is likely a partial consequence of the different geology between the Inner Piedmont and the window. The more diffuse image beneath the window may also result from imaging problems related to changes in topography and fold of cover (i.e., signal-to-noise ratio). Two alternative tectonic models for the Pine Mountain window can partially account for the observed variation in the decollement reflectivity. (1) The Pine Mountain block could be truncated below by a relatively smooth continuation of the decollement. The window would thus expose an allochthonous basement duplex or hors-block thrust upward from the south along the Late Proterozoic rifted continental margin. (2) The window represents localized exhumation of autochthonous basement and cover along a zone of distributed intrabasement shearing directly beneath the window. Either model is viable if only reflector geometry is considered; model (1) is favored if both geometry and kinematics of Blue Ridge–Piedmont thrust sheet emplacement are incorporated. In either model, the southern margin of the window merges to the west with the Iapetan early Alleghanian Central Piedmont suture, which juxtaposes North American–affinity Piedmont rocks to the north and exotic Panafrican rocks of the Carolina (Avalon) terrane to the south. Immediately south of the window, this suture dips southward and merges in the lower crust with the late Alleghanian suture joining the Appalachians with Gondwana.

Compositional zoning reveals multistage growth histories and resorption events in zircon from a high-grade terrane in the eastern Blue Ridge of North Carolina and Georgia. These zoning patterns were used to guide high-resolution ion microprobe dating that places important constraints on the evolution of the southern Appalachian crust. Zircons from granulite facies metapelite have unzoned rims that yield concordant U-Pb ages of 495 ± 14 Ma. We interpret this as the time of rim growth, which occurred during peak metamorphism early in the protracted orogenic history of the region. Detrital cores, characterized by truncated euhedral zoning, are of Grenville age (1.04–1.26 Ga). Zircons from the Whiteside and Rabun plutons have well-defined, rounded, inherited cores and euhedral, oscillatory-zoned magmatic rims. Rims of Rabun zircons record magmatic crystallization at 374 ± 4 Ma, whereas Whiteside rims yield a 466 ± 10 Ma crystallization age. Cores from both plutons include 1.1–1.3 Ga and 2.6–2.7 Ga ages. These data indicate that there was no single, voluminous episode of plutonism in this area, that similar material underpinned the region at least from 370 to 470 Ma, and that previously unrecognized Archean basement or Archean basement–derived sedimentary rock was present in the southern Appalachians. Results of this study verify the value of combining zoning and ion microprobe studies: Using conventional U-Pb methods or ion microprobe dating without knowledge of zoning would have made interpreting the events recorded in these zircons and the ages that they yield difficult or impossible.

The Ocmulgee fault is a fundamental boundary within the Piedmont of central Georgia separating North American, Piedmont terrane rocks from exotic rocks of the Avalon (Carolina) terrane. Contrasts in stratigraphy, metamorphic grade, and aeromagnetic signature coincide with the fault trace. The fault comprises a broad zone (ca. 2 km) of foliation dipping steeply southeast and containing localized syn- and post-thermal-peak right-lateral strike-slip shear zones. Oblique dextral convergence between the Avalon and Peidmont terranes, most likely around 350 Ma, produced the steep zone and its attendant dextral shear zones. Steep foliation within the fault zone resulted in its predisposition to later faulting.

A senior-first year graduate level tectonics course intended to span the entire subject might begin with the historical basis for modern tectonics concepts, then lead to an in-depth review of both the pros and cons of plate tectonics. A survey of the nature of the earth's major tectonics elements would include consideration of the evolution of ocean basins, island arcs, continental margins, shields and continental platforms, basins (marginal, foredeep, successor, intracratonic) and several well-known orogenic belts of similar and contrasting styles. New and revived old concepts, for example, thin-skinned behavior of crystalline thrust sheets, evolution of overthrust terranes, and the role played by basement, ophiolite emplacement, magma generation and emplacement, tectonic heredity of major structures through time, formation and recognition of cryptic sutures and the role of gravity, gravitational spreading and compressional tectonics in orogens should be considered. Comparisons should also be made of the...

Summary. Some 180 km of new VIBROSEIS profiles have been acquired in the southern Appalachian Inner Piedmont, Brevard fault zone and eastern Blue Ridge as part of the ADCOH Project site investigation. These data are of the highest quality yet obtained in a crystalline terrane in the US, perhaps in the world, and reveal several conclusions that should have a direct bearing upon the world-wide nature of composite crystalline thrust sheets and their modes of interaction with the platform rocks beneath. Strong reflections previously interpreted as the base of the crystalline sheet are clearly part of the platform sedimentary (clastic rocks) sequence resting upon the autochthonous basement and early Palaeozoic rift basins. This reflection package and related transparent zones are clearly repeated beneath the crystalline sheet indicating a complex of thrusts repeating units within the platform succession. Reflectors (granitoid-amplibolite contacts) in the crystalline sheet in the Inner Piedmont represent recumbent folds of similar wavelengths and amplitudes to folds mappable on the surface. Duplexing of platform rocks beneath the crystalline sheet appears to have resulted in doming of the crystalline sheet. Similarly, duplex formation in the platform was probably controlled by both the thickness of the crystalline sheet and the rheological properties of the platform succession.

