Transantarctic Mountains

One of the most spectacular discoveries of the 1963-64 field season was made by the Minnesota party under direction of Campbell Craddock (9) in the Sentinel Range of the Ellsworth Mountains. They submitted a sample of high rank coal accompanied by characteristic elements of the Glossopteris flora at a locality about 600 or 700 miles north of the nearest similar occurrences in the Transantarctic Mountains, intermediate in position between them and the Falkland Islands, where a similar flora (but no coal) has been reported from the work of early Swedish Expeditions. 

Large areas underlain by coal probably are present all along the mountainous margin of the Antarctic plateau which stretches clear across Antarctica. Only the Amery deposit and that of the Sentinel Mountains occur outside this Transantarctic Mountain area. 

Calculating elevation from climate variables requires measuring an atmospheric quantity that varies with altitude. In other chapters, paleo-pressure are inferred by techniques such as basalt vesicularity (Sahagian and Maus 1994) or measuring cosmogenic nuclide concentrations in exposed rocks. For example, Brown et al. (1991) and Brook et al. (1995) used concentrations of 10Be and 26Al to place constraints on the uplift rate and duration of exposure of rocks in the Transantarctic Mountains, Antarctica. Additional methods and further discussions are available in the present volume. 

Barnes SL (1964) An objective scheme for interpolation of data. J Appl Meteor 3 396-409 Betts AK (1982) Saturation point analysis of moist convective overturning. J Atmos Sci 39 1484-1505 Brook EJ, Brown ET, Kurz MD, Ackert Jr RP, Raisbeck GM, Yiou F (1995) Constraints on age, erosion, and uplift of Neogene glacial deposits in the Transantarctic Mountains determined from in situ cosmogenic 10Be and 26AI. Geology 23 1063-1066... 

Fitzgerald P. G. and Smmp E. (1997) Cretaceous and Cenozoic episodic denudation of the Transantarctic Mountains, Antarctica new constraints from apatite fission track thermochronology in the Scott Glacier region. J. Geophys. Res. B Solid Earth Planets 102(4), 7747—7765. 

Figure 12 Geochemical data for the Siesta paleosol of Pliocene age (3 Ma) from the Meyer Desert Formation at Oliver Bluffs, central Transantarctic Mountains (Retallack et al, 2001)...

Ultraxeric Refers to extremely dry conditions, as experienced by the inland edge of the Transantarctic Mountains (Antarctica), where precipitation (solid) is less than 50 mm/year... 

Cosmogenic nuclides can be used in two ways to estimate rates of tectonic uplift. For samples which were exposed long enough, such as those in the Antarctic Dry Valleys (see Glacier movement and ice sheet evolution section), the mere concentration of a cosmogenic nuclide provides constraints on the uplift rate because of the dependence of production rates on altitude. A maximum uplift rate is obtained under the assumption of steady uplift from sea level to the present elevation (cf. Bruno et al. 1997). This method has been applied to limit uplift in the Transantarctic Mountains to < 170 m/Ma (Brook et al. 1993 Ivy-Ochs et al. 1995 Bruno et al. 1997), as opposed to certain studies suggesting much higher rates up to 1000 m/Ma. 

G. Faure and T.M. Mensing, The Transantarctic Mountains Rocks, Ice, Meteorites and Water, DOI 10.1007/978-90-481-9390-5 l, Springer Sdence+Business Media B.V. 2010... 

The history of exploration of Antarctica was beautifully illustrated in two large books published by Reader s Digest (1985,1990) while McPherson (1975) presented pictures of the landscapes of the Transantarctic Mountains where geologists now travel and work. The wildlife in the context of the surreal landscapes of Antarctica was captured in pictures by the incomparable Elliot Porter (Porter 1978). In addition, the calendars published annually by Colin and Betty Monteath of New Zealand emphasize the serene beauty of Antarctica when the Sun happens to be shining (Monteath and Monteath 1990-2004). 

MCH 093F (folded) 2005 Davis and Blankenship Geology of the Scott-Reedy glaciers area, southern Transantarctic Mountains, Antarctica... 

Turner MD, Splettstoesser JF (eds) (1982) Geology of the central Transantarctic Mountains. Antarctic Research Series, vol. 36. American Geophysical Union, Washington, DC... 

