A swarm of basic dikes (dolerites, quartz dolerites, and camptonites) occurs in the Awatere valley, in the northeastern part of South Island, New Zealand. The dikes, up to two feet in thickness, were intruded vertically into unconsolidated sediments of Cretaceous age. Probably more than 500 dikes make up the swarm, the only regional one known in New Zealand. Evidence points to their intrusion parallel to the direction of principal horizontal stress. The attitude of the dikes has been modified by compaction of the sediments subsequent to intrusion, with marked differences between sandstones and mudstones, regional folding, and bedding-plane slip.