This dataset contains Beryllium isotope data, pH measurements, and calculations of surface process rates (denudation, weathering, erosion) from soil and drill core samples from the Coastal Cordillera, Chile. All drilling and soil sampling campaigns were conducted in the framework of the “EarthShape” project (DFG SPP1803) from March 2019 to March 2020. Rock and soil samples consist of granitoid lithology that is weathered to different degrees.
We measured the concentration of in situ 10Be in quartz samples from soil samples and calculated denudation rates thereof. Furthermore, we applied a sequential extraction method to analyse meteoric 10Be and reactive 9Be; we also measured residual 9Be and parent bedrock 9Be concentrations. Using the concentration of meteoric 10Be, we calculated the inventory assuming exponential decrease with depth. Finally, we calculated the depositional flux using the in situ 10Be denudation rate and the 10Be(meteoric)/9Be isotope ratio. From reactive 9Be, we calculated the fraction of reactive and dissolved 9Be that we interpret as weathering indicator.
All samples are indicated with a IGSN (International Generic Sample Number) which is a global unique sample identifier. These IGSNs are provided in the data tables and are linked to a short data description in the internet.
We provide sample information and geochemical data for obtaining erosion, weathering, and denudation rates from a framework based cosmogenic meteoric 10Be versus stable 9Be (10Be/9Be) ratios. We modified this published silicate framework (von Blanckenburg et al., 2012) to carbonate landscapes, and performed thorough ground-truthing and testing of assumptions, as this is the first application of the framework for carbonate lithologies. The most important methodological findings are as follows:
1) We amended a sequential extraction step specific for solubilizing total carbonate-bound Be using acetic acid. As this extraction cannot distinguish between secondary and primary carbonate, we employed carbon stable isotopes to obtain the fraction of Be associated with secondary carbonate. We find that >90% of total carbonate-bound Be is bound to secondary carbonate, meaning that distinguishing between secondary and primary carbonate and employing carbon stable isotopes may not be necessary.
2) Using radiogenic strontium isotope ratios we found that about a third of the 9Be contained in secondary carbonate is derived from the dissolution of silicate phases, likely clastic impurities such as clays. These silicate phases also adsorb meteoric 10Be during weathering. The method is thus applicable to pure limestone as well as mixed carbonate-siliciclastic lithologies.
3) Total 9Be concentrations in bedrock are heterogeneous in the Jura, and are potentially controlled by the amount of silicate impurities contained in limestone. Yet the average 9Beparent in summed carbonate- and silicate-bound fractions (0.07 ug/g) is about 9 times lower than values from existing rock databases. In limestones studies, 9Beparent must be thus determined case-by-case on local bedrock.
4) The analysis of partition coefficients Kd for 10Be and 9Be, respectively, and very similar 10Be/9Be ratios show that dissolved Be has equilibrated between reactive (amorphous and crystalline Fe-oxides) and secondary carbonate phases. Secondary carbonate phases are thus part of the reactive Be pool in limestone settings.
5) As in previous studies in silicate lithologies 10Be and 9Be concentrations show pronounced differences between soil and sediment samples that we attribute to grain size dependence and sorting. The 10Be/9Be ratios however cover a remarkably narrow range for all samples, resulting a in narrow range in denudation rates.
6) The fraction of 9Be released by weathering and partitioned into the secondary reactive or dissolved phase serves as a Be-specific proxy for the degree of weathering.
7) The atmospheric depositional flux of 10Be estimated for the Jura mountains from concentrations of dissolved and particulate 10Be and river gauging is about 80% of estimates from independent global GCM-based distribution maps. The GCM estimates thus provide sufficient accuracy.
