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Home , Aulacogen, Charnockite, Iapetus Ocean, Transform fault

2005 GSA PRESIDENTIAL ADDRESS Tectonic inheritance at a William A. Thomas, Department of Geological Sciences, University of Kentucky, Lexington, Kentucky 40506-0053, USA, [email protected]

INTRODUCTION The Grenville front, at the leading edge The pre- (pre-Grenville) conti- Forty years ago, the eastern margin of the province, is mapped through gener- nental margin is unknown; however, the of inspired Tuzo Wilson ally broad curves along the outcrop in dextral bend of the Grenville front beneath (1966) to ask, “Did the Atlantic close and Canada and southward with decreasing the Gulf Coastal Plain suggests possible then re-open?” The of clos- resolution in the subsurface, using drill inheritance from a dextral offset in the ing and opening of basins incor- and geophysical data, approximately to older continental margin. Northwest-strik- porates the cyclic assembly and breakup central Tennessee; subsurface data define ing dikes (ca. 1350 Ma) in Oklahoma of . Alternate processes of a separate segment in (Figs. 1 and (Denison, 1982) parallel the trend of the extension and compression of continental 2). No data presently are available to locate dextral bend of the Grenville front and margins suggest an important potential for the Grenville front precisely beneath a suggest the possible orientation of the off- tectonic inheritance and overprinting. thick sedimentary cover in the Mississippi set of the older rifted continental margin Now, we recognize a succession of Embayment of the Mesozoic-Cenozoic (Fig. 2). Few other hints are available to two complete Wilson cycles in eastern Gulf Coastal Plain; however, the trace must suggest the trace of the pre-Rodinia rifted North America: closing of an ocean and accommodate a substantial dextral bend margin of cratonic proto-. The assembly of the Rodinia , between the mapped Grenville (Llano) Grenville front truncates internal tectonic breakup of Rodinia and opening of the front in Texas and the approximately fabrics within, and boundaries between, , closing of Iapetus and located trace in the subsurface in central several older provinces, from the Archean assembly of the supercontinent, Tennessee (Fig. 2). Superior province to the 1500–1300-Ma and breakup of Pangaea and opening of the (Fig. 1). Precambrian rocks of cratonic North America indicate less well-defined, earlier cycles. Tectonic inheritance at a range of scales has been recognized in the successive continen- tal margins preserved within the of present eastern North America, posing several fundamental questions. Does each episode of supercontinent assembly and breakup adapt to the tectonic framework of a preexisting continental margin and, in turn, leave a mold for the next episode? Is tectonic inheritance through successive Wilson cycles a first-order constraint on the processes through which is accumulated and continental fab- rics evolve? Does tectonic inheritance in the shallow crustal structures reflect a per- vasive fabric of the deeper ?

ASSEMBLY OF RODINIA (THE GRENVILLE OROGEN) Metamorphic and igneous rocks of the Grenville province, ranging in age from ca. 1350 to 1000 Ma, record closing of an ocean and assembly of the Rodinia superconti- nent (e.g., Hoffman, 1991). The long span of ages suggests multiple events during which multiple elements were swept up Figure 1. Map showing the record of tectonic inheritance through two complete Wilson cycles in and sutured successively to cratonic proto- eastern North America (compiled from Figs. 2–5). Assembly of Rodinia, opening of the Iapetus Laurentia (e.g., McLelland et al., 1996; Ocean, assembly of Pangaea, and opening of the Atlantic Ocean are color-coded on this map and Mosher, 1998). in Figures 2–5.

