Zircon U-Pb dating of Mesozoic volcanic and tectonic events in northwest Palmer Land and southwest Graham Land, Antarctica

New whole rock Rb-Sr and zircon U-Pb geochronological data and Sm-Nd isotopic data are presented from the central magmatic arc domain of the Antarctic Peninsula in the area of northwest Palmer Land and southwest Graham Land, Rb-Sr isochrons indicate an age of 169±6 Ma for basement orthogneisses and 132±9 to 71±9 Ma for plutons. A U-Pb age of 183 ± 2.1 Ma, with no detectable inheritance, on zircons from an orthogneiss from Cape Berteaux provides the first reliable age for the orthogneisses, which are interpreted as metamorphosed silicic volcanic rocks, and Sm-Nd data indicate derivation in a mature volcanic arc. The age indicates they may be correlatives of the Jurassic ‘Chon Aike’ volcanism of the eastern Antarctic Peninsula. A U-Pb zircon age of 107 ± 1.7 Ma on a terrestrial volcanic sequence overlying an uncomformity strongly suggests a mid-Cretaceous age for the extensive volcanic cover of northwest Palmer Land that was previously thought to be Jurassic. The unconformity is interpreted to have been a result of compressional uplift related to the Palmer Land event. This is the first date for the event in the western part of the central magmatic arc terrane of the Antarctic Peninsula

Successful innominate thromboembolectomy of a paradoxic embolus

AbstractA 54 year-old man had symptoms of acute right hemispheric cerebral ischemia. He was initially considered for participation in a trial of early thrombolysis in stroke, but an innominate artery embolus was found with no apparent arterial source. The embolus was removed by means of a combined brachial and carotid bifurcation approach to protect the cerebral vasculature from embolic fragmentation during extraction. Further investigation revealed deep venous thrombosis, evidence of pulmonary emboli, and a patent foramen ovale, supporting a diagnosis of paradoxic embolus. Additional treatment included anticoagulation and placement of an inferior vena caval filter. The unusual condition of paradoxic embolus is reviewed, and the management of this patient is discussed. (J Vasc Surg 1998;28:742-5.

Stroke Prevention With Left Atrial Appendage Closure in Patients With Atrial Fibrillation and Prior Intracranial Hemorrhage

BACKGROUND Oral anticoagulation (OAC) is deemed a relative contraindication after intracranial hemorrhage (ICH) if the cause cannot be eliminated and the risk of recurrence is high. That leaves atrial fibrillation (AF) patients at high risk of thromboembolic events. Endovascular left atrial appendage closure (LAAC) can be an alternative to OAC for patients requiring stroke prevention. METHODS We performed a retrospective single-centre analysis of 138 consecutive ICH patients with nonvalvular AF and high stroke risk who underwent LAAC between 2010 and 2022 at Vancouver General Hospital. We report the baseline characteristics, procedural results, and follow-up data, comparing the observed stroke/transient ischemic attack (TIA) rate with the predicted event rate based on their CHA$_{2}$DS$_{2}$-VASc scores. RESULTS The average age was 76.1 ± 8.5 years; the mean CHA$_{2}$DS$_{2}$-VASc score was 4.4 ± 1.5; and the mean HAS-BLED score was 3.7 ± 0.9. The procedural success rate was 98.6%, and the complication rate was 3.6% with no periprocedural death, stroke, or TIA. The antithrombotic regimen post-LAAC consisted of short-term dual antiplatelet therapy (1-6 months) followed by aspirin alone for a minimum of 6 months in 86.2%. At mean follow-up of 14.7 ± 13.7 months, 9 deaths (6.5%, 7 cardiovascular, 2 noncardiovascular), 2 strokes (1.4%), and 1 TIA (0.7%) had occurred. The annualized observed stroke/TIA rate was 1.8%, which was lower than the adjusted predicted stroke rate of 7.0% (95% confidence interval: 4.8%-9.2%). Two patients (1.5%) suffered another ICH (both on aspirin monotherapy). One device-related thrombus (0.7%) was confirmed and treated with OAC without sequelae. CONCLUSION Endovascular LAAC is a feasible alternative to OAC for stroke prevention in patients with nonvalvular AF and prior ICH

Jurassic high heat production granites associated with the Weddell Sea rift system, Antarctica.

The distribution of heat flow in Antarctic continental crust is critical to understanding continental tectonics, ice sheet growth and subglacial hydrology. We identify a group of High Heat Production granites, intruded into upper crustal Palaeozoic metasedimentary sequences, which may contribute to locally high heat flow beneath the West Antarctic Ice Sheet. Four of the granite plutons are exposed above ice sheet level at Pagano Nunatak, Pirrit Hills, Nash Hills and Whitmore Mountains. A new Usingle bondPb zircon age from Pirrit Hills of 178.0 ± 3.5 Ma confirms earlier Rbsingle bondSr and Usingle bondPb dating and that the granites were emplaced approximately coincident with the first stage of Gondwana break-up and the developing Weddell rift, and ~ 5 m.y. after eruption of the Karoo-Ferrar large igneous province. Aerogeophysical data indicate that the plutons are distributed unevenly over 40,000 km2 with one intruded into the transtensional Pagano Shear Zone, while the others were emplaced within the more stable Ellsworth-Whitmore mountains continental block. The granites are weakly peraluminous A-types and have Th and U abundances up to 60.7 and 28.6 ppm respectively. Measured heat production of the granite samples is 2.96–9.06 μW/m3 (mean 5.35 W/m3), significantly higher than average upper continental crust and contemporaneous silicic rocks in the Antarctic Peninsula. Heat flow associated with the granite intrusions is predicted to be in the range 70–95 mW/m2 depending on the thickness of the high heat production granite layer and the regional heat flow value. Analysis of detrital zircon compositions and ages indicates that the high Th and U abundances are related to enrichment of the lower-mid crust that dates back to 200–299 Ma at the time of the formation of the Gondwanide fold belt and its post-orogenic collapse and extension

