Variations in oceanic crustal structure and implications for the fine‐scale magnetic anomaly signal

Abstract

Marine magnetic anomalies are traditionally modelled using a constant thickness source layer, usually defined as the extrusive lavas associated with seismic layer 2A. Recent seismic studies reveal that the thickness of layer 2A can vary by more than a factor of two, an observation which has important implications for the magnetic anomaly source layer. We model deep‐tow magnetometer data from the Endeavour Segment of the Northern Juan de Fuca Ridge, in combination with nearby seismic data and find a positive correlation between the thickness of the seismically‐defined layer 2A and the magnetic anomaly source layer. This suggests that short‐wavelength magnetic anomalies observed within individual magnetic polarity units can arise from variations in the thickness of the extrusives, rather than geomagnetic field variations or secondary magnetization.