Short Organic Carbon Turnover Time and Narrow ¹⁴C Age Spectra in Early Holocene wetland Paleosols

Authors

Lael Vetter, Tulane University
Brad E. Rosenheim, University of South FloridaFollow
Alvaro Fernandez, Tulane University
Torbjörn E. Törnqvist, Tulane University

Document Type

Article

Publication Date

2017

Keywords

ramped PyrOx, radiocarbon, paleosol, soil organic carbon, turnover time

Digital Object Identifier (DOI)

https://doi.org/10.1002/2016GC006526

Abstract

Paleosols contain information about the rates of soil organic carbon turnover when the soil was actively forming. However, this temporal information is often difficult to interpret without tight stratigraphic control on the age of the paleosol. Here we apply ramped pyrolysis/oxidation (Ramped PyrOx) ¹⁴C analyses to evaluate age spectra of transgressive early Holocene paleosols from the Mississippi Delta in southeastern Louisiana, USA. We find ¹⁴C age spectra from soil organic matter (SOM) in both paleosols and overlying basal peats that represent variability in age that is close to, or only slightly greater than, analytical uncertainty of ¹⁴C measurements, despite different sources of carbon with likely disparate ages. Such age spectra have not previously been observed in the sedimentary record. Here they indicate vigorous soil carbon turnover prior to burial, which homogenized ¹⁴C ages within SOM across the entire thermochemical spectrum. The weighted bulk ¹⁴C ages from Ramped PyrOx of paleosols and overlying peats are identical within analytical and process-associated uncertainty, and corroborate ¹⁴C ages from charcoal fragments and plant macrofossils from the overlying peat. The youngest ages from Ramped PyrOx age spectra may also potentially be applied as chronometers for stratigraphic burial ages. Our results suggest rapid turnover (≪300 years) of carbon in these soils relative to input of allochthonous carbon, indicating that the ¹⁴C age of different soil components is decoupled from thermochemical stability and instead reflects vigorous turnover processes. The concurrence of paleosol and peat ¹⁴C ages also suggests that pedogenic processes were linked with the development of coastal marshes, and that the priming effect potentially masked the signal of allochthonous carbon inputs during sea level rise.

Rights Information

This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Geochemistry, Geophysics, Geosystems, v. 18, issue 1, p. 142-155

Scholar Commons Citation

Vetter, Lael; Rosenheim, Brad E.; Fernandez, Alvaro; and Törnqvist, Torbjörn E., "Short Organic Carbon Turnover Time and Narrow ¹⁴C Age Spectra in Early Holocene wetland Paleosols" (2017). Marine Science Faculty Publications. 2431.
https://digitalcommons.usf.edu/msc_facpub/2431