Amount Of Shortening Research Articles

Multiphase deformation of an inverted Permian deepwater rift basin: The Nong Pong Formation, Khao Khwang Fold and Thrust Belt, Thailand

• Khao Khwang Fold and Thrust Belt (KKFTB) is mixture of thrusted carbonate platforms over inverted deepwater rifts. • Nong Pong Formation affected by multiphase folding, whose structural style changes with sedimentary facies . • Estimated shortening of the KKFTB (300 km), supportive of E-W suture bisecting Indochina Terrane . The bathyal Permian Nong Pong Formation is crucial for understanding the deformation style, and amount of shortening in the E-W trending, Triassic (Indosinian Orogeny) Khao Khwang Fold and Thrust Belt. The formation was deposited in a series of marine rift basins, with carbonates forming on intervening highs. The platform carbonates are shortened by a series of dominantly north-directed thrusts. The Nong Pong Formation is extensively affected by tight to isoclinal, predominantly chevron style folding. Five major variations in stratigraphy (ranging between carbonate-dominated and shale-dominated) affect the deformation styles within the formation. Shortening locally is estimated to be up to 60% in sections up to 300 m long and is concentrated into short-wavelength (10 s m) structures. The absence of proximal slope depo-belts, and juxtaposition of carbonate platform facies with deepwater deposits suggest thrusts (some initiated as inverted normal faults) located on the basin margins have displacements of c. 10–25 km. Estimates of shortening from outcrops, and analogy with Zealandia, suggest the Nong Pong Formation was deposited in a basin up to 100 km wide. Such estimates point to a significant E-W trending seaway that bisected the Indochina Terrane. Multiple fold orientations and phases are present in the Nong Pong Formation, which are related to early mass transport events, multiple tectonic phases (Indosinian and Palaeogene), the influence of inherited trends (e.g. Permian rift basin morphology), and 3D deformation during a single tectonic phase. Deformation of the Nong Pong Formation demonstrates significant differences in structural style between ribbon continents and major continents, particularly, the Indochina ribbon continent shows the widespread inversion of rift basins across a submarine continent (similar to Zealandia) 100 s kms wide.

Maintenance of First Ray Length after First Metatarsophalangeal Joint Distraction Arthrodesis Using Allograft Discs: A Statistical Analysis

Category:Midfoot/ForefootIntroduction/Purpose:The first metatarsophalangeal joint (MTPJ) is one of the most common locations for arthritis in the foot. When conservative methods fail, two main surgical treatment options exist, fusion or joint implant. For various reasons these surgeries can fail leaving relatively few salvage options. A common salvage option is the first MTPJ distraction arthrodesis. Use of allograft discs to decrease surgical time and donor site morbidity has become an increasingly popular option for MTP distraction arthrodesis. The purpose of this study was to look at the maintenance of the first ray length in first MTPJ distraction arthrodesis using allograft discs.Methods:We reviewed 14 patients who underwent first MTPJ distraction arthrodesis, measuring first ray length at the first post- operative weightbearing radiograph and most recent weightbearing radiograph. Average follow up was 12.75 months between radiographs.Results:Average shortening was 3 mm on the lateral measurements and 2.3 mm on the AP measurements. CT verified overall nonunion rate was 43% whereas, symptomatic nonunion rate was 21%.Conclusion:Amount of shortening and graft size did appear to have a positive correlation. Union rate did not affect shortening of first ray, but revision for a failed implant arthroplasty did correlate with increased shortening compared to revision for a failed first MTPJ fusion. Our data suggests a 2-3 mm shortening of the first ray can be predicted over the first 12 months after a first MTPJ distraction arthrodesis using allograft discs. Longer term studies with larger patient populations, and a comparative study to cortical autograft would provide more accurate insight to outcomes of first MTPJ distraction arthrodesis.

Chronology of thrust propagation from an updated tectono-sedimentary framework of the Miocene molasse (western Alps)

