Expanding knowledge of hothouse conditions through the study of paleosols in the Southern Golfo San Jorge Basin

Abstract

Hothouse periods, such as the mid-Cretaceous and early Eocene, were times ofglobal warming with high levels of greenhouse gases, elevated temperatures,and ice-free poles that provide a case study for understanding past climatedynamics. This study examines the paleo-Ultisols from the Bajo BarrealFormation (BBF; Cenomanian) and the Las Flores Formation (LFF; early Eocene)in central Patagonia (southern region of the Golfo San Jorge Basin). Due to theirprolonged soil formation, these well-developed paleosols serve as valuableclimate indicators. These paleosols were analyzed using a multi-proxy approachto understand their significance during those two periods in the SouthernHemisphere. The BBF Ultisols (mid-Cretaceous, ~51° paleo-S) display kaoliniterichBt horizons, formed under intense chemical weathering conditions andleaching processes, linked to a temperate and humid climate. On the other side,the LFF Ultisols (early Eocene, ~52° paleo-S) with kaolinite-dominated Bt and/or Btv horizons reflect their formation under higher chemical weathering andleaching processes, under a temperate-tropical and humid climate. For the timesof formation of both BBF and LFF paleo-Ultisols, both localities were withinthe Warm Temperate climate zone. In contrast, this zone currently extends toapproximately 40° N and S latitude. Present-day Patagonia is in the Arid climatezone, with much drier and cooler climate that contrasts with the warmer, wetterconditions of the Cenomanian and early Eocene localities analyzed. Thesefindings highlight significant latitudinal displacement of climate zones duringhothouse periods, emphasizing their importance in understanding past climatedynamics and providing insights into future climate change scenarios.