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

Abstract

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 a...