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We integrate structural, geophysical, and geodetic studies showing that the Dinarides-Hellenides orogen along the Adria-Europe plate boundary in the Western Balkan peninsula has experienced clockwise oroclinal bending since Eocene-Oligocene time. Rotation of the Hellenic segment of this orogen has accelerated since the middle Miocene and is associated with a north-to-south increase in shortening along the orogenic front. Within the Paleogene nappe pile, bending was accommodated by orogen-parallel extension, clockwise block rotation, and thrusting in the hanging wall of the Skhoder-Peja Normal Fault (SPNF). The SPNF and related faults cut the older Skhoder-Peja Transfer Zone with its pre-Neogene dextral offset of the West Vardar ophiolite nappe. Rotation of the SPNF hanging wall involved Miocene-to-recent, out-of-sequence thrusting that was transferred to the Hellenic orogenic front via lateral ramps on dextral transfer zones. Along strike of the Dinarides-Hellenides and coincident with the southward increase in Neogene shortening, the depth of the Adriatic slab increases from ~160 km north of the SPNF to ~200 km just to the south thereof, to several hundreds of kilometers to the south of the Kefalonia Transfer Zone. The geodynamic driver of tectonics since the early Miocene has been enhanced rollback of the Hellenic segment of the Adriatic slab in the aftermath of Eocene-Oligocene slab tearing and breakoff beneath the Dinarides, which focused slab pull in the south. The SW-retreating Hellenic slab segment induced clockwise bending of the southern Dinarides and northern Hellenides, including their Adriatic foreland, about a rotation pole in the vicinity of the Mid-Adriatic Ridge.

Curvature of fold-and-thrust belts (FTBs) is a rather common feature in foreland basins. The problem of how curves in FTBs originate is essential for understanding the propagation of deformation and tectonic history of orogens. In this study, we carried out systematic paleomagnetic studies in the westernmost part of the Qiulitage FTB, southern Tian Shan foreland, where thrusting, strike-slip fault, and tectonic boundary coexist. Our new results suggest that the study area has been subjected to similar to 20 degrees clockwise rotations after similar to 5Ma. Oroclinal test of the paleomagnetic data across the FTB suggests that oroclinal bending caused by the formation of the curved Qiulitage FTB is the dominate reason for these tectonic rotations. The Kalayuergun dextral strike-slip transfer fault delimiting the western boundary of the Qiulitage FTB is a thin-skinned structure accommodating the discrepancy in horizontal displacement on both sides of it. These results also suggest that the formation of the curved Qiulitage FTB should not be older than similar to 5Ma, indicating that the southern Tian Shan foreland has experienced significant tectonic shortening since the latest Miocene to early Pliocene. Our new results, together with previous studies on deformation history, estimates of crustal shortening, GPS observations and earthquake records, suggest that the southern Tian Shan foreland has been subjected to significant deformation during the past similar to 5million years, and the crustal shortening is still ongoing.

SE Asia comprises a heterogeneous assemblage of fragments derived from Cathaysia (Eurasia) in the north and Gondwana in the south, separated by suture zones representing closed former ocean basins. The western part of the region comprises Sundaland, which was formed by Late Permian‐Triassic amalgamation of continental and arc fragments now found in Indochina, the Thai Penisula, Peninsular Malaysia, and Sumatra. On Borneo, the Kuching Zone formed the eastern margin of Sundaland since the Triassic. To the SE of the Kuching Zone, the Gondwana‐derived continental fragments of SW Borneo and East Kalimantan accreted in the Cretaceous. South China‐derived fragments accreted to north of the Kuching Zone in the Miocene. Deciphering this complex geodynamic history of SE Asia requires restoration of its deformation history, but quantitative constraints are often sparse. Paleomagnetism may provide such constraints. Previous paleomagnetic studies demonstrated that Sundaland and fragments in Borneo underwent vertical axis rotations since the Cretaceous. We provide new paleomagnetic data from Eocene‐Miocene sedimentary rocks in the Kutai Basin, east Borneo, and critically reevaluate the published database, omitting sites that do not pass widely used, up‐to‐date reliability criteria. We use the resulting database to develop an updated kinematic restoration. We test the regional or local nature of paleomagnetic rotations against fits between the restored orientation of the Sunda Trench and seismic tomography images of the associated slabs. Paleomagnetic data and mantle tomography of the Sunda slab indicate that Sundaland did not experience significant vertical axis rotations since the Late Jurassic. Paleomagnetic data show that Borneo underwent a ~35° counterclockwise rotation constrained to the Late Eocene and an additional ~10° counterclockwise rotation since the Early Miocene. How this rotation was accommodated relative to Sundaland is enigmatic but likely involved distributed extension in the West Java Sea between Borneo and Sumatra. This Late Eocene‐Early Oligocene rotation is contemporaneous with and may have been driven by a marked change in motion of Australia relative to Eurasia, from eastward to northward, which also has led to the initiation of subduction along the eastern Sunda trench and the proto‐South China Sea to the south and north of Borneo, respectively., Key Points We present new paleomagnetic data from Eocene‐Miocene sedimentary rocks in Kutai Basin, Borneo, and compile all available paleomagnetic data from Mesozoic and Cenozoic rocks in Sundaland and BorneoWe compare reconstructed trenches with seismic tomography to evaluate the regional or local nature of paleomagnetic resultsWe provide a kinematic restoration of Borneo and Sundaland since the Eocene that is consistent with paleomagnetism and tomography

International audience; The core complexes of the North Aegean result from the gravity spreading of a thrust wedge, driven by the Hellenic slab rollback, since middle Eocene. The development of the Southern Rhodope Core Complex occurred in two stages: (i) core complex exhumation accommodated by the Kerdylion detachment and (ii) steep normal faulting controlling the deposition of Neogene sedimentary basins that segmented the core complex. Both stages have been controlled by a clockwise rotation of the detachment hanging wall. The bulk amount of extension along the Aegean coastline in Northern Greece reached 120 km. The transition between the two stages occurred in middle Miocene due to an increase in extensional displacement by a factor 5. This transition between two different modes of extension, from localized detachment (i.e., core complex mode) to distributed steep normal faulting (i.e., wide rift mode), occurred at Aegean scale as a result of an acceleration of slab rollback. The Neogene basins emplaced close to the detachment, where brittle upper crust was thin (around 7 km) but containing weak marble layers allowing the formation of ramp-flat extensional systems with rollover-type basin fill. Since Pliocene, the stretching direction changed, from NE-SW to NS, due to the propagation of the North Anatolian Fault in the North Aegean domain.

In their recent paper, Barnett-Moore et al. (2016) reflect on current models of Iberian plate motion in the Jurassic and Cretaceous as well as ongoing debates on the reliability of the various types of kinematic data that form independent constraints on Iberia's motion relative to Eurasia. They question the validity of various marine geophysical, seismic, tomographic, geological, and paleomagnetic data sets from the Bay of Biscay, Central Atlantic Ocean, and Iberia for kinematic reconstruction of Iberia and conclude that neither models invoking Aptian-Albian transtension, nor compression, are consistent with currently available data. An important element in their analysis is that they discard the large paleomagnetic data set from the Jurassic and Cretaceous from Iberia based on perceived limitations of that data set. In addition, they argue that seismic tomographic images exclude a scenario of subduction in the Aptian-Albian in the Pyrenees, and based on this "question the validity of current plate reconstructions, their constraints, and geodynamic scenarios, which are in support of this scenario [e.g., Vissers et al., 2016]." We welcome the discussion raised by Barnett-Moore et al. (2016) on the reliability and usefulness of paleomagnetic data as independent constraint for Iberia's plate motion in the Mesozoic. Taking these paleomagnetic data at face value, Vissers et al. (2016) recently showed that these are consistent with an ~40° counterclockwise rotation of Iberia in the Aptian, requiring up to 500 km of Aptian convergence across the Pyrenees, that is, through subduction. In this comment, we aim to critically assess whether and how the concerns on the quality of paleomagnetic data raised by Barnett-Moore et al. (2016) may allow for an alternative explanation, particularly one with a Mesozoic rotation of Iberia that is small enough so as to not requiring subduction. We also reassess whether seismic tomographic images indeed refute subduction scenarios, using 8 S wave and P wave tomographic models including those used in Barnett-Moore et al. (2016).

Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr. Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right-lateral strike-slip faulting in Washington, and SW to W directed normal faulting and right-lateral strike-slip faulting to the east. Several curvilinear NW to NNW trending high-angle strike-slip faults and seismicity lineaments in Washington and NW Oregon define a geologic pole (117.7°W, 47.9°N) of rotation relative to North America. Many faults and focal mechanisms throughout northwestern U.S. and southwestern British Columbia have orientations consistent with this geologic pole as do GPS surface velocities corrected for elastic Cascadia subduction zone coupling. Large Quaternary normal faults radial to the geologic pole, which appear to accommodate crustal rotation via crustal extension, are widespread and can be found along the Lewis and Clark zone in Montana, within the Centennial fault system north of the Snake River Plain in Idaho and Montana, to the west of the Wasatch Front in Utah, and within the northern Basin and Range in Oregon and Nevada. Distributed strike-slip faults are most prominent in western Washington and Oregon and may serve to transfer slip between faults throughout the northwestern U.S.

