Terrace types and vegetation dynamics on Macquarie Island

Selkirk, PM; Adamson, DA; Seppelt, R. D.

doi:10.26749/rstpp.122.1.59

Cited by 7 publications

(14 citation statements)

References 2 publications

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“…Notwithstanding this fact, we consider it unlikely that wind can have a major role in accounting for the curious side slopes of 6–15° along the length of the terraces. We have no explanation for this phenomenon and neither did Selkirk et al (1988), who also described a slight side slope of 0–5° along the length of the solifluction terraces on Macquarie Island.…”

Section: Discussionmentioning

confidence: 82%

“…For example, the localized area of solifluction terraces in the mid‐alpine zone on the Martial Mountains are similar to those recorded above 200 m a.s.l. from Macquarie Island, which is at approximately the same latitude (Taylor 1955; Löffler et al 1983; Selkirk et al 1988), and has generally similar climatic conditions (Selkirk et al 1990). Although the Macquarie Island terraces are on a much larger areal scale, the individual terraces, which are 1–2 m high (exceptionally up to 6 m) are of similar dimensions to those in the Martial Mountains.…”

Section: Discussionmentioning

confidence: 99%

“…Löffler et al (1983) interpreted the Macquarie Island terraces as essentially relics of periglacial phenomena, whereas more recently, Selkirk et al (1988, 1990) present evidence for their current activity. We believe the solifluction terraces in the present study are currently active through frost‐sorting.…”

Section: Discussionmentioning

confidence: 99%

“…This process would move the larger stones to the surface as well as down‐slope across the gently sloping terraces toward the crest of the next vegetated riser. Some stones may be forced onto the plant cover of the riser, as also occurs through needle ice action on Macquarie Island (Selkirk et al 1988, 1990). Beneath the vegetation on the risers, the dark brown, organic‐rich soil with some profile development contrasts with the relatively uniform, light yellow‐brown colour of the solum beneath all four non‐vegetated zones on the terraces and further indicates current frost activity in the latter.…”

Section: Discussionmentioning

confidence: 99%

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Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina

et al. 2001

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The alpine zone is examined at meso‐ and microscales in southern Tierra del Fuego (54°49′S), where the full zone is expressed. Mesoscale patterns were studied on opposing aspects, and microscale patterns were studied on a series of solifluction terraces, in a hanging valley overlooking the Beagle Channel. Plant cover and life form data were collected within 50‐m altitudinal bands on north and south aspects and comprehensive plant lists were compiled for each band. Topography and associated surface cover were recorded on the terraces. Six alpine plant communities, in lower and upper floristic zones, were differentiated with multivariate analyses and significantly related to five ecological factors. Equivalent communities were separated by approximately 185 m altitude on opposing aspects, which related to a soil temperature difference of approximately 3.0°C. The richness (and range) of 80 local vascular taxa (18.6% of the regional flora), decreased with increasing altitude (6.6 per 100 m); however, richness differed significantly with aspect (north: 5.6, south: 7.5). Upper altitudinal limits (approximately 1250 m a.s.l.), were associated with a midsummer isotherm of approximately 1.7°C. Chamaephytes and hemicryptophytes dominated throughout but the tall tussock form was conspicuously absent. Reasons for this are discussed in the context of the Nothofagus treeline, which conformed to a midsummer isotherm of only approximately 6.0°C. Such patterns are at variance with those found in the oceanic subantarctic islands, other oceanic perhumid temperate mountain regions and tropical high mountains. However, the microscale pattern of fines, pebbles, stones and rock across the active solifluction terraces, with dense vegetation on their steep risers, had a clear affinity with that of other subantarctic regions. Inferences that alpine systems of the Southern Hemisphere are necessarily equivalent to those at similar northern latitudes are cautioned against. Likewise, such comparisons within the Southern Hemisphere may also be invalid.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina

et al. 2001

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“…The assumption is also made that the beaches preserved on the island represent the major transgressions of the middle and late Quaternary, and that none are missing, with the partially exposed marine terrace close to present sea level representing the postglacial transgression between about 18 and 6 ka (Adamson et at. 1988, Selkirk, P.M. et al 1990a). As we know of 17 raised beaches between 50 m and 260 m a.s.L on Macquarie Island, we assume that the major episodes onate Pleistocene high sea level are represented by topographic features in our data set.…”

