Appalachians    
       

My work in the southern Appalachians is split between the metamorphic rocks of the Blue Ridge Province and the sedimentary rocks of the Valley and Ridge and Plateau. Research in the Blue Ridge includes structure and tectonics of the crystalline thrust sheets as well as work on eclogite and other high-pressure metamorphic rocks. We're also working on a new project that addresses the problem of the anomalously high topographic relief in the southern Appalachian highlands and the possible linkage with linear, post-orogenic fracture zones.

My work in the sedimentary rocks is focused on Mississippian-aged liquefaction features from earthquakes caused by the collision of Africa with North America about 330 million years ago.


Structural geology of the Blue Ridge        
 

We have been putting together a model for the Paleozoic tectonic evolution of the southern Appalachians. This is a work in progress and is a synthesis of field mapping, structural geology, geochronology, and metamorphic petrology. The map below shows our current thinking on the geometry of the Alleghanian thust sheets in the Blue Ridge near the Grandfather Mountain structural window.

 
       
     
       
1.7 Mb high-res image of the map

Eclogite          
           
Rod Willard (MS 1994) discovered the first known eclogite in the southern Appalachians near Bakersville, NC. Since then we have discovered other bodies and have mapped what appear to be the largest eclogite bodies in North America. This is an ongoing area of research. Check out the web page that Brent Miller put together that describes some of our recent work on the eclogite.  
           
       
  Banded eclogite with alternting garnet-rich (red) and omphacite-rich (gray-green) layers. Lick Ridge, NC.    
       

Anomalous topography in the Blue Ridge
                   
             
                   
The Blue Ridge mountains in the southern Appalachians presumably reached their peak elevation at the end of the Alleghanian orogeny, about 270 million years ago, yet the mountains are still high today. The shaded relief maps were constructed from 1:250,000 DEMs stretching from northeast Georgia to southwest Virginia. Highest elevations are in white. The image below shows the elevations that are above 800 meters.  
                       
                 
                       
We have evidence that the high topography in the Blue Ridge is at least partially the result of late Tertiary doming, which may also be associated with a distinct set of topographic lineaments, shown below.      
                   
       
                   
The lineaments appear to be fracture controlled and there is little or no offset of mapped geologic markers across the lineaments.    
                       
                 
                       
 

Above: 3-d shaded relief map of part of the Canton, NC 7.5' quadrangle. Enhanced erosion along Swananoa lineament apears to be a result of intense fracturing, perhaps related to late Tertiary doming of the Blue Ridge.

The image below is a west-looking view along part of the Laurel Creek lineament. High ridge south of the valley is the Black Mountains. Mt. Mitchell, the highest point east of the Rockies, is at the southern end.of the Black Mountains.

 
                       
           
  See this image in motion.    
           
                       
Copyright © 2003 Kevin G. Stewart
page last modified: September 19, 2005