Fremouw Formation

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 middle part of the Fremouw Formation is composed predominantly of mudstone that is overlain by the volcanic sandstone of the upper part of the formation. The middle and upper parts of the Fremouw Formation contain plant fossils but no fossil vertebrates have been found. The mudstone and volcanic sandstone are recessive and are overlain by the more resistant cliff-forming quartz sandstone of the Falla Formation. 

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. 

The sandstones are light gray in color, fine grained, well sorted, faintly laminated, and trough cross-bedded. The sandstone beds fine upward and grade into overlying mudstone layers which are several meters thick and grade up-section into fissile carbonaceous 

The Fremouw Formation of the Beardmore Glacier area extends north as far as the Mackay Glacier of southern Victoria Land where it is correlated with the Lashly Formation. It also extends southeast to the Nilsen Plateau (Barrett et al. 1972 Elliot 1975 Collinson et al. 1994). However, sedimentary rocks of Triassic age do not occur in the Scott Glacier area (Doumani and Minshew 1965 Minshew 1966, 1967), in the Ohio Range (Long 1962, 1965), and in the Pensocola Mountains (Schmidt et al. 1965 Schmidt and Eord 1969). 

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The Buckley Formation contains coal beds and was therefore referred to by Grindley (1963) as the Buckley Coal Measures (Young and Rybum 1968). The name was taken from Buckley Island near the head of the Beardmore Glacier where Frank Wild discovered coal seams during Shackleton s trek to the South Pole (1907-1909) (Section 1.4.2). The lower part of the Buckley Formation consists of sandstone which Barrett (1969) redefined as the Fairchild Formation described above. The Buckley Formation is overlain disconform-ably by the sandstones and noncarbonaceous mudstones of the Fremouw Formation of Triassic age (Table 10.7). 

Table 10.8 Chemical composition of coal samples from the Buckley and Fremouw formations in the Beardmore Glacier area in percent by weight (Barrett 1969)...

CoUinson JW, Stanley KO, Vavra CL (1978) Stratigraphy and sedimentary petrology of the Fremouw Formation (Lower Triassic), Cumulus HiUs, central Transantarctic Mountains. Antarctic J US 13(4) 21-22... 

CoUinson JW, Stanley KO, Vavra CL (1981) Triassic fluvial depositional systems in the Fremouw Formation, Cumulus HUls, Antarctica. In Cresswell MM, Vella PP (eds) Gondwana Five. Balkema, Rotterdam, The Netherlands, pp 141-148... 

The Sr/ Sr ratios of two Cambrian limestone formations of known marine origin (i.e., the Nelson Limestone, Pensacola Mountains, and limestone of the Leverett Formation, Mt. Webster, Harold Byrd Mountains) are both consistent with the Sr/ Sr ratio of Cambrian seawater. In addition, the Sr/ Sr ratio of one carbonate sample from the Triassic Fremouw Formation plots close to the seawater curve... 

Two calcites from the Triassic Fremouw Formation have identical 8 C values of -17.9%o and contain a major proportion of biogenic carbon. Apparently, vegetation was abundant and supported amphibians and reptiles whose bones were found in the sandstones of the Fremouw Formation in the area of the Beardmore and Shackleton glaciers. 

S, 162°25 E) in Figs. 11.8 and 11.9b where David Elliot recovered bone fragments from a coarse sandstone of the Fremouw Formation. Subsequently, more than 400 specimens of bone belonging to laby-rinthodont amphibians and to thecodont as well as to therapsid reptiles, including Lystrosaurus, were collected at this site. The bones were found at the base of sandstone beds that filled stream channels in the Early Triassic landscape (Elliot et al. 1970). 

The geology of Coalsack Bluff was described by Collinson and Elliot (1984) who also published a large-scale map of the nunatak which is only 5 km long and 2 km wide. The rocks exposed at Coalsack Bluff include the upper part of the Buckley Formation and the lower part of the overlying Fremouw Formation for a total thickness of approximately 500 m. The sedimentary rocks of Coalsack Bluff were intruded by three sills of Ferrar Dolerite. Four whole-rock K-Ar dates, cited by Collinson and Elliot (1984), range from 170.1 2.0 to 182.3 3.2 Ma and conhrm a Middle Jurassic age for these rocks (lUGS 2002). 

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... 

Retallack et al. (1998) briefly reviewed the literature concerning the causes of the Permo-Triassic extinction event as an introduction to their own study to determine whether boundary clays at Graphite Peak between the Buckley and Fremouw formations contain shocked quartz and anomalously high concentrations of iridium of meteoritic origin. Although they found shocked... 

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)...

Cosgriff JW, Hammer WR, Zawiskie JM, Kemp NR (1978) New Triassic vertebrates from the Fremouw Formation of the Queen Maud Mountains. Antarctic J US 13(4) 23-24 Cosgriff JW, Hammer WR, Ryan WJ (1982) The Pangean rep-tQe, Lystrosaurus maccaigi in the Lower Triassic of Antarctica. J Paleontology 56(2) 371-385 Craddock C, Bastien TW, Rutford RH, Anderson JJ (1965) Glossopteris discovered in West Antarctica. Science 148 634-637... 

IsbeU JL, MacDonald DIM (1991) Lithofacies analysis of the Triassic Fremouw Formation of the Gordon Valley vertebrate site, Antarctica. Antarctic J US 26(5) 15-16 IsbeU JL, MiUer MF, Babcock LE, Hasiotis ST (2001) Ice-marginal environment and escosy stem prior to initial advance of the late Paleozoic ice sheet in the Mount Butters area of the central Transantarctic Mountains, Antarctica. Sedimentology 48 953-970... 

Krissek LA, Homer TC (1991) Sedimentology of a vertebrate bone-bearing bed in the Triassic Fremouw Formation at Gordon Valley, Beardmore Glacier region, Antarctica. Antarctic J US 26(5) 17-19... 

Taylor TN, Taylor EL, Collinson JW (1986a) Paleoenvironment of Lower Triassic plants from the Fremouw Formation, Antarctica. Antarctic J US 21(5) 26-27 ( Formerly E.L. Smoot)... 

Vavra CL, Stanley KO, Collinson JW (1981) Provenance and alteration of the Triassic Fremouw Formation, Central Transantarctic Mountains. In CressweU MM, VeUa P (eds) Gondwana Five. A. A. BaUcema, Rotterdam, The Netherlands, pp 149-153... 

Mt. Sirius in Fig. 19.5a is a steep-sided mesa composed of sandstones of the Fremouw Formation of the Beacon Supergroup overlain by a dolerite sill of the Ferrar Group which is covered by a thick deposit of the till first described by Mercer (1972) and subsequently by McKelvey et al. (1984) and by Hagen (1988). Mt. Sirius is the type locality of the Sirius Formation which was later elevated to the stams of the Sirius Group that includes the numerous small deposits of late Cenozoic till that occur in the Transantarctic Mountains from Manhaul Bay in the Allan Hills of southern Victoria Land to the Wisconsin Range in the Horlick Mountains. 

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