Genesis and evolution of regoliths: Evidence from trace and major elements and Sr-Nd-Pb-U isotopes

Abstract

15Regoliths encompass different materials from the fresh bedrock to the top of the organic 16 horizons. The occurrence and evolution of these materials are determined by deposition, 17 erosion and weathering processes that are specific for each region. The origin and interaction 18 of the regolith layers are still important issues in the study of critical zone functioning. 19Studies that attempt to understand the processes responsible for the structure and the 20 evolution of regoliths often focus either on the soil or on the bedrock compartment, and often 21 from a narrowly focused approach using just a single tool such as major element patterns or 22 mineralogy. This limits the understanding of the complete regolith composition and evolution. 23The present study proposes the combination of mineralogy, major and trace element 24 concentrations, and Sr-Nd-Pb-U isotopes as an extremely useful procedure for tracking the 25 Pleistocene Periglacial Slope Deposits (PPSD). The data allowed the differentiation of three 29 compartments within the regolith: 1) the organic compartment, where low 206 Pb/ 207 Pb and 30 87 Sr/ 86 Sr isotopic ratios reflected the impact of atmosphere-derived components; 2) the PPSD 31 compartment, whose upper horizons were characterised by the presence of atmosphere-32 derived particles rich in Cd, Sn, Sb, Hg and Pb and by relatively low 206 Pb/ 207 Pb and 87 Sr/ 86 Sr 33 ratios, whereas the lower horizons showed Nb enrichments in their matrix and a mineralogical 34 composition pointing to ancient volcanic events; and 3) the weathered slate compartment, 35 whose weathering progression and genetic relationship with the PPSD were particularly well 36 tracked with 87 Sr/ 86 Sr and 143 Nd/ 144 Nd isotope ratios, ( 234 U /238 U) activity ratios and positive 37Ce anomalies. The results prove the efficiency of radiogenic isotopes measurements 38 combined with the analysis of major and trace elements to complete regolith studies. 39Moreover, these isotopes and elements are shown to be potential geochemical tracers of 40 exchange processes at the water-mineral interface. This approach allows for the first time the 41 description of an evolution scheme of a complete slate regolith, which covers a large part of 42 the Rhenish Massif. 43 44

Determination of heavy metals and lead strontium isotope characterization from Merlot soil samples, Dealu Bujorului vineyard

“…Regarding the distribution of U concentration on the depth of the soil profile, it can be observed that with increase of the depth the U concentration from soil decreases, as in the case of Pb. The results agree with Moragues-Quiroga et al [33] 0.03 mg/kg (U); and significantly lower than those obtained by Saat et al [34] 2.21 mg/kg (U).…”

Bedrock geology controls on catchment storage, mixing, and release: A comparative analysis of 16 nested catchments

“…In our study area, Juilleret, Iffly, Hoffmann, and Hissler () have recently shown the potential for soil surveys to add useful and complementary data to existing geological maps. Recent research in the schistous Weierbach catchment by Martínez‐Carreras et al () has revealed the importance of two distinct landscape entities (i.e., plateaus and hillslopes) and their subsequent links to bedrock weathering and soil type (Moragues‐Quiroga et al, ). Their seasonal interplay relative to streamflow generation imparts single‐ or double‐peaked (delayed) storm hydrographs.…”

How Meaningful are Plot‐Scale Observations and Simulations of Preferential Flow for Catchment Models?

“…1). The area is characterized by shallow soils overlying periglacial deposit layers and Devonian slate bedrock (Juilleret et al, 2011; Moragues‐Quiroga et al, 2017). Catchment runoff shows distinct differences between dry and wet catchment states, with single‐peak hydrographs during dry and double‐peak hydrographs (Martínez‐Carreras et al, 2016) under wet conditions.…”