Professor Kroonenberg’s research spans sedimentary and tectonic geology, with particular emphasis on sea-level variability, coastal and deltaic processes, and the geological evolution of the Guiana Shield. A major focus of his work has been the Caspian Sea, which he has established as a natural laboratory for investigating rapid sea-level fluctuations and their consequences for coastal systems. Through long-term collaboration with Moscow State University, he has investigated solar-forced highstands during the Little Ice Age and longer-term cyclic variations, while his studies of the Volga delta and Caspian barrier coasts have provided important insights into deltaic and coastal sedimentation under rapidly changing base levels. His geological research in Suriname and the wider Guiana Shield has likewise contributed to understanding the Precambrian evolution of the South American basement. His work connects deep-time geological processes with contemporary questions of coastal change and environmental adaptation. His selected publications on Caspian Sea-level dynamics, delta evolution, and the Precambrian geology of the Guiana Shield reflect a career linking fundamental geological reconstruction with a broader understanding of Earth-surface change.