Terra Digitalis

Digital Geological Map of the Upper Laja River Basin, Guanajuato, Mexico

Beatriz Coral Beltrán Martínez — 2023-12-16

A new geological map of the Upper Laja River Basin at 1:200,000 scale is presented, covering an area of ∼11,600 km² in the northern part of Guanajuato. This map was edited based on local and regional geological studies available in the literature, photo interpretations, field verification of contacts and faults and structural data acquisition. The main objective of this map is to provide a regional geological framework for future local geological and hydrological studies in the region. It displays the geology of the basin, divided into seven chronostratigraphic groups, as well as the main faults that shape the basin. In contribution to the geological knowledge of the area, five new U-Pb ages are presented, obtained from samples collected at the eastern and western edges of the basin.

First National Report on Soil Salinity Across Paraguay

Arnulfo Encina Rojas — 2023-12-17

Assessing soil salinity on a national scale provides crucial information on soil fertility. Our objective was to map soil salinity in Paraguay at the topsoil layer (0-30 cm) using indicators such as Electrical Conductivity (EC), pH, and Exchangeable Sodium Percent (ESP). We employed a model with 80 data points for Electrical Conductivity (EC) and 204 points for pH and Exchangeable Sodium Percent (ESP). The statistical model used to map soil salinity properties was the "quantile random forest." For validation and accuracy calculation, we utilized "cross-validation" with all soil sampling sites and a "Random" selection parameter. To ensure result consistency, we repeated the validation five times, calculating the average of the results. Uncertainty was estimated using "predUncertain-quantile random forest," implemented in the R programming language. In general, Paraguayan soils at a depth of 0 to 30 cm exhibit low salt levels, with the soils in the Paraguayan Chaco region showing higher levels. Two primary factors contribute to soil salinity in Paraguay: natural factors, such as a dry climate, high temperatures, and high evapotranspiration, and secondary factors, including soil parent material with alluvial deposits and groundwater with significant salt content. It’s worth noting that actual salinity values, both in Paraguayan Chaco and the eastern region, might surpass those mentioned in this study due to limited available data and the spatial resolution of the map. This study represents the first effort to develop a soil salinity map of Paraguay, providing the initial national baseline for the development of salinity/sodicity monitoring frameworks. It can be instrumental in addressing regional gaps in salinity/sodicity within South America.

From Rheic ocean opening to Pangea breakup: a chronostratigraphic and isotopic database of key localities in Mexico

Luigi A. Solari — 2023-12-17

This database includes a wealth of geochronologic, isotopic, and provenance data, published or in publication, which constitutes an effort to unravel the evolution of Mexican, pre-Cretaceous geological units that are key in reconstructing the history of the Rheic Ocean, from its opening to its closure, and the initial breakup of Pangea. The database is built on reference geological maps, that the authors compile from published works and that locally, contain novel cartographic data. Since the localities studied in this work contain successions that are different in age, P-T conditions, lithology, and geologic significance, and given that each stand-alone work (research, undergraduate and graduate theses, etc.) focused on resolving the central theme of the Rheic ocean evolution and Pangea amalgamation and breakup, we generate an open database that will be continuously updated, as soon as new data are available. Initially intended as a database to present the results of several present and previous grants obtained by the authors, and make them available to collaborators, this contribution evolved to be an open source for all the researchers that are interested in the Paleozoic–early Mesozoic Mexican tectonic evolution and the pre-Mesozoic basement characterization.