Stratigraphy and Chemical Composition

EUiot (1970a) measured 12 stratigraphic sections of the Kirkpatrick Basalt in the Queen Alexandra Range and Marshall Mountains including Mt. Falla in Fig. 12.25 as well as Mt. Kirkpatrick, Blizzard Peak, and Tanpest Peak. The section on Storm Peak in the Marshall Mountains consists of numerous basalt flows of varying thickness that add up to about 530 m. 

Most of the flows are amygdaloidal, some have diabasic texture, and one flow contains pillow-like bodies (i.e pahoehoe toes). In addition, two flows contain petrified three trunks and a sedimentary interbed near the top of the section. Elliot (1970a) also published a stratigraphic section of the basalt flows on Mt. Bumstead in the Grosvenor Mountains near the Otway Massif. 

The chemical compositions of the flows on Storm Peak vary up-section with discontinuities between flows 1 and 2 and flows 10-11 which divide the section in Fig. 12.26 into three intervals. The first flow to be erupted has low concentrations of SiO (53.14%) and total iron as FeO (9.07%), but high concentrations of AljOj (13.98%) and MgO (7.14%) compared to all other flows on Storm Peak. The concentrations of SiOj and total iron decrease up section from flow 2 to 10 whereas the concentration of Al Oj and MgO increase. The last flows (11 and 12) in Fig. 12.26 differ markedly from the chemical compositions of the underlying flows. 

The concentrations of TiO of the basalt flows on Storm Peak in Fig. 12.28 range from greater than 0.4% to less than 2.4% and include both low-Ti and high-Ti varieties. Most of the flows on Storm Peak have intermediate TiO concentrations between 1.0% and 1.6%. In this regard, the flows on Storm Peak in the Queen Alexandra Range differ from the Kirkpatrick Basalt in the Mesa Range of northern Victoria Land where the TiO concentrations have a distinctly bimodal distribution seen in Fig. 12.28. 

The lava flows in the Queen Alexandra Range and in the Marshall Mountains are interbedded in a few places with layers of tuff and lacustrine sediment. The lake sediment consists largely of finely laminated volcanic ash, partly replaced by calcite, and containing abundant organic debris including conchostracan, fish remains, and fragments of wood and plants. The composition of the volcanic ash and of the lacustrine sediment appears to be felsic, indicating that silicic ash was apparently erupted contemporaneously with the basalt lava flows. The presence of lacustrine sediment means that, at certain times, the volcanic eruptions ceased 

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