The seamount was named for the 58th emperor of Japan,
Emperor Koko (A.D. 885–887) by geologist
Thomas Davies and his colleagues in 1972, based on the results from a
bathymetric expedition and contents of two
dredge hauls, led by
Thomas Washington and undertaken with the ship
Aries-7. Site 1206 was the last and southernmost drilling site during Leg 197, and was located on the southeastern side of the lower summit terrace of Koko Seamount. A seismic survey of the region was utilized to locate a suitable place for the drill site, initially targeted near Site 308, drilled in 1973 during Leg 32. Weather conditions during the drilling had prevented it from reaching in depth, the approximate depth of the sediment cover in the region. Due to a shortage of time, priority was placed on finding a region with a thin sedimentary cover. The site eventually chosen was located at a water depth of , south of Site 308, at coordinates . The sediment cover at this site was less than half that at the 1973 drill site, and rock was hit at a subsurface depth of . Drilling continued to into the slopes. The top of sediment included
fossil-rich
calcarenite and
calcium-rich
mudstone and
siltstone, indicating a shallow-water setting at the time of deposition. The lower part of the core sample recovered a to section of shell-bearing
mudstone containing many
microfossils typical of the early to middle
Eocene (43.5-49.7 Ma). This age range fits well with a radiometric analysis (48.1 Ma) reported for a dredged rock from Koko Seamount from the 1973 expedition. Although shell fragments had been recovered from the sediment cover in 1973, none of these deposits contained microfossils. Lava flows dominate the
lithology of the main body, with a small proportion of
calcarenite. Many lavas were
pahoehoe flows laced with
a'a, evidence of
subaerial eruptions. There was a large amount of variation in the density, structure, porosity, and grain size of the recovered volcanic rock, varying widely with depth. The bulk of the volcanic rock is
basalt of
aphyric to
olivine-
phyric lava, and tholeiitic or alkalic in composition. The basaltic lavas from Koko Seamount resemble those drilled during Leg 55, at
Suiko Seamount. Studies suggested that the magnetic arrangement of the rock, used to determine its latitude at formation (magnets align to the
North Pole; also, the drift and position of the
Hawaii hotspot at various times is important to
hotspot studies), were relatively stable. 14 magnetic groupings were found on the seamount, yielding a mean latitude of 38.5 degrees south of the seamount's present location (the
percent of error is +8.4°/-10.9°). That would put the seamount at 21.7° N in latitude during its early history, before the
Pacific Plate moved it to its current position relative to Earth. ==Ancient ecology==