Thermal and mechanical constraints on the lithosphere beneath the Marquesas swell

Abstract

The Marquesas Islands, like most active or recently active hotspot chains, lie on anomalously shallow sea floor, and their subsidence history points to a fundamentally thermal origin for the swell¹, as do heat flow and subsidence data for the swells beneath Bermuda² and Hawaii^3,4. Here we apply a new linear filtering technique to geoid height and depth anomaly data over the Marquesas, to constrain the depth to the high-temperature, low-density material responsible for elevating the swell. We determine an isostatic compensation depth of 45±5 km for the swell, and best-fitting values for lithospheric flexural rigidity and island load density of 5×10²² N m and 2,700 kg m⁻³, respectively. The swell's shallow compensation depth and low flexural rigidity call for anomalously high temperatures within the lithosphere^5,6.