@article{fdi:010060454,
  title = {{D}ating chert (diagenetic silica) using in-situ produced {B}e-10 : possible complications revealed through a comparison with {C}l-36 applied to coexisting limestone},
  author = {{Z}erathe, {S}. and {B}raucher, {R}. and {L}ebourg, {T}. and {B}ourles, {D}. and {M}anetti, {M}. and {L}eanni, {L}aetitia},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his paper highlights potential complications that may arise while using in situ produced {B}e-10 to date exposure or burial events using diagenetic silica (chert). {T}he initiation and evolution of large gravitational collapses in sedimentary rocks were constrained using cosmic ray exposure dating. {B}ecause these collapses occurred in a stratigraphic level composed of chert (diagenetic silica) concretions interbedded in limestone layers, their development was studied by performing in situ-produced {C}l-36 and {B}e-10 concentration measurements in both the limestone and coexisting diagenetic silica (chert), respectively. {F}ollowing the routinely used decontamination and preparation protocols for {B}e-10 produced in diagenetic silica, large discrepancies were observed with exposure ages determined by {C}l-36 within carbonate for samples originating from the same scarp. {W}hile {C}l-36 exposure ages were clustered as expected for a unique single gravitational event, {B}e-10 exposure ages were scattered along the same studied scarps. {T}o determine the origin of such a bias, petrological investigations were carried out for chert (diagenetic silica). {T}hin sections highlighted a complex mineralogical texture characterized by remnant silicified ooids showing calcitic cores, calcite inclusions and a dominant amorphous hydrated silica (grain > 20 mu m). {T}o decipher and characterize the potential origins of the excess measured {B}e-10 within diagenetic silica, all samples were first reprocessed following the routine decontamination protocol ({HCL}-{H}2{S}i{F}6 leachings and three partial {HF} dissolutions) but starting from three different grain size fractions ({GS}1: 1000-500, {GS}2: 500 -250 and {G}53: 250-50 mu m). {T}he resulting concentrations clearly showed a decreasing {B}e-10 content as a function of the grain size, but still yielded {B}e-10 exposure ages significantly higher than {C}l-36 counterparts. {B}ecause potential adsorption of {B}e-10 at the surface of amorphous silica grains was suspected, partial dissolution steps following by a leaching step in hydroxylamine were investigated. {F}inally, it seems that an additional leaching in {KOH} allowed removal of the amorphous silica phase and the measured {B}e-10 concentrations yielded {B}e-10 exposure ages agreeing within uncertainties with the {C}l-36 ones. {T}his work suggests that measuring in situ produced {B}e-10 within chert (amongst other types of diagenetic silica, e.g. flint, hornstone, jasper, etc.) containing amorphous silica requires caution.},
  keywords = {{C}osmic ray exposure dating ; {B}e-10 ; {C}l-36 ; {C}hert ; {D}iagenetic silica ; {L}imestone ; {FRANCE}},
  booktitle = {},
  journal = {{Q}uaternary {G}eochronology},
  volume = {17},
  numero = {},
  pages = {81--93},
  ISSN = {1871-1014},
  year = {2013},
  DOI = {10.1016/j.quageo.2013.01.003},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060454},
}