MAGNETOSTRATIGRAPHIC CHRONOLOGY OF LATE MIOCENE TO EARLY PLIOCENE BIOSTRATIGRAPHIC AND OCEANOGRAPHIC EVENTS IN NEW-ZEALAND

Successions of uplifted shallow marine sediments in New Zealand were a mong the first to provide evidence of latest Miocene climatic deterior ation and were also among the first on-shore successions where late Mi ocene to early Pliocene magnetostratigraphic records were established. A revised chronology of late Miocene to early Pliocene events has bee n determined from new magnetostratigraphic results from two important successions at Blind River and Upton Brook, South Island, New Zealand (lat. 41-degrees 45'S, long. 174-degrees 05'E). Magnetostratigraphic r esults from Upton Brook are the first from strata containing the Kapit ean index mollusks and provide the first reliable estimate of the age of the Tongaporutuan-Kapitean boundary. A coherent chronology from Bli nd River and Upton Brook indicates that two synchronous low sea level and cool paleoclimatic events occurred in the late Miocene Kapitean St age. This inference is supported from other well-known coeval successi ons in the New Zealand region. The revised New Zealand chronology supp orts recent determinations from the Mediterranean that indicate a two- stage ''Messinian salinity crisis'' and a 5.2-Ma age for the Miocene-P liocene boundary. Data from New Zealand, the Mediterranean, and ocean cores around the world suggest that these latest Miocene events are re lated to glacio-eustatic sea level fluctuations. A 6.05-Ma age for the first occurrence datum of Globorotalia conomiozea indicates that sign ificant diachroneity exists in the placement of this datum between the Southwest Pacific and the Mediterranean, confirming the observation t hat G. conomiozea is unsuitable for correlation between ocean basins.