Mesa Range

The outcrops of the Kirlqiatrick Basalt identified in Table 12.2 are remnants of much larger deposits that occur from the Litell Rocks and Mesa Range of northern Victoria Land to the Otway Massif and Grosvenor Mountains at the head of the Mill Glacier in the central Transantarctic Mountains, a distance of 1,600 km. 

The Kirkpatrick Basalt does not occur in the Queen Maud, Horlick, Thiel, and Pensacola mountains. Exposures of basalt in the Shackleton Range have not been correlated with the Kirkpatrick Basalt However, sills of Ferrar Dolerite do occur in the Whichaway Nunataks (Brewer 1989), in the Theron Mountains (Blundell and Stephenson 1959 Brewer et al. 1987, 1992). In addition, basalt magma pooled in a large magma chamber in the crust beneath the Pensacola Mountains where it differentiated into the layered gabbro complex of the Dufek intrusion (Ford and Kistler 1980). 

The Mesa Range in Fig. 12.8 is a large and deeply dissected plateau consisting of flat-lying layers of 

Mesa Rmge, Monument Nunataks, LiteU Rocks, and related nunateiks in northern Victoria Land Prince Albert Mountains, Brimstone Peak, Allan Hills, and Carapace Nunatak in southern Victoria Land Westhaven Nunatak at the head of Hatherton Glacier in the Britemnia Remge 

Kirkpatrick, Mt. Falla, Tempest Peak, Blizzard Peak in the Queen Alexandra Range 

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Exposure Hill Mesa Range and nearby nunataks Deep Freeze Range northern Victoria Land... 

The Exposure Hill Formation occurs at the base of the sheet-like lava flows of Kirkpatrick Basalt that form the Mesa Range of northern Victoria Land and on nearby nunataks most of which are located in the Rennick graben in Fig. 12.6. The deposits of breccia and related pyroclastic rocks occur at Exposure Hill at the southern end of Gair Mesa and at Mt. Fazio and Scarab Peak on Tobin Mesa as well as on Mt. Carson adjacent to the Aeronaut Glacier in Fig. 12.7. hi addition, Elliot et al. (1986a) described a deposit of breccia on Agate Peak located about 26 km east of the northern tip of Pain Mesa (Fig. 12.6). 

Fig. 12.6 The geology of the Mesa Range includes the Kirkpatrick Basalt which is underlain by the sandstones of the Beacon Supergroup. The Beacon rocks were deposited uncon-formably on the granitic rocks of the local basement complex (Adapted from Gair et al. 1969 with information from Elliot et al. 1986a)...

Fig. 12.8 Aerial view of the Mesa Range in northern ctoria Land consisting of Gair Mesarn the foreground followed by Tobin and Pain mesas farther north. The Rennick Glacier west of the Mesa Range flows north to the Oates Coast. The flat-lying layers...

Kirkpatrick Basalt interbedded with occasional sedimentary interbeds of lacustrine and volcaniclastic origin. The Mesa Range consists of the Gair, Tobin, and Pain mesas and extends for nearly 80 km from the southern end of Gair Mesa to the northern tip of Pain Mesa. The highest elevation of 3,280 m occurs at the southern tip of Gair Mesa. The elevations of the summit plateaus decrease in a northerly direction toward Mt. Masley on Pain Mesa which has an elevation of 2,605 m. 

Flows of Kirkpatrick Basalt are also exposed on the Sheehan Tableland, Sculpture Mountain, the Monument Nunataks, and on many small nnnataks located east of the Mesa Range, including Solo... 

Fig. 12.9 The Mesa Range of northern Victoria Land is located along the upper reaches of the Rennick Glacier which flows north to the Oates Coast. The mesas and associated nunataks are composed primarily of basalt flows of the Kirkpatrick Basalt.

Tobin Mesa, Mesa Range, Northern Victoria Land ... 

