LaGorce Formation

However, no fossils were found. The beds strike east-west and dip steeply in most places (Murtaugh 1969). 

The metavolcanic rocks of the Wyatt Formation occur primarily on Metavolcanic Mountain and on Shapley Ridge of the Cleveland Plateau of the Watson Escarpment west of Reedy Glacier and opposite Metavolcanic Mountain in Figs. 7.4. Murtaugh (1969) 

I I Beacon Supergroup H Granite Harbor Intrusives I I Cambrian Pyroclastics B Wyatt Formation H La Gorce Formation 

The rocks of the Wyatt Formation on Metavolcanic Mountain contain no primary structures and neither their thickness nor their attitude are known. Along Shapley Ridge of the Cleveland Mesa in Fig. 7.4 the rocks of the Wyatt Formation grade into gneissic granite and are cut by dikes of the same granite. 

The chemical analyses of the Wyatt Formation in Appendix 7.8.1 demonstrate that the rocks have high silica concentrations ranging from 67.46% to 70.3%. Although the Wyatt Formation appears to be a deposit of volcanic ash that was extruded on the surface of the Earth, the pattern of decreasing concentrations of CaO + MgO, total Fe, and increasing Na O + K O with increasing silica concentration in Fig. 7.5 resembles the effects of fractional crystallization of magma. In addition, the pattern of variation of the chemical compositions of the Wyatt Formation in Fig. 7.5 

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Beardmore Not present Dunan Formation Wyatt Formation LaGorce Formation... 

Fig. 6.8 Rb-Sr age determinations of metasedimentary rocks of the LaGorce Formation from the valley of the Blackwall Glacier, Nilsen Plateau (Fig. 6.7). The dates and initial Sr/ Sr ratios were calculated by Eastin (1970) by the methods of York (1966, 1969) and have been adjusted to = 1.42 x 10" year" Isochron A is based on four colinear data points (472, 474, 475. and 476). Line B is defined by samples 471 and 473 which have the highest Rb/ Sr ratios and have lost some in situ produced radiogenic Sr. Plotted from data by Eastin (1970)...

The igneous rocks of the Wyatt Formation occur at many locations within the Queen Maud Mountains, as well as in the Horlick and Thiel Mountains. In spite of these extensive exposures, the origin of the Wyatt Formation is still uncertain because in some places it clearly intruded folded metasedimentary rocks of the LaGorce Formation, whereas in other places it over-lies them conformably. In addition, hydrothermal alteration of the rocks and the effects of regional metamorphism described by Minshew (1967) have disturbed the isotopic composition of strontium of the rocks, which has caused data points to scatter on Rb-Sr isochron diagrams and caused large uncertainties in age determinations of the Wyatt Formation listed in Table 6.5. 

Fig. 7.4 The geology of the Wisconsin Range and of the Long Hills is dominated by the Granite Harbor Intrusives of the Wisconsin Range Batholith. These granitic rocks intruded the metasedimentary rocks of the LaGorce Formation and the metavolcanic rocks of the Wyatt Formation, both of which also...

With the probable exception of the hornblende migma-tite on Spear Nunatak (Section 7.2.3), the phylUtes and metagraywackes of the LaGorce Formation are the oldest rocks in the basement of the Wisconsin Range. 

The analytical data derived from eight whole-rock samples of the LaGorce Formation in Appendix 7.8.2.1 define a straight line in Fig. 7.11 which was fitted to the data points by unweighted linear regression. The corresponding Rb-Sr date (A = 1.42 x 10 " year ) and initial Sr/ Sr ratio are ... 

Fig. 7.11 Whole-rock Rb-Sr age determinations of the LaGorce Formation in the basement complex of the Wisconsin Range of the Horlick Mountains (Data from Montigny and Faure 1969 Faure unpublished in Appendix 7.8.2.1)...

LaGorce Formation, Ford Nunataks, Wisconsin Range ... 

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