Eduardo Alonso-Herrero

Soils play a fundamental role in plant nutrition as primary sources of potassium (K) and magnesium (Mg), whose availability depends on soil properties and environmental conditions. The composition of major cations in the soil solution is governed by interacting factors, including soil texture, acidity, mineralogical composition, and seasonal variability during the growing cycle. This study examines the availability, mobility, and seasonal dynamics of K and Mg in the soil solution of seven naturally managed soils across four distinct periods of a complete growing season beginning in spring. An integrated field and laboratory approach was applied to assess the influence of clay mineralogy on K and Mg behavior and overall soil fertility. Seasonal soil samples were analyzed for mineral composition, total elemental chemistry, exchangeable cation pools, and soil solution chemistry. Total elemental concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS), and clay mineral assemblages were identified by X-ray diffraction (XRD), focusing on 2:1 clay minerals, mixed-layer phases, and hydroxy-interlayered minerals (HIMs). The soils were dominated by 2:1 and mixed-layer assemblages, including illite/smectite (Ill/Sm), mica/illite–vermiculite (M/Vm), and chlorite/smectite (Chl/Sm), as well as transitional HIMs such as hydroxy-interlayered smectite (HIS) and hydroxy-interlayered vermiculite (HIV). Exchangeable Mg (0.28–1.30 cmolc kg⁻¹) and K (0.12–0.97 cmolc kg⁻¹) occurred in relatively high amounts, with maximum base saturation values of 13.14% (Mg) and 4.55% (K). Soil solution concentrations ranged from 1.60 to 3.00 ppm for K⁺ and 0.90–1.70 ppm for Mg²⁺, indicating substantial mobility and enrichment from the solid phase. These findings demonstrate that 2:1 clay minerals and mixed-layer phases act as key reservoirs regulating K and Mg exchangeability and release under natural acidic conditions, thereby sustaining soil fertility and nutrient availability for plant uptake.

This work introduces a comparative collection located in the Prehistory Laboratory at the University of León (Spain) specialised in knappable raw materials, mainly comprising radiolarite and black chert (micro-crypto crystalline quartz), from the western Cantabrian Mountains (north of Iberian Peninsula). A standardised protocol of sample collection and data organisation was developed, which includes the use of several methodologies. First, Geographical Information Systems (GIS) for referencing lithic sources. Second, direct observation of the sample for the macroscopic characterization, both de visu and stereomicroscope. Third, petrographic microscopy for a description of main petrological, and palaeontological features, complemented with the identification of the different minerals that make up the samples by X-ray diffraction (XRD). Forth, X-Ray Fluorescence (XRF), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Thermogravimetry – Differential Scanning Calorimetry (TG-DSC) for geochemical and thermal features of the samples. Finally, the results of these analyses were entered in a database. All this information is contributing towards the creation of a physical reference collection specialised in local Palaeozoic formations (mostly from Devonian to Carboniferous) that outcrop in the western Cantabrian Mountains, a region whose potential resource base was previously not very well known. This collection would allow to compare archaeological lithic remains from different sites inside and outside the Cantabrian Mountains.

A study of the chert nodules found in the Escalada Formation (Carboniferous, Ponga region, Cantabrian Zone) was carried out as a means to characterise a number of lithic raw materials found in several prehistoric sites of the Cantabrian Mountains (NW Spain). This study comprises fieldwork aimed at locating the outcrops and obtaining samples. Some selected samples from two localities were used for both petrological (macroscopic and microscopic analyses from thin sections) and geochemical (X-ray fluorescence and powder diffraction) analysis. The macroscopic study shows a rather homogeneus coloration and a conchoidal fracture although two extreme types of cherts with a variety of intermediate forms can be differentiated according to the matrix composition. The microscopic analysis shows a high heterogeneity in carbonate versus silica percentage and gentle differences in some other features such as type of silica, origin of carbonates, occurrence of organic matter and type of skeletal components. The results of several geochemical analysis suggest that there are not geochemical features neither in the major elements nor in the traces that allows us to clearly distinguish between the analysed samples. All these studies allow us to define the main features of these chert nodules and to establish several types and varieties among them. Those varieties with high percentage of silica and with a more homogeneous matrix are the most suitable samples for knapping. These results together with the study of the geological and geographical location of archaeological sites suggest that the nodules from the Escalada Formation likely were lithic material supply sources used in knapping activitiesWhen aiming to demonstrate the use of these materials at archaeological sites the sole macroscopic analysis of the pieces does not suffice; further analyses, such as those involving thin sections, are necessary. The absence of chert from Escalada Formation in some Mesolithic sites in the area was confirmed via these additional analyses.

The so-called “Mucientes chert" is a variety that appears in the central area of the Iberian North Plateau, in theDueroBasin. It is widely known in the geological and archaeological literature and its use for knapping was especially important in Prehistory. From a macroscopic point of view it is a nodular chert, with white and very porous cortex, and brown to blackish or beige colour in the inner part.In this work we carried out a more accurate petrographic, mineralogical and chemical characterization of this lithology using SEM, XRD and XRF techniques in samples coming from “Las Canteras” (Mucientes village), a chert outcrop of the “Cuestas” Unit (Vallesian-Aragonian, Miocene Age). Also, we have made a review of its geological occurrence and archaeological distribution areas. It is intended to sketch the delimitation of the geographical area of occurrence taking into account the geological and archaeological references.