36Cl production rate from K‐spallation in the European Alps (Chironico landslide, Switzerland). (July 2014)

• Record Type: Journal Article
• Authors: SCHIMMELPFENNIG, IRENE; SCHAEFER, JOERG M.; PUTNAM, AARON E.; KOFFMAN, TOBY; BENEDETTI, LUCILLA; IVY‐OCHS, SUSAN; TEAM, ASTER; SCHLÜCHTER, CHRISTIAN
• Is Part Of: Journal of quaternary science. Volume 29:Number 5(2014)
• Page Start: 407
• Page End: 413
• Publication Date: 2014-07
• Subjects: Geology, Stratigraphic -- Quaternary -- Periodicals; Paleontology -- Quaternary -- Periodicals; 551.79
• DOI: 10.1002/jqs.2720
• Languages: English
• ISSNs: 0267-8179

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>ABSTRACT</title> <sec id="jqs2720-sec-0001" sec-type="section"> <p>The abundant production of <italic>in situ</italic> cosmogenic <sup>36</sup>Cl from potassium renders <sup>36</sup>Cl measurements in K‐rich rocks or minerals, such as K‐feldspars, potentially useful for precisely dating rock surfaces, either in single‐nuclide or in multi‐nuclide studies, for example combined with <sup>10</sup>Be measurements in quartz. However, significant discrepancies in experimentally calibrated <sup>36</sup>Cl production rates from spallation of potassium (<sup>36</sup>P<sub>K‐sp</sub>), referenced to sea‐level/high‐latitude (SLHL), limit the accuracy of <sup>36</sup>Cl dating from K‐rich lithologies. We present a new <sup>36</sup>Cl calibration using K‐feldspars, in which K‐spallation is the most dominant <sup>36</sup>Cl production pathway (>92% of total <sup>36</sup>Cl), thus minimizing uncertainties from the complex multi‐pathway <sup>36</sup>Cl production systematics. The samples are derived from boulders of an ∼13.4 ka‐old landslide in the Swiss Alps (∼820 m, 46.43°N, 8.85°E). We obtain a local <sup>36</sup>P<sub>K‐sp</sub> of 306 ± 16 atoms <sup>36</sup>Cl (g K)<sup>−1</sup> a<sup>−1</sup> and an SLHL <sup>36</sup>P<sub>K‐sp</sub> of 145.5 ± 7.7 atoms <sup>36</sup>Cl (g K)<sup>−1</sup> a<sup>−1</sup>, when scaled with a standard scaling protocol ('Lm'). Applying this SLHL <sup>36</sup>P<sub>K‐sp</sub> to determine <sup>36</sup>Cl exposure ages of K‐feldspars from <sup>10</sup>Be‐dated moraine boulders yields excellent agreement, confirming the validity of the new SLHL <sup>36</sup>P<sub>K‐sp</sub> for surface exposure studies, involving <sup>36</sup>Cl in K‐feldspars, in the Alps.</p> </sec> </abstract>