The aeromagnetic map (Fig. 9) shows the extent and structure of the magnetic dolerite sill (the irregular features) and the effect of two deep-seated magnetic sources, giving low-gradient, rounded anomalies to the west and south. The southern anomaly is spatially associated with the Alno alkaline intrusives. Outside to the north and south of the Avike Bay structure, high gradient northeast-skewed anomalies reflect the low inclination angle of the total magnetization vector and the shallow dip of the sill. Within the bay, the anomalies are subdued and have northwest skewing, indicating a larger depth and a different direction of the total magnetization vector, respectively. Roughly coincident with the present shoreline, the magnetic anomaly is discontinuous, marking the onset of significant subsidence. There are several options for the interpretation of the interior magnetic features of the bay (see discussion).
The presently available gravity data indicate a weak gravity low over the bay area and a predominant high to the west of the bay, which is also seen in the aeromagnetic map.
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