GSA Today: v. 16, no. 2, doi: 10.1130/1052-5173(2006)016<4:TIAACM>2.0.CO;2

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Granite-Rhyolite province (Fig. 2), which (760–650 Ma), pervasive rifting (620–545 and will define additional pierc- have distinct ages and tectonic origins. Ma) along most of the Laurentian mar- ing points for reconstruction of conjugate Fabrics from older cycles of tectonic accre- gin, and late-stage rifting (540–530 Ma) of margins within the assembly of Rodinia. tion may hold clues to the trace of the microcontinents. Later sedimentary burial Contrasts in crustal structure and tec- pre-Rodinia margin, perhaps extending and deformation have obscured the trace tonic history distinguish transform, upper- tectonic inheritance during cyclic assem- of the Iapetan rifted margin, segments of plate-, and lower-plate-rift segments bly and breakup of supercontinents back which are dispersed in the Appalachian along the Iapetan rifted margin of Lauren- in time to the Archean cratons. and Ouachita footwall. Data tia, consistent with a low-angle-detach- Sedimentary deposits in the Grenville from outcrop , deep wells, and ment simple- mechanism (Thomas, foreland in Ohio and Kentucky (Fig. 2) geophysical surveys provide for palinspas- 1993, Figure 2 therein). Narrow (~25 km) are interpreted to record filling of an tic reconstruction of the rift (e.g., Thomas, zones of transitional crust characterize intracratonic rift system (Drahovzal et 1977, 1991; Cawood et al., 2001). transform faults, which function as verti- al., 1992) or, alternatively, a synorogenic The palinspastically restored Iapetan cal zones to offset the rift and to (Santos et al., 2002), possi- rifted margin follows an orthogonally bound domains of opposite dip of the bly a broken foreland. Further resolution zigzag trace defined by northeast-striking detachment (e.g., Lister et al., 1986). A of the structure of the Grenville foreland rift segments offset by northwest-striking wide zone (>200 km) of extended transi- may help to constrain the shape of the transform faults (Figs. 1 and 3). Intersec- tional crust with rotated basement gra- pre-Rodinia rifted margin by analogy tions of rift segments and transform faults ben blocks and thick (>10 km) synrift with younger foreland basins that have frame promontories (convex oceanward) sediment on a lower-plate rifted margin distinct tectonic inheritance from the and embayments1 (concave oceanward) contrasts with a more narrow zone of preceding rifted margin. of the rifted continental margin. The trace transitional crust, general lack of pre- The range of ages and compositions of of the Iapetan Alabama-Oklahoma trans- served synrift sediment, and a post-rift Grenville rocks, variations in Pb isotopic form corresponds to the probable loca- residual thermal uplift on an upper-plate ratios, and tectonic fabrics indicate intra- tion of the large-scale dextral bend in the margin (e.g., Thomas, 1993; Thomas and Grenville sutures, consistent with multiple Grenville front, suggesting tectonic inheri- Astini, 1999). Despite the important con- accreted terranes and conjugate continen- tance from the shape of the Grenville oro- trasts in crustal structure, no clear asso- tal margins within the assembly of Rodinia gen, as well as from the possible dextral ciation with fabrics of Grenville and older (e.g., McLelland et al., 1996; Hatcher et al., offset in the pre-Rodinia rifted margin of rocks indicates tectonic inheritance of 2004). One possible intra-Grenville , proto-Laurentia and the northwest-strik- the internal style of the Iapetan rift; how- the New York–Alabama magnetic linea- ing 1350-Ma fabric (Fig. 3). Excepting ever, these structures did set the stage for ment (King and Zietz, 1978), has a nearly the Alabama-Oklahoma transform, no tec- pervasive inheritance during the assem- straight trace that may reflect either accre- tonic inheritance from Grenville margins, bly of Pangaea. tion along a straight segment of the pre- sutures, or other fabrics has been recog- Rift-parallel systems (Mississippi Grenville rifted margin of proto-Laurentia, nized in the Iapetan rift system. Valley, Birmingham, and Rome; Fig. 3) accretion at a margin already smoothed The trace of the Iapetan rifted margin is indicate Early to early Late , late by accreted terranes, or orogen-parallel almost entirely within rocks of the Gren- synrift extension inboard from the rifted slip cutting across the shape of the mar- ville province, leaving a belt of Grenville margin (Thomas, 1991). A dextral offset gin. A Grenville age and Pb isotopic ratios rocks along the eastern margin of Lauren- from the Mississippi Valley graben to the link the basement rocks of the Argentine tia (Fig. 3). Along the Iapetan Alabama- Rome trough, including the transverse Precordillera to Laurentia (Kay et Oklahoma transform, however, Rough Creek graben, suggests a transform al., 1996), indicating that rifting during boulders in slope deposits offset of the intracratonic graben systems breakup of Rodinia cut across intra-Gren- have ages (Bowring, 1984) that corre- (Thomas, 1993). Any possible relationship ville sutures. spond to the Granite-Rhyolite province, between the intracratonic rift-parallel gra- suggesting that the rift and transform in ben systems and older fabrics is obscure BREAKUP OF RODINIA AND the corner of the Ouachita embayment and presently unrecognized; however, like OPENING OF THE IAPETUS OCEAN cut across the Grenville front (Fig. 2). The the structures of the rifted margin, these Synrift sedimentary and igneous rocks, Iapetan rift evidently cut across intra-Gren- faults provide a mold for tectonic inheri- a post-rift unconformity, and early post-rift ville sutures, for example, leaving some tance by later structures. The Southern sedimentary strata document the breakup isotopically distinct, possibly “non-Lau- Oklahoma system parallels the Ala- of Rodinia, the opening of the Iapetus rentian Grenville” rocks of the Blue Ridge bama-Oklahoma transform and extends Ocean, and the isolation of Laurentia by attached to “Laurentian Grenville” rocks into the Laurentian craton from the Oua- Cambrian time (ca. 530 Ma). A range of (Loewy et al., 2002; Hatcher et al., 2004) chita embayment in the rifted margin (Fig. ages (e.g., Aleinikoff et al., 1995; Hogan and transferring the Laurentian Argen- 3). Bimodal igneous rocks (539–530 Ma) and Gilbert, 1998; Thomas et al., 2000; tine Precordillera terrane to along the Southern Oklahoma fault system Cawood and Nemchin, 2001; Owens (Thomas and Astini, 1996). Further reso- (Gilbert and Denison in Van Schmus et al., and Tucker, 2003) spans early extension lution of traces of intra-Grenville sutures 1993) suggest a leaky transform, which, like

