Large local magnetic anomalies observed from measured magnetic properties of pyroxenites of the marginal ultrabasic and basic rocks of the Loch Ailsh alkaline intrusion in the Assynt district of northwest Scotland are not reconcilable with the hypothesis that the intrusion is a stratified laccolith. Rather than a low-angle structure, the intrusion is a steeply dipping sheet at the contact between syenite and limestone country rock. By analogy, similar locally developed anomalies along the southern margin of the Loch Borralan complex are interpreted as due to steeply dipping rocks occupying the same general position between limestone and syenite.

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