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Noticias

11.05.2021

Publicados nuevos artículos de Paleomagnetismo

La Dra. Bet Beamud, responsable de la Unidad de Paleomagnetismo de los CCiTUB y Geociencias Barcelona (CSIC) ha participado en los artículos “Paleogeographic and sedimentary evolution of the South Pyrenean foreland basin" en la revista Marine and Petroleum Geology y “10 Myr evolution of sedimentation rates in a deep marine to non-marine foreland basin system: Tectonic and sedimentary controls (Eocene, Tremp–Jaca Basin, Southern Pyrenees, NE Spain)” en la revista Basin Research.

Los artículos són fruto de la colaboración con los Drs. Miguel Garcés y Miguel López Blanco del Dpt. de Dinámica de la Tierra y del Océano de la Facultad de Ciencias de la Tierra y el Instituto de Investigación Geomodelos, de la UB. En el artículo también han participado investigadores de la Universidad de Ginebra y de la Universidad Autónoma de Madrid.

El principal Objetivo del artículo "Paleogeographic and Sedimentary evolution of the South Pyrenean foreland basen" es sintetizar la evolución de la cuenca de antepaís sudpirinenca durante el Paleógeno y parte del Neógeno. Esta evolución se explica principalmente a partir de la reconstrucción de las rutas de transporte de sedimentos, cambios en las tasas de sedimentos y la edad de los cambios sedimentarios y sus causas. Este análisis es posible porque se dispone de un marco cronoestratigràfico robusto fruto de la datación magnetoestratigráfica de varios perfiles distribuidos a diferentes puntos de la cuenca (muchos de ellos resultado del trabajo en la Unidad de Paleomagnetismo en los últimos años). Toda esta información ha permitido la realización de varios mapas paleogeográficos por momentos claves de la evolución de la cuenca y evaluar el papel de los diferentes agentes involucrados (tectónica, clima, eustatismo).

En el artículo "10 Myr evolution of sedimentation rates in a deep marine to non-marine foreland basen system: Tectonic and Sedimentary controls (Éocène, Tremp-Jaca Basin, Southern Pyrenees, NE Spain)" se estudia la variación de las tasas de sedimentación en la cuenca de Tremp-Jaca (antepaís de los Pirineos), a lo largo de unos 10 millones de años durante el Eoceno y su relación con la evolución de la cuenca a medida que avanzaba la deformación pirenaica. En el artículo se presentan los resultados de dos series magnetoestratigràfiques nuevas (Yebra de Basa y Olson), realizadas en colaboración con el personal de la Unidad de Paleomagnetismo. El personal de la unidad ha participado en la recogida de muestras en el campo y su medida en el laboratorio. Estas nuevas series integran con trabajos magnetoestratigráficos previos del grupo y de otros autores en la cuenca de Tremp-Jaca. Esto ha permitido definir 3 tipos de depocentres en la cuenca y dos estadios evolutivos, uno durante el lutecio (49.1 a 41.2 Ma) con la cuenca compartimentada y tasas de sedimentación variables con suficiente espacio de acomodación y el otro durante el Barton-Priabona (41.2-36.9 Ma) con una reducción significativa de las tasas de sedimentación en un contexto de cuenca "wedge-top".

Los abstracts de los artículos son los siguientes:

Paleogeographic and sedimentary evolution of the South Pyrenean foreland basin

During the Paleogene and Neogene the NE Iberian plate underwent significant paleogeographic changes driven by the Iberian and European plate collision and the resulting formation of the Pyrenean orogen and its corresponding foreland basin. Shortening resulted in the advance of the orogenic wedge, emplacement of allochthonous units, and progressive basin partitioning. Sediment transfer systems reacted to the evolving paleogeographic scenario, shifting from forebulge to foredeep and wedge-top settings. Critical reorganizations included successive shifts from open to close drainage conditions, which had an strong impact on accommodation, and the stratigraphic architecture of the basin infill, overfill and later erosion. The aim of this work is to synthesize the paleogeographic and sedimentary evolution of the south-pyrenean foreland, with emphasis on the reconstruction of sediment routing, the evaluation of sedimentation rate trends, the timing of sedimentary shifts and the analysis of their causes. Stratigraphic data are compiled in a comprehensive magnetostratigraphy-based chronostratigraphic framework. Besides, sedimentary and structural data are put together to produce a series of palinspastically restored paleogeographic maps, which reflect five key stages in the evolution of the region. These stages include: 1) the Late Cretaceous tectonic inversion of the extended Iberian margin; 2) the Early Eocene formation of the southern Pyrenean foredeep; 3) the Middle Eocene widening and overfilling; 4) the late Eocene shift into an internal drainage; and 5) the Late Miocene drainage opening and erosion. In the light of these results, the variable role of tectonics, climate and eustacy at different time scales are discussed.

10 Myr evolution of sedimentation rates in a deep marine to non-marine foreland basin system: Tectonic and sedimentary controls (Eocene, Tremp–Jaca Basin, Southern Pyrenees, NE Spain)

The propagation of the deformation front in foreland systems is typically accompa-nied by the incorporation of parts of the basin into wedge-top piggy-back basins, this process is likely producing considerable changes to sedimentation rates (SR). Here we investigate the spatial-temporal evolution of SR for the Tremp–Jaca Basin in the Southern Pyrenees during its evolution from a wedge-top, foreredeep, forebulge con-figuration to a wedge-top stage. SR were controlled by a series of tectonic structures that influenced subsidence distribution and modified the sediment dispersal patterns. We compare the decompacted SR calculated from 12 magnetostratigraphic sections located throughout the Tremp–Jaca Basin represent the full range of depositional environment and times. While the derived long-term SR range between 9.0 and 84.5 cm/kyr, compiled data at the scale of magnetozones (0.1–2.5 Myr) yield SR that range from 3.0 to 170 cm/kyr. From this analysis, three main types of depocenter are rec-ognized: a regional depocenter in the foredeep depozone; depocenters related to both regional subsidence and salt tectonics in the wedge-top depozone; and a depocenter related to clastic shelf building showing transgressive and regressive trends with graded and non-graded episodes. From the evolution of SR we distinguish two stages. The Lutetian Stage (from 49.1–41.2 Ma) portrays a compartmentalized basin charac-terized by variable SR in dominantly underfilled accommodation areas. The markedly different advance of the deformation front between the Central and Western Pyrenees resulted in a complex distribution of the foreland depozones during this stage. The Bartonian–Priabonian Stage (41.2–36.9 Ma) represents the integration of the whole basin into the wedge-top, showing a generalized reduction of SR in a mostly overfilled relatively uniform basin. The stacking of basement units in the hinterland during the whole period produced unusually high SR in the wedge-top depozone.