Meteorite specimens that land on the East Antarctic ice sheet are transported to the margins of the ice sheet and may be exposed on the bare-ice fields in the zone of ablation adjacent to the Transantarctic Mountains, and at the Yamato and Grove mountains of East Antarctica. In addition, several dozen rock samples from the Moon and from Mars have been collected in Antarctica. 

The conventional orientation of the continent of Antarctica in Fig. 2.1 causes East Antarctica to be located west of an observer facing north anywhere within the Transantarctic Mountains. This contradiction arises because East Antarctica is positioned on the right-hand side of a map when the continent is oriented in the conventional manner as in Fig. 2.1. All geological maps in this book are oriented with north at the top in order to avoid any ambignity abont the directions of east and west. 

Fig. 2.1 Antarctica is conventionally oriented as shown and is subdivided into East Antarctica, West Antarctica, and the Antarctic Peninsula. The Transantarctic Mountains extend from northern Victoria Land along the Ross Sea and the Ross Ice Shelf toward the Pensacola Mountains adjacent to the...

Geophysical data indicate that the average thickness of the continental crust of East Antarctica is about 40 km. However, the crust thickens appreciably to about 55 km under the Transantarctic Mountains and under the subglacial Gamburtsev Mountains located in East Antarctica between 70° and 80°E longimde at about 80°S latitude (Bentley 1983 Kadmina et al. 1983). 

The volcanoes of Antarctica occur not only in the Transantarctic Mountains and on the islands off the coast of Victoria Land, but also in Marie Byrd Land of West Antarctica, on the Antarctic Peninsula and on its off-shore islands, on the South Sandwich Islands, in East Antarctica, and on the islands of the Southern Oceans. All of these volcanoes were described in a book edited by LeMasurier and Thomson (1990). The descriptions of the volcanoes include photographs, maps, chemical analyses of the rocks, and interpretations of these analyses. Even the Gaussberg on the coast of East Antarctica (Section 1.3.3) is included in this compilation of Antarctic volcanoes. The book also... 

The volcanoes of the Transantarctic Mountains occur between Cape Hallett in northern Victoria Land and Mount Early (87°04 S, 153°46 W), which is located only 300 km from the South Pole. The volcanic mountains and cinder cones in the Transantarctic Mountains define the McMurdo Volcanic Province which is subdivided into four regions (Kyle 1990). These volcanoes were active in Late Tertiary time starting less than 25 million years ago and continuing to the present as in the case of Mount Erebus. All of them have extruded silica-undersaturated and alkali-rich lavas in marked contrast to the Ferrar Dolerite and Kirkpatrick Basalts of Middle Jurassic age both of which consist largely of silica-saturated tholeiites. These two suites of volcanic rocks are products of quite different petrogenetic processes that nevertheless occurred at different times in the lithospheric mantle underlying the Transantarctic Mountains. The petrogenesis of these different suites of volcanic rocks is the subject of Chapter 12 (Kirkpatrick Basalt) and Chapter 13 (Ferrar Dolerite), and Chapter 16 (Cenozoic Volcanoes). 

The volcanoes in the Transantarctic Mountains and in Marie Byrd Land of West Antarctica erupted lava flows and pyroclastic ash that was deposited on the surface of the ice sheets. The ash was subsequently buried by snow and was thereby incorporated into the ice. The resulting ash layers now serve a useful purpose in the study of the ice sheets because they are unique event horizons whose age can be determined by isotopic methods (e.g., Folco et al. 2007). In addition, these horizons have preserved a record of the deformation of the ice sheets that is revealed by mapping their outcrop patterns on the bare-ice surfaces in the ablation zones. The chemical composition of the ash has been used to identify the volcanoes from which certain ash layers were erupted, while the sulfate concentration and the acidity (pH) of the ice above an ash layer provide clues to the amount of sulfuric acid that was injected into the stratosphere (Palais 1985). The volcanic dust and sulfuric acid in the stratosphere can cause temporary cooling of the global climate as demonstrated by the eruptions of Krakatau (Indonesia) in 1883, Mount St. Helens (Washington) in 1980, El Chichon (Mexico) in 1982, and Mount Pinatubo (Philippines) in 1992 (Holland and Petersen 1995 Thompson and Mosley-Thompson 1981 Kyle et al. 1981 Self etal. 1981). 

