Rapid cooling of magma-rich margins exemplified by the Eastern North American Margin
Thermal subsidence allows sediment accumulation in passive continental margins, modulating basin development, lithospheric dynamics and Earth-system processes. Classic thermal cooling models underestimate the lithospheric subsidence needed to explain thick early post-rift sedimentary sequences in magma-rich margins. Here we isolate the processes driving this anomalous subsidence at the Eastern North American Margin, a type-example for magma-rich margins. We construct an analytical model simultaneously accounting for non-uniform lithospheric extension, magmatic additions, and variable thermal diffusivity, which controls the rate at which heat spreads through rock. We then calibrate the model parameters against observed sediment and crustal thicknesses across the Baltimore Canyon Trough. Anomalous subsidence can be reconciled if early post-rift lithospheric heat transport is up to 60% faster than typically assumed, particularly at the distal margin edge. We propose that this increase represents hydrothermal fluid circulation enhancing lithospheric cooling during early post-rift periods, offering a new perspective on continental margin evolution.