Alexandra Formation

The Alexandra Formation is present only in the northern Alexandra and Holland ranges as shown in Fig. 10.13 but it does occur in a few areas of the Queen Elizabeth Range and in Holyoake and Cobham ranges of the Churchill Mountains north of the Nimrod Glacier (Laird et al. 1971 Fig. 5.8). The Alexandra Formation correlates with the Hatherton Sandstone of the Darwin Mountains (Table 10.7) and with the New Mountain sandstone in the Olympus-Boomerang area of south- 

The sandstones of the Alexandra Formation, like those of Beacon Heights Orthoquartzite and the Hatherton Sandstone, contain only a few trace fossils. Nevertheless, the Devonian age of the Alexandra Formation is indicated by its correlation to the Beacon Heights Orthoquartzite which contains impressions of lycopod stems (Plumstead 1962), while the overlying Aztec Siltstone contains abundant fossil fish and plant microfossils which constrain a Devonian age (McKelvey et al. 1970, 1972 Helby and McElroy 1969). 

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Fig. 10.13 The Beacon rocks in the Queen Elizabeth and Queen Alexandra ranges form high peaks in the central Transantarctic Mountains between the Nimrod and Beardmore glaciers. These rocks were deposited during the Devonian, Permian, and Triassic periods but the extent of the Devonian Alexandra Formation of the Taylor Group is limited as shown (Adapted from Barrett et al. 1986)...

The Pagoda Tillite, which is the oldest formation of the Victoria Group in Table 10.7, was deposited during the Late Carboniferous/Pennian on the eroded surface of the Alexandra Formation. The erosion surface is equivalent to the Maya disconformity in the Beacon rocks of southern Victoria Land. In places where the Alexandra Formation was eroded or was not deposited, the Pagoda Formation was deposited directly on the Kukri erosion surface which was polished and striated by the continental ice sheet. 

The sandstone is primarily composed of quartz grains some of which are well rounded and may have been derived from the Alexandra Formation of the Devonian Taylor Group. Grains of microcUne and sodic plagioclase occur throughout but deCTease in abundance toward the top of the formation. In addition, the sandstones contain lithic grains (schist and phyllite), biotite, muscovite, and pink garnet The matrix consists of sericite, chlorite, quartz, and calcite which are post-depositional. 

In summary, the Sr/ Sr ratios of calcite in carbonate rocks of Triassic, Permian, and Devonian age indicate that this mineral did not precipitate from seawater. Instead, the calcite probably precipitated from pore water percolating through the sediment after deposition. The strontium in solution in the pore water originated by incongruent dissolution of detrital grains of K-feldspar, biotite, and other Rb-bearing minerals in the sediment. We conclude that even marine sandstones (e.g., the Alexandra Formation) may contain diagenetic carbonate lenses and concretions that formed after deposition and therefore did not form in a marine environment. 

The temperatures estimates are based on an average global temperature of 15°C (Fremouw, Buckley, Fairchild), 5°C for the Mackellar carbonates, 0°C for the Pagoda Formation, and 20°C for the Devonian Alexandra Formation... 

The average values on the PDB scale of calcite in samples of carbonate rocks from the Beacon Supergroup in the central Transantarctic Mountains in Table 11.2 range from -24.5 %o (Alexandra Formation) to -28.4%o (Buckley Formation). The evident depletion in relative to oxygen in marine calcite is strong evidence that these calcites were not precipitated from seawater. This conclusion applies even to the calcite in the Alexandra Formation which contains trace fossils that indicate that the rocks of this formation were deposited... 

Queen Alexandra Range 94411 implications for the formation of the Bencubbin-like chondrites. Meteorit. Planet. Set 36, 96-106. 

Petaev M. 1., Meibom A., Krot A. N., Wood J. A., and Keil K. (2001) The condensation origin of zoned metal grains in Queen Alexandra range 94411 implications for the formation of the Bencubbin-like chondrites. Meteorit. Planet. Sci. 36, 93-106. 

Fig. 10.9) exhibits columnar jointing up to 1 m from the contact with a sill of the Ferrar Dolerite (50 m) which itself displays columnar jointing. This kind of jointing also occurs in a sandstone bed at the top of the Mackellar Formation (Permian) in theQueen Alexandra Range (Baiett et al. 1986). 

The Fremouw Formation in Table 10.7 is the oldest unit of Triassic age in the Beardmore area of the central Transantarctic Mountains. It was named by Barrett (1969) for Fremouw Peak which is located south of the Prebble Glacier in the Queen Alexandra Range in Fig. 10.14. The Fremouw Formation is composed of sandstones and mudstones that rest disconformably on the Buckley Formation (Barrett et al. 1986). The basal beds of the Fremouw Formation are composed of quartz sandstone and greenish-gray mudstone. This part of the formation contains vertebrate fossils that were discovered and described by Barrett et al. (1968b), Elliot et al. (1970), Kitching et al. (1972), and Hammer et al. (1986). The vertebrate fossils include bones of both reptiles and amphibians that occur as channel lag deposits in the basal Fremouw at Coalsack Bluff identified in Fig. 10.13. 

