360 UNIVERSITY OF VIRGINIA PUBLICATIONS 



between Riverton and Strasburg. This stream intercepted North Fork 

 on the west side of Massanutten Mountain and diverted its waters through 

 Moreland's Gap. Later a third tributary of Goose Creek which entered 

 it near Strasburg in a course close to the western foot of the mountain, 

 again captured North Fork opposite Moreland's Gap and diverted the 

 stream to its present course. 



While the tributaries of Goose Creek were diverting the waters of various 

 neighboring streams to Manassas Gap (pi. V, fig. 2) similar captures were in 

 progress in the southern part of the Shenandoah Valley opposite Rockfish 

 Gap. Since this is the largest and deepest wind gap in the Blue Ridge 

 between the James and Manassas gaps the size of this stream was doubt- 

 less large. It evidently was the outlet for the drainage of a large part 

 of the Valley and seems to have included all of the area between Port 

 Republic and the divide between the Shenandoah and James rivers. 



Whether or not North River, which joins Middle River at Mt. Meridian 

 and the South Fork at Port Republic, was first captured by a tributary 

 of Rockfish and led through Rockfish Gap, or by a tributary of North 

 Fork before its capture which resulted in abandoning its course across 

 Massanutten Mountain, cannot be answered at present. Since the Rock- 

 fish Gap is the nearer of the two to their junction with the Shenandoah, 

 it seems reasonable that they were first directed to the Rockfish, and are 

 so indicated on the accompanying map, figure 4. 



Manassas Gap is the only wind gap in the Blue Ridge opposite Shen- 

 andoah Valley of lower elevation than the Tertiary peneplain. The 

 approximate position of the Tertiary plain is indicated by the crests of 

 numerous rounded cherty monadnocks (pi. IV, fig 1) in the Valley and by 

 the even crests of low Cambrian ridges of about the same elevation, which 

 fiank the Blue Ridge on the northwest side (pi. V, fig. 2). It- is evi- 

 dent therefore that Goose Creek maintained its course through the Blue 

 Ridge at Manassas Gap throughout this cycle and for a short period 

 during the Shenandoah cycle. Before the completion of the Tertiary 

 cycle, however, the same tributarj^ which captured North Fork near 

 Luray worked its way back to the vicinity of Waynesboro and captured 

 the Rockfish system, diverting its waters northeastward through Manas- 

 sas Gap. After the Waynesboro capture the chief outlet of the Shenan- 

 doan Valley drainage was through Manassas Gap. The drainage at the 

 close of this cycle is indicated in figure 5. 



The Shenandoah cycle. At the close of the Tertiary cycle the streams 

 were rejuvenated by uplift of the region and a new cycle, designated the 

 Shenandoah, was begun, which resulted in the development of the Shenan- 