1Originally termed “reentrant” (Thomas, 1977) but changed to “embayment” (Thomas, 1983) to avoid confusion with the term “recess,” which denotes a cratonward concave bend in a thrust belt.

GSA TODAY, FEBRUARY 2006 5 2005 GSA PRESIDENTIAL ADDRESS the Alabama-Oklahoma transform, paral- lels the dextral bend in the Grenville front, the strike of the 1350-Ma dikes, and the possible dextral offset in the pre-Rodinia continental margin, clearly indicating tec- tonic inheritance.

ASSEMBLY OF PANGAEA (THE APPALACHIAN-OUACHITA OROGEN) The Appalachian-Ouachita records the successive, diachronous Taconic (Ordovician-), Acadian (-Mississippian), and Allegha- nian (Mississippian-) (Drake et al., 1989; Osberg et al., 1989; Hatcher et al., 1989), culminating in closure of Iapetus and assembly of the Pangaea supercontinent in Permian time. The well- mapped trace of the orogen from New- foundland to Alabama exhibits sweeping curves of salients (convex cratonward in Figure 2. Assembly of Rodinia as the direction of tectonic transport) and recorded in the Grenville orogen more angular recesses (concave craton- (compiled from Hoffman, 1989; ward) (Fig. 4). Westward from Alabama Van Schmus et al., 1993; and references cited in text). in the subsurface beneath the Gulf Coastal Plain, deep drill and seismic reflection data, as well as outcrops in the Ouachita Mountains and in the Marathon region of west Texas, document curves of similar magnitude (Thomas et al., 1989). Appalachian-Ouachita salients are located at embayments of the Iapetan margin, and recesses are on promonto- ries (Rankin, 1976; Thomas, 1976, 1977). The leading part of the thrust belt wrapped around the shape of promon- tories and embayments of the older rifted margin (Fig. 4), indicating a grand scale of tectonic inheritance. Other specific manifestations of tectonic inheritance are expressed at a range of scales. Each of the three comprehensive oro- Figure 3. Breakup of genic episodes encompasses substantial Rodinia and opening of along-strike diachroneity, which reflects a the Iapetus Ocean (com- systematic relationship to the shape of the piled from references Iapetan rifted margin. From the St. Law- cited in text). rence promontory to the Alabama prom- ontory, a stratigraphically upward transi- tion from shelf carbonates to black records Taconic tectonic loading, foreland subsidence, and synorogenic sedimen- tation (Drake et al., 1989). The times of initial Taconic tectonic loading and fore- land subsidence vary systematically in relation to the shape of the Iapetan rifted margin: first, on the St. Lawrence promon- tory in Newfoundland; next, on the Ala- bama promontory followed by migration

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Figure 4. Assembly of Pangaea as recorded in the Appalachian-Ouachita orogen (compiled from references cited in text). Patterns for synorogenic clastic wedges show areas where thickness is >50% of the maximum (in present allochthonous position not palinspastically restored); dashed line shows deeper part of the intracratonic Anadarko basin. BWb—Black Warrior basin.

Figure 5. Breakup of Pangaea and opening of the Atlantic Ocean (compiled from Klitgord and Schouten, 1986; and references cited in text). SGBfz—Southern Grand Banks (transform); SGb—South Georgia basin.