We conducted a stress field analysis of the northern part of the~700 km long north-south trending, seismically active Sistan orogenic belt of Eastern Iran formed as a result of the closure of a branch of the Neo-Tethys during the early Cenozoic. Fault kinematic data reveal drastic changes in the stress regime of Eastern Iran during the late Cenozoic, with three successive directions of compression (σ 1), from 90°N during the middle-late Miocene to 60°N during the late Pliocene and 25°N during the Plio-Quaternary, thereby evidencing a counterclockwise rotation of about 65°of σ 1 in less than 10 Myr. As shown by compilation of paleostress data, Plio-Quaternary direction of compression in Sistan coincides with the one recorded across the whole of Iran and with present-day Arabia-Eurasia convergence direction. This result suggests effective stress transfer from the Zagros collision and that Sistan is at present mechanically coupled and shortened along with the rest of the Iranian crust/lithosphere. By contrast, Miocene compression is markedly different in the Iranian hinterland (e.g., Sistan, Central Iran, and Kopet Dagh) and in the Zagros orogen. This could tentatively be related to the end of Sistan collision and/or to the imprint of active deformation occurring further to the east. The intermediate late Pliocene compression (i.e., 60°N) could correspond to the progressive reorientation of the stress regime, as Sistan gets mechanically coupled to the Zagros collision.

Analysis of the locus, style, and rate of faulting is fundamental to understanding the kinematics of continental deformation. The Ordos Plateau lies to the northeast of Tibet, within the India-Eurasia collision zone. Previous studies have suggested that it behaves rigidly and rotates anticlockwise within a large-scale zone of ENE-WSW left-lateral shearing. For this rotation to be accommodated, the eastern and western margins of the Ordos Plateau should be undergoing right-lateral shearing and yet the dominant faulting style appears to be extensional. We focus specifically on the kinematics of the faults bounding the western margin of the Ordos Plateau and make new slip rate estimates for two of the major faults in the region: the right-lateral strike-slip Luoshan Fault and the normal-slip East Helanshan Fault. We use a combination of infrared stimulated luminescence dating of offset landforms with high-resolution imagery and topography from the Pleiades satellites to determine an average right-lateral slip rate of 4.3 ± 0.4 mm/a (1σ uncertainty) on the Luoshan Fault. Similarly, we use 10Be exposure dating to determine a vertical throw rate on the East Helanshan Fault of

Structural, anisotropy of magnetic susceptibility (AMS), and paleomagnetic data record patterns of layer-parallel shortening (LPS), vertical-axis rotation, and regional fault-fold evolution across the Sweetwater Arch, a major west to WNW trending, basement-cored Laramide uplift in Wyoming. The southern arch flank is bounded by a WNW striking reverse fault zone that imbricated basement and cover rocks, the northern flank is bounded by a west striking fault zone with a component of strike-slip and NW trending en echelon folds, and the eastern plunge transitions into an area of multiple-trending faults and folds. Synorogenic strata record major arch uplift from Maastrichtian to Early Eocene time, followed by arch collapse. LPS, with development of systematic minor fault sets and AMS lineations, preceded large-scale folding. LPS directions, estimated from both minor fault and AMS data, were oriented WSW along the northern flank, subparallel to Laramide regional shortening, but were refracted to the SSW along the southern flank, and to the west along the eastern arch plunge. Additional minor faults developed along steep fold limbs during continued shortening, with directions remaining SSW along the southern flank but becoming more variable along the eastern plunge where an increasingly heterogeneous stress field developed as additional faults were activated along basement heterogeneities. Vertical-axis rotation was limited along the arch flanks, whereas the eastern plunge underwent counterclockwise rotation. Deflections in shortening directions were partly related to basement heterogeneities, including weak supracrustal belts on the arch flanks, a strong granitic core, and local reactivation of Precambrian shear zones.

At the southern tip of the Baja California peninsula, we characterize the onshore structures and kinematics associated with crustal necking leading up to the Pliocene breakup and early East Pacific Rise seafloor spreading. From a combination of tectonic field investigations, K-Ar and cosmogenic isotope dating and geomorphology, we propose that the Los Cabos block represents the exhumed footwall of a major detachment fault. This north trending detachment fault is marked by a conspicuous low-dipping brittle-ductile shear zone showing a finite displacement with top to the SE ending to the ESE. This major feature is associated with fluid circulations which led to rejuvenation of the deformed Cretaceous magmatic rocks at a maximum of 17.5 Ma. The detachment footwall displays kilometer-scale corrugations controlling the present-day drainage pattern. This major detachment is synchronous with the development of the San Jose del Cabo Basin where syntectonic sedimentation took place from the middle Miocene to probably the early Pliocene. We propose that this seaward dipping detachment fault accommodates the proximal crustal necking of the Baja California passive margin, which predates the onset of formation of the East Pacific Rise spreading axis in the Cabo-Puerto Vallarta segment. Our data illustrate an apparent anticlockwise rotation of the stretching direction in Baja California Sur from ~17 Ma to the Pliocene.

The Nigde-Kirsehir Massif, known also as the Central Anatolian Block, is bordered by the sutures of the NeoTethys Ocean. The Massif suffered several deformation phases during and after the consumption of the surrounding oceans and the post-collisional events of the continental pieces of Anatolia in latest Cretaceous to Miocene. Previous paleomagnetic studies on the Nigde-Kirsehir Massif and its surroundings displayed either insufficient data or have claimed large rotations and/or remagnetization. In order to understand the tectonic history of the Nigde-Kirsehir Massif and its adjacent blocks we have sampled 147 different sites in the age range of Upper Jurassic to Miocene from the Nigde-Kirsehir Massif throughout its W/SW and E/SE boundaries and the Central- Southeastern Taurides. The results display that except the limestones in Central Taurides, all rocks examined carry a primary magnetization. Among these an important finding is that rotations between the Massif and the Central-Eastern Taurides indicate an oroclinal bending with counterclockwise rotation of R=41.1°±7.6° in the SE and clockwise rotation of R=45.9°±9.3° in the Central Taurides from Upper Cretaceous rocks with respect to the African reference direction. Paleomagnetic rotations in the SE Taurides are compatible with the vergent direction of the thrusts generated from consumption of the Intra-Tauride ocean prior to post collisional convergence between Taurides and the Massif. In the Central Taurides it has been shown that the clockwise rotation of 45.9±9.3 started in Middle Eocene, because of a remagnetization in Upper Creataceous limestones. The deformation was linked to the final closure of the southern Neotethys and the collision between the African and Eurasian plates. In the Nigde-Kirsehir Massif counterclockwise rotation up to 25.5°±7.3° is recognised during Middle Eocene and interpreted in terms of block rotation together with the Taurides. After the Miocene a counterclockwise rotation of 16.8°±3.9° along the Eastern Taurides shows that this area was mostly affected by the westward movement of Anatolia despite the Nigde-Kirsehir Massif and its SW/W area-the Central Taurides, which is recognised as stable with counterclockwise rotation less than 10°.

The results of an integrated stratigraphic, structural, geophysical, and geochemical study reveal the presence of a crustal discontinuity in western Sicily that, at present, runs roughly N-S along a band from San Vito Lo Capo to Sciacca (SVCS). The boundary between the two zones of this discontinuity is nearly orthogonal to the main thrust propagation of the Sicilian thrust-and-fold belt. The different Permian to Tertiary sedimentary evolution recorded by the two zones appears related to this discontinuity, with thick carbonate platforms in the western sector facing deep-water successions in the eastern one. The presence of Upper Triassic reefs, huge megabreccias bodies, and widespread submarine volcanisms along the transition zone suggest the presence of a long lasting weakness zone. This zone has been reactivated episodically as transpressional and/or transtensional faults in relation to the different geodynamic stress acting in central Mediterranean area in different epochs. We speculate that this transition zone has represented a segment of the passive margin of the Ionian Tethys. During the Maghrebian convergence a different style of deformation has affected the two sectors floored by different sedimentary multilayers. The orthogonal-to-oblique differential convergence between the two sectors has resulted in right-lateral transpressional motions, leading to oblique thrusting of deep-water-derived thrusts onto platform-derived thrusts associated with clockwise rotations. The oblique convergence is still ongoing as demonstrated by the seismicity of the area, by the geothermal field with high mantle-derived helium fluxes and by the GPS measurements collected by different authors.

