Kinematic Linkage Research Articles

Kinematic link between episodic trapdoor collapse of the Negra Muerta Caldera and motion on the Olacapato-El Toro Fault Zone, southern central Andes

A combined geochronological and structural analysis of the Miocene Negra Muerta Caldera was designed to better understand caldera formation associated with prominent faults on the central Andean plateau. Rb–Sr ages of the caldera outflow facies indicate that caldera formation occurred in two volcano-tectonic episodes. The first episode commenced with explosive eruption of the 9.0±0.1 Ma andesitic Acay Ignimbrite followed by a period of volcanic quiescence and moderate tectonic activity. Dominant volcanic and tectonic activity occurred during the second episode, which is bracketed by eruption of the 7.6±0.1 Ma rhyolitic Toba 1 Ignimbrite and effusive discharge of the 7.3±0.1 Ma rhyodacitic to andesitic lava flows. Structural relationships between rocks of the Negra Muerta Volcanic Complex and collapse-induced normal faults, notably NE-striking normal faults, agree with simultaneous volcanic activity and floor subsidence of the caldera during the second episode. Floor subsidence was achieved by tilting on an outward dipping reverse fault to the northwest of the caldera floor around a hinge zone located south of the caldera floor. This induced horizontal extension of the caldera floor and was accomplished by fragmentation of, and intrusion of dikes into, the floor. Collapse-induced and post-collapse fault populations of the caldera do not differ significantly in the directions of their axes of maximum extension and are in this respect kinematically compatible with left-lateral slip on the nearby Olacapato-El Toro Fault Zone. This furnishes evidence for a kinematic control by prominent faults on the formation of collapse calderas in the central Andes. The structural analysis of the Negra Muerta Caldera shows that collapse calderas can serve as deformation markers that contribute in elucidating the regional kinematic regime and the time of activity of prominent dislocations genetically related to collapse calderas.

Conceptual development of an enhanced tripod mechanism for machine tool

In this paper, a spatial three degrees of freedom parallel mechanism enhanced by a passive leg is proposed. The proposed parallel mechanism can be used in several applications, e.g. motion simulator, micromanipulator and machine tools. First, the geometric model of the three degrees of freedom parallel mechanism is addressed, in which a fourth kinematic link—a passive link connecting the base center to the platform center—is introduced. This last link is used to constrain the motion of the platform to only three degrees of freedom, i.e. the degree of freedom of the mechanism depends on the passive leg. The passive leg also enhances the global stiffness of the structure and distributes the torque from machining. Second, the kinematic analysis with the consideration of link flexibility is conducted. A kinetostatic model of the three degrees of freedom parallel mechanism with a passive link is then established and analyzed using lumped-parameter model. With the proposed method, a significant effect of the link flexibility on the mechanism's precision has been demonstrated. The influence of the change of structure parameters, including material properties, on the system behavior is discussed. Compliance mapping is also illustrated. The kinetostatic model proposed in the paper can be extended for optimal design and control of parallel kinematic machines. Finally, design optimization is conducted using genetic algorithms and some design guideline is given.

Geomorphology, kinematic history, and earthquake behavior of the active Kuwana wedge thrust anticline, central Japan

We combine surface mapping of fault and fold scarps that deform late Quaternary alluvial strata with interpretation of a high‐resolution seismic reflection profile to develop a kinematic model and determine fault slip rates for an active blind wedge thrust system that underlies Kuwana anticline in central Japan. Surface fold scarps on Kuwana anticline are closely correlated with narrow fold limbs and angular hinges on the seismic profile that suggest at least ∼1.3 km of fault slip completely consumed by folding in the upper 4 km of the crust. The close coincidence and kinematic link between folded terraces and the underlying thrust geometry indicate that Kuwana anticline has accommodated slip at an average rate of 2.2 ± 0.5 mm/yr on a 27°, west dipping thrust fault since early‐middle Pleistocene time. In contrast to classical fault bend folds the fault slip budget in the stacked wedge thrusts also indicates that (1) the fault tip propagated upward at a low rate relative to the accrual of fault slip and (2) fault slip is partly absorbed by numerous bedding plane flexural‐slip faults above the tips of wedge thrusts. An historic earthquake that occurred on the Kuwana blind thrust system possibly in A.D. 1586 is shown to have produced coseismic surface deformation above the doubly vergent wedge tip. Structural analyses of Kuwana anticline coupled with tectonic geomorphology at 103–105 years timescales illustrate the significance of active folds as indicators of slip on underlying blind thrust faults and thus their otherwise inaccessible seismic hazards.

