Miocene basin development and volcanism along a strike-slip to flat-slab subduction transition: Stratigraphy, geochemistry, and geochronology of the central Wrangell volcanic belt, Yakutat-North America collision zone

New geochronologic, geochemical, sedimentologic, and compositional data from the central Wrangell volcanic belt (WVB) document basin development and volcanism linked to subduction of overthickened oceanic crust to the northern Pacific plate margin. The Frederika Formation and overlying Wrangell Lavas comprise >3 km of sedimentary and volcanic strata exposed in the Wrangell Mountains of south-central Alaska (United States). Measured stratigraphic sections and lithofacies analyses document lithofacies associations that reflect deposition in alluvial-fluvial-lacustrine environments routinely influenced by volcanic eruptions. Expansion of intrabasinal volcanic centers prompted progradation of vent-proximal volcanic aprons across basinal environments. Coal deposits, lacustrine strata, and vertical juxtaposition of basinal to proximal lithofacies indicate active basin subsidence that is attributable to heat flow associated with intrabasinal volcanic centers and extension along intrabasinal normal faults. The orientation of intrabasinal normal faults is consistent with transtensional deformation along the Totschunda-Fairweather fault system. Paleocurrents, compositional provenance, and detrital geochronologic ages link sediment accumulation to erosion of active intrabasinal volcanoes and to a lesser extent Mesozoic igneous sources. Geochemical compositions of interbedded lavas are dominantly calc-alkaline, range from basaltic andesite to rhyolite in composition, and share geochemical characteristics with Pliocene-Quaternary phases of the western WVB linked to subduction-related magmatism. The U/Pb ages of tuffs and Ar-40/Ar-39 ages of lavas indicate that basin development and volcanism commenced by 12.5-11.0 Ma and persisted until at least ca. 5.3 Ma. Eastern sections yield older ages (12.5-9.3 Ma) than western sections (9.6-8.3 Ma). Samples from two western sections yield even younger ages of 5.3 Ma. Integration of new and published stratigraphic, geochronologic, and geochemical data from the entire WVB permits a comprehensive interpretation of basin development and volcanism within a regional tectonic context. We propose a model in which diachronous volcanism and transtensional basin development reflect progressive insertion of a thickened oceanic crustal slab of the Yakutat microplate into the arcuate continental margin of southern Alaska coeval with reported changes in plate motions. Oblique northwestward subduction of a thickened oceanic crustal slab during Oligocene to Middle Miocene time produced transtensional basins and volcanism along the eastern edge of the slab along the Duke River fault in Canada and subduction-related volcanism along the northern edge of the slab near the Yukon-Alaska border. Volcanism and basin development migrated progressively northwestward into eastern Alaska during Middle Miocene through Holocene time, concomitant with a northwestward shift in plate convergence direction and subduction collision of progressively thicker crust against the syntaxial plate margin.

Scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment study (SPR Study): recruitment list evaluation. Study report no. 2

BACKGROUND: Accompanying the patient recruitment within the "Scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment multicentre trial (SPR)", all patients with primary rhegmatogenous retinal detachment (RRD) had to be documented in a detailed recruitment list. The main goal of this analysis was to estimate the prevalence of "medium-severe" RRD (SPR Study eligible) as defined by the SPR Study inclusion criteria. In addition, the detailed anatomical situation of medium-severe RRD is investigated. METHODS: SPR Study recruitment was evaluated via a standardised questionnaire, which contained a coloured fundus drawing and information regarding possible reasons for exclusion from the SPR Study in each case. A team of three experienced vitreoretinal surgeons evaluated all fundus drawings from a 1-year period. The review led to a decision on SPR Study eligibility on the pure basis of anatomical assessment. The main outcome measures were assessment of feasible inclusion into the SPR Study by the evaluation team based on the fundus drawing and anatomical details. RESULTS: A total of 1,115 patients with RRD from 13 European centres were prospectively enrolled in the year 2000. The quality of the drawings sufficed for assessment in 1,107 cases (99.3%). Three hundred and twelve fundus drawings (28.2%) met the anatomic inclusion criteria of the SPR Study. RRD of medium severity is characterised by an average number of 2.6 (SD 2.4) retinal breaks, 5.8 (SD 2.8) clock hours of detached retina, unclear hole situation in 15.1% of cases (n=47), attached macula in 42.9% (n=134), bullous detachment in 15.1% (n=47) and vitreous haemorrhage/opacity in 7.7% (n=24). CONCLUSIONS: In the recruitment lists of the SPR Study of the year 2000, RRD of medium severity was present in nearly one third of the patients with primary RRD. These findings emphasise the clinical relevance of the SPR Study.

