Prebble Formation

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. 

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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 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. 

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