6 research outputs found
Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum
The Paleocene-Eocene Thermal Maximum (PETM; ~55.9 Ma) was a geologically rapid warming period associated with carbon release, which caused a marked increase in the hydrological cycle. Here, we use lithium (Li) isotopes to assess the global change in weathering regime, a critical carbon drawdown mechanism, across the PETM. We find a negative Li isotope excursion of ~3‰ in both global seawater (marine carbonates) and in local weathering inputs (detrital shales). This is consistent with a very large delivery of clays to the oceans or a shift in the weathering regime toward higher physical erosion rates and sediment fluxes. Our seawater records are best explained by increases in global erosion rates of ~2× to 3× over 100 ka, combined with model-derived weathering increases of 50 to 60% compared to prewarming values. Such increases in weathering and erosion would have supported enhanced carbon burial, as both carbonate and organic carbon, thereby stabilizing climate
Tracing North Atlantic volcanism and seaway connectivity across the Paleocene–Eocene Thermal Maximum (PETM)
Abstract. There is a temporal correlation between the peak activity of the North
Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum
(PETM), suggesting that the NAIP may have initiated and/or prolonged this
extreme warming event. However, corroborating a causal relationship is
hampered by a scarcity of expanded sedimentary records that contain both
climatic and volcanic proxies. One locality hosting such a record is the island of Fur in Denmark, where an expanded pre- to post-PETM succession containing
hundreds of NAIP ash layers is exceptionally well preserved. We compiled a
range of environmental proxies, including mercury (Hg) anomalies,
paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to
trace NAIP activity, hydrological changes, weathering, and seawater
connectivity across this interval. Volcanic proxies suggest that NAIP
activity was elevated before the PETM and appears to have peaked during the
body of the δ13C excursion but decreased considerably during
the PETM recovery. This suggests that the acme in NAIP activity, dominated
by flood basalt volcanism and thermogenic degassing from contact
metamorphism, was likely confined to just ∼ 200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick (> 1 cm) basaltic ashes in the post-PETM strata
likely represent a change from effusive to explosive activity, rather than
an increase in NAIP activity. Detrital δ7Li values and clay
abundances suggest that volcanic ash production increased the basaltic reactive
surface area, likely enhancing silicate weathering and atmospheric carbon
sequestration in the early Eocene. Signals in lipid biomarkers and Os
isotopes, traditionally used to trace paleotemperature and weathering
changes, are used here to track seaway connectivity. These proxies indicate
that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings
reinforce the hypothesis that the emplacement of the NAIP had a profound and
complex impact on Paleocene–Eocene climate, both directly through volcanic
and thermogenic degassing and indirectly by driving regional uplift and
changing seaway connectivity
Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum
The Paleocene-Eocene Thermal Maximum (PETM; ~55.9 Ma) was a geologically rapid warming period associated with carbon release, which caused a marked increase in the hydrological cycle. Here, we use lithium (Li) isotopes to assess the global change in weathering regime, a critical carbon drawdown mechanism, across the PETM. We find a negative Li isotope excursion of ~3‰ in both global seawater (marine carbonates) and in local weathering inputs (detrital shales). This is consistent with a very large delivery of clays to the oceans or a shift in the weathering regime toward higher physical erosion rates and sediment fluxes. Our seawater records are best explained by increases in global erosion rates of ~2× to 3× over 100 ka, combined with model-derived weathering increases of 50 to 60% compared to prewarming values. Such increases in weathering and erosion would have supported enhanced carbon burial, as both carbonate and organic carbon, thereby stabilizing climate
Geochronological data. Tectonic evolution of syn- to late-orogenic sedimentary–volcanic basins in the central Norwegian Caledonides
Geochronological data from LA–ICP–MS analysis of zircons