Terrestrial 10Be and electron spin resonance dating of fluvial terraces quantifies quaternary tectonic uplift gradients in the eastern Pyrenees

Abstract

The 120 km-longTêt River flows out of the Pyrenees to the Mediterranean. By displaying a mappable sequence of Quaternary alluvial units between the Pleistocene frontal moraines of the high range and the offshore sedimentary depocentres, its 1400 km 2 watershed is well suited to quantifying gradients of topographic uplift. Five main generations of terrace treads had previously been inferred from constrasts in regolith weathering features, but here we present the first radiometric age constraints based on 15 ESR sediment burial ages covering the full sequence, and 3 vertical TCN age profiles restricted to three midsequence terraces. Analytically robust results were obtained for the oldest and uppermost terrace T5 (ESR age: 1099 ± 179 ka), for T3b (ESR age: 374 ± 47 ka,~MIS 10), and for T2 (ESR age: 174 ± 44 ka,~MIS 6). These results are consistent with the contrasts in weathering grade of the deposits. The TCN profiles only yielded minimum exposure ages but provided precise post-depositional denudation rates for the fluvial terrace treads. The land-to-sea geometry of the chronosequence also provided clues about valley incision rates in response to topographic uplift during the last~1 Ma. Based on a critical review of similar data obtained for other Mediterranean and Atlantic watersheds in the Pyrenees, the full regional correlation reveals that post-orogenic topographic uplift was substantial and relatively uniform throughout the entire mountain range. Patterns and magnitudes suggest a shared, probably subcrustal driving mechanism of Neogene and Quaternary mountain growth, with only subsidiary influence from isostasy, and climatic forcing.

Late Pleistocene‐Holocene Slip Rate Along the Hasi Shan Restraining Bend of the Haiyuan Fault: Implication for Faulting Dynamics of a Complex Fault System

“…CRN dating is nowadays commonly used to infer the ages of alluvial terraces from surface and subsurface samples in a wide range of tectonic and climatic contexts (e.g., Anderson et al, ; Balco et al, ; Delmas et al, ; Gold et al, ; Gosse & Phillips, ; Guilbaud et al, ; Hancock et al, ; Hetzel, ; Lal, ; Le Béon et al, , ; Meriaux et al, ; Perrineau et al, ; Repka et al, ; Saint‐Carlier et al, ; Van der Woerd et al, , ; Yang et al, ; Yang et al, ). At Site S1, we collected quartz‐rich pebbles and cobbles from the terrace surfaces and amalgamated quartz‐rich gravel samples along depth profiles in 2‐ to 3‐m‐deep pits dug within the terraces to measure the concentration of 10 Be and 26 Al.…”

“…CRN concentrations were measured in surface and subsurface samples for four and three terraces, respectively (Figure ; Table ). Comparison between subsurface model age and surface ages distribution helped assess the degree of postdepositional surface modification (e.g., Delmas et al, ; Ryerson et al, ; Saint‐Carlier et al, ). Indeed, classically, model exposure ages from surface samples are interpreted as representing the abandonment age of an alluvial surface, meaning when the surface is no longer permanently flooded.…”

“…A global mean sea level at high latitude spallogenic production rate of 4.01 ± 0.33 at·g −1 ·year −1 for 10 Be (Borchers et al, ) and a 26 Al/ 10 Be spallogenic production ratio of 6.61 (Braucher et al, ) are used to scale the local production rates. The best fit to the samples is obtained by chi‐square minimization following the method described in Yang et al (); see also Hidy et al, ; Borchers et al, ; Saint‐Carlier et al, ; Delmas et al, ). The range of solutions obtained is a proxy for the 1‐sigma confidence level based on analytical uncertainties, which represent internal uncertainties (Figure ; Table ).…”

Mapping a geothermal anomaly using apatite (U‐Th)/He thermochronology in the Têt fault damage zone, eastern Pyrenees, France

“…For the Têt valley low incision rates between 1 and 25 m/m.y. since 6 Ma have been estimated by cosmogenic nuclides (Delmas et al, ; Sartégou et al, ).…”

Tracking geothermal anomalies along a crustal fault using (U-Th)/He apatite thermochronology and REE analyses, the example of the Têt fault (Pyrenees, France)

“…These faults are well expressed near the St-Thomas hot spring cluster (Fig. 3, Taillefer et al, 2017 and2018). In the late to middle Neogene, a global regional uplift of ~1.5 to 2 km associated to thermal erosion of the subcrustal lithosphere is evidenced on the basis of a multi-disciplinary study (Gunnell et al, 2009) and thermochronological study (Fitzgerald et al, 1999).…”