The chronology and rotational kinematics in the South-Eastern Jaca Basin (Southern Pyrenees) : Las Bellostas section
Pueyo, Emilio (Universidad de Zaragoza)
Rodríguez-Pintó, Adriana (Freelance Geologist)
Serra-Kiel, Josep (Museu de Ciències Naturals de Barcelona. Departament de Paleontologia)
Barnolas, Antonio (Instituto Geológico y Minero de España)

Fecha:	2022
Resumen:	Despite the large number of magnetostratigraphic studies in the South Pyrenean Basin aiming to calibrate the basin chronostratigraphy and the biostratigraphic scales, the South Eastern Jaca Basin remains unexplored from this perspective, and its relation with the Ainsa Basin is not fully understood. In this work we contribute with new magnetostratigraphic data from the 950m thick Las Bellostas section, located in the northern hinge of the Balzes anticline. Well-proven primary signal (positive fold test and two pseudo-antiparallel polarities) supported by numerous primary data in the surroundings allow us building a reliable local polarity sequence of eight magnetozones (from R1 to N4). Additionally, seven new biostratigraphic samples (Nummulites and Assilina) in the lower part of the section (marine environment) allows tightening the section to the Geomagnetic Polarity Time Scale (GPTS) and proposing a refined age model for the southeastern Jaca Basin. The section starts in the Boltaña Fm. , of Cuisian age (Shallow Benthic Zone, SBZ11), is followed by a sedimentary gap from C22n to C20n as witnessed by biostratigraphic data (SBZ11 underneath the hiatus and SBZ16 just atop). The deltaic Sobrarbe Fm. can be tracked until the C19n (Late Lutetian). From this point (200m) until the top of the section (950m), at least, the entire C18n chron can be recognized within the molassic Campodarbe Fm. (C18n. 2n-C18n. 1r and C18n. 1n) (Bartonian) equivalent to the West to the prodeltaic Arguis marls Fm. The Middle Cusian (SBZ11) to Middle Lutetian (SBZ15) stratigraphic hiatus is, in part, enhanced by the structural position at the hinge of the Balzes anticline. These new chronostratigraphic constraints help refining the W-E and N-S stratigraphic relationships in the eastern Jaca Basin and in the Ainsa Basin. This section also allows us to accurately refine the kinematics of the rotational activity in the eastern External Sierras. The important difference in magnetic declination along the section and neighboring paleomagnetic data from the Balzes anticline (from ≈70º clockwise at the base of the stratigraphic section to non-significant at the top) together with the new age model for the Eastern Jaca Basin help characterizing the rotational activity of the Balzes thrust sheet. The rotation took place between chrons C20r (Middle Lutetian; 45Ma) and C17 (Lower Priabonian 37-38Ma) in agreement to nearby structures (Boltaña, Picodel Aguila anticlines) but clearly diachronic to western ones (Santo Domingo anticline). Besides, the rotational activity seems to follow a linear and continuous pattern (velocity 9-11º/Ma, R: 0. 83-0. 96) in contrast to closer structures that show two distinct rotational velocities (i. e. Boltaña). These new data still let open the debate on the rotational kinematics along the South Pyrenean basal thrust.
Ayudas:	Ministerio de Economía y Competitividad CGL2014 54118-C2-2-R Agencia Estatal de Investigación PID2019-104693GB-I00 Agencia Estatal de Investigación CGL2017-90632-REDT
Nota:	Acknowledgement. This paper represents our modest tribute to Pep Serra-Kiel for his inspiring work, his sharp intelligence, his working tenacity, his always fruitful discussions and his camaraderie and friendship. This work was financed by the Sobrarbe County Research fellow-UNESCO Global Geopark (ARP) and by some projects from the Spanish Science National Plan (UKRIA4D- PID2019--I00/CTA, DR3AM. CGL2014 54118-C2-2-R and MAGIBER-II. CGL2017-90632-REDT). We are also very grateful to the laboratories of the universities of Burgos (Juanjo Villalaín) and Zaragoza (Teresa Román and Sylvia Gracia), Sergio Arruej Gil for the field support and Pablo Calvin and Vicky Burriel for the Burgos logistic support. Very warm acknowledged is given to Alejandro and Pablo from "Casa Molinero" in Las Bellostas for their hospitality, friendship and human warmth during all these years. Finally, we sincerely acknowledge the thorough and constructive reviews done by Miguel Garcés, Josep Tosquella and the editor Carles Martín-Closas.
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria de l'obra original.
Lengua:	Català
Documento:	Article ; recerca ; Versió publicada
Materia:	Magnetostratigraphy ; Rotational kinematics ; Pyrenean frontal thrust ; Ypresian ; Cuisian ; Lutetian ; Bartonian
Publicado en:	Geologica acta, Vol. 20 (2022) , p. 1-29 (Biochronology of the South Pyrenean Cenozoic, in memoriam Josep Serra-Kiel) , ISSN 1696-5728

Adreça original: https://raco.cat/index.php/GeologicaActa/article/view/404563
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/41005
Adreça alternativa: https://revistes.ub.edu/index.php/GEOACTA/article/view/34854
DOI: 10.1344/GeologicaActa2022.20.12

29 p, 8.8 MB

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