Abstract. After more than a century of research, the chronology of the deformation of the external part of the western Alpine belt (France) is still controversial for the Miocene epoch. In particular, the poor dating of the foreland basin sedimentary succession hampers a comprehensive understanding of the deformation kinematics. Here we focus on the Miocene molasse deposits of the northern subalpine massifs, southern Jura, Royans, Bas-Dauphiné, Crest, and La Bresse sedimentary basins through a multidisciplinary approach to build a basin-wide tectono-stratigraphic framework. Based on sequence stratigraphy constrained by biostratigraphical, chemostratigraphical (Sr isotopes), and magnetostratigraphical data between the late Aquitanian (∼ 21 Ma) and the Tortonian (∼ 8.2 Ma), the Miocene molasse chronostratigraphy is revised with a precision of ∼ 0.5 Ma. The Miocene molasse sediments encompass four different paleogeographical domains: (i) the oriental domain outlined by depositional sequences S1a to S3 (∼ 21 to ∼ 15 Ma), (ii) the median domain characterized by sequences S2 to S5 (∼ 17.8 to ∼ 12 Ma), (iii) the occidental domain in which sequences S2a to S8 (∼ 17.8 to ∼ 8.2 Ma) were deposited, and (iv) the Bressan domain where sedimentation is restricted to sequences S6 to S8 (∼ 12 to ∼ 8.2 Ma). A structural and tectono-sedimentary study is conducted based on new field observations and the reappraisal of regional seismic profiles, thereby allowing the identification of five major faults zones (FZs). The oriental, median, and occidental paleogeographical domains are clearly separated by FZ1, FZ2, and FZ3, suggesting strong interactions between tectonics and sedimentation during the Miocene. The evolution in time and space of the paleogeographical domains within a well-constrained structural framework reveals syntectonic deposits and a westward migration of the depocenters, allowing for proposing the succession of three deformation phases at the western Alpine front. (i) The first is a compressive phase (P1) corresponding to thrusting above the Chartreuse oriental thrust (FZ1), which was likely initiated during the Oligocene and rooted east of Belledonne. This tectonic phase generated reliefs that limited the Miocene transgression to the east. (ii) The second is a ∼ WNW–ESE-directed compressive phase (P2) lasting between 18.05 ± 0.25 Ma and ∼ 12 Ma, with thrusts rooted in the Belledonne basal thrust. Thrusts were activated from east to west: the Salève (SAL) and Gros Foug (GF) thrusts and then successively FZ2, FZ3, FZ4, and FZ5. Along two WNW–ESE balanced cross sections the amount of horizontal shortening is of ∼ 6.3 to 6.7 km, corresponding to average shortening rates of ∼ 1.2 km Myr−1 and migration of the deformation toward the west at a rate of ∼ 2.9 km Myr−1. During ∼ 6 Myr, the Miocene Sea was forced to regress rapidly westwards in response to westward migration of the active thrusts and exhumation of piggyback basins atop the fault zones. Phase P2 thus deeply shaped the Miocene paleogeographical evolution of the area and appears as a prominent compressive phase at the scale of the western Alps from the Swiss molasse basin to the Rhodano–Provencal one. (iii) The third is a ∼ 300 m phase of uplift in the Bas-Dauphiné (P3) of probable Tortonian age (∼ 10 Ma), which would have induced southward sea retreat and been coeval with the folding of the Jura in the north and possibly with back-thrusting east of the Chartreuse massif.

Geomorphic analysis of active fold growth and landscape evolution in the central Qiulitage fold belt, southern Tian Shan, China

The Qiulitage fold-and-thrust system in the Kuqa foreland is a prominent NE-SW trending relief associated with active thrust-related folding in the southern Tian Shan. Based on open-access DEMs and field work, we carried out a detailed geomorphologic analysis of the Qiulitage topography based on drainage network characteristics and several morphometric indices. Our results suggest that the Qiulitage fold belt is composed of six morphological units, which are statistically confirmed by a principal component analysis. These morphologic structures have interacted during both vertical growth and lateral propagation of the folds, associated with different patterns of fold connection and deformation partitioning. The structural evolution of the Qiulitage fold belt has significantly influenced major rivers crossing the fold belt and minor ones developing on the fold ridges. We finally propose a morphotectonic evolution of the fold belt integrating the influence of décollement distribution, deep inherited structures, and changes in shortening amount.

Circum-Tharsis wrinkle ridges at Lunae Planum: Morphometry, formation, and crustal implications