Instrumented Analysis of Ankle-Subtalar Joint Complex Motion at Different Flexion Angles for Lateral Ligament Injuries

1075 PURPOSE: As part of a long-term effort (Foot Ankle, 20:12, 1999) to develop a diagnostic procedure for ankle ligament injuries, the effects of sectioning the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments on the load-displacement behavior of the ankle-subtalar joint complex were evaluated in vitro during anterior drawer and inversion rotation loading. METHODS: Eight fresh cadavers were tested using a portable instrumented arthrometer consisting of a load-measuring handle attached to a footplate and a 6-degrees-of-freedom spatial kinematic linkage connecting an anterior tibial pad to the footplate. High validity coefficients (r = .86 – .88) for ankle arthrometry have been previously reported (J Athl Train 37:4, 2002). Motion (laxity) was measured as anterior displacement (AD) (mm) at 125 N of applied force and inversion rotation (IR) (degrees ROM) at 4 N-m of applied torque at neutral and 10° dorsi- and plantar flexion. Two-way repeated-measures analysis of variance compared AD and IR before and after serial sectioning of the ATFL and CFL. RESULTS: Both flexion angle and ligament sectioning affect laxity of the ankle-subtalar joint complex. Compared to the intact ankle, sectioning the ATFL increased anterior laxity for all 3 flexion angles (neutral: 7.1 ± 2.9 vs. 9.8 ± 3.2 mm; dorsiflexion: 7.2 ± 3.4 vs. 9.7 ± 4.7 mm; plantar flexion: 7.7 ± 3.0 vs. 9.07 ± 3.2 mm; p = .001), with no differences (p >.05) between flexion angles observed. Sequentially cutting the CFL did not significantly increase (p = .137) anterior laxity compared to the ATFL condition. During inversion loading, the ankle-subtalar joint complex was most lax in plantar flexion and most stable in dorsiflexion, with the greatest laxity differences observed between neutral and dorsiflexion (p = .04). Cutting the ATFL did not significantly increase inversion laxity compared to the intact condition across the 3 flexion angles. Whereas, sectioning the CFL increased inversion laxity significantly compared to the intact ankle (neutral: 16.3 ± 4.1 vs. 23.5 ± 9.3°; dorsiflexion: 15.2 ± 4.3 vs. 21.6 ± 8.8°; plantar flexion: 17.5 ± 5.2 vs. 25.3 ± 11.9°; p = .013) and ATFL injury condition (neutral: 17.4 ± 4.8 vs. 23.5 ± 9.3°; dorsiflexion: 14.8 ± 4.5 vs. 21.6 ± 8.8°; plantar flexion: 17.8 ± 5.4 vs. 25.3 ± 11.9°; p = .021). CONCLUSIONS: Results of this study indicate that arthrometric measurements provide a basis for differentiating between the intact ankle and isolated injury of the ATFL or combined ATFL and CFL injury.

Instrumented Analysis of Ankle-Subtalar Joint Complex Motion at Different Flexion Angles for Lateral Ligament Injuries