Table 12.4 Average chemical analyses of low-Ti and high-Ti lava flows at Mills Valley, Buchanan Ridge, and Mt. Masley on Pain Mesa, Mesa Range, northern Victoria Land (Mensing 1987)...

Table 12.5 Summary of Rb-Sr dates and initial Sr/ Sr ratios of Kirkpatrick Basalt in Pain Mesa, Mesa Range, NVL (Data and interpretation by Mensing 1987, 1991)...

Fig. 12.18 On the alkali-silica diagram of Cox et al. (1979) and Wilson (1989) the flows of Kirkpatrick Basalt of Solo Nunatak extend from basalt to basaltic andesite much like the lava flows on Pain Mesa (Fig. 12.14) and on Tobin Mesa (Fig. 12.10). However, the mineral composition of the phenocrysts cause all of the flows to be classified as subalkalic tholeiite basalt. In addition, all of the flows are composed of low-Ti basalt because the high-Ti basalt flows that cap Tobin and Pain mesas of the Mesa Range are not present and may have been eroded (Mensing 1987)...

Fig. 12.19 The concentration profiles of SiO and of MgO + CaO of the flows on Solo Nunatak of the Mesa Range reveal compositional irregularities of flows 2, 3, 4, and 8. However, all of the flows at this location belong to the low-Ti suite of the Kirkpatrick Basalt (Ti02 = 0.54 to 0.79%) (Mensing 1987 Mensing et al. 1984)...

Fig. 12.20 The initial Sr ratios of the 24 basalt flows on Solo Nunatak in the Mesa Range vary systematically within narrow limits between 0.70985 and 0.71207. These ratios are typical of the isotopic composition of strontium in the low-Ti flows of the Kirkpatrick Basalt of the Mesa Range. The high initial Sr/ Sr ratios indicate that the magma was either derived from a heterogeneous source in the mantle or that it was contaminated by rocks of the continental crust. The measured Sr/ Sr ratios were corrected for decay of Rb to t = 175 Ma and 1.42 x 10" year (Mensing et al. 1984)...

Fig. 12. 21 The data points representing the flows on Solo Nunatak of the Mesa Range scatter above and below a 175-Ma reference isochron drawn through the average initial Sr/ Sr ratio at 0.71069 0.00007 (la). The failure of the data points to define a straight-line isochron indicates either that these flows had different initial Sr/ Sr ratios or that their Rb/Sr ratios were altered after crystallization, or both (Mensing et al. 1984)...

Fig. 12.27 Samples of the Kirkpatrick Basalt on Mt. Falla (Queen Alexandra Range) and Storm Peak (Marshall Mountains) range in composition from subalkalic tholeiite basaltic andesites to andesites. Alternatively, the phenocryst compositions identify these rocks as tholeiitic basalts. The high sihca concentrations of these rocks presumably arise from the aphanitic matrix. The chemical compositions of the Kirkpatrick Basalt in the Beardmore Glacier area are similar to the basalt flows of the Mesa Range in northern Victoria Land (Data from Elhot 1970a, 1972 1974 Faure et al., 1982)...

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 initial Sr/ Sr and Nd/ Nd ratios of Kirkpatrick Basalt in the Mesa Range of northern Victoria Land in Fig. 12.39 occupy an area in quadrant 4 close to the data cluster of the Tasmanian Dolerite. Therefore, this Sr-Nd isotope mixing diagram confirms... 

Measurements of the position of the virtual geomagnetic pole (VGP) have supported the hypothesis that the Rb-Sr and K-Ar dates of certain flows of the Kirkpatrick Basalt in the Mesa Range were lowered by... 

Elliot DH, Siders M, Faure G, Taylor KS (1982) The Kirkpatrick Basalt, Mesa Range, north Victoria Land. Antarctic J US 17(5) 19-20... 

Faure G, Mensing TM (1993) K-Ar dates and paleomagnetic evidence for Cretaceous alteration of Mesozoic basaltic lava flows. Mesa Range, northern Wctoria Land, Antarctica. Chem Geol 109 305-315... 

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