Long-term evaluation of anatomic and functional results after complicated retinal detachment treated with pars plana vitrectomy and heavy silicone oil tamponade

BACKGROUND: Heavier than water tamponades offer the possibility to support the inferior part of the fundus after retinal detachment. The aim of this study was to evaluate the anatomic and functional outcome of complicated retinal detachment treated with vitreous surgery and heavy silicone oil (HSO) tamponade. Surgery was performed in eyes with rhegmatogenous retinal detachment (RD) predominantly in the lower hemisphere or with penetrating injury (either as primary intervention or after development of proliferative vitreoretinopathy [PVR]). MATERIALS AND METHODS: Sixty-one eyes of 61 patients with RD - mostly complicated by PVR - and a minimum follow-up of 12 months were included in this study. Vitreoretinal surgery with HSO (Oxane HD) tamponade was performed in all patients. In 52 patients, heavy silicone oil was used in the management of complicated RD. 9 patients had surgery for complicated RD after penetrating eye injury.The mean follow-up period was 30.3 +/- 10.2 months. RESULTS: The overall final anatomic success rate was 79 %. In 39 % of the cases the retina remained attached during the entire follow-up period. CONCLUSIONS: The anatomic success rate after surgery with HSO (Oxane HD) was relatively low; however, only complex cases bearing a higher risk of retinal re-detachment received HSO in this study. Oxane HD does not appear to have major advantages compared to conventional silicone oil or other new-generation heavy silicone oils in these cases.

Pathophysiology of proliferative vitreoretinopathy in retinal detachment

Because proliferative vitreoretinopathy cannot be effectively treated, its prevention is indispensable for the success of surgery for retinal detachment. The elaboration of preventive and therapeutic strategies depends upon the identification of patients who are genetically predisposed to develop the disease, as well as upon an understanding of the biological process involved and the role of local factors, such as the status of the uveovascular barrier. Detachment of the retina or vitreous activates glia to release cytokines and ATP, which not only protect the neuroretina but also promote inflammation, retinal ischemia, cell proliferation, and tissue remodeling. The vitreal microenvironment favors cellular de-differentiation and proliferation of cells with nonspecific nutritional requirements. This may render a pharmacological inhibition of their growth difficult without causing damage to the pharmacologically vulnerable neuroretina. Moreover, reattachment of the retina relies upon the local induction of a controlled wound-healing response involving macrophages and proliferating glia. Hence, the functional outcome of proliferative vitreoretinopathy will be determined by the equilibrium established between protective and destructive repair mechanisms, which will be influenced by the location and the degree of damage to the photoreceptor cells that is induced by peri-retinal gliosis.

Social stressors at work and sleep quality on sunday night – The mediating role of psychological detachment

Purpose Recovery is a critical link between acute reactions to work-stressors and the development of health-impairments in the long run. Even though recovery is particularly necessary when recovery opportunities during work are insufficient, research on recovery during weekends, is still scarce. To fill this gap we tested, whether the inability to psychologically detach from work mediates the effect of social stressors at work on sleep quality on Sunday night. Design/Methodology Sixty full-time employees participated in the study. Daily assessment included diaries on psychological detachment and ambulatory actigraphy to assess psychophysiological indicators of sleep quality. Results Hierarchical regression analyses revealed social stressors at work to be related with psychological detachment and with several sleep quality parameters on Sunday night. Furthermore, psychological detachment from work mediated the effect of social stressors at work on sleep quality. Limitations Methodological considerations regarding the use of actigraphy data should be taken into account. Research/Practical Implications Our results show that social stressors at work may lower resources just before people get started into the new working week. Originality/Value This is the first study to show that social stressors at work are an antecedent of psychological detachment on Sunday evening and of objective sleep quality on Sunday.