1075 PURPOSE: As part of a long-term effort (Foot Ankle, 20:12, 1999) to develop a diagnostic procedure for ankle ligament injuries, the effects of sectioning the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments on the load-displacement behavior of the ankle-subtalar joint complex were evaluated in vitro during anterior drawer and inversion rotation loading. METHODS: Eight fresh cadavers were tested using a portable instrumented arthrometer consisting of a load-measuring handle attached to a footplate and a 6-degrees-of-freedom spatial kinematic linkage connecting an anterior tibial pad to the footplate. High validity coefficients (r = .86 – .88) for ankle arthrometry have been previously reported (J Athl Train 37:4, 2002). Motion (laxity) was measured as anterior displacement (AD) (mm) at 125 N of applied force and inversion rotation (IR) (degrees ROM) at 4 N-m of applied torque at neutral and 10° dorsi- and plantar flexion. Two-way repeated-measures analysis of variance compared AD and IR before and after serial sectioning of the ATFL and CFL. RESULTS: Both flexion angle and ligament sectioning affect laxity of the ankle-subtalar joint complex. Compared to the intact ankle, sectioning the ATFL increased anterior laxity for all 3 flexion angles (neutral: 7.1 ± 2.9 vs. 9.8 ± 3.2 mm; dorsiflexion: 7.2 ± 3.4 vs. 9.7 ± 4.7 mm; plantar flexion: 7.7 ± 3.0 vs. 9.07 ± 3.2 mm; p = .001), with no differences (p >.05) between flexion angles observed. Sequentially cutting the CFL did not significantly increase (p = .137) anterior laxity compared to the ATFL condition. During inversion loading, the ankle-subtalar joint complex was most lax in plantar flexion and most stable in dorsiflexion, with the greatest laxity differences observed between neutral and dorsiflexion (p = .04). Cutting the ATFL did not significantly increase inversion laxity compared to the intact condition across the 3 flexion angles. Whereas, sectioning the CFL increased inversion laxity significantly compared to the intact ankle (neutral: 16.3 ± 4.1 vs. 23.5 ± 9.3°; dorsiflexion: 15.2 ± 4.3 vs. 21.6 ± 8.8°; plantar flexion: 17.5 ± 5.2 vs. 25.3 ± 11.9°; p = .013) and ATFL injury condition (neutral: 17.4 ± 4.8 vs. 23.5 ± 9.3°; dorsiflexion: 14.8 ± 4.5 vs. 21.6 ± 8.8°; plantar flexion: 17.8 ± 5.4 vs. 25.3 ± 11.9°; p = .021). CONCLUSIONS: Results of this study indicate that arthrometric measurements provide a basis for differentiating between the intact ankle and isolated injury of the ATFL or combined ATFL and CFL injury.

The direct linearization method applied to position error in kinematic linkages

This paper demonstrates the direct linearization method (DLM) applied to position error in kinematic linkages due to link-length and angle variations. It combines the mathematical techniques used in assembly tolerance analysis and kinematic error analysis to demonstrate a method that is applicable to models that can be described using vector loops. A bivariate model using DLM is introduced and compared to other deterministic and probabilistic methods using a multiple-loop mechanism as an example. The bivariate model is shown to be an efficient and accurate means of estimating the position error in kinematic linkages.

Extension of Hellenic forearc shear zones in SW Turkey: the Pliocene–Quaternary deformation of the Eşen Çay Basin

The Pliocene–Quaternary Eşen Çay Basin in southwestern Turkey has a key position in the southern Aegean to gain insight into both lateral and temporal changes in stresses exerted by plate convergence at the Hellenic–Cyprus arc junction. A tectonosedimentary study of the basin development in combination with a structural analysis helped to reveal internal basin deformation and adjacent basement kinematics in order to delineate 3D strain through time. In the Pliocene the basin originated as a fluviolacustrine basin situated in a depression related to a ramp-fold geometry in the Lycian nappe stack. During the late Pliocene, E–W extension caused the development of N–S normal faults, displacement along which caused the differentiation of the relief and deposition of local alluvial fan systems. The Pleistocene is also marked by widespread alluvial-fluvial sedimentation that is triggered by activity at 020° faults. This fault system resulted from WNW–ESE extension and caused disruption of the former basin floor by uplift and tilting of intrabasinal areas, which initiated development of new source areas for the fan sedimentation. The Holocene–Recent period is characterized by a complex combination of faults of which 070° sinistral strike-slip faults are the most important. Fault-slip analysis reveals that deformation occurred in transtension, explained by the addition of a sinistral shear component. This implies that stresses evolved from simple tensional to transtensional over the Pliocene–Quaternary period. The initial extension phase is explained by the kinematic effects of outward growth of the Hellenic forearc, comparable with observations from the island of Rhodes and the eastern Anaximander Mountains. The time-transgressive addition of a sinistral shear component was likely produced by the northeastward propagating transcurrent motions of forearc slivers sheared from the expanding forearc as has been previously inferred for Crete and Rhodes. The latter process is related to the incipient continental collision of an African promontory south of Crete. This implies a kinematic linkage between the studied domain in southwestern Turkey and the eastern Hellenic Arc.

