Palynology of theAcacia-bearing beds in the Komako district, Pohangina Valley, North Island, New Zealand

Abstract

In the Pohangina Valley, north of Ashhurst, upper Nukumaruan-Okehuan sediments, underlain by limestones, mudstones, and sandstones and overlain by sands containing marine fossils, contain pollen of Acacia (represented by its form genus Acaciapollenites) throughout a minimum thickness of 90 m. Ecologically the pollen assemblages consist of coastal swamp sedges together with scrub and grassland species. Inference of a coastal environment is supported by the presence of dinoflagellate cysts of Spiniferites. Tree pollen is relatively rare and trees may have been restricted to the surrounding hills (Ruahine Range). The presence of Acacia and the paucity of tree pollen indicate dry, cool to mild conditions. It is suspected that such conditions extended well north of the study area during late Nukumaruan-Okehuan time.Acacia appeared in New Zealand during the Pliocene, became prominent in the late Pliocene-early Pleistocene, and then became extinct.

Vegetational and climatic history during oxygen isotope stage 7 and early stage 6, Taranaki, New Zealand

“…These pollen assemblages are unusual in that they appear to have no present-day analogue in the region. The presence of an Acaciatype* polyad in one sample is of interest, because the Metrosideros-Leptospermum-type assemblages described here are similar to previously described fossil pollen assemblages from elsewhere that include/Icada-type (Mildenhall 1972(Mildenhall ,1975a(Mildenhall , 1975b. These communities, and the possible presence (and abundance?)…”

Lower Pleistocene Palynomorphs from the Ohuka Carbonaceous Sandstone, South-West Auckland, New Zealand

“…2), is distinctive; it is here tentatively called the Acaciapollenites Assemblage. This assemblage has also been recognised in the Hautawan of Pohangina Valley, north-east of Palmerston North (Mildenhall 1975). Calystegia (Figs 6-8) first appears in the Hautawan but its scarcity precludes it from being a useful stratigraphic indicator; it occurs in the uppermost sample (N55/f767).…”

“…The presence of Nothofagus menziesii with extinct species, including N. "brassi' group pollen, and extant species, including Dodonaea oiscosa, indicates that simple cooling of climate is not the reason for its abundance in the Hautawan. Climatic conditions are known to have been harsh in the Hautawan from the association of Pbyllocladus and Microcachryidites pollen in South Island samples (Mildenhall 1973), but this assemblage has not been recognised in the North Island. These two assemblages are either time-stratigraphic equivalents or else the Acaciapollenites Assemblage is slightly older.…”

“…Since the presence of Acacia in the New Zealand fossil flora was first established by Mildenhall (1972) it has been learnt that the species is an important, although rare, component of coastal Hautawan and Okehuan (lower middle Pleistocene) palynofloras. The Hautawan pollen assemblage, characterised by Triorites waitahuensis Couper (last appearance), Proteacidites minimus Couper (Fig.…”