Time filter

Source Type

Martos Y.M.,University of Granada | Catalan M.,Real Instituto Y Observatorio Of La Armada | Galindo-Zaldivar J.,University of Granada | Maldonado A.,University of Granada | Bohoyo F.,Instituto Geologico Y Minero Of Espana
Global and Planetary Change | Year: 2014

Analysis of a new regional compilation of magnetic anomalies from marine, aeromagnetic and satellite data reveals the main structural/tectonic elements of the Scotia Arc. The most relevant magnetic anomaly in the continental crust, the Pacific Margin Anomaly (PMA), is related to composite magmatic arc batholiths. It was emplaced by subduction processes along the Pacific continental margin of the Antarctic Peninsula and can be followed within the continental blocks of the South Scotia Ridge and South America. Four representative magnetic profiles also show the structure in depth, and allow us to characterize the main crustal elements of the region. The new compilation and models improve our knowledge of the Scotia Arc's development. The PMA is seen to have a roughly W-E orientation, decreasing in intensity eastwards from the Pacific Margin of the Antarctic Peninsula, and extending towards the South Scotia Ridge to Discovery Bank and even to Herdman Bank. However, the identification of the PMA in the North Scotia Ridge is uncertain, since the magnetic anomalies and the modeled profiles do not support the presence of an important batholithic body. This setting can be attributed to the kinematics of subduction, almost orthogonal to the Pacific margin of the Antarctic Peninsula and oblique along the South American margin. Based on the new magnetic anomaly map, magnetic modeling, and the continuity of the PMA along the Antarctic Peninsula and South Scotia Ridge, we propose a reconstruction of the initial distribution of the main continental blocks in the initial stages during the Cretaceous. The anomalies identified in the northern Scotia Sea are probably related to local basic and/or intermediate igneous rocks intruded in pull-apart basins that developed in the South America-Antarctica plate boundary deformation zone during the initial stages of South Atlantic Ocean and Weddell Sea spreading. © 2014 Elsevier B.V. All rights reserved. Source

Muinos J.L.,Real Instituto Y Observatorio Of La Armada | Evans D.W.,Institute of Astronomy
Astronomische Nachrichten | Year: 2014

CMC15 is the last of the series "Carlsberg Meridian Catalogue, La Palma" and comprises all the observations made between March 1999 and March 2011 with the Carlsberg Automatic Meridian Circle in El Roque de los Muchachos Observatory on the island of La Palma (Spain). The catalogues CMC12, CMC13, and CMC14 are superseded by this one. It contains more than 122 million observations of right ascension, declination, and magnitude of stars in the magnitude range of 9m < r′ < 17m and declination range of -40° < δ < +50°. The catalogue internal errors in astrometry are below 30 mas in both coordinates for stars brighter than r′ = 13, reaching 60 mas for r′ = 16. The internal magnitude error is below 0.020 mag for stars brighter than r′ = 13, and about 0.090 mag for r′ = 16. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Martos Y.M.,University of Granada | Galindo-Zaldivar J.,University of Granada | Catalan M.,Real Instituto Y Observatorio Of La Armada | Bohoyo F.,Instituto Geologico Y Minero Of Espana | Maldonado A.,University of Granada
Geophysical Research Letters | Year: 2014

The Drake Passage is considered a gateway for oceanic and asthenospheric flows since its opening, entailing widespread consequences for climate and plate tectonics, respectively. Both the surface and the 50 km upward continued Bouguer anomaly maps of the Scotia Sea and surrounding areas, based on Gravity Recovery and Climate Experiment gravity satellite data, improve our knowledge of deep lithospheric structures and the asthenosphere. We show that the West Scotia Sea is likely to be underlain by an anomalously low-density upper mantle. Gravity data are compatible with variable lithospheric thicknesses related to asthenospheric currents. The new data suggest that the development of the Shackleton Fracture Zone since the middle Miocene was probably a main factor that determined the evolution of the eastward Pacific mantle flows and the extinction of the West Scotia Sea oceanic spreading around 6 Ma ago. Deep lithospheric roots are likely to divert asthenospheric currents around them, flowing eastward through Drake Passage. Key Points Pacific mantle outflow is still present through the Drake Passage The Shackleton Fracture Zone modified asthenospheric flow patterns A redistribution of mantle flow may have caused West Scotia Ridge extinction ©2013. American Geophysical Union. All Rights Reserved. Source

Villasenor A.,CSIC - Institute of Earth Sciences Jaume Almera | Chevrot S.,University Paul Sabatier | Harnafi M.,Mohammed V University | Gallart J.,CSIC - Institute of Earth Sciences Jaume Almera | And 5 more authors.
Tectonophysics | Year: 2015

New tomographic images of the upper mantle beneath the westernmost Mediterranean suggest that the evolution of the region experienced two subduction-related episodes. First subduction of oceanic and/or extended continental lithosphere, now located mainly beneath the Betics at depths greater than 400 km, took place on a NW-SE oriented subduction zone. This was followed by a slab-tear process that initiated in the east and propagated to the west, leading to westward slab rollback and possibly lower crustal delamination. The current position of the slab tear is located approximately at 4°W, and to the west of this location the subducted lithosphere is still attached to the surface along the Gibraltar Arc. Our new P-wave velocity model is able to image the attached subducted lithosphere as a narrow high-velocity body extending to shallow depths, coinciding with the region of maximum curvature of the Gibraltar Arc, the occurrence of intermediate-depth earthquakes, and anomalously thick crust. This thick crust has a large influence in the measured teleseismic travel time residuals and therefore in the obtained P-wave tomographic model. We show that removing the effects of the thick crust significantly improves the shallow images of the slab and therefore the interpretations based on the seismic structure. © 2015 Elsevier B.V. Source

Bezada M.J.,University of Oregon | Humphreys E.D.,University of Oregon | Davila J.M.,Real Instituto Y Observatorio Of La Armada | Carbonell R.,CSIC - Institute of Earth Sciences Jaume Almera | And 3 more authors.
Geochemistry, Geophysics, Geosystems | Year: 2014

The elevation of the intracontinental Atlas Mountains of Morocco and surrounding regions requires a mantle component of buoyancy, and there is consensus that this buoyancy results from an abnormally thin lithosphere. Lithospheric delamination under the Atlas Mountains and thermal erosion caused by upwelling mantle have each been suggested as thinning mechanisms. We use seismic tomography to image the upper mantle of Morocco. Our imaging resolves the location and shape of lithospheric cavities and of delaminated lithosphere ∼400 km beneath the Middle Atlas. We propose discontinuous delamination of an intrinsically unstable Atlas lithosphere, enabled by the presence of anomalously hot mantle, as a mechanism for producing the imaged structures. The Atlas lithosphere was made unstable by a combination of tectonic shortening and eclogite loading during Mesozoic rifting and Cenozoic magmatism. The presence of hot mantle sourced from regional upwellings in northern Africa or the Canary Islands enhanced the instability of this lithosphere. Flow around the retreating Alboran slab focused upwelling mantle under the Middle Atlas, which we infer to be the site of the most recent delamination. The Atlas Mountains of Morocco stand as an example of large-scale lithospheric loss in a mildly contractional orogen. Key Points We image lithospheric cavities beneath the Middle Atlas and central HighAtlas We image the delaminated lithosphere of the Middle Atlas at ∼400 km depth We propose piecewise delamination of Atlas lithosphere © 2014. American Geophysical Union. All Rights Reserved. Source

Discover hidden collaborations