Magnetostratigraphy and integrated chronostratigraphy of the Eocene–Oligocene in the Austral Basin of Tierra del Fuego, Argentina. Tectonosedimentary and paleoclimatic implications

This study integrates magnetostratigraphy, with previous data of, calcareous nannofossil biostratigraphy, and U-Pb dating to refine the chronostratigraphy of Eocene–Oligocene formations exposed along the Atlantic coast of Tierra del Fuego, in the Austral Basin. The new results establish the age of the Punta Torcida Formation in the early–middle Eocene (∼51-46.2 Ma), the Leticia Formation in the middle Eocene (∼43.2-40 Ma), the Cerro Colorado Formation in the late Eocene to early Oligocene (∼37.9-∼30 Ma, and the Tchat-chii and María Cristina formations in the early Oligocene (∼28.5-? Ma). Correlation among magnetozones, biozones, and absolute ages shows remarkable consistency and reveals significant stratigraphic hiatuses, particularly at the base of the Leticia and Cerro Colorado formations, likely linked to erosional episodes within a compressive tectonic setting. The sedimentary succession records an evolution from slope and siliciclastic shelf marine environments to deeper turbiditic systems accompanied by progressive increase in subsidence. The Eocene–Oligocene transition coincides with tectonosedimentary changes along the southern margin and the global cooling event. Collectively, the data indicate that the depositional history of the María Luisa Sub-basin was controlled by the interplay of compressional tectonics, flexural subsidence, sea-level variations, and global-scale climatic forcing (MECO; Oi-1). This chronological and paleoenvironmental framework provides a robust foundation for future regional correlations in the Austral Basin and adjacent areas of the Southern Hemisphere, particularly across the Eocene–Oligocene transition, where the Cerro Colorado section emerges as a reference for future paleoenvironmental studies.