Late Cretaceous stratigraphy of northern Chile between 28.5 and 30°S: Record of a greenhouse event during early Andean orogenesis

Abstract

The Late Cretaceous epoch was marked by significant climatic and tectonic events that shaped the evolution of the South American continental margin. In northern Chile, between 28.5° and 30°S, extensive sedimentary and volcanic sequences provide a crucial record of these processes. However, inconsistencies in stratigraphic nomenclature and the lack of precise chronological constraints have hindered a comprehensive understanding of this period. This study presents a revised stratigraphic framework for Upper Cretaceous units in the region, integrating recent geological mapping, U-Pb zircon dating, and new field observations.
Three distinct north-south trending stratigraphic domains are identified, each characterized by unique sedimentary and volcanic successions linked to regional tectonic and climatic events. The study reveals five key evolutionary stages from the Albian to the Maastrichtian, including a transition from marine to continental sedimentation, phases of volcanic activity, and the development of retro-arc basins. Notably, evidence of a previously undocumented marine transgression during the Turonian-Santonian interval suggests the influence of the global Late Cretaceous greenhouse event on sedimentation patterns in northern Chile.
These findings highlight the complex interplay between tectonics, sedimentation, and climate during early Andean orogenesis. The revised stratigraphic framework provides a foundation for future geological studies in the region, improving correlations with adjacent areas and contributing to broader reconstructions of South America's geodynamic evolution during the Late Cretaceous.