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<p>Cryogenic cave carbonates (CCCs) are a type of speleothem, typically dated with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><mo>/</mo><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="43pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="9d0a396b451698ee2c327cdb6628050e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00004.svg" width="43pt" height="15pt" src="gchron-4-617-2022-ie00004.png"/></svg:svg></span></span> disequilibrium methods, that provide evidence of palaeo-permafrost conditions. In the field, CCCs occur as distinct patches of millimetre- to centimetre-sized loose crystals and crystal aggregates on the floors of cave chambers, so they lack a framework that would allow ages to be validated by stratigraphic order. Correction factors for the initial <span class="inline-formula">²³⁰</span>Th (<span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀)</span> are often based on the bulk-earth-derived initial <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><msup><mo>/</mo><mn mathvariant="normal">232</mn></msup><mi mathvariant="normal">Th</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="61pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="9cdbb0c7f20e3abf3a8f3624d7bcd32e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00005.svg" width="61pt" height="15pt" src="gchron-4-617-2022-ie00005.png"/></svg:svg></span></span> activity ratio (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mo>(</mo><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><msup><mo>/</mo><mn mathvariant="normal">232</mn></msup><mi mathvariant="normal">Th</mi><msub><mo>)</mo><mn mathvariant="normal">0</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="73pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="e034424ea2fde900b35e74597ca7f9b1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00006.svg" width="73pt" height="16pt" src="gchron-4-617-2022-ie00006.png"/></svg:svg></span></span>), which is a well-established approach when <span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀</span> is moderately low. For samples with elevated levels of <span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀</span>, however, accuracy can be improved by constraining <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mo>(</mo><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><msup><mo>/</mo><mn mathvariant="normal">232</mn></msup><mi mathvariant="normal">Th</mi><msub><mo>)</mo><mn mathvariant="normal">0</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="73pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="93d0ed589c89b7b7c56ef82f08a6a24f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00007.svg" width="73pt" height="16pt" src="gchron-4-617-2022-ie00007.png"/></svg:svg></span></span> independently. Here, we combine detailed morphological observations from three CCC patches found in Water Icicle Close Cavern in the Peak District (UK) with <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><mo>/</mo><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="43pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="748535f74c19861e46f83837bf4c6ac1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00008.svg" width="43pt" height="15pt" src="gchron-4-617-2022-ie00008.png"/></svg:svg></span></span> analyses. We find that individual CCC crystals show a range of morphologies that arise from non-crystallographic branching in response to the chemical evolution of the freezing solution. Results of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><mo>/</mo><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="43pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="3b838327a3da28315661f70b328c1f77"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00009.svg" width="43pt" height="15pt" src="gchron-4-617-2022-ie00009.png"/></svg:svg></span></span> dating indicate that samples with a large surface area relative to the sample volume are systematically more affected by contamination with <span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀</span>. By fitting isochrons to these results, we test whether the CCCs in a patch formed during the same freezing event, and demonstrate that <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mo>(</mo><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><msup><mo>/</mo><mn mathvariant="normal">232</mn></msup><mi mathvariant="normal">Th</mi><msub><mo>)</mo><mn mathvariant="normal">0</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="73pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="f00c843c46b636c7675826586840a390"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00010.svg" width="73pt" height="16pt" src="gchron-4-617-2022-ie00010.png"/></svg:svg></span></span> can deviate substantially from the bulk-earth-derived value and can also vary between the different CCC patches. Where CCCs display elevated <span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀</span>, isochrons are a useful tool to constrain <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mo>(</mo><mn mathvariant="normal">230</mn></msup><mi mathvariant="normal">Th</mi><msup><mo>/</mo><mn mathvariant="normal">232</mn></msup><mi mathvariant="normal">Th</mi><msub><mo>)</mo><mn mathvariant="normal">0</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="73pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="d184d9679e21552770c0556509cb5ad1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-617-2022-ie00011.svg" width="73pt" height="16pt" src="gchron-4-617-2022-ie00011.png"/></svg:svg></span></span> and obtain ages with improved accuracy. Detritus absorbed to the crystal surface is shown to be the most likely source of <span class="inline-formula">²³⁰</span>Th<span class="inline-formula">₀</span>. Our results suggest that some previously published CCC ages may merit re-assessment, and we provide suggestions on how to approach future dating efforts.</p>