The North American Cordillera is a classic example of accretionary orogen, consisting of multiple oceanic terranes attached to the western margin of Laurentia during the Mesozoic times. Although the Cordillera is linear for most parts, terrane boundaries are at a high angle to the overall structural grain in several segments of the orogen, which has been a matter of longstanding controversy as to how and when these orogenic curvatures formed. This paper discusses mechanisms, kinematics, and timing of initiation of one of these major curvatures, the Blue Mountains Province in northeastern Oregon. Here magmatic fabric patterns and anisotropy of magnetic susceptibility in the Wallowa batholith record three phases of progressive deformation of the host Wallowa terrane during Early Cretaceous. First is terrane-oblique ~NE-SW shortening, interpreted as recording attachment of the amalgamated oceanic and fringing terranes to the continental margin during dextral convergence at ~140 Ma. Deformation subsequently switched to pure shear-dominated ~NNE-SSW shortening associated with crustal thickening, caused by continued impingement of the amalgamated Blue Mountains superterrane into a presumed westward concave reentrant in the continental margin at ~135–128 Ma. Upon impingement (at ~126 Ma), the northern portion of the superterrane became “locked,” leading to reorientation of the principal shortening direction to ~NNW-SSE while its still deformable southern portion rotated clockwise about a vertical axis. We thus propose oblique bending as the main mechanism of the orocline formation whereby horizontal compressive forces resulting from plate convergence acted at an angle to the terrane boundaries.

In this study we use the anisotropy of magnetic susceptibility (AMS) and paleomagnetic data for deciphering the origin of magnetic lineation in weakly deformed sedimentary rocks and for evaluating oroclinal processes within the Arabia-Eurasia collision zone. In particular, we have analyzed the Miocene Upper Red Formation (URF) from the outer curved front of the southern Central Alborz Mountains of north Iran, to test for the first time with paleomagnetic data the origin (primary versus secondary) of this orogenic arc. AMS data document the existence of a magnetic lineation parallel to the orientation of the major tectonic structures, which vary along strike from WNW to ENE. These directions are highly oblique to the paleoflow directions and hence suggest that the magnetic lineation in the URF was produced by compressional deformation during layer-parallel shortening. In addition, our paleomagnetic data document clockwise and anticlockwise rotations along vertical axis for the western and eastern sectors of the Central Alborz Mountains, respectively. Combined, our results suggest that the orogen represents an orocline, which formed not earlier than circa 7.6 Ma most likely through bending processes caused by the relative motion between the rigid crustal blocks of the collision zone. Moreover, our study provides new insights into the Iran-Southern Caspian Basin kinematic evolution suggesting that the present-day SW motion of the South Caspian Basin with respect to Central Iran postdates oroclinal bending and hence cannot be as old as late Miocene to early Pliocene but a rather recent configuration (i.e., 3 to

In this paper we review the structure of the most external thrust belt of the Alps between the Rhein valley and Salzburg based on a new tectonic map and the (re)interpretation of seismic sections. Specifically we address the correlation between deformation in the Subalpine Molasse and the Alpine thrust belt in general and focus on the control of sedimentary facies on the structural style. A dramatic change in architecture from a ramp-flat structure to buckle folding is related to a change from coarse-grained fans to fine-grained deposits within the Subalpine Molasse. Additionally the interaction of escape tectonics with postcollisional shortening controls the decrease of late Early Miocene and younger shortening within the Subalpine Molasse from 50 km near the Rhine valley to almost zero near Salzburg. Transfer of shortening into the hinterland, which is the zone of lateral escape, ended foreland propagation of the Alpine thrusts and initiated a general break-back sequence of thrusting. Throughout this time the thrusts remained active. In such a scenario, tectonic units on top of the Subalpine Molasse are expected to undergo clockwise rotation around vertical axes. As thrusting in the Subalpine Molasse is closely related to contemporaneous transport and shortening within the tectonically higher Helvetic thrust sheets, amounts of Miocene differential shortening and related clockwise vertical axis rotation are minimum amounts. True clockwise vertical axis rotation is probably larger than the 12° deduced from the Subalpine Molasse thrust belt.

The Magallanes fold and thrust belt (FTB) presents a large-scale curvature from N-S oriented structures north of 52°S to nearly E-W in Tierra del Fuego Island. We present a paleomagnetic and anisotropy of magnetic susceptibility (AMS) study from 85 sites sampled in Cretaceous to Miocene marine sediments. Magnetic susceptibility is lower than 0.0005 SI for 76 sites and mainly controlled by paramagnetic minerals. AMS results indicate that the sedimentary fabric is preserved in the undeformed areas of Tierra del Fuego and the more external thrust sheets units, where an incipient lineation due to layer parallel shortening is recorded. Prolate AMS ellipsoids, indicating a significant tectonic imprint in the AMS fabric, are observed in the internal units of the belt. AMS results show a good correlation between the orientation of the magnetic lineation and the fold axes. However, in Peninsula Brunswick, the AMS lineations are at ~20° counterclockwise to the strike of the fold axes. Pretectonic stable characteristic remanent magnetizations (ChRM) were determined in seven sites. A counterclockwise rotation (21.2° ± 9.2°) is documented by ChRM data from four sites near the hinge of the belt in Peninsula Brunswick and near Canal Whiteside while there is no evidence of rotation near the nearly E-W oriented Vicuna thrust within Tierra del Fuego. The curved shape of the Cenozoic Magallanes FTB is not related to vertical axis rotation, and thus, the Magallanes FTB can be considered as a primary arc.

We report the paleomagnetic and magnetic fabric results of 58 sites from Cretaceous-Miocene marine and continental strata from the Eastern Cordillera (EC) and the Cucuta zone, at the junction between the Santander Massif and the Merida Andes of Colombia. The EC is an intracontinental doubly vergent range inverting a Triassic to Early Cretaceous rift zone. Twenty-three sites reveal nonsystematic tectonic rotations, including unrotated areas of the EC range with respect to stable South America. Our data show that the EC inverted a NNE oriented rift zone and that the orientation of the Mesozoic rift and the mountain chain roughly correspond. Interestingly, magnetic lineations from anisotropy of magnetic susceptibility analysis do not trend parallel to the chain but rather are oblique to the main orogenic trend. By also considering GPS evidence of a ~1 cm/yr ENE displacement of central western Colombia accommodated by the EC, we suggest that the Miocene-Recent deformation event of this belt arises from ENE oblique convergence reactivating a NNE oriented rift zone. Oblique shortening was likely partitioned into pure dip-slip shear characterizing thick-skinned frontal thrust sheets (well known along both chain fronts) and by range-parallel right-lateral strike-slip faults, which have not been identified yet, but likely exist in the axial part of the EC. Finally, the 35° ± 9° clockwise rotation observed in four post-Miocene magnetically overprinted sites from the Cucuta zone reflects late Cenozoic and ongoing right-lateral strike-slip displacement occurring along faults parallel to the Bocono fault system, possibly connected with the right-lateral faults inferred to exist along the axial part of the EC.

The Liquine-Ofqui fault zone (LOFZ) is a major ~1000 km long dextral shear zone of southern Chile, likely related to strain partitioning of Nazca Plate oblique convergence with South America. To understand block rotation pattern along the LOFZ, we paleomagnetically sampled 55 sites (553 samples) between 38°S and 41°S. We gathered Oligocene to Pleistocene volcanics and Miocene granites at a maximum distance of 20 km from the LOFZ, and at both sides of it. Rotations with respect to South America, evaluated for 36 successful sites, show that crust around the LOFZ is fragmented in small blocks, ~1 to 10 km in size. While some blocks (at both fault edges) undergo very large 150°–170° rotations, others do not rotate, even adjacent to fault walls. We infer that rotations affected equidimensional blocks, while elongated crust slivers were translated subparallel to the LOFZ, without rotating. Rotation pattern across the LOFZ is markedly asymmetric. East of the fault and adjacent to it, rotations are up to 150°–170° clockwise, and fade out ~10 km east of fault. These data support a quasi-continuous crust kinematics, characterized by small rigid blocks drag by the underlying ductile crust flow, and imply 120 km of total fault offset. Conversely, crust west of the LOFZ is cut by seismically active NW-SE sinistral antithetic faults, and yields counterclockwise rotations up to 170° at 8–10 km from LOFZ, besides the unrotated blocks. Further data from the Chile fore arc are needed to understand block rotation kinematics and plate dynamics west of the LOFZ.

Jamming of the Hikurangi Plateau (large igneous province) subduction, within the Chatham Rise convergent margin of Gondwana at circa 105 Ma, led to offset and rotation of the convergent margin before subduction ceased in the New Zealand region at circa 100 Ma. The southern limit of the plateau, following leading slab break off, is highlighted by a lineament of prominent horst blocks in the southern Bounty Trough. Subduction jamming of the Gondwana margin, and accompanying compression of the onshore margin and/or extension of the offshore margin, has led to two 60 km left-lateral SSE offsets of the Chatham Rise convergent margin at the coast and in inland Canterbury. Recognition of the onshore Chatham Rise using the gravity data also highlights the correlation of the inland Chatham Rise and central South Island seismicity. In a similar manner to the rotation of Cretaceous spreading-ridge and transform-fault fabric adjacent to the Osbourn Trough spreading ridge, the convergence direction at the Gondwana margin was rotated anticlockwise to N-S between 105 and 100 Ma. Most of this rotation has been accommodated by offshore extension and margin offset. The divergence between the anticlockwise rotation of offshore crustal structure and the jammed onshore margin led to the development of the Great South Basin at 105–100 Ma. Further offshore in the Bounty Trough, extensional zones, formed between crustal blocks rotated to adjust to a changed Cretaceous direction of subduction, are evident in gravity and seismic profiles.

