17:15 〜 19:15
[BCG06-P03] Marine osmium isotopic records from the Late Jurassic sediments in the northwestern Tethys
The Earth’s surface experienced several remarkable environmental changes driven by oceanographic shifts associated with the breakup of Pangaea. The Late Jurassic (Oxfordian, Kimmeridgian and Tithonian), in particular, marks a crucial transition towards the Cretaceous greenhouse climate (e.g., Weissert et al., 1996). Reconstructing changes in hydrothermal activity during the Jurassic period is crucial for understanding the linkage between igneous activities and environmental changes during the Jurassic period.
Marine strontium isotope ratios (87Sr/86Sr), reflecting the relative contributions from mantle-derived and continental crustal sources, reached the lowest value during the early Oxfordian, followed by a long-term increasing trend throughout the Late Jurassic (Wierzbowski et al., 2017). This trend is interpreted to reflect either a decrease in seafloor spreading, an increase in continental weathering, or a combination of both.
In contrast, marine osmium isotope ratios (187Os/188Os) have the potential to capture shorter-term fluctuations linked to magmatic or hydrothermal activities, bolide impacts, and rapid shifts in continental weathering. However, osmium isotopic data for the Late Jurassic remain scarce. Existing osmium isotope records from this period are predominantly limited to the Boreal region and are often accompanied by significant chronological uncertainties (e.g., Park et al., 2024), restricting their utility for broader paleoceanographic and paleoenvironmental interpretations.
To address this gap, we present continuous osmium isotopic records from well-preserved sediments in the Lombardy Basin (Breggia section, Switzerland), located within the northwestern Tethysan realm. This represents the first osmium isotopic dataset from the Late Jurassic in this region, providing an opportunity to refine our understanding of Late Jurassic marine geochemistry and environmental change on both regional and global scales. In this presentation, we will present this new dataset and discuss its global and regional implications through comparisons with previous studies.
Marine strontium isotope ratios (87Sr/86Sr), reflecting the relative contributions from mantle-derived and continental crustal sources, reached the lowest value during the early Oxfordian, followed by a long-term increasing trend throughout the Late Jurassic (Wierzbowski et al., 2017). This trend is interpreted to reflect either a decrease in seafloor spreading, an increase in continental weathering, or a combination of both.
In contrast, marine osmium isotope ratios (187Os/188Os) have the potential to capture shorter-term fluctuations linked to magmatic or hydrothermal activities, bolide impacts, and rapid shifts in continental weathering. However, osmium isotopic data for the Late Jurassic remain scarce. Existing osmium isotope records from this period are predominantly limited to the Boreal region and are often accompanied by significant chronological uncertainties (e.g., Park et al., 2024), restricting their utility for broader paleoceanographic and paleoenvironmental interpretations.
To address this gap, we present continuous osmium isotopic records from well-preserved sediments in the Lombardy Basin (Breggia section, Switzerland), located within the northwestern Tethysan realm. This represents the first osmium isotopic dataset from the Late Jurassic in this region, providing an opportunity to refine our understanding of Late Jurassic marine geochemistry and environmental change on both regional and global scales. In this presentation, we will present this new dataset and discuss its global and regional implications through comparisons with previous studies.