These rates are comparable to the lower end of the range of spreading rates for the modern East Pacific Rise. Site 1149 acoustic stratigraphy conforms to that originally described by Ewing et al. The upper opaque seismic layer has been correlated to the uppermost abundant chert in much of the North Pacific. Drilling in Holes 1149B and 1149C, however, encountered oceanic basement at 410 and 401 mbsf, respectively, thus demonstrating that Horizon B in the Nadezhda Basin corresponds to true oceanic crust. Based on the few records available, the seismic stratigraphy of the Nadezhda Basin is laterally continuous and correlates well with the lithostratigraphy developed for Site 1149.
Volcanic ash is present as both discrete ash layers and disseminated throughout the clay sequences.
Unit II clays are also noted by a change in porosity, pore water chemistry, and bulk sediment chemistry. Clays from Unit II are barren of siliceous or calcareous microfossils, and thus their ages at this point remain undetermined. These clays, however, contain ichthyolith assemblages that increase in abundance downhole, probably as a result of a decreased sedimentation rate. Shore-based analyses of the ichthyolith assemblages should allow for relative ages for this unit to be determined. The recovered sediments consist of radiolarian chert, porcellanite, and zeolite-bearing clay, whose age is undetermined at this point.