SILICEOUS MICROFOSSILS IN THE CALCAREOUS PALEOSOLS FROM FLUVIAL-EOLIAN DEPOSITS OF THE ANGASTACO FORMATION (OLIGOCENE–MIOCENE), SALTA PROVINCE, ARGENTINA

This work reports the first occurrence of siliceous microfossils in the Angastaco Formation (upper Oligocene–Upper Miocene) in the Salta Province, Argentina. Two samples were collected from the Quebrada Escalera section to conduct a prospective analysis for phytoliths in paleosols, aiming to infer paleovegetation and paleoenvironmental conditions. The sedimentary succession comprises ephemeral sheet-like fluvial deposits and fluvial-eolian interaction deposits with calcareous paleosol development on eolian dunes. The microfossil analysis revealed multicellular and unicellular phytoliths, diatom frustules, chrysostomataceae stomatocysts, cutinous epidermal fragments, carbonised microremains, and sponge spicules. The samples showed varied abundances of autochthonous microremains suggesting different hydrological conditions. Sample 2550, with abundant diatoms and stomatocysts, indicates a lentic water environment while sample 2551, rich in sponge spicules, suggests higher energy conditions. The phytolith assemblage, including Poaceae, Cyperaceae, and Arecaceae indicates wet interdune and/or extradune areas.