GSA TODAY, FEBRUARY 2006 7 2005 GSA PRESIDENTIAL ADDRESS into the Tennessee embayment; then, on of the rifted margin, the thrust belt prop- because accretion of successive terranes the New York promontory followed by agated to a greater width and farther cra- modified the shape of the margin. migration into the Pennsylvania embay- tonward in salients than in recesses (Fig. The latest episodes of Alleghanian ment; and finally, in the Quebec embay- 4). The geometry of the salients adapted foreland thrusting appear nonsystem- ment (Bradley, 1989, Figures 1 and 7 to the greater thickness of sedimentary atically diachronous along the orogen. therein). Taconic terrane accretion must cover and to greater depth to crystalline Although not precisely dated, the last of a have modified the shape of the margin; basement rocks beneath foreland basins succession of Alleghanian events around however, initial Acadian foreland sub- in the embayments. Along the Appala- the Alabama promontory was continent- sidence migrated progressively south- chian orogen, the thin-skinned décolle- continent collision with African conti- ward from the St. Lawrence promontory ment in salients is within the nental crust, now marked by a suture to the Virginia promontory (Ettensohn, sedimentary cover succession above beneath the Gulf Coastal Plain (Fig. 4). 1985, Figures 1 and 2 therein). Along Precambrian crystalline basement rocks. The suture is oblique to the Iapetan the Appalachian orogen, late Paleozoic On some promontories along the arms rifted margin, diverging eastward from Alleghanian foreland subsidence over- of thrust-belt recesses, the Appalachian the corner of the Alabama promontory. printed the Taconic and Acadian fore- allochthon incorporates crystalline base- Continent-continent collision drove pre- lands; however, along the Ouachita mar- ment rocks in external basement massifs viously accreted terranes onto the conti- gin westward from the corner of the Ala- (Fig. 4), indicating that the décollement nental shelf of the Alabama promontory, bama promontory, a per- cuts down from the thick sedimentary accounting for a diachronous succession sisted until Mississippian time (Thomas, cover in embayments along strike into of Ouachita and Appalachian thrust- 1989). Ouachita tectonic loading of the basement rocks beneath a thinner sedi- ing (Thomas, 2004). The shape of the Laurentian margin began in middle Mis- mentary cover on promontories. Uncon- Iapetan margin, and not the shape of the sissippian time in the Black Warrior fore- formable overstep of Silurian conglomer- collider, evidently controlled the orien- land basin along the southeastern part ate onto basement rocks on the southern tation of Appalachian-Ouachita foreland of the Alabama-Oklahoma transform on part of the New York promontory (Drake structures. the Alabama promontory and migrated et al., 1989) indicates that the Taconic Appalachian-Ouachita structures, from northwestward along the transform to the foreland, like the later Alleghanian fore- the scale of salients and recesses to fore- Arkoma foreland basin in the Ouachita land, incorporated an external basement land basins to individual thrust ramps embayment in Early Pennsylvanian time massif on the promontory. and basement faults, have a clear pattern (Fig. 4) (Houseknecht, 1986; Thomas, Synorogenic brittle reactivation of of tectonic inheritance from the trace and 1989), continuing the pattern of adapta- Iapetan synrift intracratonic faults structures of the Iapetan rifted margin tion of the shape of the orogen to that of inboard from the rifted margin is evident of eastern Laurentia. Most of the inher- the Iapetan rifted margin. from the proximal to the distal foreland, ited structures are in the brittle, shallow Regardless of the diachroneity of fore- indicating compressive stress from Appa- crust; however, localization of maximum land subsidence and synorogenic sedi- lachian-Ouachita orogenesis (e.g., Kolata synorogenic flexural subsidence of the mentation along the orogen, maximum and Nelson, 1991). The thin-skinned foreland in embayments of the Iapetan subsidence, as indicated by maximum thrust belt includes both frontal and margin along transform faults (at ocean- thickness of synorogenic sediment along lateral ramps that rise above basement ward concave intersections of trans- the Taconic, Acadian, and Alleghanian extensional faults and transverse faults, form faults with rift segments) suggests forelands, is centered consistently in respectively (e.g., Thomas and Bayona, tectonic inheritance at a lithospheric embayments of the Iapetan rifted mar- 2005). Reactivated faults and a south- scale. The assembly of Pangaea also set gin (Fig. 4) (Thomas, 1977, Figures 5–10 plunging arch overprinted the Iapetan the mold for subsequent structures that therein). Although the differences in the M ississippi Val ley g raben (T homas, 19 91). formed during supercontinent breakup. magnitude of subsidence could reflect Reactivation of the Southern Oklahoma along-strike variations in the magnitude fault system generated the Arbuckle- BREAKUP OF PANGAEA of the tectonic loads, the systematic rela- Wichita-Amarillo basement uplifts AND OPENING OF THE ATLANTIC tionship of differentially greater foreland (Perry, 1989); the associated Anadarko OCEAN subsidence in the embayments than on basin along the fault system is among the Triassic adjacent to the Atlan- the promontories suggests a systematic deepest known cratonic basins. tic Coastal Plain document inboard spatial variation in the strength of the In the Appalachian metamorphic extension associated with the breakup lithosphere in relation to the shape of the internides, which include accreted ter- of Pangaea, the opening of the modern older rifted margin. Brittle structures in ranes and internal basement massifs, Atlantic Ocean, and the isolation of the the shallow crust define the shape of the orogen-parallel strike-slip faults (Gates et North American continent. Unlike the rifted continental margin; however, the al., 1988) show no systematic adaptation records of earlier Wilson cycles, this distribution of magnitudes of foreland to the shape of the older Iapetan rifted latest event is recorded in the modern subsidence suggests tectonic inheritance margin (Fig. 4), suggesting oblique colli- and ocean floor, includ- at a lithospheric scale. sion, transpression, and orogen-parallel ing transform faults that extend from In addition to thrust-belt curvature tectonic transport. The effects of tectonic the Mid-Atlantic Ridge to offsets in the convex toward the craton, where thrust- inheritance evidently diminish outboard shelf margin (Fig. 5). In addition to the belt salients bend around embayments from the older rifted margin, probably exposed Triassic faults, subsurface data

