Methods

Site U1371

“…Cell concentrations were approximately two orders of magnitude higher at 5 mbsf than at similar depths in the South Pacific Gyre sites. Preliminary molecular study of archaeal 16S rRNA genes in three clone libraries (0.6, 1.5, and 2.1 mbsf) suggested the presence of Marine Crenarchaeota Group 1 (MG-1) and other non-MG-1 archaeal groups in shallow sediment (Durbin and Teske, 2010).…”

Site U1369

“…The structure in Unit I is massive with occasional burrows and rare very pale brown laminations. The burrows are Planolites associated with horizontal traces formed in the seafloor transition layer (5-8 cm) (Ekdale et al, 1984). A thoroughly bored hardground of very pale brown sediment was recovered from interval 329-U1369E-1H-2, 115-117 cm (Fig.…”

Site U1368

“…The dark color of the upper 25 cm of sediment is distinct from the underlying pale brown sediment and contains traces of horizontal burrowers of transitionlayer (5-8 cm) organisms (Ekdale et al, 1984). Although the sediment is mottled, individual Planolites and Zoophycos burrows are evident (see core photographs from Site U1368 in "Core descriptions").…”

“…The Subunit IA/IB boundary represents an event in which reduced sediment accumulation is inferred. The irregularity of this surface and abundance of indurated clay clasts may have resulted from prolonged bioturbation and not subsequent removal of previously deposited sediment (Stow and Lovell, 1979;Ekdale et al, 1984;Ujiié, 1984;Uchman, 2007). The great abundance of RSO in the sediment is consistent with very slow sediment accumulation rates (~0.001 m/m.y.…”