Wrinkle ridges are one of the most widespread tectonic landforms on Mars developed under a compressional stress regime within the lithosphere. In this study, we investigate the morphology and structure of wrinkle ridges at northern Lunae Planum, which belongs to the circum-Tharsis wrinkle ridge system. We use methods to construct balanced cross-sections of fold-and-thrust belts that are based on conservation of area and volume to assess the nature of deformation and to quantify the amount of shortening and the depth of detachment faulting. Our morphometric analyses indicate that height and width of wrinkle ridges at Lunae Planum systematically decrease with increasing distance from the center of the Tharsis rise from west to east. The results indicate that horizontal shortening decreases from 4.75% to 1.25%, or ~116 m to ~56 m from west to east, and this shortening is accommodated by the formation of complex asymmetric ridges. Sections through wrinkle ridges provided by an escarpment at Kasei Valles and steep walls of impact craters expose thrust faults beneath the wrinkle ridges that dip at 38° +/− 5°. We model wrinkle ridges as fault-propagation folds and show that the observed thrust faults form along the frontal fold axial planes of the anticlines. At depth these faults merge into more gentle thrust ramps of 20°+/− 5° dip. Kinematic modeling further implies that the thrust ramps transition into a sub-horizontal detachment, which rises from −4 km in the west to −2.6 km in the east, measured from the surface. The very gentle eastward dipping topographic slope of Lunae Planum and the eastward rising detachment define a narrow wedge that is interpreted as an incipient critical taper with a tectonic push induced by the Tharsis rise. We propose here that the mechanically weak detachment is localized in a water-bearing crustal layer underneath a crust whose pore space is sealed by ice. Fluid overpressure conditions may enable yielding and slip on the detachment. Hydrous mineral reactions on the slip planes and flood basalt layers that gently dip to the Tharsis center due to flexural loading may additionally weaken the basaltic rocks and contribute to detachment faulting.

Effects of plyometric training on muscle-tendon mechanical properties and behavior of fascicles during jumping.

The purpose of this study was to investigate the effects of plyometric training on the muscle–tendon mechanical properties and behavior of fascicles during jumping in order to elucidate the mechanisms of improved jump performance due to plyometric training. Eleven subjects completed a 12‐week unilateral training program for plantar flexors. Active muscle stiffness with (100°·s−1) and without (250°·s−1) stretch reflex were calculated according to changes in muscle force and fascicle length during fast stretching after submaximal isometric contractions. Stiffness and hysteresis of tendon were measured using ultrasonography during ramp and ballistic contractions. Three kinds of unilateral jump heights using only ankle joint (no counter‐movement jump: no‐CMJ; counter‐movement jump: CMJ; drop jump: DJ) on sledge apparatus were measured. During jumping, electromyographic activities (mEMG) of plantar flexors and fascicle length of the medial gastrocnemius muscle were measured. Active muscle stiffness at 250 and 100°·s−1 and maximal tendon elongation during ballistic contraction significantly increased after training. Tendon hysteresis during ballistic contraction significantly decreased after training, whereas that during ramp contraction did not. The heights of three jump tests, the ratio of mEMG during eccentric to that during concentric phases for CMJ, and the amount of fascicle shortening and shortening velocity during eccentric phase of DJ significantly increased after training. These results suggest that an increase in CMJ height was associated with changes in the muscle–tendon mechanical properties and muscle activation strategy, whereas an increase in DJ height could be explained by changes in the muscle–tendon mechanical properties, but not muscle activation strategy.

Analysis of the factors that are important in re-displacement in pediatric diaphyseal femur fractures treated with a spica cast

BackgroundThere is no detailed data on the factors affecting the re-displacement in pediatric femoral fractures treated with closed reduction and early spica casting. This study aimed to investigate the factors effective in re-displacement in pediatric diaphyseal femur fractures (PDFF) treated with spica casting. MethodsIn all, 151 displaced PDFF were evaluated retrospectively. Demographic data of the patients were evaluated. Type of fractures, anteroposterior and lateral angulations, amount of shortening, translation ratio, cast index (CI), gap index (GI), and three-point index (TPI) measurements were evaluated radiologically. Thigh flexion angle (TFA) and knee flexion angle (KFA) were measured. After casting, angulation of more than 10° in any plane and a shortening of more than 10 mm was accepted as re-displacement. Binary logistic regression analysis was used to evaluate the risk factors of re-displacement. Receiver operating characteristic analysis was performed for TFA and KFA. ResultsRe-displacement was detected in 40 patients (26.5%). Transverse type fracture (p = 0.001), TFA ˂71.4° (p <0.001), and KFA ˂52.6° (p = 0.002) were found to be statistically significant factors on re-displacement. It was determined that the combination of transverse femoral fracture and TFA ˂71.4° increased the probability of re-displacement by approximately 14 times. It has been observed that indices such as CI, GI, and TPI were not effective in predicting the risk of re-displacement. ConclusionWhen treating a PDFF with spica casting, one should be aware of re-displacement if the fracture type is transverse, TFA is ˂71.4°, and KFA is ˂52.6°. Level of evidenceLevel III, prognostic

Contrasting along-strike deformation styles in the central external Dinarides assessed by balanced cross-sections: Implications for the tectonic evolution of its Paleogene flexural foreland basin system