The north Caribbean plate boundary zone is a broad deformation zone with several fault systems and tectonic blocks that move with different velocities. The indentation by the Bahamas Platform (the “Bahamas Collision”) is generally invoked as a cause of this fragmentation. We propose that a second driver of deformation is the western edge of the south dipping Puerto Rico slab moving sideways with the North America plate. The westward motion of the slab edge results in a push on the Caribbean plate farther west. We refer to this second mechanism for deformation as “Slab Edge Push.” The motion of the North America plate relative to the Caribbean plate causes both drivers to migrate from east to west. The Bahamas Collision and Slab Edge Push have been operating simultaneously since the Miocene. The question is the relative importance of the two mechanisms. We use mechanical finite element models that represent the two mechanisms from the late Oligocene (30 Ma) to the present. For the present, both models successfully reproduce observed deformation, implying that both models are viable. Back in time the Slab Edge Push mechanism better reproduces observations. Neither mechanism successfully reproduces the observed Miocene counterclockwise rotation of Puerto Rico. We use this rotation to tune a final model that includes fractional contributions of both mechanisms. We find that the Slab Edge Push was the dominant driver of deformation in the north Caribbean plate boundary zone since 30 Ma.

GPS field and seismic data show that the southeastern margin of the Tibetan Plateau is tectonically and seismically active. This activity is due to the southeastward extrusion of the Chuandian fragment, a large crustal block rotating clockwise around the northeastern syntaxis of the Himalayas. The eastern boundary fault of this fragment is defined by the left-lateral Xianshuihe-Xiaojiang fault, which abruptly truncates the Sichuan basin of the Yangtze block. Our paper presents evidence indicating that the Sichuan basin experienced right-lateral shear along its margin, including the Longmen Shan fault belt, as shown by the presence of a large number of interference deformation features, including S-shaped and Z-shaped folds and faults, aligned in an en echelon pattern. This study hypothesizes that the Sichuan basin experienced counterclockwise rotation, dragged by the left-lateral movement along the Xianshuihe fault, and it is this rotation that was the underlying cause of the 12 May 2008 Wenchuan Ms 7.9 earthquake. During the rotation, the Sichuan basin decoupled along a subhorizontal decollement fault zone that developed along Triassic gypsum- and coal-bearing rocks, at a mean depth of ~5000 m, below which the Paleozoic rocks experienced much more intense deformation than the overlying Mesozoic rocks, suggesting that the lower part of the basin experienced a larger-scale rotation relative to the uppermost part of the basin. Based on thermal data from the western margin of the Sichuan basin and from along the Xianshuihe fault, the counterclockwise bending/rotation of the Sichuan basin initiated in late Cenozoic time (~13 Ma).

We report on an extensive paleomagnetic study (36 sites) of the Tuscan Nappe succession from the Northern Apennines Arc, aimed to reconstruct the tectonic evolution of the internal sector of this chain. We analyzed Eocene pelagic foreland ramp deposits (Scaglia Toscana Formation) and Oligocene–lower Miocene siliciclastic turbidites (Macigno and Falterona Formations). Paleomagnetic results show that the internal sector of the Northern Apennines underwent large counterclockwise (CCW) rotations with respect to the Adria-Africa foreland. A decrease in the rotation magnitude was observed from the southern to the northern sector of the arc (from 91 to 36°). This trend is opposite to that observed in the more external units of Northern Apennines and demonstrates that the oroclinal bending model, which has been proposed for the external units of the chain, is not appropriate to explain the evolution of the internal sector of the arc. On the basis of the observed paleomagnetic pattern, we propose a new tectonic model in which the Tuscan and Falterona-Cervarola units in the southern area were first rotated CCW along with the Corsica-Sardinia block during its lower Miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector (Umbria domain), thus yielding the final curved shape of the Northern Apennines chain. Data from this study represent the first paleomagnetic evidence of the influence of the Corsica-Sardinia CCW rotation in the Apennines orogenic wedge deformation, in the general framework of the geodynamic evolution of the Central Mediterranean subduction system.

Despite the importance of the Pamir range in controlling Asian paleoenvironments and land-sea paleogeography, its tectonic evolution remains poorly constrained in time and space, hindering its potential for understanding deep to surface processes. We provide here new constraints on vertical-axis tectonic rotations from the southwest Tarim Basin along the eastern flank of the Pamir arcuate range based on paleomagnetic results. Two well-dated Eocene to Oligocene sections, previously analyzed using biostratigraphy and magnetostratigraphy, yield consistently clockwise rotations of 21.6 ± 4.2° in 41 to 36 Ma strata then 17.1 ± 6.5° in 33 to 28 Ma strata at the Aertashi section and 14.2 ± 11.5° in 41 to 40 Ma strata at the Kezi section. Combined with a regional review of existing paleomagnetic studies, these results indicate that most of the clockwise rotations along the eastern Pamir occurred during Oligocene times and did not extend systematically and regionally into the Tarim Basin. In contrast, on the western flank of the Pamir tectonic rotations in Cretaceous to Neogene strata are regionally extensive and systematically counterclockwise throughout the Afghan-Tajik Basin. This timing and pattern of rotations is consistent with paleogeographic reconstructions of the regional sea retreat out of Central Asia and supports a two-stage kinematic model: (1) symmetric rotations of either flanks of the Pamir arcuate range until Oligocene times followed by (2) continued rotations on its western flank associated with radial thrusting and, along the eastern flank, no further rotations due to decoupled transfer slip starting in the Early Miocene.

Early- and late-stage, outcrop-scale faults have been documented in Paleogene strata of the Muroto Peninsula of southwest Japan. The former were active early in the consolidation history of the sediment and are crosscut by the latter, which were active after regional-scale imbrication, folding, and penetrative deformation (i.e., regional, spaced pressure solution cleavage). Orientation distributions of striae and kinematic axes indicate that the two generations of faults reflect distinct kinematic regimes. The orientations and crosscutting relations indicate a counterclockwise (viewed downward) rotation of the principal shortening direction between early- and late-stage faulting. Existing fossil and radiometric age data suggest this transition occurred during Eocene-Oligocene time. The fault kinematic data are interpreted to reflect a change in relative plate motions between Eurasia and an oceanic plate subducting beneath Eurasia in Paleogene time. These results, coupled with existing paleothermal and paleopressure data, are consistent with the presence of a spreading ridge in the western Pacific basin during this time.

We report new paleomagnetic and anisotropy of magnetic susceptibility (AMS) results from upper Tortonian to middle Pleistocene sediments which were deposited upon and adjacent to active thrust structures in southwestern Sicily. The data show that the Plio-Pleistocene sediments from the Belice and Menfi basins (covering the Saccense shelf limestones) underwent any internal shortening after the early Pleistocene (Santernian), as well as any net rotation. Sediments around this area (which overlie basinal Meso-Cenozoic successions) record systematic rotations: one upper Tortonian site to the west is ∼30° counterclockwise rotated, while to the east, lower Pliocene to middle lower Pleistocene sites within the Gela Nappe domain show 25° to 56° clockwise (CW) rotations. These data show that the ductile basinal sediments were bent and rotated around the rigid Saccense carbonates during the thin-skinned southward propagation of the orogenic front. We document here that the coastal sediments from the southwestern Gela Nappe underwent both a post middle early Pleistocene ∼30°CW rotation and a post middle Pleistocene E–W to ESE–WNW flattening (revealed by AMS). Our data then constrain to the late Pleistocene-Holocene the age of the last shortening episode occurring in the southwestern Gela Nappe front. Pleistocene rotations of similar amount also characterize the Sicanian domain, implying that it was incorporated in the Gela Nappe wedge during the recentmost episodes of deformation. This evidence allows us to better understand the very large (up to 114°) post Mesozoic rotations reported by Channell et al. [1980, 1990] for the Sicanian limestones, as related to both Miocene (or older?) deformational episodes and the Plio-Pleistocene evolution of the Gela Nappe.

The evolution of the Carpathians is in its final stage with intermediate seismic activity (70–200 km, Mw = 4–7.7) localized beneath its southeastern salient (Vrancea zone). Our analysis, in the transition area between south Carpathians and east Carpathians, reveals that the termination of convergence is characterized by a clockwise rotation of the Carpathian belt transport direction. Using structural maps and cross sections, we show that this change of convergence direction had several structural consequences including (1) the Pliocene-Quaternary activation of out-of-sequence structures in the southern east Carpathians and (2) the creation of dextral strike-slip faults bounding the mobile belt to the west, in the south Carpathians. Our fracture analysis in syntectonic deposits allows us to distinguish and stratigraphically date two fanning stress patterns, corresponding to the two last transport directions of the Carpathian system (1) a Burdigalian to early Tortonian stress field with compression directions rotating along with the Carpathian curved orogenic belt but with transpression (NW–SE compression) and a low-strain partitioning along east trending internal strike-slip faults in the south Carpathians and (2) a late Tortonian to Pleistocene rotated and smaller radial stress pattern, with N–S compression in the south Carpathians. The rotation of the convergence direction is interpreted as the result of the Miocene migration and progressive collision of the Carpathian system with the thick crust of the NW trending Tornquist-Teisseyre line and its prolongation in Romania. The area able to subduct, determined by thickness of crust entering the subduction zone, was progressively restricted to a foreland corner in front of the southeastern Carpathians. The progressive collision forced the convergence to slow down and rotate from eastward to southeastward in late Miocene. The Dobrogea hills in front of the latest migrating system may represent the late Neogene NE–SW flexural bulge of the subducting foreland panel. This clockwise rotation of the transport direction can be compared with the clockwise rotation that occurred in other subduction systems (Tyrrhenian subduction, Caribbean subduction, etc.) which were controlled by the location of oceanic versus continental crust in front of the orogenic belt.