Thermal and Barometric Constraints on the Intrusive and Unroofing History of the Black Mountains: Implications for Timing, Initial Dip, and Kinematics of Detachment Faulting in the Death-Valley Region, California

Unroofing of the Black Mountains, Death Valley, California, has resulted in the exposure of 1.7 Ga crystalline basement, late Precambrian amphibolite facies metasedimentary rocks, and a Tertiary magmatic complex. The Ar-40/Ar-39 cooling ages, obtained from samples collected across the entire length of the range (>55 km), combined with geobarometric results from synextensional intrusions, provide time-depth constraints on the Miocene intrusive history and extensional unroofing of the Black Mountains. Data from the southeastern Black Mountains and adjacent Greenwater Range suggest unroofing from shallow depths between 9 and 10 Ma. To the northwest in the crystalline core of the range, biotite plateau ages from approximately 13 to 6.8 Ma from rocks making up the Death Valley turtlebacks indicate a midcrustal residence (with temperatures >300-degrees-C) prior to extensional unroofing. Biotite Ar-40/Ar-39 ages from both Precambrian basement and Tertiary plutons reveal a diachronous cooling pattern of decreasing ages toward the northwest, subparallel to the regional extension direction. Diachronous cooling was accompanied by dike intrusion which also decreases in age toward the northwest. The cooling age pattern and geobarometric constraints in crystalline rocks of the Black Mountains suggest denudation of 10-15 km along a northwest directed detachment system, consistent with regional reconstructions of Tertiary extension and with unroofing of a northwest deepening crustal section. Mica cooling ages that deviate from the northwest younging trend are consistent with northwestward transport of rocks initially at shallower crustal levels onto deeper levels along splays of the detachment. The well-known Amargosa chaos and perhaps the Badwater turtleback are examples of this "splaying" process. Considering the current distance of the structurally deepest samples away from moderately to steeply east tilted Tertiary strata in the southeastern Black Mountains, these data indicate an average initial dip of the detachment system of the order of 20-degrees, similar to that determined for detachment faults in west central Arizona and southeastern California. Beginning with an initially listric geometry, a pattern of footwall unroofing accompanied by dike intrusion progress northwestward. This pattern may be explained by a model where migration of footwall flexures occur below a scoop-shaped banging wall block. One consequence of this model is that gently dipping ductile fabrics developed in the middle crust steepen in the upper crust during unloading. This process resolves the low initial dips obtained here with mapping which suggests transport of the upper plate on moderately to steeply dipping surfaces in the middle and upper crust.

Microfabric memory of vein quartz for strain localization in detachment faults: A case study on the Simplon fault zone

This manuscript deals with the adaptation of quartz-microfabrics to changing physical deformation conditions, and discusses their preservation potential during subsequent retrograde deformation. Using microstructural analysis, a sequence of recrystallization processes in quartz, ranging from Grain-Boundary Migration Recrystallization (GBM) over Subgrain-Rotation Recrystallization (SGR) to Bulging Nucleation (BLG) is detected for the Simplon fault zone (SFZ) from the low strain rim towards the internal high strain part of the large-scale shear zone. Based on: (i) the retrograde cooling path; (ii) estimates of deformation temperatures; and (iii) spatial variation of dynamic recrystallization processes and different microstructural characteristics, continuous strain localization with decreasing temperature is inferred. In contrast to the recrystallization microstructures, crystallographic preferred orientations (CPO) have a longer memory. CPO patterns indicative of prism and rhomb glide systems in mylonitic quartz veins, overprinted at low temperatures (�400 �C), suggest inheritance of a high-temperature deformation. In this way, microstructural, textural and geochemical analyses provide information for several million years of the deformation history. The reasons for such incomplete resetting of the rock texture is that strain localization is caused by change in effective viscosity contrasts related to temporal large- and small-scale temperature changes during the evolution of such a long-lived shear zone. The spatially resolved, quantitative investigation of quartz microfabrics and associated recrystallization processes therefore provide great potential for an improved understanding of the geodynamics of large-scale shear zones.