The Cenozoic foreland fold and thrust belt of the external Dinarides along the eastern shore of the Adriatic Sea shows an overall NW-SE structural strike that changes to E-W in its central part, between Zadar and Mostar. This change is associated with a dextrally transpressive zone, named Split-Karlovac Fault. Segments of this fault straddle the Eo-Oligocene flexural foreland basin system of the external Dinarides. Two balanced cross-sections across the northern and southern segments of this transverse fault zone document highly contrasting styles of deformation and amount of shortening. The northern segment across Velebit Mountain is characterized by a triangle structure with a minimum shortening of 44 km. This triangle structure is formed by a set of thick-skinned top-SW thrust duplexes, topped by a thin-skinned passive top-NE roof backthrust. By contrast, the southern segment, traversing north of Split, shows a thin-skinned top-SW to top-S directed nappe stack, associated with a minimum shortening of 127 km and rooting into a basal detachment in the Paleozoic basement. To better understand parameters controlling these contrasting styles of deformation, we modelled the flexural response of the foreland lithosphere that provided the accommodation space for the Eocene to Oligocene syn-orogenic Promina Beds, a prevailingly carbonate-clastic and conglomerate-bearing sequence making a part of the foreland basin fill. Tectonic load exerted by the hinterland nappe stack was estimated using the two balanced cross-sections. Estimates of tectonic load allowed modelling the amount of flexural response that yielded depth and shape of the basin containing the Promina Beds. The best fitting modelling results provided additional confidence in the validity of the balanced cross-sections. It is shown that shortening in the two structurally contrasting segments of the thick-skinned thrust belt were contemporaneous with dextral strike-slip along the thick-skinned Split-Karlovac Fault and coeval with sedimentation of the Promina Beds. We propose that the Velebit triangle structure acted as a back-stop that prevented the propagation of the deformation front towards the SW. Instead shortening was transferred along the Split-Karlovac Fault into the southern transect, where deformation propagated towards the foreland along a successively shallowing stepped detachment. The contrasting style of Eo-Oligocene deformation probably resulted from the interplay of Permo-Triassic evaporites with the reactivation of inherited Middle Triassic normal faults to both sides of the transpressive zone. • Nappe stack vs. triangle structure in the external Dinarides fold and thrust belt. • Substantial along-strike difference of crustal shortening. • Effects of mechanically weak lithologies on the style of deformation. • Lithosphere deflection modelling in combination with balanced cross-sections. • Impacts of a transverse zone on the flexural foreland basin system geometry.

Difference of shortening strain for the crustal deformation model in the eastern and western Qaidam Basin and their implications, northern Tibetan Plateau, China

To recognize the differences in the west–east crustal deformation model of the Qaidam Basin, we presented the shortening amount of each fold and fault along 12 sections. According to the eastward weakening trend of shortening strain in the southwestern part of the basin and the non‐continuous trend in the northeastern part of the basin, the Qaidam Basin can be divided by a new line into the western Qaidam Basin (WQB) and the eastern Qaidam Basin (EQB). The WQB is characterized by a maximum shortening strain of 25%, transpressional structures, and crust–mantle decoupling, which is possibly weakened by the eastward extension of the crust–mantle mix zone caused by upwelling material along the Altyn Tagh Fault (ATF). In contrast, the EQB is characterized by a minimum shortening strain of 2%, pure thrust boundary faults, and gentle folds, which is defined as a rigid craton basin. The crust–mantle mix zone beneath ATF and the low‐velocity zone beneath the eastern Kunlun Shan show the limited impact of the lithospheric weakening on the EQB. The Miocene reorganization of the ATF is the key tectonic event that accounts for the differences in the east–west crustal deformation model of the Qaidam Basin, as it weakened the lithosphere and facilitated the transpressional structures of the WQB. The WQB was originally a rigid craton basin like the EQB, but it became a destabilized craton after the a forementioned tectonic event.