Section: Cross-matching the Timing Of High Global Sea Levels With Thementioning

confidence: 99%

Pleistocene uplift and palaeoenvironments of Macquarie Island: evidence from palaeobeaches and sedimentary deposits

Adamson¹,

Selkirk²,

Price³

et al. 1996

PPRST

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Macquarie Island (54°30'5, l 59°00'E) is an emergent part of the Macquarie Ridge Complex composed of ocean-floor rocks of Miocene age now 4000 m above the ocean floor. A number oflandforms, including palaeobeaches now above sea level (a.s.l.)on Macquarie Island, were formed by marine erosion during uplift of the island. During the last Pleistocene period oflow sea level (c. 20 ka) the island was three times larger than now. Thermoluminescence (TL) dating of two palaeobeaches indicates Pleistocene ages: 172 ± 40 ka for one at 100 m a.s.l. and 340 ± 80 ka for another at 263 m a.s.l. Matching the altitude sequence of palaeobeaches on Macquarie Island with the pattern of peaks in world sea level determined from deep sea cores allows an independent estimate of beach ages. Comparison of the altitude and sea level sequences most plausibly places the 100 m palaeobeach in Oxygen Isotope Stage Se (130-125 ka) and the 263 m palaeobeach in Stage 9 (340-330 ka), matching reasonably with the TL dates. Other palaeobeaches at about 50 m and 170-190 m a.s.l. then correlate with high sea levels. We calculate an average rate of uplift for the island of0.8 mma-1 • At this rate, 4000 m of Macquarie Ridge uplift would have taken about five million years and the top of the island may fi rst have emerged some 700 to 600 ka. During the six Pleistocene glacial interglacial cycles since then, there has been periglacial rather than glacial activity on cold uplands, but conditions suitable for vegetation of the present type persisted close to sea level.

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Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island

Kiernan¹,

McConnell²

1999

Australian Geographer

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The geomorphology of Heard Island± McDonald Island is primarily the product of close interplay between volcanism, glaciation, and vigorous marine processes in a stormy sub-Antarctic environment. The dominant landform is the strato-volcano Big Ben (2745 m), which is the highest mountain on Australian territory outside Antarctica. Other volcanic landforms include scoria cones, domes, open vertical volcanic conduits, lava ¯ows and lava tubes. Volcanic activity is ongoing from the summit of Big Ben, and from Samarang Hill on McDonald Island. Early, but unproven, glacial sediments may exist within the Late Miocene± Early Pliocene Drygalski Formation, which forms a 300 m high plateau along the northern coast of Heard Island. Growth of the present glaciers, some of which reach sea level, has been a response to progressive growth of the volcanoes. A variety of erosional and depositional glacial landforms is present, including major lateral moraines and extensive hummocky moraines. Vigorous longshore drift and an abundant sediment supply have produced a large spit at the downdrift end of the island, and formed bars from reworked glacigenic sediment that now impound proglacial estuarine lagoons, some of which have grown rapidly over recent decades as tidewater glaciers have retreated. Integrated study of the volcanic, glacial and coastal sequences offers the possibility of constructing a well-dated record of climate change. Research into the geomorphology, sur® cial sediments, and contemporary geomorphological processes, including glacio¯uvial sediment ¯ux, is also important as an aid to environmental management on land, and to management of the adjacent marine environment.

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Terrace types and vegetation dynamics on Macquarie Island

Cited by 7 publications

References 2 publications

Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina

Vegetation patterns, plant distribution and life forms across the alpine zone in southern Tierra del Fuego, Argentina

Pleistocene uplift and palaeoenvironments of Macquarie Island: evidence from palaeobeaches and sedimentary deposits

Geomorphology of the Sub-Antarctic Australian Territory of Heard Island-McDonald Island

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