The local conditions that affect the weather alluded to above include the katabatic wind that blows from the polar plateau through the valleys of the outlet glaciers in the Transantarctic Mountains. The wind is generated when the layer of cold air that forms directly above the surface of the polar plateau drains downslope toward the coast. The speed of the wind on a gentle slope... 

Fig. 2.4 During whiteout conditions in the Transantarctic Mountains the horizon becomes invisible and surface definition is lost. In the case shown here, the whiteout conditions resulted from high wind associated with snowfall near the coast of northern Victoria Land. The Scott tent, strU used by geological fieldpar-ties in the Transantarctic Mountains and on the polar plateau, is well suited for use in cold and windy weather, especially when it is set up in well-packed snow or neve. Mills Valley, Pain Mesa, northern Victoria Land, December 1982 (Photo by G. Faure)...

The effects of the low air temperatures in the Transantarctic Mountains are magnified by wind which accelerates the loss of heat from the human body. This phenomenon is expressed quantitatively by the wind-chill scale (Rees 1993) that converts the measured temperature into an equivalent wind-chill temperature. For example, the arrow in Fig. 2.5a indicates that the measured air temperature of -10°C at a wind speed of 8 m/s corresponds to a wind-chill temperature of-20 C. In addition, a wind speed of 8 m/s in Fig. 2.5b is equivalent to a speed of 28.8 km/h. The wind-chill temperature also permits the definition of the discomfort index in Table 2.1. Accordingly, a wind-chill temperature of -20°C is perceived as being bitterly cold. Such conditions are not unusual during the austral sununer on the polar plateau and in the Transantarctic Mountains, except along the coast. 

The discomfort experienced by humans because of the cold and windy conditions that characterize the summer weather in the Transantarctic Mountains and on the polar plateau is aggravated by the extremely low humidity of the air. Humans working out-of-doors under these conditions must protect themselves by wearing appropriate cold-weather clothing. Their ability to cope with the stressful environmental conditions improves when they are physically fit, well rested, well nourished, healthy, and when they are highly motivated to accomplish their mission (Gunderson 1974). 

American scientists and support personnel who are scheduled to work in the Transantarctic Mountains or on the polar plateau of East Antarctica, in Marie Byrd Land in West Antarctica, and at South Pole Station will, in most cases, depart from Christchurch, New Zealand, and fly to McMurdo Station which is located at the tip of the Hut Point Peninsula on Ross Island in Fig. 2.8 (Section 1.2). This site was originally selected in 1955 by Admiral George J. Dufek as a logistics base for Operation Deep Freeze in preparation for research to be carried out by American scientists during the IGY (1957-1958). The site was chosen because it is located in a broad basin adjacent to a deep harbor where supply ships can unload cargo either onto a floating ice dock or directly to the shore. These favorable conditions also caused Robert Scott in 1901 to select this site for his winter-over base where he set up his Discovery Hut in Fig. 2.9 which still contains some of the equipment and supplies that he and his men left behind (Section 1.4.1). 

Former residents of McMurdo Station will also recall the windstorms that suddenly reduce visibility to less than 100 ft (30.48 m), with wind speeds in excess of 55 knots (101.9 km/h), and wind-chill temperatures that drop below -100°F (-73.3°C). Under these conditions, all personnel in McMurdo are required to remain in-doors (Condition 1) and all travel is suspended for the duration of the storm that may last several days. The classification of weather conditions detailed in Table 2.3 is the responsibility of the McMurdo Weather Office (Mac Weather). Condition 1 storms can occur anywhere within the Transantarctic Mountains during the austral spring and fall especially on major outlet glaciers, such as the Reedy Glacier in Fig. 2.11, that channel the katabatic winds from the polar plateau to the Ross Ice Shelf or to the Ross Sea. Field parties that experience such storms learn first-hand that weather still rules in Antarctica. 

The rocks of the basement complex formed and were subsequently altered while Antarctica was an integral part of the supercontinent Gondwana, which contained all of the southern continents we know today. The lithologic and structural diversity of the basement rocks is compounded by their fragmentary exposure along the Transantarctic Mountains. Therefore, we have chosen to describe the basement rocks in each of the five segments defined in Fig. 3.1 and we will also use these subdivisions of the Transantarctic Mountains to describe the rocks that overlie the basement complex. 

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