Holocene marine terraces and tectonic uplift in the Waimarama coastal plain, eastern North Island, New Zealand

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Abstract
The Waimamma coastal plain, eastern North Island. New Zealand. is a sheltered progradational plain preserving two marine terraces (terrace I and terrace II) partly overlain by sand dunes. Paleoshoreline heights of terrace I decrease southwards from c. 10 m to 5 m above mean sea level (a.m.s.1.), and those of terrace II decrease from 4 to 1.5 m a.m.s.1. Four radiocarbon dates from tetrace I range from 4300 ± 40 to 5390 ± 120 yr B.P., and shells probably derived from beach deposits underlying terrace I are dated at 4450 ± 30 and 5520 ± 50 yr B.P. Shells from terrace II are dated at 3970 ± 40 yr B.P. The short time interval (c. 300 years) and the height difference (3.5 m) between the seaward part of terrace I and the inner part of terrace II suggest an episodic earthquake uplift of at least 3.5 m. A spread of c. 1200 years in radiocarbon dates for terrace I implies that it took some time for terrace I to emerge entirely, probably as a result of continued crustal uplift. Terrace II probably emerged as a result of the 2300 yr B.P. coseismic event which raised the 25 km long coastal area from Cape Kidnappers to the south of Waimarama. Southward tilt of both marine terraces indicates continued growth of the Kidnappers Anticline.