AN INVENTORY OF JOINTS IN THE ROANOKE RAPIDS TAILRACE, NORTHEASTERN NORTH CAROLINA

A systematic inventory of 1191 joints and fractures along a one kilometer traverse in the tailrace of the Roanoke Rapids Dam near Roanoke Rapids, North Carolina reveals several sets and trends. The dominant system trends along an approximate azimuth of 330 (325 to 335). This trend also contains the greatest average length of joints. A second significant trend is approximately due north (355 to 005), and a third significant trend is approximately 060 (050 to 070). Weaker trends include (approximate) 040, 305, and 090. The 040 trend has the lowest average joint lengths in this inventory. All joints exhibit both systematic and nonsystematic characteristics within the different sets. Relationships between rock type, composition with joint lengths and trends are ambiguous. The trends of the joints in this study at Roanoke Rapids compare favorably with regional neotectonic trends reported in the literature for brittle fractures in crystalline and sedimentary rocks in the Piedmont and Coastal Plain of the Carolinas.