From application of these new principles, weathering and erosion in the French Jura Mountains can be described as follows: The proportion of weathering in total denudation W/D is >0.9, due to the high purity of the limestone that almost completely dissolved except for a small silicate mineral fraction that, however, carries 50% of the bedrock’s 9Be. Resulting 10Be/9Be-derived denudation rates are on average 300 t/km2/yr for soils and 580 t/km2/yr for river sediments. The soil-derived values agree well with previous estimates from gauging data despite their entirely different (decadal vs. millennial) integration time scales. That sediment-derived denudation rates exceed those from soil we attribute to a 30-60% contribution from subsurface bedrock weathering. On a global scale, our data provides the first cosmogenic-based denudation rates for the precipitation (MAP) range of 1200 to 1700 mm/yr under a temperate climate and dense vegetation cover. Previous millennial-scale denudation rates from in situ-36Cl in calcite from less vegetated sites do not exceed 250 t/km2/yr in this precipitation range. With 500-600 t/km2/yr our denudation rates peak at MAP of 1200-1300 mm/yr, and then show a trend of decreasing D with increasing MAP.
Concentrations of in-situ-produced cosmogenic 10Be in river sediment are widely used to estimate catchment-average denudation rates. Typically, the 10Be concentrations are measured in the sand fraction of river sediment. However, the grain size of bedload sediment in most bedrock rivers covers a much wider range. Where 10Be concentrations depend on grain size, denudation rate estimates based on the sand fraction alone are potentially biased. To date, knowledge about catchment attributes that may induce grain-size-dependent 10Be concentrations is incomplete or has only been investigated in modelling studies. Here we present an empirical study on the occurrence of grain-size-dependent 10Be concentrations and the potential controls of hillslope angle, precipitation, lithology, and abrasion. We first conducted a study focusing on the sole effect of precipitation in four granitic catchments located on a climate gradient in the Chilean Coastal Cordillera. We found that observed grain size dependencies of 10Be concentrations in the most-arid and most-humid catchments could be explained by the effect of precipitation on both the scouring depth of erosion processes and the depth of the mixed soil layer. Analysis of a global dataset of published 10Be concentrations in different grain sizes (n=73 catchments) – comprising catchments with contrasting hillslope angles, climate, lithology, and catchment size – revealed a similar pattern. Lower 10Be concentrations in coarse grains (defined as “negative grain size dependency”) emerge frequently in catchments which likely have thin soil and where deep-seated erosion processes (e.g. landslides) excavate grains over a larger depth interval. These catchments include steep (> 25°) and humid catchments (> 2000mm yr-1). Furthermore, we found that an additional cause of negative grain size dependencies may emerge in large catchments with weak lithologies and long sediment travel distances (> 2300–7000 m, depending on lithology) where abrasion may lead to a grain size distribution that is not representative for the entire catchment. The results of this study can be used to evaluate whether catchment-average denudation rates are likely to be biased in particular catchments.Samples from the Chilean Coastal Cordillera were processed in the Helmholtz Laboratory for the Geochemistry of the Earth Surface (HELGES). 10Be/9Be ratios were measured at the University of Cologne and normalized to the KN01-6-2 and KN01-5-3 standards. Denudation rates were calculated using a time-independent scaling scheme according to Lal (1991) and Stone (2002) (St scaling scheme) and the SLHL production rate of 4.01 at g-1 yr-1 as reported by Phillips et al. (2016)The global compilation exists of studies that measured 10Be concentrations in different grain sizes from the same sample location. We only included river basins of <5000 km2 which measured 10Be concentrations in at least one sand-sized fraction <2 mm and at least one coarser fraction >2 mm. Catchment parameters have been recalculated using a 90-m SRTM DEM.The data are presented in Excel and csv tables. Table S1 describes the characteristics of the samples catchments, Table S2 includes the grain size dependent 10Be-concentrations measured during this study and Table 3 the global compilation of grain size dependent 10Be-concentrations. All samples of this study (the Chilean Coastal Cordillera) are assigned with International Geo Sample Numbers (IGSN). The IGSN links are included in Table S2 and in the Related References Section on the DOI Landing Page. The data are described in detail in the data description file and in van Dongen et al. (2018) to which they are supplementary material to.