Mid-term results of total hip arthroplasty with subtrochanteric Z-osteotomy in Crowe type 3-4 developmental hip dysplasia

Background/aim Total hip arthroplasty (THA) is technically more difficult and has higher complication rates in patients with Crowe type 3–4 developmental dysplasia of the hip (DDH). Due to the difficulties and different treatment options, there is still no consensus on the optimal treatment. We aimed to evaluate the mid-term results of our patients who had undergone subtrochanteric femoral shortening Z-osteotomy.Materials and methods This study included 37 hips of 29 patients with the diagnosis of Crowe 3-4 DDH between June 2010 and December 2016 and who underwent femoral shortening Z-osteotomy with cementless total hip arthroplasty. Acetabular component was determined according to the patient’s age and functional capacity and all patients were operated with a posterior approach. Functional results, postoperative complications, Harris and visual analogue scale (VAS) scores were evaluated. Results The average Harris hip score was 41.3 ± 3.1 preoperatively and 84.7 ± 4.3 postoperatively (p < 0.05). The mean preoperative hip pain score on the VAS was 7.9 (range: 6–9) and this was significantly lower at the last follow-up (mean: 3.4; range: 2–4) (p < 0.05). The final mean limb-length discrepancy was 1.3 cm. The average amount of femoral shortening was 3.2 cm. Regarding complications, 3 (10.3%) patients had dislocations. These patients underwent closed reduction. Sciatic palsy developed in 1 (3.4%) patient. The patient was reoperated on for sciatic nerve dissection in the early period.Conclusion Subtrochanteric shortening Z-osteotomy combined with cementless total hip replacement can be considered an effective and successful method in selected patients with Crowe 3-4 coxarthrosis.

Geodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)

Abstract. We make a thorough review of geological and seismological data on the long-lived Schio-Vicenza Fault System (SVFS) in northern Italy and present for it a geodynamic and seismotectonic interpretation. The SVFS is a major and high-angle structure transverse to the mean trend of the eastern Southern Alps fold-and-thrust belt, and the knowledge of this structure is deeply rooted in the geological literature and spans more than a century and a half. The main fault of the SVFS is the Schio-Vicenza Fault (SVF), which has a significant imprint in the landscape across the eastern Southern Alps and the Veneto-Friuli foreland. The SVF can be divided into a northern segment, extending into the chain north of Schio and mapped up to the Adige Valley, and a southern one, coinciding with the SVF proper. The latter segment borders to the east the Lessini Mountains, Berici Mountains and Euganei Hills block, separating this foreland structural high from the Veneto-Friuli foreland, and continues southeastward beneath the recent sediments of the plain via the blind Conselve–Pomposa fault. The structures forming the SVFS have been active with different tectonic phases and different styles of faulting at least since the Mesozoic, with a long-term dip-slip component of faulting well defined and, on the contrary, the horizontal component of the movement not being well constrained. The SVFS interrupts the continuity of the eastern Southern Alps thrust fronts in the Veneto sector, suggesting that it played a passive role in controlling the geometry of the active thrust belt and possibly the current distribution of seismic release. As a whole, apart from moderate seismicity along the northern segment and few geological observations along the southern one, there is little evidence to constrain the recent activity of the SVFS. In this context, the SVFS, and specifically its SVF strand, has accommodated a different amount of shortening of adjacent domains of the Adriatic (Dolomites) indenter by internal deformation produced by lateral variation in strength, related to Permian–Mesozoic tectonic structures and paleogeographic domains. The review of the historical and instrumental seismicity along the SVFS shows that it does not appear to have generated large earthquakes during the last few hundred years. The moderate seismicity points to a dextral strike-slip activity, which is also corroborated by the field analysis of antithetic Riedel structures of the fault cropping out along the northern segment. Conversely, the southern segment shows geological evidence of sinistral strike-slip activity. The apparently conflicting geological and seismological data can be reconciled considering the faulting style of the southern segment as driven by the indentation of the Adriatic plate, while the opposite style along the northern segment can be explained in a sinistral opening “zipper” model, where intersecting pairs of simultaneously active faults with a different sense of shear merge into a single fault system.

Growth acceleration results in faster telomere shortening later in life.

There is a wealth of evidence for a lifespan penalty when environmental conditions influence an individual's growth trajectory, such that growth rate is accelerated to attain a target size within a limited time period. Given this empirically demonstrated relationship between accelerated growth and lifespan, and the links between lifespan and telomere dynamics, increased telomere loss could underpin this growth-lifespan trade. We experimentally modified the growth trajectory of nestling zebra finches (Taeniopygia guttata), inducing a group of nestlings to accelerate their growth between 7 and 15 days of age, the main phase of body growth. We then sequentially measured their telomere length in red blood cells at various time points from 7 days to full adulthood (120 days). Accelerated growth between 7 and 15 days was not associated with a detectable increase in telomere shortening during this period compared with controls. However, only in the treatment group induced to show growth acceleration was the rate of growth during the experimental period positively related to the amount of telomere shortening between 15 and 120 days. Our findings provide evidence of a long-term influence of growth rate on later-life telomere shortening, but only when individuals have accelerated growth in response to environmental circumstances.

