Cosmogenic in situ 14C-10Be reveals abrupt Late Holocene soil loss in the Andean Altiplano

Abstract

Soil sustainability is reflected in a long-term balance between soil production and erosion for a given climate and geology. Here we evaluate soil sustainability in the Andean Altiplano where accelerated erosion has been linked to wetter climate from 4.5 ka and the rise of Neolithic agropastoralism in the millennium that followed. We measure in situ cosmogenic 14C directly on cultivated hilltops to quantify late Holocene soil loss, which we compare with background soil production rates determined from cosmogenic 26Al and 10Be. Our Monte Carlo-based inversion method identifies two scenarios to account for our data: an increase in erosion rate by 1–2 orders of magnitude between ~2.6 and 1.1 ka, or a discrete event stripping ~1–2 m of soil between ~1.9 and 1.1 ka. Coupled environmental and cultural factors in the Late Holocene signaled the onset of the pervasive human imprint in the Andean Altiplano seen today.

A Combined Cosmogenic Nuclides Approach for Determining the Temperature‐Dependence of Erosion

“…But unlike 10 Be, the contribution of negative muon capture to the total 14 C production rate is higher-around 20% of the total surface 14 C production rate (Lupker et al, 2015). When measured together, the two nuclides can yield additional information about temporal changes in erosion rates, as well as evidence for rapid exhumation events in the past (Hippe et al, 2019(Hippe et al, , 2021. Surficial 14 C/ 10 Be ratios are set by the erosion rate.…”

Transient hillslope erosion in slow evolution landscapes

“…However, their decay constant are of the same order of magnitude, which greatly limits the sensitivity of this system for the identification of transient adjustment conditions (Mudd, 2016). Instead, this has oriented research efforts toward the 10 Be– 14 C pair as the most promising system to resolve recent changes in denudation (Hippe, 2017; Hippe et al, 2021; Skov et al, 2019). Nevertheless, it should be noted that, in the particular case of slowly eroding landscapes, where the 10 Be and 26 Al half‐lives are comparable to the TCN denudation integration timescale, the amplitude of the deviation of the isotopic ratio away from steady‐state denudation predictions may become analytically resolvable (Figure 2).…”

Technical note: A software framework for calculating compositionally dependent in situ 14C production rates

“…25-30 ka (e.g., Briner et al, 2014). In addition, its short half-life means measured concentrations are sensitive only to very rapid erosion rates (e.g., Gosse and Phillips, 2001;von Blanckenburg, 2005;Hippe et al, 2017Hippe et al, , 2021, making many eroding landscape elements good targets for in situ 14 C studies. In situ 14 C is thus emerging as a powerful addition to the CN toolkit.…”