Granite Harbor Intrusives Southern Nilsen Plateau

7 Granite Harbor Intrusives (Southern Nilsen Plateau) 

The basement of the southern part of the Nilsen plateau in Fig. 6.5, mapped by McLelland (1967), consists of the Granite Harbor Intrusives which are 

McLeUand (1967) reported two isotopic age determinations for biotites of the Lonely Ridge Granodiorite (Mirsky 1969)  

The Rb-Sr date is anomalous and was later corrected by Felder and Faure (1979) who obtained a Rb-Sr date of 470 17 Ma for biotite from a specimen of the Lonely Ridge Granodiorite collected by McLelland (McLelland 208). Consequently, McLelland s date (846 35 Ma) should not be cited in the literature. 

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Fig. 6.7 The basement complex of the northern part of the Nilsen Plateau consists of the La Gorce and Wyatt formations and of the Granite Harbor Intrusives. The volcano-sedimentary rocks predominate in the northern part of the Nilsen Plateau, whereas Granite Harbor Intrusives dominate the basement rocks of the southern part in Fig. 6.5. The Blackwall Glacier was referred to as the Black Rock Glacier by McLelland (1967). The Kukri Peneplain that divides the basement from the overlying Beacon Supergroup is not flat in this area but has elevation differences of about 34 m (Adapted from Stump 1985, 1995)...

These insights concerning the history of magmatic activity in the Wisconsin Hills remind us that McLelland (1967) divided the Granite Harbor Intrusives in the southern part of the Nilsen Plateau into four distinctive facies (Section 6.3.1). Three of these facies are cata-clastically deformed (i.e., syntectonic), whereas the North Quartz Monzonite is not foliated (i.e., post-tectonic) and may be younger than the other facies. 

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