Vertical coupling and decoupling in the lithosphere

Recent advancements in the understanding of mountain belts have focused on vertical coupling of the lithospheric layers. This volume describes the extent to which observed or inferred sub-horizontal coupling or attachment zones provide vertical kinematic linkage between rheologically distinct layers in the continental lithosphere. A common theme is whether the deformation, which partitioned differently in each layer, is linked kinematically across attachment zones and driven by flow in the deeper crust and mantle lithosphere. The papers are divided into six sections. The first analyses the extent to which mantle flow controls deformation of the overlying layers. The Vertical axis block rotations section uses geological and palaeomagnetic data to constrain the role and magnitude of basal shear across mid-crustal attachment zones. The Lower crustal flow and topography section addresses the time-dependent development of orogenic plateaux and their role in the orogenic cycle. Multiple examples of the spatial and temporal development of lithospheric coupling are given in both the Orogenic examples and Subduction examples sections. Finally, rheological constraints of vertical coupling in the lithosphere are investigated.

About this title

Recent advancements in the understanding of mountain belts have focused on vertical coupling of the lithospheric layers. This volume describes the extent to which observed or inferred sub-horizontal coupling or attachment zones provide vertical kinematic linkage between rheologically distinct layers in the continental lithosphere. A common theme is whether the deformation, which partitioned differently in each layer, is linked kinematically across attachment zones and driven by flow in the deeper crust and mantle lithosphere. The papers are divided into six sections. The first analyses the extent to which mantle flow controls deformation of the overlying layers. The Vertical axis block rotations section uses geological and palaeomagnetic data to constrain the role and magnitude of basal shear across mid-crustal attachment zones. The Lower crustal flow and topography section addresses the time-dependent development of orogenic plateaux and their role in the orogenic cycle. Multiple examples of the spatial and temporal development of lithospheric coupling are given in both the Orogenic examples and Subduction examples sections. Finally, rheological constraints of vertical coupling in the lithosphere are investigated.

Force- and moment-generating capacities of muscles in the distal forelimb of the horse.

A detailed musculoskeletal model of the distal equine forelimb was developed to study the influence of musculoskeletal geometry (i.e. muscle paths) and muscle physiology (i.e. force-length properties) on the force- and moment-generating capacities of muscles crossing the carpal and metacarpophalangeal joints. The distal forelimb skeleton was represented as a five degree-of-freedom kinematic linkage comprised of eight bones (humerus, radius and ulna combined, proximal carpus, distal carpus, metacarpus, proximal phalanx, intermediate phalanx and distal phalanx) and seven joints (elbow, radiocarpal, intercarpal, carpometacarpal, metacarpophalangeal (MCP), proximal interphalangeal (pastern) and distal interphalangeal (coffin)). Bone surfaces were reconstructed from computed tomography scans obtained from the left forelimb of a Thoroughbred horse. The model was actuated by nine muscle-tendon units. Each unit was represented as a three-element Hill-type muscle in series with an elastic tendon. Architectural parameters specifying the force-producing properties of each muscle-tendon unit were found by dissecting seven forelimbs from five Thoroughbred horses. Maximum isometric moments were calculated for a wide range of joint angles by fully activating the extensor and flexor muscles crossing the carpus and MCP joint. Peak isometric moments generated by the flexor muscles were an order of magnitude greater than those generated by the extensor muscles at both the carpus and the MCP joint. For each flexor muscle in the model, the shape of the maximum isometric joint moment-angle curve was dominated by the variation in muscle force. By contrast, the moment-angle curves for the muscles that extend the MCP joint were determined mainly by the variation in muscle moment arms. The suspensory and check ligaments contributed more than half of the total support moment developed about the MCP joint in the model. When combined with appropriate in vivo measurements of joint kinematics and ground-reaction forces, the model may be used to determine muscle-tendon and joint-reaction forces generated during gait.

Direct dating of left‐lateral deformation along the Red River shear zone, China and Vietnam

Exposures of high‐grade, midcrustal rocks within the Red River shear zone (RRSZ), which separates the Indochina and South China blocks, exhibit clear evidence of left‐lateral, ductile deformation. Assuming that the South China Sea represents a pull‐apart basin formed at the southeastern termination of the RRSZ, it has been argued that seafloor magnetic anomalies constrain the timing of sinistral slip accommodated by the RRSZ between ∼32 and 17 Ma at a rate of ∼4 cm/yr. While 40Ar/39Ar thermochronometry indicates that left‐lateral slip occurred along the RRSZ between 25 and 17 Ma, the timing of earlier high‐temperature deformation has not been directly constrained. In situ Th‐Pb ion microprobe dating of monazite inclusions in garnets allows direct assessment of the timing of amphibolite‐grade metamorphism and synchronous left‐lateral shearing. Results from northern segments of the RRSZ in Yunnan, China, indicate that synkinematic garnet growth occurred between 34 and 21 Ma and are the first to document late Oligocene metamorphism and left‐lateral shearing. Data from the southern RRSZ within Vietnam are complicated by Tertiary overprinting of rocks that experienced amphibolite facies metamorphism during the Indosinian orogeny (∼220 Ma). The period during which sinistral deformation is now constrained to have occurred along the RRSZ (i.e., 34–17 Ma) is essentially coincident with spreading of the South China seafloor (32–17 Ma). This temporal and kinematic link between left‐lateral shearing along the RRSZ and opening of the South China Sea supports the view that Indochina was extruded from Asia as a block along lithospheric‐scale strike‐slip faults.

