The Pepe Núñez alkaline suite represents the first record of subvolcanic rocks of alkaline affinity in the Norte Basin (southern extreme of the Paraná Basin, Uruguay) [1]. These Late Cretaceous to Cenozoic occurrences comprise nine subvolcanic plugs (Ne-tephrites, alkali trachybasalts, and alkali basalts) that cross-cut the tholeiitic basaltic pile of the Paraná Magmatic Province [2]. This work presents Sr-Nd isotopic data from 30 representative samples to characterize their petrogenesis. Analyses were performed by TIMS (Sr) and ICP-MS (Nd). Initial 87Sr/86Sr (Sri) ratios range from 0.7038 to 0.7044, εNd(i) values range from -0.17 to +1.54. Depleted mantle model ages (TDM) vary between 663 Ma and 885 Ma. Geochemically, the samples form a tight cluster plotting within the Mantle Array, overlapping with the OIB (Ocean Island Basalts) field. Notably, the isotopic signature of these alkaline rocks is clearly distinct from the Low-Ti basalts of the Paraná Magmatic Province, showing no evidence of the significant crustal contamination typically observed in the tholeiitic sequences. The Ne-tephrites show slightly more depleted signatures (εNd(i)= +0.73 to +1.54) compared to the alkali basalts and trachybasalts (εNd(i)= -0.17 to +1.08). The data suggest that the Pepe Núñez Alkaline Suite originated from a mantle source with OIB-like affinity (resembling FOZO-PREMA, or metasomatized SCLM), likely related to partial melting of metasomatized lithospheric mantle or asthenospheric components that ascended rapidly, avoiding interaction with the continental crust.