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The actively spreading Chile Ridge has been subducting beneath Patagonian Chile since the Middle Miocene. After subduction, continued separation of the faster Nazca plate from the slow Antarctic plate has opened up a gap--a slab window--between the subducted oceanic lithospheres beneath South America. We examined the form of the asthenospheric mantle flow in the vicinity of this slab window using S waves from six isolated, unusual 2007 earthquakes that occurred in the generally low-seismicity region just north of the ridge subduction region. The S waves from these earthquakes were recorded at distant seismic stations, but were split into fast and slow orthogonally polarized waves at upper mantle depths during their passage through the slab window and environs. We isolated the directions of fast split shear waves near the slab window by correcting for upper mantle seismic anisotropy at the distant stations. The results show that the generally trench-parallel upper mantle flow beneath the Nazca plate rotates to an ENE trend in the neighborhood of the slab gap, consistent with upper mantle flow from west to east through the slab window. doi: 10.1130/G30920.1

The average depth of crustal and upper mantle compensation interfaces are obtained from the power spectra of free air gravity anomalies in the eastern Caribbean-South American plate boundary zone. The inferable regional structures are associated with the crustal and upper mantle of the foreland basin. The foreland basin is not associated with the detaching oceanic subducted slab.

Shear-wave splitting of S and SKS phases reveals that anisotropy and s train field of the mantle beneath the subducting Nasca plate, Cocos plate, and the Caribbean region. These observations can be used to test models of mantle flow. Two-dimensional entrained mantle flow beneath the subducting Nazca slab is not consistent with the data Rather, there is evidence of horizontal trench-parallel flow in the mantle beneath the Nazca plate along much of the Andean subduction zone. Trench-parallel flow is attributable to retrograde motion of the slab, the decoupling of the slab and underlying mantle, and a partial barrier to flow at depth, resulting in lateral mantle flow beneath the slab. Such flow facilities the transfer of material from the shrinking mantle reservoir beneath the Pacific basin to the growing mantle reservoir beneath the Atlantic basin. Trench-parallel flow may explain the eastward motions of the Caribbean and Scotia sea plates, the anomalously shallow bathymetry of the eastern Nazca plate, the long-wavelength geoid high over western South America, and it may contribute to the high elevation and intense deformation of the central Andes., One of the most important implications of the plate tectonic revolution is that the mantle is convecting; yet progress in the characterization of mantle flow over the subsequent decades has [...]

Our studies of the surface structures, seismicity, and gravity anomalies of the Caribbean-South American plate-boundary zone of northeast Venezuela and Trinidad show that the crystal and upper lithospheric structure and kinematics of this zone are complex and differ markedly along strike. We propose a model of the zone's lateral transition from near Trinidad west to Caracas, emphasizing three concepts: (1) the steepening, detachment, and then sinking away of Atlantic oceanic lithosphere that is (was) attached to the northern edge of continental South America; (2) the wedging seaward and imbricate thickening of the northern margin of the continent in the region of the detaching Atlantic slab; the continental wedge overrides the slab and is overridden by terranes attached to the Caribbean plate; and (3) that the structural and kinematic transitions are a consequence of the progressive oblique collision between continental South America and the overriding Caribbean terranes.

Introduction: Despite considerable debate in the medical literature about the educational utility of pharmaceutical representatives (PR), little is known about their attitudes towards their role as marketers and/or educators, their ability to provide comprehensive information about products and their learning needs. Design: A survey. Subjects and Method: Questionnaires were mailed to 606 PRs from five Canadian pharmaceutical companies. Results: Of 309 (51%) respondents, 98% strongly agreed or agreed they had a role in educating doctors, while 52% strongly disagreed or disagreed their main goal was marketing. Overall, 92% agreed they had received adequate training to perform a well-informed detail, and 96% reported the information they provide is accurate. The majority (66%) felt a university-accredited program would improve the quality of their detailing. Conclusion: Most PRs believe their main goal is education. Despite most reporting that they had received adequate training, they felt that a university-accredited educational program would improve the quality of detailing. The number of years that a PR spent in the industry appears to have an effect on how they perceive their role. [ABSTRACT FROM AUTHOR]

Examines the link between the opening of ocean basins and cordillera formation and between ocean basins and marginal basin formation in the Andes Region. Cordillera and marginal basin formation as consequences of the Wilson cycle; Mantle anisotropy; Displacement of the mantle; Sea-floor spreading.