Kinematic Linkage between the Broad- and Narrow-Line–emitting Gas in Active Galactic Nuclei

We investigate the radial velocity difference between the [O III] λλ4959, 5007 and Hβ lines for a sample of ≈200 low-redshift active galactic nuclei. We identify seven objects showing an [O III] λ5007 blueshift relative to Hβ with an amplitude larger than 250 km s-1 (blue outliers). These line shifts are found in sources where the broad high-ionization lines (e.g., C IV λ1549) also show a large systematic blueshift. Such blueshifts occur only in the population A region of the Eigenvector 1 parameter domain (that also contains narrow-line Seyfert 1 galaxies). We suggest that [O III] λλ4959, 5007 blueshifts are also associated with the high-ionization outflow originating in these highly accreting sources. This is a direct kinematic linkage between narrow- and broad-line-emitting gas.

Dextral Shear along the Eastern Margin of the Colorado Plateau: A Kinematic Link between Laramide Contraction and Rio Grande Rifting (Ca. 75–13 Ma)

Abstract Kinematic data associated with both Laramide‐age and ‐style and Rio Grande rift‐related structures show that the latest Cretaceous to Neogene interaction between the Colorado Plateau and the North American craton was dominantly coupled with a component of dextral shear. Consistent with earlier studies, minor‐fault data in this study yielded results of varied kinematics. Inverted to a common northeast‐oriented hemisphere, the mean trend of kinematic shortening associated with Laramide‐age structures is \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6}...

Mid-crustal partitioning and attachment during oblique convergence in an arc system, Palaeoproterozoic Ketilidian orogen, southern Greenland

Abstract: The Ketilidian orogen in SE Greenland contains a continental magmatic arc (Julianehåb batholith) and forearc which formed in the overriding plate of a Palaeoproterozoic oblique subduction boundary between c. 1854 and 1795 Ma. During uplift and deformation of the forearc between c. 1795 and 1780 Ma, its sedimentary sequences were invaded by arc-type magmas and metamorphosed at HT–LP upper amphibolite facies conditions which led to widespread anatexis and generation of abundant S-type granites. Transpression during early deformation (D 1 ) was partitioned into arc-parallel, sinistral strike-slip in the magmatic arc rocks of the batholith and arc-normal contraction in the sedimentary and volcaniclastic sequences of the proximal forearc (Psammite Zone). Subsequently, D 1 fabrics in the Psammite Zone were overprinted and transposed in an intense, flat-lying, D 2 ductile shear zone with arc-parallel stretching lineations and top-NE kinematic indicators. The kinematic significance of the D 2 shear zone is that it accommodated vertical differences in strain and displacement and permitted deformation to be partitioned differently at different levels in the crust. As such, it is an attachment or coupling zone that provided kinematic linkage between deformation at different crustal levels during NE transport of a forearc sliver. Overprinting of the upper crustal domain of D 1 strike-slip partitioned transpression in the forearc during D 2 is attributed to migration of the attachment zone to a higher crustal level. This migration was a consequence of an enhanced geothermal gradient in the proximal part of the forearc due to the emplacement of batholith-related plutonic suites during D 2 .

Inverse kinematic and dynamic analyses of 6-DOFPUS type parallel manipulators

This paper presents inverse kinematic and dynamic analyses of HexaSlide type six degree-of-freedom parallel manipulators. The HexaSlide type parallel manipulators (HSM) can be characterized as an architecture with constant link lengths that are attached to moving sliders on the ground and to a mobile platform. In the inverse kinematic analyses, the slider and link motion (position, velocity, and acceleration) is computed given the desired mobile platform motion. Based on the inverse kinematic analysis, in order to compute the required actuator forces given the desired platform motion, inverse dynamic equations of motion of a parallel manipulator is derived by the Newton-Euler approach. In this derivation, the joint friction as well as all link inertia are included. Relative importance of the link inertia and joint frictions on the computed torque is investigated by computer simulations. It is expected that the inverse kinematic and dynamic equations can be used in the computed torque control and model-based adaptive control strategies.

