“…The Alpine thrust structure of the Axial Zone of the Pyrenees has been extensively studied (Séguret, 1972;Williams and Fischer, 1984;Roure et al, 1989;Muñoz, 1992;Vergés, 1993;Beaumont et al, 2000;Mouthereau et al, 2014;Muñoz et al, 2018;Teixell et al, 2018;García-Senz et al, 2019;Calvet et al, 2020), defined as an antiformal stack of Paleozoic basement-involved, south-directed thrust sheets. The frontal part of the antiformal stack, detached by erosion from its root to the north, consists of forelanddipping thrusts and related downward-facing folds referred to as the Nogueres têtes plongeantes (Séguret, 1972).…”
Section: Geological Setting and Previous Studiesmentioning
confidence: 99%
“…Finally, the emplacement of the lowermost Rialp thrust sheet, at around 30 My, marks a stage of slower cooling and exhumation up to the present day (Gibson, 2004;Sinclair et al, 2005;Metcalf et al, 2009;Whitchurch et al, 2011;Calvet et al, 2020).…”
Section: Geological Setting and Previous Studiesmentioning
The northern margin of the Organyà basin (Southern Pyrenees) has a complex structure in which syn-rift Lower Cretaceous carbonates flank a wide Keuper evaporite province, featuring the leading edges of the basement-involved thrust sheets of the Pyrenean antiformal stack. Recent observations show that Keuper diapirs and salt walls grew during the Cretaceous extensional episode, conditioning the development of differentiated depocenters and minibasins. The role of salt tectonics during the Pyrenean orogeny has not been addressed in previous structural studies, but present-day cross-sections indicate a Keuper evaporite-bearing vertical thickness of up to 3000 m in the Senterada-Gerri de la Sal area. We infer that salt migration was a determinant mechanism in triggering a gentle northward tilting of the Organyà basin during the Eocene-Oligocene, recorded in the La Pobla de Segur and Gurp syn-tectonic conglomerates in a basin-wide progressive unconformity and a large north-directed onlap, opposite to the main sedimentary influx direction. Contemporaneously, salt migration, promoted by conglomerate differential loading, enabled the sinking and rotation of the unrooted Nogueres thrust units (têtes plongeantes). We use new and published structural data for the Lower Cretaceous margin of the Organyà basin, combined with structural and clast provenance data from the Cenozoic alluvial fan conglomerates of La Pobla and Gurp, to understand the Lutetian to late Oligocene evolution of the northern margin of the Central South-Pyrenean Unit. The tectono-sedimentary evolution of this area and the salt evacuation patterns are closely related to the exhumation history of the stacked Paleozoic thrust sheets of the Pyrenean hinterland to the north. In this study we correlate the movements over a mobile substratum and the paleogeographic changes of conglomeratic basins at the toe of an exhuming orogenic interior.
“…The Alpine thrust structure of the Axial Zone of the Pyrenees has been extensively studied (Séguret, 1972;Williams and Fischer, 1984;Roure et al, 1989;Muñoz, 1992;Vergés, 1993;Beaumont et al, 2000;Mouthereau et al, 2014;Muñoz et al, 2018;Teixell et al, 2018;García-Senz et al, 2019;Calvet et al, 2020), defined as an antiformal stack of Paleozoic basement-involved, south-directed thrust sheets. The frontal part of the antiformal stack, detached by erosion from its root to the north, consists of forelanddipping thrusts and related downward-facing folds referred to as the Nogueres têtes plongeantes (Séguret, 1972).…”
Section: Geological Setting and Previous Studiesmentioning
confidence: 99%
“…Finally, the emplacement of the lowermost Rialp thrust sheet, at around 30 My, marks a stage of slower cooling and exhumation up to the present day (Gibson, 2004;Sinclair et al, 2005;Metcalf et al, 2009;Whitchurch et al, 2011;Calvet et al, 2020).…”
Section: Geological Setting and Previous Studiesmentioning
