VOLCANIC HISTORY OF MACAULEY ISLAND, KERMADEC RIDGE, NEW-ZEALAND

Macauley Island (3 km(2)) is the tiny emergent part of the large subma rine Macauley volcano (c. 380 km(2) at the 900 m isobath) on the Kerma dec Ridge. It is composed mainly of are tholeiite basalts, with a sing le interbedded dacite tephra. The oldest rocks seen are subaerial aa f lows (North Cliff Lavas), overlain by basaltic tephra deposits (Boulde r Beach Formation). Continued eruption of thin basalt flows (Annexatio n Lavas) built a large shield volcano, at least 150 m above sea level, with a crater in the vicinity of what is now Mt Haszard. A large erup tion of dacite tephra (Sandy Bay Tephra) caused collapse of the flanks of the submarine volcano, to form a caldera immediately northwest of the present island. Renewed basaltic volcanism produced scoria cones, flows, and tephra (Haszard Formation), and the final stage of this eru ptive phase was associated with the collapse of the northwest edge of the island into the caldera.The freshness of the exposed rocks on Maca uley Island indicates a late Quaternary (possibly Holocene) age for th e whole succession, and this is supported by a radiocarbon date of 631 0 +/- 90 yr B.P. on the Sandy Bay Tephra.