pS Na 25T* JOHN H. KERR RESERVOIR BASIN — MILLER 5 



terials consist of poorly stratified and sometimes cross-bedded sheets 

 of sandj gravel, and clay, with loam predominating on the surface. 

 On the other hand, Francis Langley (1917, p. 60) places the position 

 of the dam and reservoir wholly within the Piedmont Plateau 

 Province. He states : 



Beginning at the "Fall Line" and extending westward to tlie foot of the Blue 

 Ridge is a belt of moderate elevations — 300 to 700 feet above mean sea level. 

 Relief is moderate and the general appearance is that of a moderately level 

 region diversified with low-lying, weii-rouuded hills, and gently sloping valleys. 

 The streams are fairly well graded and are not on the whole very swift-moving. 

 The rocks are for the most part of Paleozoic and pre-Cambrian age, and are 

 of both igneous and sedimentary origin. They have suffered intense dynamic 

 metamorphism, which has changed them for the most part more or less com- 

 pletely into schists and gneisses. The region has long been deeply covered with 

 a thick mantle of soil and more or less completely disintegrated and decomposed 

 rock. The region is regarded as the stumps of an ancient range of mountains 

 which have been worn away by long periods of weathering and erosion. This 

 belt or province is known as the Piedmont Plateau. 



GEOLOGY 



The Piedmont Plateau is composed largely of granitic and meta- 

 morphic rocks with small areas of sedimentary rocks appearing in 

 scattered localities. The oldest and most widespread of the rocks 

 are pre-Cambrian metamorphic types that were originally sedimentary 

 and igneous rocks of both intrusive and extrusive origin. During the 

 Triassic Period large regional stresses were applied from the north- 

 west and southeast causing the metamorphosis of the igneous and 

 sedimentary rocks into gneisses and schists that strike from southwest 

 to northeast. Accompanying the metamorphosis of the older rocks 

 was the intrusion, at considerable depth, of magma, which cooled to 

 form the even-grained granites and monzonites that are prevalent 

 throughout the region. That the region was not much above sea 

 level at this time is indicated by the fact that portions of the area have 

 sandstone that originated below the water level. Late in the Triassic 

 Period both the pre-Cambrian and early Triassic rocks were cut ex- 

 tensively by diabase and pegmatite dikes; these exist today as rela- 

 tively small bodies with no great longitudinal extent. In Cretaceous 

 times the entire area was reduced to sea level, and then raised above 

 its present level where its dissection began. 



Although erosional agents appear to be quite active in unprotected 

 areas, the rate of erosion for the entire Piedmont region is below the 

 rate of rock decomposition, as evidenced by the heavy mantle of 

 residual soil that occurs throughout the region. 



The dam is located at a point on the Roanoke Eiver where a mature 

 valley has been eroded from a formation known as the Red Oak 

 Granite, and where relatively small depths of soil exist on the river 



