lithology in the upper subhottom units between New River Inlet and Cape 

 Lookout. Northeast of the unit III limit (Fig. 6) the characteristic 

 forset-type internal reflectors immediately underlying the first sub- 

 bottom reflector are no longer apparent and the reflectors in this inter- 

 val are nearly horizontal. However, few profile lines are available for 

 this area and they could be nearly on strike with these reflectors. Core 

 data suggest that unit III may persist farther eastward to near Bogue 

 Inlet. At that location, reflector patterns change to a more complex 

 arrangement showing that the segment to as far as core 95 contains ero- 

 sional intervals and sections of complex fill (App. A, profiles 2, 3, 4, 

 and 5) . Unit III probably continues below this complex section as sug- 

 gested by the deeper reflector patterns in profile 3. From just west of 

 core 95 to Cape Lookout, secondary reflectors in the section below the 

 first subbottom reflector (App. A, profiles 1 and 2) become more regular 

 and lie in a semiparallel pattern. 



III. SEDIMENT CHARACTERISTICS 



1. General . 



Most of the sediments and rocks recovered in the ICONS cores were 

 categorized into several broadly defined sediment types, based on lithol- 

 ogy and mode of occurrence. General characteristics of these types are 

 sijmmarized in Table 2. Although particular sediments have certain common 

 characteristics, the use of classes is primarily for descriptive purposes 

 and does not necessarily reflect stratigraphic relationships. However, 

 some classes encompass sediments which are apparently part of a single 

 chronostratigraphic unit. These relationships are discussed later in Sec- 

 tion IV. The type class of all classifiable sediments in the core logs is 

 indicated in Appendix B; size-frequency data for selected samples are in 

 Appendix C; and a constituent analysis of sediments representative of the 

 various types is in Appendix D (Tables D-1 and D-2) . The particle-size 

 terminology in this study follows the Wentworth classification (Table 3). 



2. Sediment Composition . 



Representative samples from the various sediment types and from sev- 

 eral unclassified sediments were examined to find the frequency of occur- 

 ence of their principal constituents. The constituents were primarily 

 identified by examining the particles under a light microscope and digest- 

 ing the acid soluable components; heavy mineral separations on a small 

 number of samples were made using bromoform (specific gravity of 2.87). 

 Tabulated results of the constituent analysis and acid digestion, together 

 with notes on the procedures used and category definition, are in Appendix 

 D. Photos of various constituents are shown in Figure 15 (a to k) . 



Several general observations on sediment composition were made from 

 the constituent analysis of selected samples during the core logging 

 process. The sediments in the study area consist of two main elements: 

 quartz and biogenic calcium carbonate. The most common accessories are 

 feldspar, phosphorite, and glauconite; opaque and translucent heavy min- 

 eral grains and mica are present in very small quantities. 



31 



