Biostratigraphy of the Pliocene sequence containing the Hikawera, Missing, Seddelbahr, and Spooner tuff, Wairarapa, New Zealand

Abstract

The associated foraminiferal biostratigraphy of the Spooner, Seddelbahr, Missing, and Hikawera rhyolitic tuffs in the Pliocene of Wairarapa is described. The foraminifera were examined in two sections east of Martinborough, one along Hinakura Road and the other in the head of Whakarua Stream. Correlations were established between the two sections, and with the previously well-studied Mangaopari Stream section. Stratigraphic positions of three evolutionary planktonic foraminiferal datum surfaces were determined, namely the first appearance of GLOBOROTALIA PUNCTICULATA, first appearance of GLOBOROTALIA INFLATA, and last appearance of GLOBOROTALIA PUNCTICULATA. Four local ecologically controlled planktonic foraminiferal zones are in order of decreasing age: 1 - a lower cool-water zone, 2 - GLOBIGERINELLA SIPHONIFERA (relatively warm water) zone, 3 - upper cool-water zone, and 4 - sparse planktonic foraminifera (S.P.F) zone. A few benthonic foraminifera are of some biostratigraphic value. Biostratigraphy enables the Hikawera Tuff to be distinguished from the other three tuffs, by the absence or presence respectively of GLOBOROTALIA INFLATA, but cannot be used to distinguish the other three one from another.