Examinando por Materia "cooling"

Mostrando 1 - 2 de 2
  • No hay miniatura disponible
    Ítem
    Detrital zircon fission-track thermochronology and magnetic fabric of the Amagá Formation (Colombia): Intracontinental deformation and exhumation events in the northwestern Andes
    (ELSEVIER SCIENCE BV, 2017-07-01) Piedrahita, V.A.; Bernet, M.; Chadima, M.; Sierra, G.M.; Marín-Cerón, M.I.; Toro, G.E.; Piedrahita, V.A.; Bernet, M.; Chadima, M.; Sierra, G.M.; Marín-Cerón, M.I.; Toro, G.E.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y Tectónica
    New detrital zircon-fission track (ZFT) and magnetic fabric data are presented to constrain the time of deposition, provenance and deformation of the of Lower and Upper members of the Amagá Formation in the Amagá Basin. The Amagá Basin is located in the northern Andes, between the Western and Central Cordilleras of Colombia. The Amagá Formation was deposited in a transpressive geodynamic context and is allegedly synchronous with tectonic events such as the Andean orogeny and the Panama-Choco Block collision with the northwestern South American Plate. Detrital ZFT data confirm an Oligocene age for the Lower Member and a middle-Miocene age for the Upper Member of the Amagá Formation. In addition to constraining the depositional age, the ZFT data presented in this study also reflect Paleocene-Eocene, late to early Oligocene and late to middle Miocene cooling in sediment source areas mainly located in the Central and Western Cordilleras of Colombia. These ages can be associated with regional exhumation events in the central and northern Andes of South America. Collisional stages of the Panama-Choco Block against northwestern South America, subduction of the Farallon-Nazca Plate and strike-slip reactivation periods of the Cauca-Romeral fault system, caused NW-SE compression and NE-SW simple shear in the Amagá Basin. This deformational regime, identified by magnetic fabric data, induces syn- and post-depositional deformation over the Amagá Formation. © 2017 Elsevier B.V.
  • No hay miniatura disponible
    Ítem
    Southwest Pacific Ocean response to a warmer world: Insights from marine isotope stage 5e
    (AMER GEOPHYSICAL UNION, 2013-09-01) Cortese, G.; Dunbar, G. B.; Carter, L.; Scott, G.; Bostock, H.; Bowen, M.; Crundwell, M.; Hayward, B. W.; Howard, W.; Martinez, J. I.; Moy, A.; Neil, H.; Sabaa, A.; Sturm, A.; Universidad EAFIT. Departamento de Geología; Ciencias del Mar
    Paleoceanographic archives derived from 17 marine sediment cores reconstruct the response of the Southwest Pacific Ocean to the peak interglacial, Marine Isotope Stage (MIS) 5e (ca. 125 ka). Paleo-Sea Surface Temperature (SST) estimates were obtained from the Random Forest model - an ensemble decision tree tool - applied to core-top planktonic foraminiferal faunas calibrated to modern SSTs. The reconstructed geographic pattern of the SST anomaly (maximum SST between 120 and 132 ka minus mean modern SST) seems to indicate how MIS 5e conditions were generally warmer in the Southwest Pacific, especially in the western Tasman Sea where a strengthened East Australian Current (EAC) likely extended subtropical influence to ca. 45°S off Tasmania. In contrast, the eastern Tasman Sea may have had a modest cooling except around 45°S. The observed pattern resembles that developing under the present warming trend in the region. An increase in wind stress curl over the modern South Pacific is hypothesized to have spun-up the South Pacific Subtropical Gyre, with concurrent increase in subtropical flow in the western boundary currents that include the EAC. However, warmer temperatures along the Subtropical Front and Campbell Plateau to the south suggest that the relative influence of the boundary inflows to eastern New Zealand may have differed in MIS 5e, and these currents may have followed different paths compared to today. Key Points Oceanic conditions at 125 kyr seem to agree with recent observations/trendsEast Australian Current probably stronger and Tasman Front cooler during MIS 5eObserved oceanographic changes likely linked to increases in wind stress curl ©2013. American Geophysical Union. All Rights Reserved.