Thermomechanical Analysis of the Louisville Seamount Chain: Implications for Late Cretaceous Pacific Plate Evolution

Abstract

We calculated elastic thickness (T_e), flexural deflection, and gravity anomalies of the oceanic lithosphere beneath 14 seamounts of the Louisville Seamount Chain to investigate seamount formation timing and tectonic settings. Using dense core modeling to approximate seamount mass, we compared T_e estimates with plate age at loading time. The northwestern seamounts (T_e = 6–8 km) formed over the Louisville hotspot earlier than age-dated volcanism, consistent with Osbourn Trough tectonic motion. The middle seamounts (T_e = 18–28 km) formed on lithosphere with consistent thermal age of 45 Myrs at loading time. The southeastern seamounts (T_e = 4–12 km) formed on lithosphere with similar thermal age, with elastic thickness reduced by additional thermal stress from juxtaposed younger lithosphere across fracture zones. This consistent loading age (∼45 Ma) across both middle and southeastern groups indicates limited Louisville hotspot motion during seamount formation. Based on our T_e estimates and thermal age patterns, we determined that the oceanic lithosphere beneath the middle section was produced by Late Cretaceous spreading centers between 105 and 84 Ma, providing new constraints on Pacific plate reconstructions during the Cretaceous Normal Superchron when traditional magnetic anomaly dating methods are limited.