Perennial grasslands enhance biodiversity and multiple ecosystem services in bioenergy landscapes

Agriculture is being challenged to provide food, and increasingly fuel, for an expanding global population. Producing bioenergy crops on marginal lands—farmland suboptimal for food crops—could help meet energy goals while minimizing competition with food production. However, the ecological costs and benefits of growing bioenergy feedstocks—primarily annual grain crops—on marginal lands have been questioned. Here we show that perennial bioenergy crops provide an alternative to annual grains that increases biodiversity of multiple taxa and sustain a variety of ecosystem functions, promoting the creation of multifunctional agricultural landscapes. We found that switchgrass and prairie plantings harbored significantly greater plant, methanotrophic bacteria, arthropod, and bird diversity than maize. Although biomass production was greater in maize, all other ecosystem services, including methane consumption, pest suppression, pollination, and conservation of grassland birds, were higher in perennial grasslands. Moreover, we found that the linkage between biodiversity and ecosystem services is dependent not only on the choice of bioenergy crop but also on its location relative to other habitats, with local landscape context as important as crop choice in determining provision of some services. Our study suggests that bioenergy policy that supports coordinated land use can diversify agricultural landscapes and sustain multiple critical ecosystem services

Palaeozoic – Early Mesozoic geological history of the Antarctic Peninsula and correlations with Patagonia: Kinematic reconstructions of the proto-Pacific margin of Gondwana

The Antarctic Peninsula preserves geological evidence of a long-lived continental margin with intrusive, volcaniclastic and accretionary complexes indicating a convergent margin setting from at least the Cambrian to the Cenozoic. We examine the poorly understood units and successions from the Palaeozoic to the Early Mesozoic and develop detailed kinematic reconstructions for this section of the margin. We use existing geochronology, along with newly presented Usingle bondPb detrital zircon geochronology, combined with detailed field evidence to develop correlations between geological units and tectonic events across Patagonia and the proto-Antarctic Peninsula. The continental margin of Gondwana/Pangea was a convergent margin setting punctuated by crustal block translation, deformation, magmatic pulses (flare-ups) and development of thick accretionary complexes. These events are strongly linked to subducting slab dynamics and a para-autochthonous model is proposed for the long-lived margin. Major magmatic pulses are evident during the Ordovician (Famatinian) and Permian, and the magmatic record is reflected in the detrital zircon age profiles of metasedimentary successions of the northern Antarctic Peninsula and Tierra del Fuego. Major tectonic events during the Carboniferous – Permian (Gondwanide Orogeny) and Triassic (Chonide Event – Peninsula Orogeny) are recognised across the Antarctic Peninsula – Patagonia and are correlated to potential terrane suturing and flat slab dynamics. Our kinematic reconstructions developed in GPlates, combined with geological field relationships have allowed us to model the locus of magmatism relative to the active margin and also the likely source for thick sedimentary successions

Evaluation and comparison of trace metals accumulation in different tissues of potential bioindicator organisms: Macrobenthic filter feeders Styela plicata, sabella spallanzanii and Mytilus galloprovincialis

Trace metal concentrations were measured in different tissues of Sabella spallanzanii, Styela plicata and Mytilus galloprovincialis collected in Termini Imerese harbor, located in Sicily (Italy), in order to evaluate the potential use of these species as bioindicators. The higher bioaccumulation factors (BAFs) were calculated in tube of Sabella spallanzanii, except for As which shows the higher BAF in branchial crown of the same specie. Regarding the other species analyzed, higher BAFs were found in the digestive gland of Mytilus galloprovincialis. An exception is represented by Pb that is significantly more concentrated in branchial basket and tunic of Styela plicata. The BAFs here calculated, show that all the species analyzed are able to accumulate a certain amount of metals as a consequence of filter feeding mechanisms, and thus assess the suitability of the species Styela plicata, Sabella spallanzanii and Mytilus galloprovincialis as indicators of water quality. Particularly, the tube of Sabella spallanzanii is an important compartment in metal retention and the more suitable for the evaluation of the contamination caused by trace elements. This article is protected by copyright. All rights reserved

City of El Campo Downtown Revitalization Plan

The Revitalization Plan for Downtown El Campo is a planning document that provides guidance for the development of Downtown El Campo. This planning document includes an overview and analysis of the existing conditions in the City of El Campo and the El Campo Downtown Revitalization Area, a design proposal with vision, goals, and objectives for enhancing Downtown El Campo and a detailed implementation chapter for successful execution of the plan.This planning document presents the revitalization plan for downtown El Campo, Texas. This document was developed by Texas Target Communities (TTC) in partnership with the City of El Campo. The City of El Campo collaborated with Texas Target Communities in fall 2016 through the summer of 2017 to create a plan for revitalization of downtown El Campo. The purpose of the collaboration was to assess current community conditions, develop goals, objectives, and implementation strategies related to future development & growth strategies, through a public participatory process, in order to help guide the future growth of the City