Southern Hemisphere Climatic Similarities
Quaternary Similarities in South America, New Zealand and Tasmania
Although New Zealand's, Tasmania's and South America's Quaternary records indicate the same climatic changes during the Last Glacial Maximum (LGM) there were some differences. Recent scientific research on Quaternary terrestrial glacial records throughout the world has indicated there have been several large climatic events in the last 100ka (ka = thousand years) including the Last Glacial Maximum (LGM).
Terrestrial records for these regions have recorded climatic changes and environmental events that were dated and coincide with each other. Data from pollen, vegetation and marine Isotope records were used to evaluate these records. These records for the three regions show at several times in geological history, New Zealand, Tasmania and South America seemed to be going through the same climatic changes even though they were separated by vast lands and seas. These regions, all situated in the Southern Hemisphere, have vast North/South running mountain ranges and are latitudinally very similar (Colhoun et al., 1994).
New Zealand, Tasmania and South American Quaternary Records
New Zealand has a detailed Quaternary record as it is a relatively young country with young Geology and unconsolidated soils. Sites such as the Wanganui basin marine sediments and volcanic tephras from the Taupo Volcanic Zone (TVZ) were used as stratigraphic indicators in Lancashire's study, providing good stratigraphic and chronological records. Because New Zealand is young, it has the added advantage that its vegetation records showed no human impact until recently (Lancashire, 2002).
Tasmania is a small Island, situated at the bottom of Australia’s southern coast. It is an Island that is well known to New Zealand but overall but is not well represented. Recent research into Tasmanian Quaternary records indicate that similarities in beetle data from 14-12.5 ka BP correlate with New Zealand and Chilean records in the withdrawal (retreating) of glaciers to the valleys. Tasmanian glacial information indicates the main glaciation occurred after 25ka BP. There are no known records for Late Glacial or Holocene ice development, and late glacial stages are confined to the upper King Valley, found in a paleosol sequence there (Colhoun et al., 1994).
Tasmania is known for its westerly winds, these winds are also known to have occurred during the LGM, with a possible Milankovitch cycle influence (Shulmeister, 2004). Evidence from Peru and Bolivia indicate that climatic change and glaciation coincided at the same time as the Little Ice Age in the northern hemisphere and may have been caused by changes in temperature and an increase in precipitation, producing phases of glaciation in the Southern Hemisphere (Seltzer, 1990). Tasmania’s, Lake St Clair glacier was the largest glacier during the LGM, spanning ~27km with ~350m thick deposit and was surrounded by Tasmania’s highest mountains and has been extensively studied (Barrows, 2002).
South America is made up of many countries, however, Chile, Brazil and Peru have been used in this comparison because research data information comparisons with Tasmania and New Zealand could be made.
Chile has a long North/South running coastal mountain range, similar to New Zealand’s South Island both are susceptible to cold Westerly winds, driving in snow. Final withdrawal of glaciers in the Chilean valleys is thought to have occurred rapidly after 14.5 ka BP and beetle fauna data indicates a transition period of moorland to forest faunas from 14 – 12.5 ka BP, which correlates with Tasmanian data, which, in turn also agrees with New Zealand data (Colhoun, 1994).
Dating Methods
To date, carbon dating is accepted as one of the most accurate dating methods and is probably the most widely used. Carbon dates are used as comparisons with other proxies (Pollen, Tephra), for correlating new dates. Marine Oxygen Isotope records are also a widely used and accepted method but are usually used in conjunction with pollen, vegetation and diatom records.
Data gathered shows similarities of climate and vegetation during the different stages over the past 25 ka. These similarities have been gathered by comparison of Oxygen Isotope data, pollen and vegetation records, and give an understanding of the impact and extent to which the Last Glacial Maximum had on the Southern Hemisphere.
Tasmanian and Brazilian Pollen records have indicated there may have been other cyclical influences attributing to the changes in glaciations throughout the world over the time period of the LGM. Influences such as the ocean and atmosphere may have played a bigger part in glacial-interglacial stages throughout the world than originally thought.
The study of Quaternary records has become more important as work on understanding how past climatic changes affected the environment. As the climate changes, researchers have begun to take more notice of what is significant, and why these changes happen, and possible consequences. These findings could be significant in the understanding of global climatic changes. As the different methods of dating stratigraphy are understood and refined, researchers should be able to constrain dates and identify specific large scale events of the past and maybe help with future climatic changes.
References –
Barrows, T.T., Stone, J.O., Fifield, L.K., Cresswell, R.G., (2002). The timing of the Last Glacial Maximum in Australia. Quaternary Science Reviews. Vol, 21, 159-173.
Colhoun, Eric, C., Van De Geer, G., Fitzsimons, S.J., and Heusser, L.E. (1994). Terrestrial and marine records of the last glaciation from Western Tasmania: Do they agree? Quaternary Science Reviews, Vol 13, pp. 293-300.
Lancashire, A.K., Flenley, J.R., Harper, M. (2002). Late Glacial beech forest: an 18,000-5000 BP pollen record from Auckland, New Zealand. Global and Planetary Change, Vol., 33, 315-327.
Suggart, P.R., Almond, P.C., (2004). The Last Glacial Maximum (LGM) in western South Island, New Zealand: implications for the global LGM and MIS 2. Quaternary Science Reviews, Vol. 24: 2913-1940.
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