Paired assessments of carbon (d13Clipids) and hydrogen isotopic compositions of leaf-wax lipids (d2Hlipids) from warm intervals in Earth’s history have been used to investigate the relationship between greenhouse gases, hydrological cycle and global warming. Modern studies, however, show that d2Hlipids can exhibit significant variability due to secondary factors including differences in biosynthetic fractionation and 2H-enrichments in soil- and leaf-water. To evaluate the intra-basinal variability of sedimentary compound-specific isotopic records, we generated new carbon and hydrogen isotopic compositions of leaf-wax lipids for the Paleocene-Eocene Thermal Maximum (PETM; ~57 Ma) from Cicogna Creek (Belluno Basin, Northern Italy), and compared results with published PETM records from the proximal Forada Creek section. Similar isotopic trends are observed at both localities. The magnitude of the negative carbon isotope excursion at Cicogna is ~2.5‰. Pre-event 2H-enrichment recorded in the Forada section is missing at Cicogna, likely due to a disturbed interval at the Paleocene/Eocene boundary. A 2H-depletion of ~10-15‰ during the body of the PETM at Cicogna is observed in several PETM sections, implicating a primary change in the global hydrological cycle. Given the proximity of Cicogna and Forada, isotopic compositions of paleo-meteoric water are expected to be similar. However, a ~15‰ offset between the records is apparent. Possible reasons include differences in vegetation, biomarker transport, and precipitation altitude, underscoring the complexity of using a single record for zonal reconstructions and data-model comparisons. Ultimately, this study shows that while 2H/1H-trends can be applied for paleoclimate analysis with reasonable certainty, absolute magnitudes can be biased by secondary local factors

Leaf waxes as recorders of paleoclimatic changes during the Paleocene-Eocene Thermal Maximum: Regional expressions from the Belluno Basin

AGNINI, CLAUDIA
2015

Abstract

Paired assessments of carbon (d13Clipids) and hydrogen isotopic compositions of leaf-wax lipids (d2Hlipids) from warm intervals in Earth’s history have been used to investigate the relationship between greenhouse gases, hydrological cycle and global warming. Modern studies, however, show that d2Hlipids can exhibit significant variability due to secondary factors including differences in biosynthetic fractionation and 2H-enrichments in soil- and leaf-water. To evaluate the intra-basinal variability of sedimentary compound-specific isotopic records, we generated new carbon and hydrogen isotopic compositions of leaf-wax lipids for the Paleocene-Eocene Thermal Maximum (PETM; ~57 Ma) from Cicogna Creek (Belluno Basin, Northern Italy), and compared results with published PETM records from the proximal Forada Creek section. Similar isotopic trends are observed at both localities. The magnitude of the negative carbon isotope excursion at Cicogna is ~2.5‰. Pre-event 2H-enrichment recorded in the Forada section is missing at Cicogna, likely due to a disturbed interval at the Paleocene/Eocene boundary. A 2H-depletion of ~10-15‰ during the body of the PETM at Cicogna is observed in several PETM sections, implicating a primary change in the global hydrological cycle. Given the proximity of Cicogna and Forada, isotopic compositions of paleo-meteoric water are expected to be similar. However, a ~15‰ offset between the records is apparent. Possible reasons include differences in vegetation, biomarker transport, and precipitation altitude, underscoring the complexity of using a single record for zonal reconstructions and data-model comparisons. Ultimately, this study shows that while 2H/1H-trends can be applied for paleoclimate analysis with reasonable certainty, absolute magnitudes can be biased by secondary local factors
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3040769
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