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document other Triassic faults beneath The Southern Grand Banks fracture and differential crustal subsidence along a post-rift unconformity at the base of zone (transform) along the southern mar- transform faults at rift offsets in continen- the Mesozoic-Cenozoic passive-margin gin of the Grand Banks of Newfoundland tal embayments. A pervasive fabric may successions in the Atlantic and Gulf (Keen and Haworth, 1985) is aligned vertically partition the lithosphere, both Coastal Plains (Fig. 5). The Triassic faults with the trace of the Iapetan transform at controlling the locations of transforms are analogous to the intracratonic faults the southern margin of the St. Lawrence during successive events of supercon- associated with Iapetan rifting. promontory (Fig. 5). The trace of the tinent breakup and reducing the elastic The trace of the rifted continental mar- Atlantic rifted margin east of the Grand strength of the lithosphere along trans- gin includes promontories and embay- Banks promontory roughly parallels the forms, thereby accounting for locations ments analogous to those of the Iapetan trace of the Iapetan rifted margin, but it of greatest differential subsidence. margin. The Bahamas fracture zone is far outboard of the Iapetan rift, leaving Kinematics of plate boundaries require () offsets the continental accreted terranes attached to the North that transform faults are small circles margin from the Florida promontory American margin, a pattern that persists around the pole of rotation, are paral- into the Gulf embayment; along the Gulf southward to the Florida promontory. lel to the direction of plate motion, and margin, a northwest-trending alignment Tectonic inheritance on a large scale is are essentially vertical, consistent with of Triassic faults parallels the transform reflected in the coincidence in location extent down through the lithosphere. (Fig. 5). The traces of the Bahamas trans- of large transform offsets of the rifted In contrast, rift segments are brittle form and the Triassic faults are aligned continental margins. The extraordinary upper-crustal structures above low-angle with the trace of the Iapetan Alabama- subsidence and sediment accumula- detachments that flatten downward Oklahoma transform in a clear expres- tion in the Mississippi River delta along within the crust, consistent with inheri- sion of large-scale tectonic inheritance the Bahamas fracture zone (transform) tance at the scale of individual faults in (Thomas, 1988). within the Gulf embayment is compa- shallow (brittle) crust. The width of transitional crust differs rable to other examples of differentially Recognition of tectonic inheritance has on opposite sides of the Gulf of Mexico, greater subsidence along transforms. implications for a range of applications suggesting a lower-plate structure on Inboard from the Bahamas transform beyond the fundamental questions of the Texas-Louisiana margin (Buffler and margin, subsidence of the Mississippi crustal structure and evolution of con- Thomas, 1994). The attenuated lower- Embayment, a south-plunging tinental crust and lithosphere. Differen- plate crustal structure overprints the in the Gulf Coastal Plain, overprints the tial subsidence at zones of lithospheric Ouachita accretionary complex (Keller Pangean (late Paleozoic) south-plunging weakness, primarily along transform et al., 1989), suggesting the possibility arch and the Iapetan intracratonic Mis- systems, localizes the potential for petro- that distinctive crustal properties may sissippi Valley graben, documenting suc- leum provinces in exceptionally thick be inherited by the geometry of conti- cessive inheritance at a pervasive zone of sedimentary accumulations. Mineralizing nental rifting. Deep subsidence of the weak crust. The same zone of weak crust brines may be selectively driven from lower plate along the Bahamas