Seven sites (991-997; Fig. 1) on the Carolina continental margin were drilled during Leg 164 to refine understanding of the in situ characteristics and amounts of natural gas hydrates stored in sediments. Three sites on the Blake Ridge (Sites 994, 995, 997) were drilled to 750-m depths and extend through the zone where the gas hydrate is stable to the sedimentary section below. Short holes (50 m) were drilled at the other four sites on the crests of two diapirs on the Carolina rise, where the intrusion of the diapirs has disturbed the gas-hydrate-bearing sections (Paull, Matsumoto, Wallace et al., 1996). Cores from the three >700-m-deep sites on the Blake Ridge (994, 995, and 997; Fig. 1) contain continuous upper Miocene to Holocene sections of hemipelagic mud, which appear to record changes in mineral composition and possibly paleoclimate. Sediments in the upper 150 mbsf of these holes consist of light greenish gray hemipelagic foraminifer-bearing nannofossil-rich clays, with widely varying carbonate contents (~8%-65%); whereas sediments below ~150 mbsf consist of dark greenish gray diatom- and nannofossil-bearing clays and claystones with low carbonate contents (~6%-30%) (Paull, Matsumoto, Wallace, et al., 1996). Cores from the diapirs (Sites 991-993 and 996) show widely varying lithologies ranging from gray silty clays to limestones as a result of diapirism, mass-wasting, and growth of chemosynthetic communities (Paull, Matsumoto, Wallace, et al., 1996). Shipboard scientists recorded spectral readings from all Leg 164 cores at 10 to 30 cm intervals down each core. In addition, we collected ~1350 core samples for carbonate and spectral analyses in the laboratory at the University of Texas at Arlington (UTA).