Quaternary sediments and plant microfossils from Enderby Island, Auckland Islands

Abstract

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 ...

Further discussion of Phyllocladus and its pollen in Victoria during the Holocene

“…Similarly low percentages are shown for Nothofagus and Phyllocladus in Churchill and Dodson's (1980) Dodson (1980 p, 281) use the upper two radiocarbon dates to calculate an approximate sedimentation rate of 10 cm every 250 years. On the same basis, it seems reasonable to date the absence of Nothofagus pollen in the Keilambete sediments at 170 cm and 180 cm at approximately 2200 BP-2500 BP This period was clearly not characterized by low Nothofagus percentages at Lake Hordern, Phyllocladus pollen is abundant in the pollen rain over Tasmania (Macphail 1975(Macphail , 1979, and it has a demonstrated capacity to travel many hundreds of kilometres from its source (Moar 1969;Dodson 1976;Fleming et al 1976;Mildenhall 1976;Salas 1983), Macphail (pers, comm,) considers that pollen found in the Tyndall Ranges of western Tasmania, which he refers to the New Zealand taxa Ascarina lucida and Dacrydium bidwilliilbiforme. was more likely to be derived from circumpolar transport than direct westward movement.…”

Reconnaissance sediment and microfossil analyses of a laminated short piston core from Lake Tekapo, South Island, New Zealand

“…Analysis of pollen from the sediments of Lake Tekapo has the potential to provide information on wind strength and direction based on the amount and sources of pollen found in the lake. Long distance dispersal of pollen in the New Zealand area has been recorded by a number of authors since the pioneering studies of Moar (1969b) within New Zealand, and from islands offshore of New Zealand (Moar 1958(Moar ,1969a(Moar , 1970Dodson 1976;Fleming et al 1976;Mildenhall 1976). Previous summaries on this topic have been published by Close et al (1978), Pocknall (1982), and Randall (1990).…”

Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand

“…In contrast, the east coast is dominated by sloping ridges, heavily vegetated valleys, inlets and sheltered fjords. The presence of U-shaped valleys, fjords, and other glacial landforms (Fleming et al, 1976), combined with radiocarbon-dated peat sequences immediately overlying glacial sediments indicates that the east coast of the Auckland Islands was likely glaciated during Marine Isotope Stage 2, and that deglaciation was well underway by 15 000 yr BP (McGlone, 2002;McGlone et al, 2000;McGlone and Moar, 1997). The Auckland Islands are situated at 51 • S, within the modern core of the SHWW in the southwest Pacific Ocean (Fig.…”