This data publication is supplementary to a study on the effect of the formation of cation-rich authigenic aluminosilicate clays during the early diagenesis of detrital sediments on the seawater lithium isotope composition by Läuchli et al., (2025).
The dataset contains elemental ratios and lithium isotope ratios from (1) river sediments sampled in March 2019 the vicinity of the coastline, (2) marine surface sediments from Multlicorer sampling device from the R/V Sonne Cruise SO156 and the R/V Sonne Cruise SO102 and (3) marine samples from the gravity core sites GeoB 7139-2 (R/V Sonne Cruise SO156), GeoB 3304-5 (R/V Sonne Cruise SO102) and 22SL (Sonne Cruise SO161-5).
The dataset is provided here as a single .xlsx file containing one data sheet. Metadata including International Generic Sample Numbers (IGSNs) are provided for each sample.
The data were acquired as part of the German Science Foundation (DFG) priority program SPP-1803 “EarthShape: Earth Surface Shaping by Biota” initiated and lead by Friedhelm von Blanckenburg and Todd Ehlers. The GeoB cores samples were provided by the MARUM Research Center (Bremen). The 22SL Gravity Core was stored and supplied by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR, Hannover).
The adsorption of boron on detrital particles like clay or metal oxides is thought to be a major mechanism driving changes in the boron isotopic composition of seawater on geologic timescales. However, the sensitivity of adsorption parameters to long-term changes in the seawater concentration of major ions (Mg2+, Ca2+, SO42-) and dissolved inorganic carbon (HCO3-, CO32-) is not known. We conducted multiple sets of adsorption experiments that consist of suspending pretreated clay minerals (either kaolinite, smectite or illite) in artificial seawater with a modified chemical composition. Specifically, we investigate adsorption in seawater with a major ion composition resembling that of the Cretaceous (100 Ma) and the Eocene (50 Ma), as well as modern seawater with either reduced or elevated concentrations of dissolved inorganic carbon. We finally combine the results with modeled values for the mineral assemblage of detrital sediment to constrain boron adsorption fluxes in the past. The dataset consists of two sheets that store (1) the results of our adsorption experiments and (2) the modeled sediment properties.
Experiments were performed on KGa-1b kaolinite, SWy-3 smectite and IMt-2 illite obtained from the Clay Mineral Society. For each of these clays, a consistent particle size fraction of 2 – 0.2 μm was extracted by repeated centrifugation and decantation. As a result, clay samples used in the experiments have a high mineralogical purity of 95% (in the case of kaolinite and illite) and 50% (in the case of smectite).
Pretreated clays were submerged in one of four different boron-containing artificial seawater solutions. These seawater solutions were prepared by mixing trace element-grade salts with ultrapure water according to the recipe of Millero (2013). Specifically, the amounts of added MgCl2, CaCl2, Na2SO4 and NaHCO3 were varied to produce four different seawater stock solutions that have (i) a major ion concentration similar to Eocene seawater; (ii) a major ion concentration similar to Cretaceous seawater; (iii) a DIC concentration half as high as in modern seawater; (iv) a DIC concentration twice as high as in modern seawater. Clay and seawater were allowed to interact for 48h through continuous agitation, after which solution samples were extracted.
As reverse weathering has been shown to impact long-term changes in atmospheric CO2 levels, it is crucial to develop quantitative tools to reconstruct marine authigenic clay formation. We explored the potential of the beryllium (Be) isotope ratio (10Be/9Be) recorded in marine clay-sized sediment to track neoformation of authigenic clays. The power of such proxy relies on the orders-of-magnitude difference in 10Be/9Be ratios between continental Be and Be dissolved in seawater. On riverine and marine sediments collected along a Chilean margin transect we chemically extracted reactive phases and separated the clay-sized sediment fraction. We compare the riverine and marine 10Be/9Be ratio of this fraction. Moreover, we compare the elemental and mineralogical composition and the Nd and Sr-isotopic composition of these samples. 10Be/9Be ratios increase four-fold from riverine to marine sediment. We attribute this increase to the incorporation of Be high in 10Be/9Be from dissolved biogenic opal, which also serves as a Si-source for the precipitation of marine authigenic clays. 10Be/9Be ratios thus sensitively track reverse-weathering reactions forming marine authigenic clays.