Upper Cretaceous-Cenozoic stratigraphy of the Austral-Malvinas basins in the Fuegian Andes: review and synthesis.

Abstract

Upper Cretaceous-Cenozoic stratigraphy of the Austral-Malvinas basins in the Fuegian Andes: review and synthesis. Based on new field data, biostratigraphy from nannoplankton, dinocysts, mollusks, and vertebrates, as well as zircon U-Pb geochronology,
this study presents a synthesis of the complex Upper Cretaceous–Cenozoic stratigraphy of the Austral and Malvinas foreland
basins in Tierra del Fuego. To simplify the analysis, thirty geological formations are grouped into four higher-rank stratigraphic units
that reflect the major tectonic, sedimentological, and architectural characteristics of the Fuegian Andes' depositional systems during
this time. The orogenic evolution of the Fuegian Andes was punctuated by multiple phases of contractional deformation, associated
with two primary tectonic events: an arc-continent collision and the development of a fold-and-thrust belt. These events generated
four major clastic wedges, bounded by key regional unconformities (u1, u3–u4, and u5), corresponding to the following stratigraphic
groups: i) San Diego Group (Upper Cretaceous–Danian), ii) Río Claro Group (Paleocene–early to middle Eocene), iii) La Despedida
Group (middle Eocene–Oligocene), and iv) Cabo Domingo Group (Oligocene–Miocene). The sedimentary deposits of these groups
are primarily turbiditic, comprising both axial (southeast- and east-directed, parallel to the foredeep) and transverse (northeast- and
north-directed, perpendicular to the foredeep) depositional systems.