trans- hosts the modern New Madrid seismic the thicker sedimentary thrust loads in form within the Gulf embayment accom- zone. On a smaller scale, Atlantic-open- thrust-belt salients at rift-margin embay- modated the very thick accumulation of ing extensional faults reactivated accre- ments, including into the distal foreland. sediment in the Mississippi River delta, tionary compressional fabrics of the Pan- On a smaller scale, frontal thrust ramps inheriting the location of the Iapetan gaean assembly (e.g., Bobyarchick and over older basement faults, thin-skinned Ouachita embayment and the Pangaean Glover, 1979). transverse zones over basement trans- Ouachita thrust-belt salient. verse faults, and reactivation of basement The Bahamas transform reoccupied CONCLUSIONS faults in the foreland provide predictable the position of the older Alabama-Okla- Transform faults and aligned compres- controls on fracture sets that affect fluid homa transform; however, the Atlantic sional structures show repeated tectonic flow in both petroleum and groundwater rifted margin of North America crosses inheritance through successive Wilson systems. Repeated inheritance of zones Pangaean sutures and does not fol- cycles of supercontinent assembly and of crustal weakness suggests a focus for low older Iapetan rift segments (Fig. 5). breakup (Fig. 1). In contrast, rift seg- modern seismicity. The Bahamas transform and the Trias- ments of continental margins accumulate Studies of tectonic inheritance gener- sic faults cross the Pangaean Suwannee accreted terranes, because subsequent ally rely on data from the shallow crust, suture; however, the fault boundaries of break across terrane boundaries, limiting evaluations to a crustal scale. the Triassic South Georgia basin approx- fragmenting the supercontinent assem- The pervasiveness of zones of crustal imately parallel the Suwannee suture. bly. Brittle extensional structures and weakness associated with transform Northward from the Bahamas transform, upper-crustal orogenic structures reflect faults, however, requires a lithospheric the Atlantic rifted margin follows nei- processes in the shallow crust, as do the scale of investigation. Recent studies of ther the Iapetan rifted margin nor Pan- many examples of smaller scale tectonic seismic anisotropy define lithosphere- gaean sutures; instead, it is outboard of inheritance and reactivation of individual penetrating zones of distributed shear the Iapetan rift, leaving accreted African faults. Two relationships, however, sug- along transform systems (e.g., Baldock crust of the Suwannee terrane attached gest inheritance at a lithospheric scale: and Stern, 2005). The probable signifi- to North America, forming the Florida successive reoccupation of traces of cance of transform inheritance and litho- promontory. transform faults at the continental margin spheric properties suggests a fruitful line

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D.R., Oltz, D.F., and Eidel, J.J., eds., Interior cra- of investigation, because transform faults covery: Kentucky Geological Survey Special tonic basins: American Association of Petroleum Publication 18, 25 p. appear to be the dominant controls on Geologists Memoir 51, p. 263–285. Drake, A.A., Jr., Sinha, A.K., Laird, J., and Guy, R.E., Lister, G.S., Etheridge, M.A., and Symonds, P.A., 1986, tectonic inheritance at large scales along 1989, The Taconic orogen, in Hatcher, R.D., Detachment faulting and the evolution of passive Jr., Thomas, W.A., and Viele, G.W., eds., The continental margins during superconti- continental margins: Geology, v. 14, p. 246– Appalachian-Ouachita orogen in the United nent breakup and assembly, as well as 250, doi: 10.1130/0091-7613(1986)14<246: States: Geological Society of America, The DFATEO>2.0.CO;2. on locations of differential subsidence Geology of North America, v. F-2, p. 101–177. 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