Lithium isotope evidence for enhanced weathering and erosion during the Paleocene-Eocene Thermal Maximum

Abstract

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.

Swift Weathering Response on Floodplains During the Paleocene‐Eocene Thermal Maximum

“…The >3‰ negative excursion in δ 7 Li clay values in this study is likely driven by changes in weathering resulting from these environmental changes because long‐term sediment aggradation rates (van der Meulen et al., 2020), provenance (May et al., 2013), and δ 7 Li source values remained constant across the PETM (Figure 1b; see Section S1 in Supporting Information ). Notably, the magnitude of this excursion agrees with others from marine shale and carbonate transects that span the PETM (Pogge von Strandmann et al., 2021).…”

“…Altogether, these findings demonstrate that floodplain weathering dynamically responds to climate change and further illustrate the utility of Li isotope ratios in detecting weathering changes in sedimentary archives (Pogge von Strandmann et al, 2021). Unlike weathering on mountain hillslopes, the climatic sensitivity of which is tied to the kinetics of silicate mineral dissolution (Bufe et al, 2021), floodplain weathering involves mineral residence times long enough to counter these dissolution kinetics (Dosseto et al, 2006;Torres et al, 2017).…”

“…Continental erosion rates increased after the onset of the PETM (John et al., 2012; Sharman et al., 2017) which likely enhanced riverine fluxes of OC and dissolved weathering products to the ocean (Hilton & West, 2020). The composition of marine sediments (Dickson et al., 2015; Komar & Zeebe, 2011; Penman et al., 2016; Pogge von Strandmann et al., 2021; Ravizza et al., 2001; Self‐Trail et al., 2012) and models of the carbon and silicon cycles (Komar & Zeebe, 2011; Panchuk et al., 2008; Penman, 2016) corroborate these increases, but comparatively less is known about how or where silicate weathering responded on continents. To improve upon these marine records and model findings, more geochemical evidence from nonmarine sedimentary archives needs to be gathered.…”

The Dissolution of Olivine Added to Soil at 4°C: Implications for Enhanced Weathering in Cold Regions

“…The burial of this organic carbon is also assisted by the supply of continent-derived particulate material (Kennedy and Wagner, 2011). Hence, silicate weathering influences both the inorganic and organic pathways of the long-term carbon cycle, on timescales from yearly (for organic carbon) to tens of kyr (for carbonate precipitation) (e.g., Colbourn et al, 2015;Pogge von Strandmann et al, 2017, 2021a.…”

Shallow Water Records of the PETM: Novel Insights From NE India (Eastern Tethys)

“…(2022) recognize a deepening in the section, although vary slightly in their exact facies determinations. Alternatively, this increase in clay content could also be interpreted as an increase in clay deposition into the region, caused by increased weathering on land across the PETM (Pogge von Strandmann et al., 2021) also supported by abundant microstylolites in the foralgal grainstone‐packstones, coinciding with the advent of the CIE.…”