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<front>
<journal-meta>
<journal-id journal-id-type="publisher">EGUsphere</journal-id>
<journal-title-group>
<journal-title>EGUsphere</journal-title>
<abbrev-journal-title abbrev-type="publisher">EGUsphere</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">EGUsphere</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub"></issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/egusphere-2026-2284</article-id>
<title-group>
<article-title>Challenges of initial Thorium and Approaches to Robust Speleothem Age Models: A case study from the Yucat&amp;aacute;n peninsula, Mexico</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Schorndorf</surname>
<given-names>Nils</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Warken</surname>
<given-names>Sophie F.</given-names>
<ext-link>https://orcid.org/0000-0002-3339-1488</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Eichstädter</surname>
<given-names>René</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Mielke</surname>
<given-names>Aaron S.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Avilés Olguín</surname>
<given-names>Jerónimo</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Keppler</surname>
<given-names>Frank</given-names>
<ext-link>https://orcid.org/0000-0003-2766-8812</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Hennhöfer</surname>
<given-names>Dominik</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Tec Pool</surname>
<given-names>Fátima</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Evia</surname>
<given-names>Carlos</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Gómez</surname>
<given-names>María José</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Stinnesbeck</surname>
<given-names>Wolfgang</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Frank</surname>
<given-names>Norbert</given-names>
<ext-link>https://orcid.org/0000-0002-0416-9546</ext-link>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Institute of Environmental Physics, Heidelberg University, Heidelberg, 69120 Heidelberg, Germany</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Institute of Earth Sciences, Heidelberg University, Heidelberg, 69120 Heidelberg, Germany</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Museo del Desierto, Saltillo 25022, Coahuila, Mexico</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Grupo Espeleológico Ajau, Merida, Yucatán, Mexico</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>Hessisches Landesmuseum Darmstadt, Friedensplatz 1, 64283 Darmstadt, Germany</addr-line>
</aff>
<aff id="aff6">
<label>6</label>
<addr-line>deceased</addr-line>
</aff>
<pub-date pub-type="epub">
<day>23</day>
<month>04</month>
<year>2026</year>
</pub-date>
<volume>2026</volume>
<fpage>1</fpage>
<lpage>31</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Nils Schorndorf et al.</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2284/">This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2284/</self-uri>
<self-uri xlink:href="https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2284/egusphere-2026-2284.pdf">The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2284/egusphere-2026-2284.pdf</self-uri>
<abstract>
<p>Speleothems, such as stalagmites and flowstones, are invaluable archives of past environmental and climatic conditions due to their layered growth and suitability for precise &lt;sup&gt;230&lt;/sup&gt;Th/U dating. These natural formations record hydroclimatic variability over time, offering insights into how environmental changes have influenced ecosystems and human societies. In the context of Mesoamerica, speleothem records provide an opportunity to explore potential links between climate variability and sociopolitical transformations during Maya cultural evolution. Paleoclimate archives from this region document severe dry conditions during the Terminal Classic Period (&amp;sim;800&amp;ndash;1000 AD), a time marked by societal decline and urban abandonment among the Maya. Yet, existing records often suffer from limited chronological precision, and high-resolution multi-proxy datasets from the area remain scarce. This study presents extensive &lt;sup&gt;230&lt;/sup&gt;Th/U dating of several speleothems from &amp;Aacute;aktun K&amp;oacute;opo Cave, Yucat&amp;aacute;n, revealing continuous carbonate deposition over the past 2.7 kyr, encompassing the entire era of Maya cultural evolution, as well as evidence of speleothem growth during earlier glacial and interglacial periods. High uranium concentrations in the speleothems (averaging 1 ppm) enabled precise dating, despite challenges from elevated and variable detrital thorium contamination. These challenges were addressed by combining multiple techniques, including isochron analysis, stratigraphic approaches, and annual layer counting, to constrain elevated and initial (&lt;sup&gt;230&lt;/sup&gt;Th/&lt;sup&gt;232&lt;/sup&gt;Th) activity ratios. Notably, we infer a high and largely unsystematic variability of high initial (&lt;sup&gt;230&lt;/sup&gt;Th/&lt;sup&gt;232&lt;/sup&gt;Th) activity ratios in space and time, with values spanning between 4 and 68. Still, our approach yields stalagmite chronologies from &amp;Aacute;aktun K&amp;oacute;opo Cave that provide a robust foundation for detailed multi-proxy reconstructions of hydroclimate and vegetation changes over the past 2.7 kyr. These chronologies address a critical gap in high-resolution data for this region and enable future studies to better resolve environmental conditions throughout Maya history.</p>
</abstract>
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<funding-source>Deutsche Forschungsgemeinschaft</funding-source>
<award-id>247825108</award-id>
<award-id>256561558</award-id>
<award-id>497323584</award-id>
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