Structural initiation along the frontal fold-thrust system in the western Indo-Burman Range: Implications for the tectonostratigraphic evolution of the Hatia Trough (Bengal Basin)

The Bengal Basin accommodates an extremely thick Cenozoic sedimentary succession that derived from the uplifted Himalayan and Indo-Burman Orogenic Belts in response to the subduction of the Indian Plate beneath the Eurasian and Burmese Plates. The Hatia Trough is a proven petroleum province that occupies much of the southern Bengal Basin. However, the style of deformation, kinematics, and possible timing of structural initiation in the Hatia Trough and the relationship of this deformation to the frontal fold-thrust system in the outer wedge (namely, the Chittagong Tripura Fold Belt) of the Indo-Burman subduction system to the east are largely unknown. Therefore, we have carried out a structural interpretation across the eastern Hatia Trough and the western Chittagong Tripura Fold Belt based on 2D seismic reflection data. Our result suggests that the synkinematic packages correspond to the Pliocene Tipam Group and the Pleistocene Dupitila Formation. This implies that the structural development in the western Chittagong Tripura Fold Belt took place from the Pliocene. In the Hatia Trough, the timing of structural activation is slightly later (since the Plio-Pleistocene). In general, fold intensity and structural complexity gradually increase toward the east. The presence of reverse faults with minor strike-slip motion along the frontal thrust system in the outer wedge is also consistent with the regional transpressional structures of the Indo-Burman subduction system. However, to the west, there is no evidence for strike-slip deformation in the Hatia Trough. The restored sections indicate that the amount of east–west shortening in the Hatia Trough is very low (maximum 1.2%). In contrast, to the east, the amount of shortening is high (maximum 13.5%) in the western margin of the Chittagong Tripura Fold Belt. In both areas, the key trapping mechanism includes anticlinal traps, although stratigraphic and combinational traps are possible, but this requires further evaluation.

Mechanical Influence of Inherited Folds in Thrust Development: A Case Study from the Variscan Fold-and-Thrust Belt in SW Sardinia (Italy)

Fold-and-thrust belts have a high variability of structural styles, whose investigation provides continuous updates of the predictive models that try to better approximate the geometries recognized in the field. The majority of studies are focused on the geometry and development of folds and thrust surfaces and the amount of displacement, taking into account the role played by the involved stratigraphic succession assumed as a layer cake. We present a case study from the external zone of the Variscan fold-and-thrust belt in SW Sardinia, where it was possible to investigate the lateral and vertical variations of the mechanical properties of the involved succession, how they related to previous folding, control thrust geometry, and kinematics. In this case, the superposition of two fold systems acted as a buttress that induced extensive back-thrusting. We found that there is a close connection between the attitude of the bedding and the geometry of back thrust surfaces, shear strength during thrust propagation, and variation in the shortening amount, depending on which part of the folds were cut across. The folding-related mechanical anisotropy also seems to have induced a ductile deformation in the footwall of back-thrusts. Although the case study considers the development of back-thrust, the relations between thrust and not-layer cake geometries could also be applied to fore-thrust development.

Neogene kinematics of the Giudicarie Belt and eastern Southern Alpine orogenic front (northern Italy)

Abstract. Neogene indentation of the Adriatic plate into Europe led to major modifications of the Alpine orogenic structures and style of deformation in the Eastern and Southern Alps. The Giudicarie Belt is a prime example of this, as it offsets the entire Alpine orogenic edifice; its activity has been kinematically linked to strike-slip faulting and lateral extrusion of the Eastern Alps. Remaining questions on the exact role of this fold-and-thrust belt in the structure of the Alpine orogen at depth necessitate a quantitative analysis of the shortening, kinematics, and depth of decoupling beneath the Giudicarie Belt and adjacent parts of the Southern Alps. Tectonic balancing of a network of seven cross sections through the Giudicarie Belt parallel to the local NNW–SSE shortening direction reveals that this belt comprises two kinematic domains that accommodated different amounts of shortening during overlapping times. These two domains are separated by the NW–SE-oriented strike-slip Trento-Cles–Schio-Vicenza fault system, which offsets the Southern Alpine orogenic front in the south and merges with the Northern Giudicarie Fault in the north. The SW kinematic domain (Val Trompia sector) accommodated at least ∼ 18 km of Late Oligocene to Early Miocene shortening. Since the Middle Miocene, this domain experienced at least ∼ 12–22 km shortening, whereas the NE kinematic domain accommodated at least ∼ 25–35 km shortening. Together, these domains contributed an estimated minimum of ∼ 40–47 km of sinistral strike-slip motion along the Northern Giudicarie Fault, implying that most offset of the Periadriatic Fault is due to Late Oligocene to Neogene indentation of the Adriatic plate into the Eastern Alps. Moreover, the faults linking the Giudicarie Belt with the Northern Giudicarie Fault reach ∼ 15–20 km depth, indicating a thick-skinned tectonic style of deformation. These fault detachments may also connect at depth with a lower crustal Adriatic wedge that protruded north of the Periadriatic Fault and are responsible for N–S shortening and eastward, orogen-parallel escape of deeply exhumed units in the Tauern Window. Finally, the E–W lateral variation of shortening across the Giudicarie Belt indicates internal deformation and lateral variation in strength of the Adriatic indenter related to Permian–Mesozoic tectonic structures and paleogeographic zones.

