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<p>During the Early Jurassic, at least two important climate changes were recorded, the Late Pliensbachian cooling event which was followed by the Early Toarcian superwarming interval. This warming interval conditioned a second-order mass extinction. Some other significant events usually concurred this interval, such as the presence of an oceanic anoxic event (TOAE) and a negative carbon isotope excursion (CIE). However, no much research has been carried out concerning the consequences of this warming interval in the atmosphere, such as the evidence of extreme climatic events, linked to the enhancement of the hydrological cycle. For this purpose, 71 trace elements&#xa0;were analyzed on 15 diagenetically screened belemnites from the Rodiles section of North Spain. Several anomalous values were recorded below and above the extinction boundary virtually in all the analyzed elements. Correlation coefficient between the redox sensitive elements (RSEs) as well as many other trace elements respect to aluminium (Al), indicates that these trace elements were mainly derived from terrestrial debris and, consequently, interpretations of the redox conditions from the RSEs are unreliable. The mercury (Hg) anomalies coincide with the anomalies of many other trace elements, suggesting that this element could be derived from terrestrial sources, and probably would not be linked to volcanism, but this possibility cannot be discarded. The increase of nutrient-type elements below the extinction boundary indicates that the substantial decrease or lack of nutrient-type elements cannot be argued to explain this extinction. Selenium (Se) depletion, pointed by previous authors as an important proxy of extinction events, has not been recorded, as Se distribution shows a positive peak value below the extinction boundary, during the extinction interval. Rare earth elements show a very similar trend to the other analyzed elements, a well-marked anomaly immediately below the extinction boundary, and other smaller anomaly located above the extinction boundary, also visible in the Total rare earth elements. Among the calcareous nannofossils, few species experienced size reduction and/or morphological and abundance changes during this time interval. All these events could be linked to accelerate weathering and strong perturbations recorded in the atmosphere in the early stages of the warming processes.</p>

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Extreme climatic events linked to the early Toarcian warming and mass extinction indicated by trace elements distribution in seawater, in North Spain

  • 期刊论文

  • 发表日期：

    2025年4月20日

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  • Juan J. Gómez,
  • Ángela Fraguas,
  • Ricardo L. Silva,
  • Antonio Goy

摘要

During the Early Jurassic, at least two important climate changes were recorded, the Late Pliensbachian cooling event which was followed by the Early Toarcian superwarming interval. This warming interval conditioned a second-order mass extinction. Some other significant events usually concurred this interval, such as the presence of an oceanic anoxic event (TOAE) and a negative carbon isotope excursion (CIE). However, no much research has been carried out concerning the consequences of this warming interval in the atmosphere, such as the evidence of extreme climatic events, linked to the enhancement of the hydrological cycle. For this purpose, 71 trace elements were analyzed on 15 diagenetically screened belemnites from the Rodiles section of North Spain. Several anomalous values were recorded below and above the extinction boundary virtually in all the analyzed elements. Correlation coefficient between the redox sensitive elements (RSEs) as well as many other trace elements respect to aluminium (Al), indicates that these trace elements were mainly derived from terrestrial debris and, consequently, interpretations of the redox conditions from the RSEs are unreliable. The mercury (Hg) anomalies coincide with the anomalies of many other trace elements, suggesting that this element could be derived from terrestrial sources, and probably would not be linked to volcanism, but this possibility cannot be discarded. The increase of nutrient-type elements below the extinction boundary indicates that the substantial decrease or lack of nutrient-type elements cannot be argued to explain this extinction. Selenium (Se) depletion, pointed by previous authors as an important proxy of extinction events, has not been recorded, as Se distribution shows a positive peak value below the extinction boundary, during the extinction interval. Rare earth elements show a very similar trend to the other analyzed elements, a well-marked anomaly immediately below the extinction boundary, and other smaller anomaly located above the extinction boundary, also visible in the Total rare earth elements. Among the calcareous nannofossils, few species experienced size reduction and/or morphological and abundance changes during this time interval. All these events could be linked to accelerate weathering and strong perturbations recorded in the atmosphere in the early stages of the warming processes.