The northern margin of the Organyà basin (Southern Pyrenees) has a complex structure in which syn-rift Lower Cretaceous carbonates flank a wide Keuper evaporite province, featuring the leading edges of the basement-involved thrust sheets of the Pyrenean antiformal stack. Recent observations show that Keuper diapirs and salt walls grew during the Cretaceous extensional episode, conditioning the development of differentiated depocenters and minibasins. The role of salt tectonics during the Pyrenean orogeny has not been addressed in previous structural studies, but present-day cross-sections indicate a Keuper evaporite-bearing vertical thickness of up to 3000 m in the Senterada-Gerri de la Sal area. We infer that salt migration was a determinant mechanism in triggering a gentle northward tilting of the Organyà basin during the Eocene-Oligocene, recorded in the La Pobla de Segur and Gurp syn-tectonic conglomerates in a basin-wide progressive unconformity and a large north-directed onlap, opposite to the main sedimentary influx direction. Contemporaneously, salt migration, promoted by conglomerate differential loading, enabled the sinking and rotation of the unrooted Nogueres thrust units (têtes plongeantes). We use new and published structural data for the Lower Cretaceous margin of the Organyà basin, combined with structural and clast provenance data from the Cenozoic alluvial fan conglomerates of La Pobla and Gurp, to understand the Lutetian to late Oligocene evolution of the northern margin of the Central South-Pyrenean Unit. The tectono-sedimentary evolution of this area and the salt evacuation patterns are closely related to the exhumation history of the stacked Paleozoic thrust sheets of the Pyrenean hinterland to the north. In this study we correlate the movements over a mobile substratum and the paleogeographic changes of conglomeratic basins at the toe of an exhuming orogenic interior.
“…In the Pyrenees, in addition to the low temperature thermochronology data already mentioned, post-10 Ma uplift is suggested by geological data (Calvet et al, 2020) including recent paleoelevation estimates (e.g. Huyghe et al, 2020).…”
“…This orogenic sequence is reflected, north of the Ebro Basin, in the syn-orogenic tectonic-stratigraphic relationships well preserved in the South Pyrenean Zone (SPZ), a classical thin-skin fold and thrust belt made of Mesozoic to Cenozoic sediments detached in the Triassic evaporites (Muñoz, 1992;Vergés et al, 1995Vergés et al, , 2002Mouthereau et al, 2014;Carola et al, 2015;Saura et al, 2016). It was followed by a post-orogenic phase of exhumation reported throughout the Pyrenees at about 10 Ma (Morris et al, 1998;Fitzgerald et al, 1999;Whitchurch et al, 2011;Fillon et al, 2013Fillon et al, , 2020Mouthereau et al, 2014;Bosch et al, 2016;Monod et al, 2016;Huyghe et al, 2020; see also the review by Calvet et al, 2020).…”
“…This issue was resolved by detailed offshore seismic constraints that document canyons buried offshore in the Ebro delta filled by pre-Messinian sediments (Urgeles et al, 2011). Based on the above arguments, we consider the Ebro Basin opening toward the Mediterranean Sea occurred between 7.5 and 13 Ma (see also Calvet et al, 2020 for a synthesis).…”
Section: Timing Of Ebro Basin Opening To the Mediterranean Seamentioning
The Ebro Basin constitutes the central part of the southern foreland of the Pyrenees. It was endorheic during the Cenozoic and accumulated sediments. By the end of the Miocene, erosion and river incision reconnected the basin to the Mediterranean Sea, establishing a post-opening drainage network. Those rivers left terraces that we study in this work. We first synthesize previous works on river terraces that are widely dispersed in the basin. We provide new age constraints, up to 3 Ma, obtained thanks to cosmogenic nuclides using both profile and burial methods. We derive a unified fluvial terrace chronology and a homogenized map of the highest terraces over the entire Ebro Basin. The dated terraces labeled A, B, C, D, and E are dated to 2.8 ± 0.7 Ma, 1.15 ± 0.15 Ma, 850 ± 70 ka, 650 ± 130 ka, and 400 ± 120 ka, respectively. The chronology proposed here is similar to other sequences of river terraces dated in the Iberian Peninsula, around the Pyrenees, and elsewhere in Europe. The oldest terraces (A, B, C) are extensive, indicating they form a mobile fluvial network while from D to present, the network was stable and entrenched in 100 to 200 m-deep valleys. The transition from mobile to fixed fluvial network is likely to have occurred during the Middle Pleistocene Transition (MPT, between 0.7 and 1.3 Ma), when long-period/high-intensity climate fluctuations were established in Europe. We estimate that between 2.8–1.15 Ma and present, the incision rates have tripled.
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