The Fremouw Formation is widely distributed in the central Transantarctic Mountains and occurs in the Queen Alexandra and Queen Ehzabeth ranges as well in the Dominion and Supporters ranges at the head of the Beardmore Glacier (McGregor 1965a, b). In addition, Collinson and Elliot (1984) mapped the Fremouw Formation in the Shackleton Glacier area of the Queen Maud Mountains. Barrett et al. (1986) estimated that the total thickness of the Fremouw Formation lies between 670 and 800 m. 

Fig. 10.14 The southern part of the Queen Alexandra Range in Fig. 10.13 exposes the Fremouw and Falla formations of the Beacon Supergroup as well as the overlying Prebble Formation and Kirkpatrick Basalt of the Ferrar Group. This part of the Queen Alexandra Range is located west of the Beardmore Glacier and east of the Walcott Nive. Excerpt of the Buckley Island (S V 61-60/3) and Cloudmaker (SV 51-60/4) topographic maps of Antarctica. US Geological Survey, 1967, Washington, DC...

The Falla Formation is composed of sandstone, shale, and tufifaceous beds as defined by Barrett et al. (1986) in the Queen Alexandra Range. In the Shackleton Glacier area only the lower part of the formation is present composed primarily of quartz sandstones which... 

Faure G, Hill RL (1973) The age of the FaUa Formation (Triassic), Queen Alexandra Range, Antarctica. Antarctic J US 8(5) 264-266... 

Table 11.2 Average isotopic composition of oxygen in calcite of carbonate rocks in Permian formations of the Queen Elizabeth and Queen Alexandra ranges, central Transantarctic Mountains (Lord et al. 1988 Faure and Lord 1990)...

Bones of vertebrate animals were also recovered from the upper Eremouw Formation in Gordon Valley in the Queen Alexandra Range (Fig. 10.14) and from the upper Falla Formation on Mt. Kirkpatrick (Hammer et al. 1987). The Fremouw Formation in Gordon Valley actually contains foot prints of vertebrates which were described and photographed by Macdonald et al. (1991). The bones recovered by W.R. Hammer and his... 

Fig. 11.16 A silicifled tree stump in the growth position was found in the upper Fremouw Formation (Middle Triassic) at the head of the Gordon Valley at 84°11 S, 164°54 E in the Queen Alexandra Range. The height of the stump is about 1 m. This photograph was first published in 1991 on the cover of the Antarctic Journal of the United States (Vol. 16, No. 5) and in the report by Taylor et al. (1991) (Photo by R. Cuneo and T.N. Taylor reproduced with permission. This image was published in Paleobotany by Thomas N. Taylor, Edith L. Taylor, and Michael Krings, second edition. Figure 1.54, p. 29. Copyright Elsevier, 2009)...

Fig. 11.17 The cross-section of a stem of Antarctixylon sp. collected by P. J. Barrett from the Early Triassic Fremouw Formation on Fremouw Peak in the Queen Alexandra Range. The width and shape of the rings constitute a climate record that is difficult to interpret in this case. High-contrast reproduction of a photo of the etched surface of specimen (CB 365-3 (B-2) by Schopf (1973)...

In the Queen Alexandra Range of the Central Transantarctic Mountains diamictites and pyroclastic rocks of the Prebble Formation occur below the Kirkpatrick Basalt. The Prebble Formation overUes the felsic tuffs of the upper Falla Formation which Elliot (1996) renamed the Hanson Formation. Whole-rock samples of the tuff yielded a Rb-Sr date of 186 9 Ma corresponding to an Early Jurassic age (Faure and Hill 1978) which was later confirmed by Hammer and Hickerson (1994) based on the bones of tetrapod vertebrates. 

Fig. 12.24 The Kirkpatrick Basalt in the Queen Alexandra Range occurs primarily on Mt. Kirkpatrick (4,528 m) and on Mt. FaUa (3,825 m). In addition, basalt flows form the summits of the Marshall Mountains including Tempest Peak (3347 m). Storm Peak (3,280 m), Bhzzard Peak (3,379 m), and Mt. Marshall (3,160 m) identified in Fig. 10.14. The basalt flows of the Kirkpatrick Basalt were deposited on the sedimentary rocks of the Beacon Supergroup (Chapter 10) which rest unconform-ably on the metasedimentary rocks of the Goldie Formation (Beardmore Group) (Adapted from Grindley and Laird (1969))...

Triassic Fremouw and Falla formations in the Queen Alexandra Range was documented by Vavra et al. (1981) and Vavra (1982). 

The MacAlpine Hills in Fig. 13.21 are located along the south side of the upper Law Glacier which flows into the Bowden Neve between the Queen Elizabeth and Queen Alexandra ranges. Mt. Achernar is located at the junction of the MacAlpine Hills and the Lewis Cliff in Fig. 13.22. It consists of flat-lying sandstones and coal seams of the Permian Buckley Formation which was intruded by three sills of the Ferrar Dolerite. The elevation of the summit plateau of Mt. Achernar is 2,691 m a.s.l. while its base is at 2,000 m. The sills are exposed on the steep slopes of two large cirques that face the Law Glacier in Fig. 13.23. 

Fig. 13.23 Mount Achernar in the Queen Alexandra Range contains three sills of the Ferrar Dolerite which intruded the Buckley Formation of the Beacon Supergroup. The base of the...

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