Chunky Gal Mountain

Andrew Gregory

Goals:

  • Observe the structural styles typical to this region
  • Taking note of the deformation and metamorphism
  • View overprinting and lithologies of the Hayesville thrust sheet

Introduction:

Chunky Gal Mountain in North Carolina is named after a local Indian story about a chubbier female Indian who falls in love with someone from another tribe. This stop provides an example of the Blue Ridge structures in this region. The site also gives views of the Hayesville thrust sheet and the different types of rocks associated with it. Overall the outcrop helps us to see some of the metamorphism and deformation that has taken place in this region.

Figure 1: From Hatcher 1986

Geology:

Chunky Gal Mountain can be put into two different groups, the Buck€™ Creek ultramafic unit and the mafic envelope rocks, which are comprised primarily of forms of Dunite and Amphibolite respectively. Possible origins of these ultramafic rocks are a diapir or formerly subducted ophiolites (McElhaney and McSween, 1983). Chunky Gal’€™s deformation began with the foliation of isoclinal folds. These were then deformed again by vertical passive flow folds, and lastly the rocks began brittle faulting (Hatcher, 1986). There is also a fault that moved the amphibolite over the clastic rocks of the Coweeta Group (Hatcher and Butler, 1979). Beside the fault, there are ductile shear zones in the biotite gneiss that have the same sense of shear as the Chunky Gal Mountain fault trace. This insinuates that the fault could be folded thrust or extensional fault (Hatcher, 1986).

Lithology:

This outcrop is made up of quartz-feldspar-biotite gneiss, hornblende-plagioclase gneiss, calc-€“silicate, and quartzite (Hatcher, 1986). There are rocks with trondhjemite dikes and at other places there are boudins that contain quartz filled fractures (Hatcher and Butler, 1979). All of the rocks are interpreted to have formed as either deep water clastic and volcanic metasedimentary rocks of the Coweeta Group or rocks from the Chunky Gal complex (McElhaney and McSween, 1983).

 

Location:

Chunky Gal Mountain is about 14 miles East of Hayesville,North Carolinaon Highway 64. The GPS coordinates are N35° 03.711′ and W 83° 37.178′.

References:

Hatcher, R. D., Jr., Butler, J. R., 1979, Guidebook for Southern Appalachian field trip in the Carolinas, Tennessee and northeastern Georgia: International Geological Correlation Program-Caledonide Orogen Project (27), 67-74.

Hatcher, R. D., Jr., 1986, Chunky Gal Mountain and Glade Gap: Southeastern Section of the Geological Society of America, Centennial Field Guide, v. 6, 261-263.

McElhaney, M. S., McSween, H. Y. , Jr., 1983, Petrology of the Chunky Gal Mountain mafic-ultramafic complex, NorthCarolina: Geological Society of America Bulletin, v. 94, 855-874.