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<p>Cosmogenic nuclide production rates depend on the excitation functions of the underlying nuclear reactions and the intensity and energy spectrum of the cosmic-ray flux. The cosmic-ray energy spectrum shifts towards lower average energies with decreasing altitude (increasing atmospheric depth), so production rate scaling will differ for production reactions that have different energy sensitivities. Here, we assess the possibility of the unique scaling of <span class="inline-formula">³⁶Cl</span> production from <span class="inline-formula">Fe</span> by modeling changes in the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">Fe</mi></msub></mrow><mo>/</mo><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">K</mi></msub></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="63pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="485d52190ee909dfec7a0472ad775cad"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-541-2024-ie00001.svg" width="63pt" height="16pt" src="gchron-6-541-2024-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">Fe</mi></msub></mrow><mo>/</mo><mrow class="chem"><msup><mi/><mn mathvariant="normal">10</mn></msup><msub><mi mathvariant="normal">Be</mi><mi mathvariant="normal">qtz</mi></msub></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="71pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="ee2a1a9371e279dabad9d60553edcaa8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-541-2024-ie00002.svg" width="71pt" height="17pt" src="gchron-6-541-2024-ie00002.png"/></svg:svg></span></span> production ratios with altitude. We evaluate model predictions against measured <span class="inline-formula">³⁶Cl</span> concentrations in magnetite and <span class="inline-formula">K</span>-feldspar and <span class="inline-formula">¹⁰Be</span> concentrations in quartz from granitic rocks exposed across an elevation transect (ca. 1700–4300 <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">m</mi><mspace width="0.125em" linebreak="nobreak"/><mi mathvariant="normal">a</mi><mo>.</mo><mi mathvariant="normal">s</mi><mo>.</mo><mi mathvariant="normal">l</mi><mo>.</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="36pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="d5af2e0a2caa5fbd9f04cb396c6b57b4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-541-2024-ie00003.svg" width="36pt" height="10pt" src="gchron-6-541-2024-ie00003.png"/></svg:svg></span></span>) in western North America. The data are broadly consistent with model predictions. The null hypothesis that <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">Fe</mi></msub></mrow><mo>/</mo><mrow class="chem"><msup><mi/><mn mathvariant="normal">10</mn></msup><msub><mi mathvariant="normal">Be</mi><mi mathvariant="normal">qtz</mi></msub></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="71pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="b4904afedb3a78f3325dc434a19143a8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-541-2024-ie00004.svg" width="71pt" height="17pt" src="gchron-6-541-2024-ie00004.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">Fe</mi></msub></mrow><mo>/</mo><mrow class="chem"><msup><mi/><mn mathvariant="normal">36</mn></msup><msub><mi mathvariant="normal">Cl</mi><mi mathvariant="normal">K</mi></msub></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="63pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="b4f4171c80b1509e144b35d8559da9c3"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-6-541-2024-ie00005.svg" width="63pt" height="16pt" src="gchron-6-541-2024-ie00005.png"/></svg:svg></span></span> production ratios are invariant with altitude can be rejected at the 90 % confidence level. Thus, reaction-specific scaling factors will likely yield more accurate results than non-reaction-specific scaling factors when scaling <span class="inline-formula">³⁶Cl</span> production in <span class="inline-formula">Fe</span>-rich rocks and minerals.</p>