147764 20250107140859.0 doi 10.1007/s00531-021-02091-z sideral 125460 ART-2021-125460 eng Brlek, Mihovil Karst bauxite formation during Miocene Climatic Optimum (central Dalmatia, Croatia): mineralogical, compositional and geochronological perspectives 2021 Access copy available to the general public Unrestricted The Miocene Climatic Optimum (MCO) represents a global warm period (approximately 17‚Äì14.7¬†Ma) interrupting a long-term period of Cenozoic cooling. To elucidate if bauxitization took place in southeastern European mid-latitude areas during the MCO, we studied a section of undated massive karst bauxite (Crveni Klanac, CK) in central Dalmatia, Croatia, hosted in Upper Cretaceous limestones and overlain by Miocene Sinj Basin lacustrine deposits. Integrated mineralogical, morphological and geochemical analyses indicate the predominant mineral phases of the homogenous bauxite matrix are authigenic, subhedral to euhedral kaolinite and gibbsite. The in-situ mineralization was a consequence of pedogenic processes, indicating the CK bauxites formed autochthonously. In situ U‚ÄìPb zircon ages of the lower, middle and upper parts of the CK bauxite are very similar, dominated by Miocene and Oligocene ages, indicating that they all share similar protolith(s). Subsequent high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) analyses indicate a maximum depositional age (MDA) for the pre-bauxitic material of 16.9576 ¬± 0.021¬†Ma (2œÉ uncertainty, incorporating decay constant uncertainty). This MDA, a maximum age of autochthonous bauxitization, coincides with the onset of the MCO. Based on currently available geochronological constraints, the maximum timeframe for CK bauxitization was less than ~ 700¬†ka, which matches the records of the MCO in paleo-mid-latitude Europe. The potential imprint of pre-17¬†Ma bauxitization and contribution of older (i.e., Upper Paleogene) bauxite deposits resedimented to the CK profile, as well as degree of potential parautochthonous origin of the CK bauxites, is yet to be investigated. More than simply aligning with regional and local reconstructions of continental climatic conditions during the onset and the early stages of the MCO, the high degree of autochthony of the CK bauxites provide a precise climatic constraint. For in-situ bauxitization to occur in the southeastern parts of mid-latitude continental Europe, paleoclimatic and paleoenvironmental conditions must have had mean annual temperature greater than 17‚Äì22¬†¬8C and mean annual precipitation of more than 1100‚Äì1200¬†mm. info:eu-repo/semantics/openAccess All rights reserved http://www.europeana.eu/rights/rr-f/ 2.698 2021 GEOSCIENCES, MULTIDISCIPLINARY 114 / 202 = 0.564 2021 Q3 T2 0.859 2021 Earth and Planetary Sciences (miscellaneous) 2021 Q1 4.6 2021 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Gaynor, Sean P. Mongelli, Giovanni Bauluz, Blanca Universidad de Zaragoza (orcid)0000-0002-4970-6333 Sinisi, Rosa Brcic, Vlatko Peytcheva, Irena Mišur, Ivan Tapster, Simon Trinajstic, Nina Laita, Elisa Yuste, Alfonso Universidad de Zaragoza (orcid)0000-0002-2169-4561 Šuica, Sanja Grizelj, Anita Kukoc, Duje Schaltegger, Urs Laita, Elisa Universidad de Zaragoza (orcid)0000-0002-1954-6180 2000 120 Universidad de Zaragoza Dpto. Ciencias de la Tierra Área Cristalografía Mineralog. 110, 8 (2021), 2899-2922 Int. j. earth sci. International Journal of Earth Sciences 1437-3254 1354492 http://zaguan.unizar.es/record/147764/files/texto_completo.pdf Versión publicada 1672348 http://zaguan.unizar.es/record/147764/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:147764 articulos driver 2025-01-07-14:07:07 ARTICLE