10. FERRAR GROUP, KIRKPATRICK BASALT

McMurdo Volcanic Group Ferrar and Kirkpatrick Basalt groups... 

Fig. 4.19 The Bowers Terrane occupies the central area of northern Victoria Land flanked by the Wilson Terrane in the west and the Robertson Bay Terrane in the east The major rock types of this segment of the Transantarctic Mountains are identified by capital letters in alphabetical order A = Admiralty Intmsives, B = Beacon Supergroup, BT = Bowers Terrane, G = Granite Harbor Intrusives, P = Galhpoli Porphyries, R = Robertson Bay Group, W = Wilson Group. The Kirkpatrick Basalt has been onritted from this map for the sake of clarity and the Ferrar Dolerite sills are included with the Beacon Supergroup. The Lanterman and Salamander ranges constitute the eastern province of the Wilson Terrane (Adapted from Gair et al. 1969)...

The Exposure Hill Formation of northern Victoria Land occupies the same stratigraphic position as the Mawson Formation in the Allan and Coombs hills of southern Victoria Land. Both formations are composed of volcanic breccias and related pyroclastic rocks that formed at the start of the eruption of the Kirkpatrick Basalt and the intrusion of sills of the Ferrar Dolerite of the Middle Jurassic Ferrar Group which is the subject of Chapter 12. 

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...

Kirkpatrick Basalt (Ferrar Group) at the Otway Massif (85°27 S, 172°00 E). The K-Ar dates of the trachyte pebble and the basalt boulder constrain the age of the Falla Formation to be younger than 203 3 Ma but older than 183.2 10 Ma. 

The Mawson Formation in the Coombs HiUs is locally overlain by the Kirkpatrick Basalt and was intruded by dikes and sills of the Ferrar Dolerite. This evidence could mean that the Mawson Formation predates the Ferrar Group. However, the presence of basalt and dolerite clasts in the Mawson Diamictite indicates that basalt was already erupting and that sills of dolerite had already intruded the underlying Beacon rocks when the phreatomagmatic explosions occurred. Therefore, the Mawson Formation is part of the Ferrar... 

The petrogenesis of the Kirkpatrick Basalt and the Ferrar Dolerite in the Transantarctic Mountains was once the subject of an intense debate. The contributions by various research groups were concerned with ... 

Important contributions were made by Harrington (1958) who named the Ferrar Dolerite and by Grindley (1963) who discovered the Kirkpatrick Basalt in the Beardmore Glacier area. Subsequently, Grindley and Warren (1964) considered the Ferrar Dolerite and the Kirkpatrick Basalt to be Formations which together constitute the Ferrar Group. This usage has prevailed until the present time (Barrett et al. 1986). 

The initial Sr/ Sr ratios (corrected for decay of Rb to 170 Ma) of the basalt flows on nunataks B and Tunga measured by Faure et al. (1979) range from 0.7027 to 0.7063 and have a poly-modal distribution in Fig. 14.5 with an average of 0.7044 0.0010 (la). This value is significantly lower than the average Sr/ Sr ratio of the Kirkpatrick Basalt of the Ferrar Group in the Queen Alexandra Range of the Transantarctic Mountains. 

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