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.
Sampling large river´s sediment at outlets for cosmogenic nuclide analysis yields mean denudation rates of the sediment producing areas that average local variations in denudation commonly found in small rivers. Using this approach, we measured in situ cosmogenic 26Al and 10Be concentrations in sands of >50 large rivers over a range of climatic and tectonic regimes covering 32% of Earth’s terrestrial surface.River samples were processed in the Helmholtz Laboratory for the Geochemistry of the Earth Surface (HELGES) (von Blanckenburg et al., 2016). 10Be/9Be ratios were measured by Accelerator Mass Spectrometry (AMS) at the University of Cologne and normalized to the KN01-6-2 and KN01-5-3 standards. Denudation rates were calculated using a time-dependent scaling scheme according to Lal/Stone ”Lm” scaling (see Balco et al., 2008) together with a sea level high latitude (SLHL) production rate of 4.13 at/(gxyr) as reported by Martin et al. (2017).Measured in the mineral quartz, the cosmogenic nuclides 26Al and 10Be provide information on how fast Earth´s surface is lowering through denudation. If sediment is however stored in catchments over time spans similar to the nuclides half-lives (being 0.7 Myr and 1.4 Myr for 26Al and 10Be, respectively), the nuclide´s budget is disturbed, and meaningful denudation rates cannot be calculated. The ratio of 26Al/10Be informs us about these disturbances. In 35% of analyzed rivers, we find 26Al/10Be ratios significantly lower than these nuclides´ surface production rate ratio of 6.75 in quartz, indicating sediment storage and burial exceeding 0.5 Myr. We invoke mainly a combination of slow erosion, long transport, and low runoff for these low ratios.In the other 65% of rivers we find 26Al/10Be ratios within uncertainty of their surface production-rate ratio, indicating cosmogenic steady state, and hence meaningful denudation rates can be calculated. For these rivers, we derive a global source-area denudation rate of 140 t/km^2/yr that translates to a flux of 3.10 Gt/yr. By assuming that this sub-dataset is geomorphically representative of the global land surface, we upscale this value to the total surface area for exorheic basins, thereby obtaining a global denudation flux from cosmogenic nuclides of 15.1 Gt/yr that integrates over the past 5 kyr.In Table S1, we provide detailed 10Be nuclide production rates and their correction due to ice shielding and carbonates that are necessary to calculate denudation rates. We provide International GeoSample Numbers (ISGN) for samples used in the analysis, except values that were compiled from published sources. We then compare these denudation rates, converted to sediment fluxes, to published values of sediment fluxes from river load gauging. We find that our cosmogenic nuclide-derived sediment flux value is similar, within uncertainty, to published values from cosmogenic nuclides from small river basins (23 Gt/yr) upscaled using a global slope model, and modern sediment and dissolved loads exported to the oceans (23.6 Gt/yr). In Table S3, we compiled these modern sediment loads and give their references. We also compiled runoff values (mm/yr) from published sources (Table S2) that are used to infer what controls denudation rates.For more details on the sampling and analytical methods, please consult the data description part of this publication.
These datasets were used to evaluate the main controls on last ~6 million years erosion rate variability of the northwestern Himalaya. The Earth’s climate has been cooling during the last ~15 million years and started fluctuating between cold and warm periods since ~2-3 million years ago. Many researchers think that these long-term climatic changes were accompanied by changes in continental erosion. However, quantifying erosion rates in the geological past is challenging, and previous studies reached contrasting conclusions. In this study, we quantified erosion rates in the north-western Indian Himalaya over the past 6 million years by measuring in situ-produced cosmogenic 10Be in exhumed older foreland basin sediments. The 10Be is produced by cosmic rays in minerals at the Earth's surface, and its abundance indicates erosion rates. Our reconstructed erosion rates show a quasi-cyclic pattern with a periodicity of ~1 million year and a gradual increase towards the present. We suggest that both patterns—cyclicity and gradual increase—are unrelated to climatic changes. Instead, we propose that the growth of the Himalaya by repeatedly scraping off rocks from the Indian plate (basal accretion), resulted in changes of its topography that were accompanied by changes in erosion rates. In this scenario, basal accretion episodically changes rock-uplift patterns, which brings landscapes out of equilibrium and results in quasi-cyclic variations in erosion rates. We used numerical landscape evolution simulations to demonstrate that this hypothesis is physically plausible.
Datasets provided here includes summary of the location, depositional age, and stratigraphic position of 41 Siwalik sandstone samples collected from the Haripur section in Himachal Pradesh, India (Dataset S1); 10Be analysis results of Siwalik samples (2021-006_Mandal-et-al_Dataset-S1); sample location and 10Be analysis results of modern river sands from the Yamuna River and its tributaries near the Dehradun Basin (2021-006_Mandal-et-al_Dataset-S2); input parameters for the calculation of paleoerosion rates (2021-006_Mandal-et-al_Dataset-S3); and reconstructed 10Be paleoconcentrations and paleoerosion rates (Dataset S4). Moreover, the data include a compilation of published magnetostratigraphy-derived sediment accumulation rates in the late Cenozoic Himalayan foreland basin (2021-006_Mandal-et-al_Dataset-S5). We also include a movie (2021-006_Mandal-et-al_Movie-S1) that is a complete numerical landscape evolution model run with four consecutive accretion cycles of equal magnitude.
For more information (for e.g., sampling method, analytical procedure, and data processing) please refer to the associated data description file and the main article (Mandal et al., 2021).
Because of the multi-stepped pathways of sediment comprising the foreland fold-thrust belt (FFTB), detrital quartz grains that recycle from the FFTB sources contain cosmogenic radionuclides (CRN), such as 10^Be and 26^Al, accumulated during previous exposure, resulting in inheritance and, hence, anomalously low erosion rates. This inhibits the straightforward use of 10^Be as tracers for modern erosion rates and sediment discharge from the FFTB, prevalent at the external edges of collisional orogens such as the Himalaya. We present a novel approach for quantifying the erosion rates of FFTB by comparing measured and modeled CRN concentrations in fluvial sediments. We apply this approach to the Mohand Range, an emergent fault-related fold in the frontal part of the northwestern Himalaya (see the location map below). The 10^Be and 26^Al datasets presented here were used to calibrate our model, which we used to quantify the erosion rates in and sediment flux from the Mohand Range.
Datasets provided here include a summary of the location and depositional age of 33 fluvial sediments and two sandstone samples collected from the Mohand Range, 10^Be analysis results of 23 of these fluvial sediments and two bedrock samples, and 26^Al-10^Be pair analysis results of the remaining ten fluvial sediment samples (Dataset S1). Moreover, the data include the depositional age map of uplifted older foreland sediments across the western Mohand Range (Dataset 2) and the map of best-fit 10^Be concentration inherited from Himalayan paleoerosion (Dataset 3) and sediment burial in the foreland (Dataset 4). We also include a map of the best-fit 10^Be concentration produced during modern erosion of the Mohand Range (Dataset 5) and a map of the best-fit uplift/erosion rates across the western Mohand Range (Dataset 6).
For more information (e.g., sampling method, analytical procedure, and data processing), please refer to the main article (Mandal et al., 2023).