Kinematic linkage between internal zone extension and shortening in more external units in the NW Alps

In the Alps a major extensional shear zone unroofed eclogites in its footwall from 30 kbar to c. 10 kbar, implying of the order of 60 km of relative vertical movement in the period 45–36 Ma. The horizontal component of divergence was of the order of 100 km. We use the foreland basin sedimentary record to prove that the extension was contemporaneous with thrusting in units structurally beneath the eclogites (the Briançonnais and/or External Zones). This thrust-related convergence during that time period was of the order of 44–56 km and therefore of the same order of magnitude as internal zone divergence. Extension may have been driven by internal density contrasts. Buoyant continental crust underneath the mafic eclogites, or dense subducted slab offset from the orogen, can induce extension. Any dynamic model must account for the comparable magnitudes of extension and shortening in adjacent parts of the orogen: relative plate motions in the period 45–36 Ma played a subsidiary role.

Cenozoic normal faulting and regional doming in the southern Hangay region, Central Mongolia: implications for the origin of the Baikal rift province

The Hangay Dome in central Mongolia is a mountainous region covering more than 200,000km2 with numerous flat-topped peaks over 3000m that preserve a Late Cretaceous–Paleogene erosion surface. Doming began in the middle Oligocene producing more than 2000m of regional topographic uplift. The range represents an important kinematic link between the Baikal rift province to the north and Altai transpressional ranges to the south and west. Structural field investigations of major faults visible on satellite imagery indicate that the southern Hangay Dome region is dominated by Late Cenozoic normal faults that bound small half-graben. Most faults are NE-striking and faults at the highest elevations are the most recently active. Most graben appear to be isolated systems that constitute small sediment sinks perched on the flanks and crests of the dome. The first-order feature is the dome itself and most sediment eroded off of the dome is deposited in the Mongolian Valley of Lakes or is carried northwards by the Selenga river and its extensive tributaries.The basement of the dome is a Precambrian craton although the shape and dimensions of the craton are poorly constrained to the north and east. Late Cenozoic uplift of the southern dome region appears to be confined to the area underlain by cratonic basement whereas the Altai region to the south and west is underlain by mechanically weaker Palaeozoic arc and accretionary belts. With respect to the regional northeast directed SHmax, the Hangay craton appears to have acted as a rigid passive indentor focusing Late Cenozoic transpressional deformation around its west and southern margins. Models invoking a Late Cenozoic plume as the driving force for doming and widespread alkaline volcanism on the dome are not strongly supported by geochemical and isotopic data on Neogene–Recent volcanics and the spatial correlation between areas that are domed and older cratonic crust appears too coincidental to be ignored. Convective removal of an overthickened lithospheric root leading to adiabatically decompressed asthenosphere could explain regional doming and volcanism, however major crustal thickening last occurred in the Permian in the southern Hangay region and the time lag between thickening and postulated root removal and plateau uplift (>200Myr) appears too long. An alternative model is explored based on speculated lithospheric mantle flow patterns driven by India's continued northeastward indentation. It is suggested that lithospheric mantle flow diversion around the overthickened Hangay craton crustal keel could cause lithospheric thinning beneath the craton and passive asthenospheric upwarp leading to regional topographic uplift and decompression melting/alkali volcanism. In general, the angular relationship between Precambrian craton boundaries and the prevailing northeasterly SHmax appears to control the kinematics of late Cenozoic deformation throughout the Hangay, Altai, Sayan and Baikal regions.

