Fig 1.
Spatial distribution of geological units.
Geological sketch map of the studied area based on the available geological map of Bertolini (1995; Mapa Geologico de la Provincia de Entre Ríos, 1:500000), Rimoldi (1999; Mapa Geologico y Minero de la Provincia de Buenos Aires, 1:750000), Pereyra et al. (2005, Hoja Geologica 3360IV, Gualeguaychù, 1:250000, 2) and Loureiro Olivet et al. (2024, Actualización de la Carta Geológica del Uruguay a escala 1:500.000, Ministerio De Industria, Energía Y Minería, Dirección Nacional De Minería Y Geología) [55,56,59,62]. Quaternary Sediments, Fluvial Uruguay River, Actual Delta, Inner Delta, Holocene Delta Sand Bars, Coastal Deposits, F. Querandi and F. Junin are Holocene. F. Tezanos Pintos, F. Buenos Aires, F. Hernandarias and F. Ensenada are Pleistocene. F. Ituzaingo is Pliocene. F. Camacho is Miocene. F. Fray Bentos is Oligocene.
Fig 2.
Strontium isotope distribution results.
Geographical distribution of new and literature samples in the studied area coloured based on 87Sr/86Sr values.
Fig 3.
87Sr/86Sr distribution across latitude, longitude, and geological units.
87Sr/86Sr values of samples used for the model along latitude and longitude and divided for geological units as in Table 1. Plio. is for Pliocene, Mio. is for Miocene, Ol. is for Oligocene and Cre. is for Cretaceous.
Table 1.
Sr isotopic data by geological formation. Average Sr isotopic data of modern samples collected for this study for main geological formations. The order is based on stratigraphic positions.
Fig 4.
Spatial distribution of strontium isotopes in the Paraná Delta and surrounding areas.
Isoscape RF model (a) and associated spatial uncertainty map (b).
Fig 5.
Predictive variables and model accuracy in Sr Isoscape analysis.
Cross-validation scatterplots of observed vs. predicted values for the test–validation sample splits, Increase in Mean Squared Error (%IncMSE), Increase in Node Purity (IncNodePurity) and most predictive variables from Bataille et al. (2018; 2020) [18,43]: r.elevation is referred to SRTM topography (m), r.bulk is Bulk Density (kg*m−3), r.fert is Global Fertilization, r.dust is Multi-models average (g.m−2.yr−1), r.pet is Global Potential Evapo-Transpiration, r.cec is Cation Exchange Capacity. Other variables in Bataille et al. (2018; 2020) [18,43] and Reich et al. (2024) [71].
Fig 6.
Estimating mobility for Arroyo Fredes individuals.
Geographic origin probability estimated for two individuals from Arroyo Fredes, following the protocol described in Ma et al. (2020) [95]. Probability estimates (i.e., cell values) are scaled between 0 (low probability, purple) and 1 (high probability, yellow).