Two ancient magnetizations have been isolated in rocks of the Caborca terrane, northwest Mexico. The characteristic magnetizations of Neoproterozoic and Paleozoic miogeoclinal shelf-strata, arc-derived Lower Jurassic marine strata, and Jurassic volcanic and volcaniclastic rocks are of dual polarity and east-northeast declination (or south-south-west) and shallow inclination. Magnetizations in Neoproterozoic and Paleozoic miogeoclinal strata are interpreted as secondary (J*) and to be of similar age to those observed in Lower and Middle Jurassic rocks. Remanence acquisition is bracketed between about 190 and 160 Ma. The overall mean (D=15.0°, I=8.5°; n=38 sites; six localities; k=19.1, α95=5.5°) suggests a moderate to large clockwise rotation of 12 to 50° (depending on reference direction assumed) of the Caborca terrane, and rocks of the Sonoran segment of the Cordilleran volcanic arc, with respect to the North America craton. When compared with expected inclinations, observed values are not anomalously steep, arguing against statistically significant southward latitudinal displacement of the Caborca block after remanence acquisition. Late Cretaceous intrusions yield primary, dual-polarity steep inclination “K” magnetizations (D=341.4°, I=52.3°; n=10 sites; five localities; k=38.3, α95=7.9°) and have locally remagnetized Neoproterozoic and Jurassic strata. When present, secondary (K*) magnetizations in Neoproterozoic strata are of higher coercivity and higher unblocking temperature than the characteristic (J*) magnetization. Importantly, the regional internal consistency of data for Late Cretaceous intrusions suggests that effects of Tertiary tilt or rotation about a vertical axis over the broad region sampled (∼5000 km2) are not substantial. Late Cretaceous primary (K) magnetizations and secondary (K*) magnetizations yield a combined mean of D=348.1°, I=50.7° (N=10 localities; 47 sites; k=53.5, α95=6.7°), indicating at most small (

We have undertaken a combined analysis of tectonic subsidence, heat flow and uplift data for the Gulf of Suez. Results show significant differences along the length of the rift. The heat flow and subsidence in the northern Gulf of Suez can be fitted by close to uniform extension in the early Miocene with minimal extension since the middle Miocene. In contrast, the southern Gulf of Suez requires that the early Miocene extension is followed by both continuous slow (∼1 mm/yr) extension and mantle thinning greatly in excess of the crustal thinning. The continued extension of the southern Gulf of Suez is interpreted as indicating a counterclockwise rotation of the Sinai Peninsula that allows the southern Gulf of Suez to accommodate 10–15% of the motion of the Dead Sea transform. Our best estimate of the net crustal and mantle extension factors for southern Suez are δ=1.4–1.5 and β=2.2–2.6, respectively. While these values are approximate, they indicate a significant input of heat into the southern Gulf of Suez rift that is in excess of that directly advected by extension. Modeling indicates that while ∼1/2 of the extension occurred in the early Miocene, most of the lithospheric thinning, and virtually all of the excess thinning of the mantle lithosphere, developed since then. In addition, the Gulf of Suez is bordered by large and growing rift flank uplifts, particularly on the Sinai Peninsula. The geometry of the motions at the Sinai triple junction region has created a large contrast in extension between the Red Sea and Gulf of Suez-Sinai since the middle Miocene. These lateral temperature gradients drove the flow of hot material that is responsible for the extra heating beneath southern Suez and Sinai. The rift flank uplift along most of the Gulf of Suez is interpreted as resulting from a combination of secondary convection and flexure. The much greater uplift in southern Sinai is produced by the additional convective flow from the Red Sea.

Paleomagnetic data for two sections of Cretaceous forearc strata with different structural attitudes on Santa Margarita and Magdalena Islands in Baja California Sur, Mexico, indicate that these rocks have been remagnetized, probably during the late Cenozoic. The in situ paleomagnetic directions, however, are similar to data from other Cretaceous rocks on peninsular California with unexpectedly shallow inclinations and easterly declinations. These data have been interpreted as indicating either northward tectonic transport (10°–15° of latitude) and clockwise rotation (>20°) or compaction shallowing of magnetic inclinations in sedimentary rocks combined with southwestward tilting of plutonic rocks. The available paleomagnetic data for Cretaceous forearc strata in southern and Baja California can be divided into three groups: (1) sections with normal-polarity magnetizations that fail fold tests and are remagnetized, (2) sections with normal-polarity magnetizations with no or inconclusive fold tests that may or may not be remagnetized, and (3) sections with both normal-and reversed-polarity intervals where pervasive remagnetization has not occurred. Other rocks of the Mesozoic Great Valley Group, Coast Range ophiolite, and Franciscan Complex in California also have secondary magnetizations with directions similar to younger geomagnetic field directions. Although these widespread remagnetizations could have variable local causes, we propose regional burial and uplift, related to changes in subduction parameters, as a possible explanation. Two episodes of remagnetization are apparent: one in the Late Cretaceous and a second in the late Cenozoic. On the other hand, the unremagnetized and apparently reliable data from sedimentary and plutonic rocks on the Baja Peninsula consistently indicate northward translation (14° ± 3°) and clockwise rotation (29° ± 8°) with respect to North America since the Late Cretaceous.

The Periadriatic Line (PAL) is a remarkable, several hundred kilometer long fault system of the Alpine orogen. Its dextral character was documented by several authors using diverse criteria, but detailed kinematics and timing of movements had not been investigated along its whole length. Structural and paleomagnetic measurements, mapping, and stratigraphic and sedimentological studies have helped to unravel the Miocene-Pliocene evolution of the Slovenian segment of the PAL. Brittle deformation was characterized by NW-SE to N-S compression and perpendicular tension. Deformation has resulted in dextral strike-slip faulting, folding, and tilting of beds. The first transpressional event corresponds to the first phase of lateral extrusion of the East Alpine-Western Carpathian-Northern Pannonian block in the early Miocene (24–17.5 Ma). After a short period of transtension during the Karpatian (17.5–16.5 Ma), dextral transpression reoccurred during the middle Miocene to Pliocene and lasted up to the Quaternary. Middle Miocene dextral slip can be connected to the second phase of extrusion. The highly deformed rocks within the dextral shear zones show variable clockwise, sometimes counterclockwise, rotations. The mechanism of rotation seems to be complex, ranging from regional rotation to local folding due to pure or simple shear (domino-type rotation).

The kinematic history of the Rocky Mountain foreland and adjacent areas is computed back to 85 Ma, using virtually all the structural, paleomagnetic, and stress data in the literature. A continuous velocity field is fit to the data in each time step by weighted least squares, and this velocity is integrated back through time. As proposed by Hamilton [1981], the net movement of the Colorado Plateau was a clockwise rotation about a pole in northern Texas; but the rotation was less (3°) than some have inferred from paleomagnetism. The Laramide orogeny occurred during 75–35 Ma, with peak Colorado Plateau velocities of 1.5 mm yr−1 during 60–55 Ma. The mean azimuth of foreland velocity and mean direction of foreland shortening was stable at 40° for most of the orogeny, increasing to 55° in 50–40 Ma; the counterclockwise rotation of shortening directions proposed by some previous authors is incorrect. Comparing the computed histories of foreland flow speed and direction with the known motions of the Kula and Farallon plates confirms that the Laramide orogeny had a different mechanism from the early Sevier orogeny: it was driven by basal traction during an interval of horizontal subduction, not by edge forces due to coastal subduction or the spreading of the western cordillera or by accretion of terranes to the coast. Tentatively, a minor clockwise rotation of shortening directions at 50 Ma may record the passage of an active Kula-Farallon transform within the subducted slab.

