A continental-scale Eurasian ice sheet 2.4 million years ago

Understanding when ice sheets first developed over the continents is essential for attributing ice volume to marine records of global sea-level change. We resolve a long-standing terrestrial-marine mismatch in the timing of the first Eurasian Ice Sheet (EIS) expansion by dating the earliest glaciogenic unit in northwest Europe, the Hattem Bed Complex (HBC). Paired cosmogenic ²⁶Al-¹⁰Be burial dating and detrital zircon fingerprinting indicate that glacially-derived Fennoscandian gravels reached the Netherlands ${2.41}_{-0.29}^{+0.51}$ Ma, while ages from the overlying Appelscha Formation record a second EIS advance and attendant shutdown of the Baltic River System ${1.72}_{-0.25}^{+0.25}$ Ma. Cyclic stratification of the HBC could reflect freshwater discharge to the North Atlantic associated with episodic disruption of meridional overturning circulation. The timing of the first trans-Baltic EIS overlaps the Laurentide Ice Sheet maximum ( ${2.42}_{-0.14}^{+0.14}$ Ma), underscoring substantial Northern Hemisphere ice growth more than a million years prior to the Mid-Pleistocene Transition.