Percutaneous Fixation of Unstable Proximal Phalanx Fractures: A Biomechanical Study.

Unstable extra-articular proximal phalanx fractures are common injuries to the hand that are often treated by closed reduction and percutaneous pinning. Fracture-induced shortening of the proximal phalanx leads to an extensor lag at the proximal interphalangeal joint. We describe a biomechanical study in cadaver hands to compare the ability of each of three different pin configurations to resist shortening in unstable fractures. Seventeen fresh frozen hands were disarticulated at the proximal ends of the metacarpals. The second, third, and fourth proximal phalanges were tested. A 5-mm section of bone was resected from the mid-shaft of proximal phalanx to simulate an unstable fracture. Three techniques were employed and randomized for each finger: transmetacarpophalangeal joint pinning using 1 or 2 Kirschner wires (K-wires) and periarticular cross pinning using 2 K-wires. Compressive axial loads and energy at 1 mm, 2 mm, 3 mm, 4 mm, and 5 mm of subsidence were examined. The forces and energy required to shorten the finger for each amount of subsidence were similar for all 3 pinning techniques and for all 3 finger types. Greater amounts of shortening were found to require larger forces. Closed reduction and percutaneous pinning using any of the presented techniques is an adequate method of treatment for unstable proximal phalanx fractures. All of the techniques were equivalent in their ability to resist axial loading, regardless of the complexity of technique, the number of pins used, or finger that was pinned.

Architecture of an upper-level weak detachment zone: Mexican Fold and Thrust Belt, central Mexico

The mechanical properties of detachment zones significantly influence the geometry, structural style, and amount of shortening in the fold and thrust belts. The shale layers in a sedimentary package can act as a detachment zone at different levels of a fold and thrust belt. Detachment zones are not exposed in the active fold and thrust belts, making the detailed study of these detachment zones impossible. This situation makes it difficult to know the architecture and main deformation mechanisms. In this work, we use detailed structural analysis to investigate deformational mechanisms of an ancient and exhumed detachment zone in the Mexican Fold and Thrust Belt, in central Mexico, as an analogue to active modern-day examples. We describe the architecture of the detachment zone through detailed field mapping, strain measuring, and vorticity analysis. Our observations suggest that the studied shear zone is an upper-level detachment zone developed during the Late Cretaceous-Paleogene orogeny. The upper-level detachment zone accommodates the deformation through brittle-ductile structures related to localized mylonitic foliation, s-c structures, duplexes, sheath folds and reverse faults. The mesoscopic structures described in the shear zone suggest a heterogeneous shear deformation. The kinematic vorticity values (Wk = 0.73 in average) and the strain data (RXZ ~3 in average) suggest a sub-simple shear mechanism of deformation. Our results show the role of weak layers during the contraction of a sedimentary package and demonstrate the presence of simple and pure shear mechanisms in the development of the complex detachment zones in fold and thrust belts.

POSTERIOR SCLERAL CONTRACTION TO TREAT MYOPIC FOVEOSCHISIS IN HIGHLY MYOPIC EYES.

