Portable X-ray fluorescence identification of the Cretaceous–Paleogene boundary: Application to the Agost and Caravaca sections, SE Spain

It is shown that portable X-ray fluorescence (pXRF) is a powerful tool for the identification and geochemical characterization of prospective Cretaceous–Paleogene (K–Pg) boundary sites. Field measurements in two well-known K–Pg boundary sequences, located at Agost and Caravaca, SE Spain, have been performed. A sizable enrichment around the K–Pg horizon of several elements such as K, Ti, Fe, Ni, Cr, Cu, Zn, As or Pb, together with a strong reduction in the Ca content, is found with the pXRF instrument. These observations represent a primary geochemical signature of the K–Pg boundary in distal marine sections such as those of Agost and Caravaca. Also, the intensities of the pXRF peaks correlate well with elemental composition data obtained by inductively coupled plasma-mass spectrometry (ICP-MS) on collected samples. Hence, the pXRF field measurements are shown to provide fast and useful quantitative information about K–Pg boundary sequences.
Work co-funded by ERDF-EU Ref. CSIC10-4E-141 (XRD-pXRF laboratory) and by ERDF-EU Ref. CSIC08-516 4E-001 (LabGEOTOP infrastructure). This study was carried out within the framework of the Research Consolidated Group GEOPAM (Generalitat de Catalunya, 2014SGR869). VF and JP-C acknowledge support from the Spanish Ministerio de Economía, Industria y Competitividad (FPI grants BES-2012-052366 and BES-2016-076469, respectively).