No abstract

No abstract

Exotic pollen and spores have been found in two drillholes and in a vertical face cut in Quaternary peats in the Chatham Islands. They form an average of 4'5% of the total palynoflora at Te Pukaha and in a drillhole near Mt Dieffenbach, and 10% of the total palynoflora in a drillhole in the southern uplands. The nearest source for this pollen is New Zealand, approximately 725 km to the west. These palynomorphs aid in the pollen zonation of the peats. Similar percentages of pollen, especially of beech and podocarp, in New Zealand peats cannot be used to imply a local presence.

The Cretaceous Kyeburn Fonnation is a 4000-m thick terrestrial sequence dominated by coarse detritus, which was deposited in a fault-angle depression. The distribution of lithofacies, direction of fining and of increasing pebble roundness, nature of clasts, imbrication, and orientation of channels, indicate derivation of the sediment from the southwest and southeast, where the sequence is today bounded by the Dansey Pass and Waihemo Faults. Breccias close to the boundary faults represent talus deposits; alluvial fan, floodplain, and lacustrine deposits occur in successively more distal (northward) parts of the basin. The more distal part of the sequence has scattered carbonaceous material and is dominantly grey in colour; the more proximal part is largely red because of a hematite stain, possibly fanned by post-depositional oxidation of mafic minerals..

At Enderby Island, a deposit of till, here named the Enderby Formation, locally separated into upper and lower members by lenses of laminated lake siltstone, overlies a sequence of flat-lying basalt flows, perhaps benched by ,the sea during an interglacial period of high sea level. Except on the coast these deposits are blanketed by zonal peat, 3 m thick, which contains the record of post-glacial vegetation.The Lower Till was deposited by the extended glacier that spread out from Laurie Harbour, at the head of Port Ross, flowing from the higher parts of the Ross Volcano when sea level was low, presumably during an early stadial of the last (or Otiran) glacial stage.The Laminated Siltstone (5 m), deposited in a pro-glacial meltwater lake dammed by moraine during a lateral swing or temporary retreat of the glacier, is injected by curious carrot-shaped structures of till, each apparently emplaced by the rapid sinking of a ma.'''11 of rock-laden iceberg which penetrated the unconsolidated silts to depths of almost two metres. The emplacement of such "till carrots" was contemporary with deposition of the silt. The ice re-advanced to deposit an Upper Till Member over the underlying members, locally deforming them and picking up siltstone clasts.The Laminated Siltstone and a clast of siltstone from the Upper Till contain pollen 'and spores indicating a cold-climate vegetation of dominant Compositae with associated herbs, grass, sedge and scrub (Coprosma, Dracophyllum, and Myrsine) but lacking Metrosideros and other trees of the present Auckland Island vegetation.The till members may represent two stadials of the last glaciation and the siltstone an interstadial between them, or they may merely represent fluctuations of minor significance.The blanket peat overlying the till sequence has three members, a lower peat with tree stumps, a middle sandy peat containing angular sand 'and subangular basalt clasts (up to 45 cm through), and an upper peat with scattered well-rounded basalt pebbles, identified as seal gastroliths. The sandy peat is tentatively attributed to the influence of blown sand advancing inland when the post-glacial sea (also represented by an elevated beach) first 'approached its maximum level.Four zones in the peat can be defined from pollen analysis. In Zone 1, woody elements (e.g. Myrsine, Coprosma) and Compositae are abundant, with sedge and grass, and at the top of the zone rooted stumps of Dracophyllum (underrepresented by pollen) gave a HC age of 8630 ± 80 yr BP. In Zone 2, Anisotome pollen increases, Myrsine, Coprosma and Olearia-type pollen grains decrease, Dracophyllum enters with various herbs, and persistent grass is dominant over sedge. In Zone 3, Metrosideros pollen is relatively common.Tillaea and sedges rise steeply as grass declines but Myrsine, Coprosma and Dracophyllum decrease. In Zone 4, grass increases once more (with Myosotis and Myrsine) while Bulbinella, Anisotome and woody shrubs decrease.The Metrosideros phase in Zone 3 (reflecting a warm interval from ca. 6000 to 3000 yr ...

No abstract

Boreholes and offshore seismic profile surveys in southern Evans Bay, WelIington Harbour, indicate that a drowned river valley has been partly infilled with sediments during two glacial/interglacial cycles. The original valley was probably eroded along the shatter zone of a late Pliocene fault situated on the eastern side of the bay. The infilling sediments include two assemblages: (I) interglacial age (including Holocene) shelly marine sands and muds, which have a palynoflora from flourishing rimu-podocarp forest, and (2) g1acial age gravelly and carbonaceous terrestrial deposits, wh ich have a palynoflora dominated by grasses or, in slightly milder times, by beech and manuka. Postdepositional deformation of early Holocene sediments may indicate either further faulting along the shatter zone of the Pliocene fault or an effect of sediment compaction during earthquake stress. Deformation of late Holocene sediments is interpreted as differential compaction and slumping being a secondary effect of earthquake shaking.

No abstract