The most widely accepted model for the opening of Canada Basin invokes 66° of counterclockwise rotation of Arctic Alaska and Chukotka away from the Canadian Arctic in Early Cretaceous time. Late Paleozoic structural trends and paleogeography have been used in support of the rotation hypothesis. Recent refinements in the ages of Paleozoic tectonic events in Arctic Alaska, Yukon, and the Canadian Arctic Islands provide new controls on correlations of late Paleozoic paleogeography and raise doubts about whether the Paleozoic tectonics of the Arctic Alaska-Yukon region necessitate a rotational reconstruction of Arctic Alaska against the Canadian Arctic Islands. A rotational restoration of Arctic Alaska requires the Alaskan and Canadian margins to be conjugates of comparable age and evolution. The rift-drift transition age for the Alaskan margin is most likely Hauterivian (Early Cretaceous), but for the Canadian Arctic margin it is most likely post-Albian (mid-Cretaceous). Crustal structure data from the Beaufort Sea continental margin in Canada define a rifted margin segmented by fracture zones which constrain the kinematics of ocean spreading to be northwestward, perpendicular to that required by the rotation hypothesis but subparallel to that suggested by seismic velocity anisotropy in the upper mantle. The Alaska-Chukotka rotation hypothesis also fails to account for up to 600 km of continental overlap upon restoration of 66° of rotation and the absence of any accommodating contractional structures in northern Yukon and adjacent Northwest Territories. Because the Alaska-Chukotka rotation hypothesis fails to account for much of the available data, senous doubt is cast on its viability. An existing multistage tectonic model for the evolution of Canada and Makarov basins is summarized as an example of a model which can account for the existing data.

Mapping and the construction of balanced cross-sections reveal dextral rotation in addition to N-S contraction during the late middle to late Miocene Jura phase both at the northern and the southern front of the Central Alps (Jura and Lombardic Southern Alps, respectively). These rotations may be ascribed to one and the same shallow domain or sublid, rotated clockwise around a pivot somewhere at the southwestern end of the Aar massif. In a crude first approximation model the sublid may be considered rigid, although the data indicate differential rotations and longitudinal stretching within the lid. The eastern boundary of the sublid crosses the Alps at the Giudicarie-Brenner line, which, according to very recent data, in the Jura phase formed a kinematically linked system, whereas from Innsbruck to the northwest it is postulated to join, as a diffuse or accommodation zone, the eastern tip of the Jura. In the southwest, the Lombardic thrusts enter into the interior of the Western Alps. From there to the southwestern end of the Jura the lid boundary is tentatively chosen arbitrarily to pass somewhere near the northern end of the Belledonne Massif. A similar sublid, though less well substantiated, may comprise the Tauern and the Venetian Southern Alps. The rotational components are superimposed on elements of internal strain, particularly transverse contraction and longitudinal stretching due to simple dextral shear and lateral escape. The model of dextrally rotating sublids pulls together a number of hitherto unexplained structures and opens new perspectives on such recalcitrant problems as the eastward disappearance of the Jura and the Adige embayment in the Southern Alps. Dextral rotation of such shallow sublids may be considered to constitute “mode 1” of the dextral component at the Europa-Adria plate boundary. There is also a “mode 2” that affects its deep parts. At the surface, its manifestation is a dextral belt of en echelon folds and pull-apart domains that crosses the sublids diagonally. It consists of the Massifs line in the west and the Neo-Pustertal line in the east. They approximately join in the Brenner area, where they cross and interfere with the sublid boundaries. The combined Massifs-Pustertal line describes an arcuate partial northern boundary of the Adriatic plate with an apparent center of sinistral rotation in central Italy. This sinistral rotation may be responsible for the contractional features in the southern part of the western Alps which cannot be accounted for by SE-NW Adria-Europa convergence. It could have caused the development of the fold and thrust belts of Sisteron, Castellane and Nice. These arcs, in turn, suggest the action of more or less independent shallow sublids also in this part of the Alps.

In the Fort Irwin region of the northern Mojave desert, late Cenozoic east striking sinistral faults predominate over northwest striking dextral faults of the same age. Kinematic indicators and offset marker units indicate dominantly sinistral strike slip on the east striking portions of the faults and sinistral-thrust slip on northwest striking, moderately dipping segments at the east ends of the blocks. Crustal blocks ∼7–10 km wide by ∼50 km long are bounded by complex fault zones up to 2 km wide at the edges and ends of each block. Faulting initiated after ∼11 Ma, and Quaternary deposits are faulted and folded. We document a minimum of 13 km cumulative sinistral offset in a north-south transect from south of the Bicycle Lake fault to north of the Drinkwater Lake fault. Paleomagnetic results from 50 sites reveal two direction groups in early and middle Miocene rocks. The north-to-northwest declinations of the first group are close to the middle Miocene reference pole. However, rock magnetic studies suggest that both primary and remagnetized directions are present in this group. The northeast declinations of the second group are interpreted as primary and 63.5° ± 7.6° clockwise from the reference pole and suggest net post middle Miocene clockwise rotation of several of the east trending blocks in the northeast Mojave domain. The Jurassic Independence Dike Swarm in Fort Irwin may be rotated 25–80° clockwise relative to the swarm north of the Garlock fault, thus supporting the inference of clockwise rotation. Using a simple-shear model that combines sinistral slip and clockwise rotation of elongate crustal blocks, we predict ∼23° clockwise rotation using the observed fault slip, or one-third that inferred from the paleomagnetic results. The discrepancy between slip and rotation may reflect clockwise bending at the ends of fault blocks, where most of our paleomagnetic sites are located. However, at least 25°–40° of clockwise tectonic rotation is consistent with the observed slip on faults within the domain plus possible “rigid-body” rotation of the region evidenced by clockwise bending of northwest striking domain-bounding faults. Our estimates of sinistral shear and clockwise rotation suggest that approximately half of the 65 km of dextral shear in the Eastern California Shear Zone over the last 10 m.y. occurred within the northeast Mojave Domain. The remainder must be accommodated in adjacent structural domains, e.g., east of the Avawatz Mountains and west of the Goldstone Lake fault. Supporting Appendices 1 and 2 are available on diskette or via Anonymous FTP from kosmos.agu.org, directory APEND (Username -- anonymous, Password = guest). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W, Washington, DC 20009 or by phone at 800-966-2481; $15.00. Payment must accompany order.

Details of the Oligocene-present-day motion of the Adriatic block with respect to Europe can be determined by palinspastic restorations of the outer Carpathians thrust sheets. The arcuate nature of the Carpathians poses problems for simple restorations of sections because they create converging restoration paths which require large amounts of strike-parallel extension (40–50%). Such large amounts of extension are not seen on maps or in the field. A combination of thrust transport directions changing with time between and within thrust sheets and divergent transport directions helps minimise the arc-parallel extension necessary (18–25%). The Pannonian basin can be treated either as an area dominated by strike-slip motion (rigid block movements) or as an area of back arc extension. The differences in restoration geometry produced by these two scenarios help to indicate which of the two mechanisms was dominant. The consequences of the rigid block restoration indicate the model is inappropriate because it requires approximately 20° clockwise rotation of the Adriatic block during the late Tertiary. It also indicates at least 300 km strike-slip motion distributed among the late Tertiary faults of the Dinaride-Balkanide and Hellenide Mountain belts. The back arc extension model alleviates the the 20° clockwise rotation of the Adriatic block and requires about 200 km distributed strike-slip motion in Yugoslavia and Bulgaria.

Structure developed in association with oblique motions on the dextral, strike-slip Finlay-Ingenika fault (FIF) in the McConnell Creek area, north-central British Columbia, is dominated by subvertical to vertical strike-slip faults. Some of the faults cut the area into discrete, fault-bounded blocks several kilometres wide. Stress tensors for 24 sites were inverted from the regional cleavage which predates the block-bounding faults. The site-mean stress tensors indicate that the fault-bounded blocks were rotated clockwise about a subvertical axis during progressive oblique motions on the FIF. Rotation varies systematically, being maximal (58.7±3.3°) close to the FIF and minimal (0.0±1.6°) about 20 km away. Paleomagnetic samples were collected from 13 sites in the widespread Early Jurassic to Cretaceous plutonic rocks. Interpretable magnetic components of presumed Late Cretaceous age were obtained from six sites. The observed paleopole is significantly different from the Late Cretaceous reference pole for cratonal North America (CNA). After corrections for the local block rotations, the precision is much improved (K increased from 48 to 383), and the paleopole moves closer to the reference pole but is not coincident with it. Rotation about the Eulerian pole for the best-fitting small circle to the Tintina trench and northern Rocky Mountain trench fault zone, however, brings the observed pole into coincidence with that for CNA and requires ∼670 km of dextral displacement on the fault zone. It is evident therefore that local structures associated with large dextral strike-slip faults could account for at least part of the paleomagnetic disparity between some western parts of the Canadian Cordillera and CNA.

Published paleomagnetic data from the Pontides indicate anomalously low Jurassic and Early Cretaceous paleolatitudes compatible with the southern Neo-Tethyan (African) continental margin and significantly different from paleolatitudes predicted for the northern (Eurasian) Neo-Tethyan margin. We present a new set of paleomagnetic data from 50 Late Cretaceous sites mainly from the Western Pontides and from the Eastern Pontides, and 11 Early Jurassic sites mainly from the Eastern Pontides. Fold tests indicate that the characteristic magnetization components predate Eocene folding. Late Cretaceous site mean declinations are northerly in the Eastern Pontides and rotated to the west by a few tens of degrees in the Western Pontides. Late Cretaceous site mean declinations are affected by local clockwise rotation in one sampling region close to the North Anatolian Fault. The mean Late Cretaceous inclinations and resulting paleolatitudes are 41.1° (23.5°N) and 43.7° (25.5°N) for the Western and Eastern Pontides, respectively. For the Eastern Pontides, the Early Jurassic (Liassic) mean inclination is 60.5°, yielding a paleolatitude of 41.4°N, considerably further north than previous paleolatitude estimates for the Eastern Pontides at this time. The paleolatitude estimates for the Western and Eastern Pontides are consistent with these units being close to the Eurasian continental margin during Liassic and Late Cretaceous time.

