Rich marine paleobiodiversity and rapid ecosystem changes in the North Alpine Foreland Basin during the Aquitanian (Early Miocene)

Sediments of the North Alpine Foreland Basin preserve evidence of considerable biodiversity, including a wide range of fossil groups that enable paleoenvironmental reconstructions from the land to the deepest marine parts of the basin floor. In this study, we use a multidisciplinary approach to characterize three different lithofacies, all deposited in the deep basin but representing different paleoenvironments. Periods of undisturbed, well-oxygenated conditions hosted a diverse elasmobranch fauna comprising at least eleven genera with different feeding ecological niches and habitat preferences ranging from epipelagic apex-predators (e.g., Galeocerdo) to durophagous bottom dwellers (e.g., Raja) and characteristic deep-marine Squaliformes (e.g., Etmopterus). High-energy deposits alternate with these undisturbed, bioturbated sediments and have led to an accumulation of a typical deep-marine elasmobranch fauna mixed with taxa more characteristic of shelf environments (e.g., Carcharias, Carcharhinus). Periodic increases in nutrient influx promoted pteropod blooms and led to higher plankton productivity, which had severe consequences for demersal life, but enabled pristine preservation of epi- to mesopelagic bony fishes. This Konservat-Lagerstätte not only comprised well-preserved articulated fish skeletal remains, but also preserved fragile plant remains from the hinterland to help infer paleoclimate during the time of deposition. The flora indicates a temperate-subtropical climate, including high precipitation rates during the Early Miocene (Aquitanian).