Neo-Alpine evolution of the Southern Eastern Alps

The Eastern Southern Alps, located to the east of the N Giudicarie Line, have been originated by polyphase compressional evolution of Tertiary age. The oldest structural system corresponds to the Mesoalpine (Eocene) and early Neoalpine (Oligomiocene) compressional events, which originated the Dinaric system (NW–SE trending) present in the NE side of the Southern Alps. The subsequent tectonic belt is the Valsugana structural system, ENE–WSW trending, Serravallian– Tortonian in age. The intense activity of this compressional event is documented both by stratigraphic and structural data and by fission track studies which indicate uplifting of some 4 km in the hangingwall of the Valsugana overthrust between 12 and 8 Ma B.P. The more external structures NE–SW trending are located in the Montello–Friuli zone which were generated by the Messinian–Pliocene compressions (whose principal stress axis is SE–NW oriented). Structural and kinematic links between the Montello–Friuli belt and the Giudicarie zone have been recognized by new analytical data documenting that the Schio–Vicenza fault system transferred compressive deformations to the Giudicarie belt, where, the previous structures (belonging to the Valsugana system) were strongly enhanced by the subsequent compressions. Since the Montello–Friuli belt and the Schio–Vicenza system developed during the Messinian–Pliocene Adriatic compressional event, the out-of-sequence tectonic reactivations in the Giudicarie belt have to be considered mostly Messinian–Pliocene in age rather than Tortonian, as previously proposed. This compressional Adriatic event produced wide deformations in the Alps, both internally, like in the Montello–Friuli and Giudicarie, and, very likely, also externally, as in the Jura and the frontal external French Western Alps. The three structural systems here described are clearly represented in a N–S trending balanced profile crossing the Central Dolomites, close to the Italian trace of the Central European Profile (CEP) where a seismic reflexion acquisition campaign is presently in progress according to the German, Austrian and Italian joint program of the TRANSALP Project. The crustal and lithospheric interpretation using available data (revision of previous refraction profiles) assumes strong indentation of the Adriatic lithosphere to the N coupled by southward delamination of the Adriatic crust, coherent with the setting of the upper crust shown in the balanced cross section. Similar indentation processes were recognized up to date only in the Western and Central Alps (CROP–ECORS and NFP20 Profiles).

A Kinematic Link Between Boxy Bulges, Stellar Bars, and Nuclear Activity in NGC 3079 and NGC 4388

We present direct kinematic evidence for bar streaming in two active galaxies with boxy stellar bulges. The Hawaii Imaging Fabry-Perot Interferometer was used on the Canada-France-Hawaii 3.6-m telescope and the University of Hawaii 2.2-m telescope to derive the two-dimensional velocity field of the line-emitting gas in the disks of the Sc galaxy NGC 3079 and the Sb galaxy NGC 4388. In contrast to previous work based on long-slit data, the detection of the bar potential from the Fabry-Perot data does not rely on the existence of inner Lindblad resonances or strong bar-induced shocks. Simple kinematic models which approximate the intrinsic gas orbits as nonintersecting, inclined elliptical annuli that conserve angular momentum characterize the observed velocity fields. In NGC 3079, bar streaming motions with moderately eccentric orbits (e = b/a approx. 0.7) aligned along PA = 130 deg. intrinsic to the disk (PA = 97 deg. on the sky) are detected out to R(sub b) = 3.6 kpc. The orbits become increasingly circular beyond that radius (e = 1 at R(sub d) approx. = 6 kpc). The best model for NGC 4388 includes highly eccentric orbits (e approx. 0.3) for R(sub) less than or equal to 1.5 kpc which are aligned along PA = 135 deg. intrinsic to the disk (PA = 100 deg. on the sky). The observed spiral arms are produced by having the orbits become increasingly circular from the ends of the bar to the edge of the disk (R(sub d) approx. = 5 kpc), and the intrinsic bar PA shifting from 135 deg. to 90 deg.. Box-shaped bulges in both NGC 3079 and NGC 4388 are confirmed using new near-infrared images to reduce dust obscuration. Morphological analysis of starlight in these galaxies is combined with the gas kinematics derived from the Fabry-Perot spectra to test evolutionary models of stellar bars that involve transitory boxy bulges, and to quantify the importance of such bars in fueling active nuclei. Our data support the evolutionary bar models, but fail to prove convincingly that the stellar bars in NGC 3079 and NGC 4388 directly trigger or sustain the nuclear activity.

Linking onshore and offshore structures: Mesozoic extension in the Scottish Highlands

Geological relationships in the offshore basins flanking northern Scotland suggest that a regional Caledonian control on the structure of these basins is far from proven, but conversely Mesozoic faults of the offshore set may extend onshore. The Strathconnon fault, long held to be late Caledonian, may be Mesozoic in age, forming the principal kinematic link between the east and west coast basins of northern Scotland. The numerous outcrops of Precambrian basement within the Minch/Hebrides basin nearly all lie in the uplifted footwalls of Mesozoic faults. Similar fault controls on the distribution of onshore outcrop within the Precambrian may exist.