News
11.05.2021Publication of new paleomagnetism papers
PhD. Bet Beamud, head of the CCiTUB Paleomagnetism Unit and Geociències Barcelona (CSIC) has participated in the papers " Paleogeographic and sedimentary evolution of the South Pyrenean foreland basin " in the journal Marine and Petroleum Geology and “ 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) ” in the journal Basin Research.
The papers are the result of the collaboration with Dr. Miguel Garcés and Miguel López Blanco of the Dpt. of Earth and Ocean Dynamics from the Faculty of Earth Sciences and the Geomodels Research Institute, UB. Researchers from the University of Geneva and the Universidad Autónoma de Madrid also took part in the paper.
The main objective of the paper "Paleogeographic and sedimentary evolution of the South Pyrenean foreland basin" is to synthesize the evolution of the South Pyrenean foreland basin during the Paleogene and part of the Neogene. This evolution is mainly explained from the reconstruction of sediment transport routes, changes in sedimentation rates and the age of sedimentary changes and their causes. This analysis is possible because it has a robust chronostratigraphic framework resulting from the magnetostratigraphic dating of various profiles distributed in different points of the basin (many of them the result of work in the Paleomagnetism Unit in recent years). All this information has allowed the realization of various paleogeographic maps for key moments in the evolution of the basin and assess the role of the different agents involved (tectonics, climate, eustatism).
The article “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)” studies the variation of rates of sedimentation in the Tremp-Jaca basin (foreland of the Pyrenees), over about 10 million years during the Eocene and its relationship with the evolution of the basin as the Pyrenean deformation advanced. The paper presents the results of two new magnetostratigraphic series (Yebra de Basa and Olsón), made in collaboration with the staff of the Paleomagnetism Unit. The staff of the unit has participated in the collection of samples in the field and their measurement in the laboratory. These new series are integrated with previous magnetostratigraphic works by the group and other authors in the Tremp-Jaca basin. This has made it possible to define 3 types of depocenters in the basin and two evolutionary stages, one during the Lutetian (49.1 to 41.2 Ma) with the compartmentalized basin and variable sedimentation rates with sufficient accommodation space and the other during the Bartonian-Priabonian. (41.2–36.9 Ma) with a significant reduction in sedimentation rates in a “wedge-top” basin context.
The abstracts of the papers are:
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.