To evaluate the efficacy of posterior scleral contraction to treat myopic foveoschisis (MF). The records of MF patients treated with posterior scleral contraction were reviewed. During posterior scleral contraction, a cross-linked fusiform strip from allogeneic sclera was used and designed axial length (AL) shortening amount was around 2.0∼3.0 mm based on preoperative AL. The middle part of the strip was placed at the posterior pole of the eye. After few aqueous humors were released, the strip was tightened to contract posterior sclera and shorten AL. Clinical data were collected at pre-operation (op) and post-op follow-ups for 12 months. Twenty-four eyes were collected. The AL at pre-op, post-op 1-week, 3-month, 6-month, and 12-month were 29.84 ± 1.24, 27.39 ± 1.32, 27.73 ± 1.23, 27.86 ± 1.26, and 27.91 ± 1.29 mm. There was no AL difference between post-op 6-month and 12-month (P = 0.242). The accumulated MF reattachment rate at post-op 1-week, 3-month, 6-month, and 12-month were 8.3%, 16.7%, 50.5%, and 95.8%. The best-corrected visual acuity at post-op 6-month and 12-month were 0.71 ± 0.39 (Snellen acuity 20/80) and 0.64 ± 0.37 (Snellen acuity 20/63), improving significantly compared with pre-op (P = 0.006 and <0.001). The posterior scleral contraction was effective to treat MF. The AL stabilized after post-op 6-month and MF reattached gradually with improved visual acuity up to post-op 12-month.

Migration of Late Miocene to Quaternary alkaline magmatism at the Alpine-Pannonian transition area: Significance for coupling of Adria plate motion with the Alpine-Carpathian front

Within-plate migration of alkaline basaltic centers is generally related to translation of the lithosphere with a hot spot above a largely stationary mantle plume. Here, we report, for the first time, a hitherto unrecognized migration of small-sized Late Miocene to Early Quaternary alkali-basaltic volcanic centers at the transition from Eastern Alps to Pannonian Basin. The volcanic centers migrated along the South Burgenland High in a regular sequence over a 95 km distance from NNE to SSW between 11 Ma and 1.7 Ma. The basaltic magmatism was also associated with thinning of the crust and lithosphere and an increase of the thermal gradient. In detail, three stages of migration are recognized as follows: (i) Stage 1 with a 55 km SSW-towards shift of volcanism between 11 and 5 Ma; (ii) Stage 2 with a ~ 35 km-WSW shift and enlargement of the distribution of volcanic centers between ca. 5 and 3.5 Ma; and (iii) Stage 3 with a S-directed shift of ca. 25 km between 3.5 and 1.7 Ma. The Stage 1 shift of alkali-basaltic volcanism can be also observed in the Little Hungarian Plain and South Slovakia–Nógrád volcanic fields, and the Stage 2 in the Balaton-Bakony of the Pannonian Basin (north of Lake Balaton). We propose that this pattern and mechanism of migration of the volcanic centers along the South Burgenland High resulted from thermally induced progressive thinning of the lithosphere over a mantle plume underneath the ALCAPA block, which was moving from SSW to the NNE between 11 and 1.7 Ma. The migration was interrupted by a marked eastward shift between 5 and 3.5 Ma (Stage 2). The migration of volcanic centers correlates with orientation and timing of regional shortening phases and inversion of the Alpine-Carpathian-Pannonian system although the overall amount of shortening remains uncertain. The deformation events allow to correlate Adria motion with deformation along the frontal parts of Eastern Alps, and Western and Eastern Carpathians across the western Pannonian Basin.

Tectono-sedimentary evolution of the Dehdasht structural basin (Central Zagros, Iran)

This paper deals with the tectono-sedimentary evolution of the Dehdasht Basin, located at the boundary between the Izeh Zone and the Dezful Embayment, in the Central Zagros. The structural evolution of the basin is closely related to the coeval sedimentation of Neogene Fars Group foreland basin deposits. The analysis of five geological cross-sections reveals the interaction between tectonics, Gachsaran Formation diapirism and coeval sedimentation as well as the influence of hidden basement-involved faults. The great thickness of the Miocene Gachsaran evaporites contributes to the internal structure of the Dehdasht Basin as well as decouples the Competent Group structure at depth from the Passive Group structure cropping out at surface. The basin forms a synclinorium limited by high amplitude NW-SE trending anticlines filled with Neogene deposits. Its internal structure is characterized by relatively thin growth synclines-minibasins separated by Gachsaran diapiric ridges formed under a combination of shortening and diapirism. The amount of shortening across the basin ranges between 7.5 and 13.1 km (16–24%) whereas the restored preserved thickness of Gachsaran evaporites increases southeastwards from 2 to 2.85 km. This high thickness is interpreted as partly accumulated by gravity gliding from the rising surrounding anticlines. Observed changes in structural relief across and along the Dehdasht Basin suggests its development above an array of hidden and linked basement faults including segments of the Mountain Frontal Flexure with NW-SE Zagros trend under the northern and southern boundary anticlines and a transfer fault with N-S Arabian trends at the SE border. The observed structural variations both along-strike and across the Dehdasht Basin at a local scale are similar to those already found at larger scales along the major Kazerun Fault Zone.