[1] The large number and distribution of rollback systems in Mediterranean orogens infer the possibility of interacting extensional back-arc deformation driven by different slabs. The formation of the Pannonian back-arc basin is generally related to the rapid Miocene rollback of a slab attached to the European continent. A key area of the entire system that is neglected by kinematic studies is the connection between the South Carpathians and Dinarides. In order to derive an evolutionary model, we interpreted regional seismic lines traversing the entire Serbian part of the Pannonian Basin. The observed deformation is dominantly expressed by the formation of Miocene extensional detachments and (half) grabens. The extensional geometries and associated synkinematic sedimentation that migrated in time and space allow the definition of a continuous and essentially asymmetric early to late Miocene extensional evolution. This evolution was followed by the formation of few uplifted areas during the subsequent latest Miocene–Quaternary inversion. The present-day extensional geometry changing the strike across the basin is an effect of the clockwise rotation of the South Carpathians and Apuseni Mountains in respect to the Dinarides. Our study infers that the Carpathian rollback is not the only mechanism responsible for the formation of the Pannonian Basin; an additional middle Miocene rollback of a Dinaridic slab is required to explain the observed structures. Furthermore, the study provides constraints for the pre-Neogene orogenic evolution of this junction zone, including the affinity of major crustal blocks, obducted ophiolitic sequences and the Sava suture zone.

The history of motion of the Philippine Sea Plate is poorly known because it is isolated from the oceanic ridge system. Interpretation of palaeomagnetic results from the plate has been controversial because declination data have been obtained only from the eastern margin where subduction-related tectonic processes may have caused local rather than plate-wide rotations. New palaeomagnetic data relevant to the problem have been obtained from 34 sites north of the Sorong Fault and 29 sites within the Sorong Fault system. These sites record south- ward movement during the Eocene and northward movement during the Neogene. Sites within the Sorong Fault system record both counterclockwise and clockwise rotations interpreted as the result of Neogene block movements at the southern boundary of the Philippine Sea Plate. North of the Sorong Fault, all sites record clockwise declinations. Neogene rocks have small deflections consistent with rotation about the present-day Eurasia-Philippine Sea Plate pole. Oligocene-middle Eocene rocks show consistent clockwise declination deflections of-40 o . Declinations of lower Eocene rocks indicate -90 o of clockwise rotation. We propose that the entire area north of the Sorong Fault in east Indonesia has always been part of the Philippine Sea Plate and that the whole plate has rotated clockwise in a discontinuous manner by approximately 90 o since the early Eocene. The new data from north of the Sorong Fault provide a basis for determining rotation poles which satisfy all the palaeomagnetic data from the Philippine Sea Plate and permit its reconstruction.

[1] The La Trocha fault zone acted as a major left-lateral transfer zone and is bounded by the La Trocha (LTF), Zaza-Tuinicu (ZTF), Cristales (CTF) and Taguasco (TGF) faults. These faults were consistent with the clockwise rotation of convergence and shortening in central Cuba. From the Paleocene to the Early Eocene (65–48 Ma), a SSW-NNE shortening produced transtension in the LTF and transpression in the ZTF. Subsequently, during the Middle Eocene (48–37 Ma), shortening shifted to a SW-NE direction, resulting in the normal component of the LTF and transpression in the ZTF and CTF. Since the Late Eocene (37 Ma), central Cuba has been welded to the North American Plate. The post-welding deformation gave rise to transtension of the LTF and TGF. This deformation is consistent with a WSW-ENE shortening and reflects activity in the transform boundary of the Cayman Trough. Both the normal and thrust displacements of these previous faults are corroborated by structural data whereas left-lateral displacement is deduced from the concordance between oblique collision and structural features. Plate-kinematics and the structural evolution of the La Trocha fault zone indicate that the related Central Basin is a strike-slip polygenetic basin and that the formation of this system (i.e., fault zone – strike-slip basin) was a consequence of the Paleogene oblique collision between the Caribbean Volcanic Arc and the Bahamas Borderland (North American plate).

Paleomagnetic data are presented for Late Cretaceous volcanic and intrusive rocks in the Tombstone district and Dos Cabezas Mountains of southeastern Arizona. The resultant paleopole (73°N, 224°E, A95= 8°) is similar to a Late Cretaceous reference pole for North America (82°N, 210°E, A95= 7°), implying that these rocks have not been significantly rotated about vertical or near-vertical axes relative to the continental interior. Generally, concordant results have also been published for Pennsylvanian terra rosa paleosols within the Black Prince Limestone at localities in the nearby Gunnison Hills, Whetstone Mountains, and Naco Hills. Together, however, these Carboniferous data indicate a 9°±7° clockwise rotation, with respect to North America, similar to that determined for the Colorado Plateau (5°–14°) since the mid-Cretaceous. Published paleomagnetic data for rocks south and west of the Tombstone vicinity indicate much larger clockwise rotations ranging from ∼25° to ∼60°, implying that a rotational domain boundary runs between the Mustang Mountains and Canelo Hills to the southeast and between the Silver Bell and Tucson Mountains to the northwest. This boundary roughly coincides, in part, with the Sawmill Canyon fault zone and is parallel to other northwest trending strike-slip faults in the region that were active during the Laramide orogeny. The clockwise rotations in southern Arizona are likely part of a larger pattern of dextral shear along the western margin of North America during the Late Cretaceous and early Tertiary caused by northward oblique subduction of oceanic plates relative to the stable craton.

Large-magnitude relative rotations of range-scale structural blocks are inferred to be products of crustal extension in the Death Valley region, in California and Nevada. Reconstructions of the extended terrain restore pre-Tertiary contractile structures with currently diverse trends into a relatively simple, north-northeast trending thrust belt. We interpret trends of major contractile structures throughout the Death Valley region as characteristically discordant to, and thus geometrically independent from, stratigraphic trends. We compare trends of pre-Tertiary contractile structures with paleoflow orientations in Lower Cambrian strata throughout the extended terrain. Significant differences between mean paleoflow orientations are consistent in magnitude and sense with differences observed in the structural trends. Available evidence does not support interpretation of paleoflow data from apparently rotated areas as representing an original paleogeography distinct from that of adjacent areas. Facies variations are present within the contractile structures. We interpret the strong covariance throughout the study area between structural and paleoflow trends of diverse orientations as evidence for vertical axis rotations. Combined rotation estimates from these data indicate clockwise rotations of 85° ± 12° for Bare Mountain and 73° ± 24° for the Striped Hills but anticlockwise rotations of 30° ± 35° and 87° ± 29°, respectively, for the northern and southern Grapevine Mountains. Such large rotations of opposite sense may be related to north-south shortening accommodated by conjugate strike-slip faults during large-magnitude extension in the Death Valley region but are difficult to explain as products of regional dextral shear within the southern Walker Lane belt.

Exotic and far-traveled oceanic crustal rocks of the Cache Creek terrane (CC) are bordered by less exotic Quesnel (QN) and Stikine (ST) arc terranes to the east, north, and west. All of these terranes are enveloped by an arcuate belt of displaced continental margin rocks; the Kootenay (KO), Nisling (NS), and parts of the Yukon-Tanana (YTT) terranes, that have indirect ties to ancestral North America (NA). Initial 87Sr/86Sr isopleths conform to this arcuate pattern. Such a pattern of concentric belts presents a geological conundrum: How did the QN, ST, and CC come to be virtually enveloped by terranes with ties to NA? Past and current models that explain assembly of the Canadian Cordillera are deficient in their treatment of this problem. We propose that Early Mesozoic QN and ST were joined through their northern ends as two adjacent arc festoons that faced south toward the Cache Creek ocean (Panthalassa?). Oceanic plateau remnants within the CC today were transported from the Tethyan realm and collided with these arcs during subduction of the Cache Creek ocean. Counterclockwise oroclinal rotation of ST and NS terranes in the Late Triassic to Early Jurassic caused enclosure of the CC. Rotation continued until these terranes collided with QN in the Middle Jurassic. Paleomagnetic declination data provide support for this model in the form of large average anticlockwise rotations for Permian to Early Jurassic sites in ST but moderate clockwise rotations for sites in QN. Specific modern analogues for the Cordilleran orocline include the Yap trench, where the Caroline rise is colliding end-on with the Mariana Arc and the Banda Arc, located on the southeastern “tail” of the Asian plate, which is being deformed into a tight loop by interactions with the Australian and Pacific plates.

