Geochemical and isotopic characterization of trace fossil infillings: New insights on tracemaker activity after the K/Pg impact event |
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| Affiliation: | 1. Department of Geography, University College London, Gower Street, London WC1E 6BT, UK;2. Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK;3. College of Marine Science, University of South Florida, 140 7th Ave South, St. Petersburg, FL 33701, USA;1. Department of Stratigraphy and Paleontology, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Ap. 644, 48080 Bilbao, Spain;2. Área de Geología, Geomorfología y Cartografía Geológica, Instituto Geológico y Minero de España (IGME), La Calera 1, Tres Cantos, Madrid, Spain;3. C/ Mayor 30, 1°, Jaca, Huesca, Spain;1. Department of Stratigraphy and Paleontology, Faculty of Science and Technology, University of the Basque Country UPV/EHU, Ap. 644, 48080 Bilbao, Spain;2. Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, I-50121 Firenze, Italy;3. PetroStrat Ltd, Tan-y-Graig, Parc Caer Seion, Conwy, Wales LL32 8FA, UK;4. Department of Stratigraphy and Paleontology, Faculty of Science, University of Granada, 18002 Granada, Spain;5. Division of Nuclear Physics, Department of Physics, University of Lund, P.O. Box 118, SE-221 00 Lund, Sweden;1. Smith College, Department of Geosciences, Northampton, MA 01063, USA;2. Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, USA;3. Department of Paleobiology, Smithsonian Institution, Washington, DC 20013-7012, USA;4. Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA;5. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA,02139, USA;6. Department of Earth Sciences, Oxford University, Oxford OX1 3AN, UK;1. Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, Bremerhaven 27570, Germany;2. P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovsky Pr., 36, Moscow 117997, Russia;3. Senckenberg am Meer, German Centre for Marine Biodiversity Research (DZMB), Martin-Luther-King-Platz 3, Hamburg 20146, Germany |
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| Abstract: | Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ13C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ18O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures. |
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| Keywords: | K/Pg boundary Caravaca section Geochemical anomalies Trace fossils Tracemarker recovery Bioturbational disturbance |
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