Quaternary surfaces and sediments at Waihi Beach

Abstract

Levelling, accurate to 1 ft in height, of coastal terraces in the Waihi Beach area, has indicated past sea levels at 6–10 ft (Waihi Beach Surface, 50–100% preserved), 15–20 ft (Ocean View Surface, about 30% preserved); c.60–70 ft (Athenree Surface, about 15% preserved), and c.110–115 ft (unnamed, preserved solely as accordant ridges) above present sea level. Less accurate levelling by an aneroid barometer showed bench remnants at c.340–390 ft and c.550 ft. (Values indicated by “c.” were calculated using the arbitrary assumption that the positions of present and past coastlines were identical). The correlation of levels with those previously established at South Kaipara, is sufficiently good to assume that the Waihi Beach area was relatively stable in at least the late Pleistocene, and to correlate the indicated sea levels with the Post-glacial (6–10 ft), Late Monastirian (15–20 ft), Main Monastirian (c. 60–70 ft), Tyrrhenian (c.110–115 ft), Sicilian (c.340–390 ft), and Calabrian (c. 550 ft) of Europe. The formations are named after the surfaces below which they accumulated by aggradation, and consist of locally derived clays and sands, with angular pebbles near the hills, rounded pebbles in the river valleys, and dune sands at the coast.