The Appalachian orogen was constructed along the ancient Precambrian continental margin of eastern North America by a series of compressional events that began in the Ordovician and episodically spanned much of the Paleozoic era. The processes of accretion of suspect and exotic terranes, together with terrane collision and ultimately completion of the Wilson cycle by continent-continent collision, resulted in construction of the Appalachian orogen (Figure 1). These paleogeographic elements are rep­ resented by the various lithotectonic units visible today in the southern and central Appalachians (Figure 2). These subdivisions represent the late Precambrian rifted margin and early Paleozoic platform that were formed directly upon North American Grenvillian basement (Cumberland/ Allegheny Plateau, Valley and Ridge, and western Blue Ridge), the offshore North American slope-rise assemblage (Hamburg klippe, southern Appalachian eastern Blue Ridge and Inner Piedmont, and higher thrust sheets of the Maryland-northern Virginia Piedmont), and the exotic Carolina, or Avalon, and Wilmington terranes. The Carolina ter­ rane contains the Alleghanian high-grade metamorphic core. These elements form the basis for this analysis and review of the present state of knowledge of the tectonic history of the southern and central Appalachian internides. The Appalachian orogen has been the subject of study by geologists at least since the early nineteenth century. Early fundamental concepts, such as the geosynclinal theory of mountain building (Dana 1873, Hall 1883)

Includes 14 chapters on the Appalachian orogen, 15 of the Ouachita orogen, and a chapter on the connection between them beneath the eastern Gulf Coastal Plain. The Appalachian chapters synthesize the geologic development of the orogen by tectonostratigraphic intervals (pre-orogenic, Taconic, Acadian, Alleghanian, and post-Alleghanian), and also treat Paleozoic paleontologic control, regional geophysics, thermal history of the crystalline terranes, parts of the orogen buried beneath the Atlantic and eastern Gulf coastal plains, regional geomorphology, mineral and energy resources; an integration chapter also is included. The Ouachita chapters cover physical stratigraphy and biostratigraphy of the Paleozoic rocks, structural geology, a synthesis of the subsurface geology beneath the western Gulf Coastal Plain, a review of the mineral and energy resources, regional geophysics, and a tectonic synthesis. Twelve excellent plates provide four-color geologic maps, structural cross sections, tectonic syntheses, and geophysical maps; a black-and-white synthesis of Appalachian mineral deposits, and a reflection seismic cross section.

Most geologic studies of orogenic terranes are primarily two-dimensional, with some dependence upon down-plunge and down-dip projections of structures. Potential field and seismic reflection/refraction studies provide some information aobut the third dimension, but these data may be interpreted in a variety of ways without direct calibration using drilling. Drilling is therefore a necessary tool to provide the ultimate test of a scientific hypothesis regarding crustal evolution and structure. A hole may be drilled as an attempt to solve a problem or, more commonly, to prove existence of some potentially economic deposit. If we totally accepted the interpretations based upon structural crosssections, seismic refraction and reflection studies, potential field studies, or studies which combine results from these and other techniques, it would never be necessary to drill except to recover economic minerals or hydrocarbons. However, the results of these types of analysis are generally not sufficiently precise to achieve to unique resolution of crustal structure and reduce the possibilities for alternative interpretations.

Recent mapping within the metamorphic core of the southern Appalachians has led to the identification of several internal basement massifs interpreted to be windows that expose parautochthonous basement beneath the main thrust sheet. One such internal massif is exposed within the Inner Piedmont of North Carolina by the Sauratown Mountain window and is overlain by a cover sequence of arkose, schist, and quartzite. Detailed examination of the primary cross-stratification types preserved within the quartzite at Pilot Mountain indicates that deposition took place in several marine environments ranging from foreshore to inner shelf. Deposits of similar origin within the Early Cambrian North American passive-margin sediments appear to thin west to east, from 80 m at the Chilhowee Group type locality at Chilhowee Mountain (300 km west-southwest of Pilot Mountain) to 40 m within the Unaka belt (150 km west of Pilot Mountain). The quartzite at Pilot Mountain is more than 45 m thick and therefore does not appear to represent a distal part of this passive-margin sequence. Alternatively, two paleotectonic interpretations seem plausible: (1) quartzites of the Sauratown Mountains window, North Carolina, represent Late Proterozoic (Tallulah Falls-Ashe Formation equivalent) deposition along a sea-floor high associated with the rifted basement terrane during the rift phase prior to the opening of Iapetus; or (2) quartzites of the Sauratown Mountains window, North Carolina, represent latest Proterozoic to Early Cambrian (Chilhowee Group time equivalent) deposition on an isolated, rifted continental fragment during the drift phase of the North American-Iapetus margin evolution.

The Pine Mountain terrane is exposed in a complex window within the Piedmont of Georgia and Alabama. The eastern end of the terrane is framed by three ductile faults of demonstrably different ages. The polydeformed pre-thermal peak Box Ankle fault is truncated to the south by the younger pre-thermal peak Goat Rock fault, and to the north by the even younger post-thermal peak Towaliga fault. The three faults framing the eastern termination of the window are clearly neither (1) part of the same detachment nor (2) part of the Appalachian detachment.

This study presents a classification/characterization of Appalachian faults. Characterization factors include timing of movement relative to folding, metamorphism, and plutonism; tectonic position in the orogen; relations to existing anisotropies in the rock masses; involvement of particular rock units and their ages, as well as the standard Andersonian distinctions. Categories include faults with demonstrable Cenozoic activity, wildflysch-associated thrusts, foreland bedding-plane thrusts, premetamorphic to synmetamorphic thrusts in medium- to high-grade terranes, postmetamorphic thrusts in medium- to high- grade terranes, thrusts rooted in Precambrian basement, reverse faults, strike-slip faults, normal (block) faults, compound faults, structural lineaments, faults associated with local centers of disturbance, and geomorphic (nontectonic) faults.