Retinal layer measurements after successful macula-off retinal detachment repair using optical coherence tomography

PURPOSE Optical coherence tomography (OCT) was used to analyze the thickness of various retinal layers of patients following successful macula-off retinal detachment (RD) repair. METHODS Optical coherence tomography scans of patients after successful macula-off RD repair were reanalyzed with a subsegmentation algorithm to measure various retinal layers. Regression analysis was performed to correlate time after surgery with changes in layer thickness. In addition, patients were divided in two groups. Group 1 had a follow-up period after surgery of up to 7 weeks (range, 21-49 days). In group 2, the follow-up period was >8 weeks (range, 60-438 days). Findings were compared to a group of age-matched healthy controls. RESULTS Correlation analysis showed a significant positive correlation between inner nuclear-outer plexiform layer (INL-OPL) thickness and time after surgery (P=0.0212; r2=0.1551). Similar results were found for the ellipsoid zone-retinal pigment epithelium complex (EZ-RPE) thickness (P=0.005; r2=0.2215). Ganglion cell-inner plexiform layer thickness (GCL-IPL) was negatively correlated with time after surgery (P=0.0064; r2=0.2101). For group comparison, the retinal nerve fiber layer in both groups was thicker compared to controls. The GCL-IPL showed significant thinning in group 2. The outer nuclear layer was significantly thinner in groups 1 and 2 compared to controls. The EZ-RPE complex was significantly thinner in groups 1 and 2 compared to controls. In addition, values in group 1 were significantly thinner than in group 2. CONCLUSIONS Optical coherence tomography retinal layer thickness measurements after successful macular-off RD repair revealed time-dependent thickness changes. Inner nuclear-outer plexiform layer thickness and EZ-RPE thickness was positively correlated with time after surgery. Ganglion cell-inner plexiform layer thickness was negatively correlated with time after surgery.

Social stressors at work and sleep during weekends: The mediating role of psychological detachment

Social stressors at work may result in long-term health impairments if recovery is insufficient. In the present psychophysiological field study, we tested whether the inability to psychologically detach from work issues mediates the negative effect of social stressors at work on sleep during weekends. Sixty full-time employees participated in the study. Daily assessment included diaries on psychological detachment and continuous ambulatory actigraphy to assess psychophysiological indicators of sleep. Hierarchical regression analyses revealed that enduring social stressors at work were negatively related with psychological detachment on Sunday evening and negatively related with various sleep indicators on Sunday night. Furthermore, psychological detachment from work on Sunday evening partially mediated the effect of social stressors at work on two sleep indicators. Social stressors at work may threaten recovery processes just before the working week starts.

The late Miocene to Holocene erosion pattern of the Alpine foreland basin reflects Eurasian slab unloading beneath the western Alps rather than global climate change

We synthesized published data on the erosion of the Alpine foreland basin and apatite fission-track ages from the Alps to infer the erosional sediment budget history for the past 5 m.y. The data reveal that erosion of the Alpine foreland basin is highest in front of the western Alps (between 2 and 0.6 km) and decreases eastward over a distance of 700 km to the Austrian foreland basin (similar to 200 m). For the western Alps, erosion rates are >0.6 km/m.y., while erosion rates for the eastern foreland basin and the adjacent eastern Alps are <0.1 km/m.y., except for a small-scale signal in the Tauern Window. The results yield a large ellipsoidal, orogen-crossing pattern of erosion, centered along the western Alps. We suggest that accelerated erosion of the western Alps and their foreland basin occurred in response to regional-scale surface uplift, related to lithospheric unloading of the Eurasian slab along the Eurasian-Adriatic plate boundary. While we cannot rule out recent views that global climate change led to substantial erosion of the European Alps since 5 Ma, we postulate that regional-scale tectonic processes have driven erosion during this time, modulated by an increased erosional flux in response to Quaternary glaciations.