This paper analyzes the importance of preexisting structure for the evolution of the Cenozoic Malawi rift, which constitutes the southernmost part of the western branch of the East African rift system. Kinematic analyses demonstrate that the regional extension direction rotated clockwise from ENE to SE during rifting. Cenozoic rift faults (of dip-, oblique-, and strike-slip character) rejuvenated crustal structures whenever those were properly oriented with respect to the extension directions. Depending on these boundary conditions the rift attempts to find the easiest pathway in order to develop in a mechanically modest way. Proterozoic basement structures represent the basic anisotropy which already influenced pre-Cenozoic rifts and also the Cenozoic Malawi rift. Amongst these basement structures, Pan-African retrograde to cataclastic, strike-slip shear zones have the strongest influence on later rift structures. Rift-related transfer faults appear as differently striking passive structures, and their orientation seems to be controlled by a variety of steep basement structures (retrograde shear zones, foliation planes, and fracture arrays).

Middle Miocene rocks of the southwestern Nevada volcanic field (SWNVF) lie across the projection of the Walker Lane belt within the Basin and Range province and thus provide an interesting opportunity to test for late Cenozoic vertical-axis rotation. Paleomagnetic data from individual ash flow sheets document no significant relative vertical-axis rotation among localities within central SWNVF, an area of relatively low stratal tilts and widely spaced faults. A time-averaged mean paleomagnetic direction (D = 351.4°, I = 52.7°, α95 = 4.5°) calculated from data from numerous separate rock units suggests that the central SWNVF underwent minimal counterclockwise vertical-axis rotation (R = −7.1° ± 6.6°) with respect to the North American craton. No clockwise vertical-axis rotation is found to support projection of dextral faults of the Walker Lane beneath the central SWNVF. Clockwise rotation of variable magnitude is common at numerous sites from southern and western margins of the field. These clockwise rotations probably reflect dextral shear strain developed at the interface between the little extended central SWNVF block and more strongly extended areas to the south and southwest of the field. Negligible rotation of 11.45-Ma to 13.25-Ma tuffs relative to the central SWNVF was found at the southeast margin of the field where 90° clockwise rotation at the northwest termination of the Las Vegas Valley shear zone had been postulated. Any clockwise rotation in this area must predate 13.25 Ma, and thus dextral shear within this part of the Walker Lane belt was not synchronous or connected across the southern margin of the field. Small counterclockwise vertical-axis rotation relative to the craton, as found for the central SWNVF block, might be a regional feature in the western Great Basin.

Comparison of patterns of paleomagnetic poles from orogenic belts with appropriate reference poles for the craton can help to delineate important large-scale tectonic processes. Comparison of the paleomagnetic signatures of the western Cordillera of North America and the central Andes shows that the western edges of these belts have had profoundly different Mesozoic and Cenozoic histories. Specifically, the North American Cordilleran pattern shows strong evidence of post-middle Cretaceous relative northward displacement of outboard crustal blocks, but there is almost no comparable evidence of margin-parallel displacement in the Andes. We speculate that this may largely be a consequence of a simple difference in shape: the convex-westward western margin of North America facilitates margin-parallel displacement as a response to oblique subduction, whereas the concave-westward margin of South America inhibits it. The patterns of block rotations found along the western edge of the two orogens also are quite different. Nearly everywhere within the western North American Cordillera crustal blocks have rotated clockwise since mid-Cretaceous time, reflecting a pervading state of dextral shear. Within the western Andes of Peru and northern Chile, however, Mesozoic and Cenozoic rocks in Peru (and northernmost Chile) are rotated strongly counterclockwise, whereas rocks of the same age in the remainder of Chile (to about latitude 48°S) are rotated clockwise. A model combining oroclinal bending and block rotations driven by oblique subduction can account for the paleomagnetic observations.

Prefolding high unblocking temperature magnetization components have been resolved from 28 sites of red siltstones from the Lower Triassic Werfen Formation in the Dolomites (Southern Alps). Site mean declinations are more scattered than site mean inclinations, indicating small-scale relative rotation among thrust sheets, particularly in the eastern part of the Dolomites affected by “Dinaric” (Paleogene) thrusting. Two sites from close to the Valsugana Line indicate large-scale (∼80°) anticlockwise rotation in this zone of Alpine sinistral transpression. The overall mean direction (number of sites (N) = 26, Declination = 331°, Inclination = 13°, α95 = 6.6°), excluding sites close to the Valsugana Line, gives a pole position (Latitude = 42°N, Longitude = 233°E, dp/dm = 3.4°/6.8°) which lies close to published Early Permian poles from the Southern Alps and to Permian and Early Triassic poles for Africa, implying very little net rotation of the Dolomites relative to Africa since Permian time.

[1] We use paleomagnetic data from Tertiary volcanic rocks to address the rates and timing of vertical-axis block rotations across the central Sierra Nevada-Walker Lane transition in the Bodie Hills, California/Nevada. Samples from the Upper Miocene (∼9 Ma) Eureka Valley Tuff suggest clockwise vertical-axis block rotations between NE-striking left-lateral faults in the Bridgeport and Mono Basins. Results in the Bodie Hills suggest clockwise rotations (R ± ΔR, 95% confidence limits) of 74 ± 8° since Early to Middle Miocene (∼12–20 Ma), 42 ± 11° since Late Miocene (∼8–9 Ma), and 14 ± 10° since Pliocene (∼3 Ma) time with no detectable northward translation. The data are compatible with a relatively steady rotation rate of 5 ± 2° Ma−1 (2σ) since the Middle Miocene over the three examined timescales. The average rotation rates have probably not varied by more than a factor of two over time spans equal to half of the total time interval. Our paleomagnetic data suggest that block rotations in the region of the Mina Deflection began prior to Late Miocene time (∼9 Ma), and perhaps since the Middle Miocene if rotation rates were relatively constant. Block rotation in the Bodie Hills is similar in age and long-term average rate to rotations in the Transverse Ranges of southern California associated with early transtensional dextral shear deformation. We speculate that the age of rotations in the Bodie Hills indicates dextral shear and strain accommodation within the central Walker Lane Belt resulting from coupling of the Pacific and North America plates.

[1] Six hundred fault slip data have provided robust paleostress fields within an approximately 35 km3 volume of Paleoproterozoic (1.9 Ga) rocks in the southwestern Fennoscandian Shield, Forsmark, Sweden. These rocks were affected by penetrative ductile strain from 1.87 to 1.86 Ga, folding, ductile strain along discrete zones around 1.8 Ga, and semibrittle or brittle deformation around and after 1.8 Ga. Compatible paleostress fields have been identified using site-by-site and merged data sets from outcrops and oriented drill cores. Transpressive deformation with a regional NNW-SSE σ1 axis, associated with clockwise stress deviation inside a tectonic lens, resulted in dextral slip along regionally significant, steep WNW-ESE and NW-SE deformation zones. The semibrittle and most of the brittle structures, including specifically the epidote-bearing fractures, were established during this oldest regime around 1.8 Ga (latest Svecokarelian). A younger paleostress field with a NE-SW σ1 axis, which was also transpressive in character, is inferred to have been active at 1.7–1.6 Ga. The best defined paleostress field is transpressive in character with a WNW-ESE σ1 axis that resulted in sinistral reactivation along the WNW-ESE and NW-SE zones. The main set of laumontite-stepped faults developed at this stage at 1.1–0.9 Ga (Sveconorwegian). It is impossible to exclude fully the influence of reactivation during even younger Phanerozoic tectonic events. Subordinate extensional paleostress fields were related either to the latest Svecokarelian and Sveconorwegian transpressive regimes, due to σ1 and σ2 stress permutations, or to regional extensional tectonic regimes during the Meso- or Neoproterozoic or later during the Permo-Carboniferous and/or Mesozoic.

We report new paleomagnetic results from 55 out of 76 sites sampled at different localities along a transect from Nazca to Cuzco where the general structures of the Peruvian Andes are strongly offset across the Abancay deflection. Nine new 39Ar/40Ar ages better constrain the timing of volcanism along the western edge of the Western Cordillera at the latitude of Nazca. A mean paleomagnetic result from 22 sites in the lower Miocene volcanics does not show significant rotation (R = −2.3° ± 7.7°) of the western margin of the Central Andean Plateau since the early Miocene. Within the Western Cordillera we sampled three structural blocks bounded to the north by the Abancay fault system. In the westernmost block, a large counterclockwise rotation (R = −65.0° ± 11.1°) is found in Mesozoic limestones and Paleocene-Eocene red beds. Magnitude of rotation decreases toward the east from (R = −35.6° ± 12.8°) in the central block to (R = −4.5° ± 8.4°) south of the town of Cuzco. The anisotropy of magnetic susceptibility (AMS) recorded by the red beds sediments is the consequence of compaction and tectonic strain during the early stages of deformation. We show that the magnetic lineations were also rotated counterclockwise as the remanent magnetizations. The present study confirms results from the Peruvian fore arc, showing that rotations are not older than circa 40 Ma and likely not younger than circa 20 Ma. The spatial variation in the amount of counterclockwise rotation suggests a large component of shear along the Abancay deflection concomitant with a broad late Eocene-Oligocene oroclinal deformation in southern Peru.