Cretaceous black mud from the central Arctic Ocean

Perhaps the oldest sediment yet recovered from the central Arctic Ocean is a black, organic carbon‐rich mud of late Campanian or Maastrichtian age. The sediment is known in a single piston core, F1‐533, taken from the eastern Alpha Ridge. The black mud has an average organic carbon content of 14 wt % and contains abundant woody plant fragments and pollen in addition to amorphous organic matter in a marine dinoflagellate‐rich matrix. Moderate hydrogen and high oxygen indices determined by Rock‐Eval pyrolysis suggest a substantial contribution of terrestrial plant debris to the marine sediment. The black mud is younger than organic‐rich strata deposited during the Oceanic Anoxic Events proposed for Aptian‐Albian and late Cenomanian to early Turonian times in the Atlantic and Pacific oceans. The high content of organic carbon and the abundance of terrestrial organic matter in the Arctic black mud suggest a marine setting influenced by an abundant supply of organic detritus rather than by a low level of oxygenation in the water column. Sediment in this core demonstrates that the central Arctic Ocean may have been in existence by the late Campanian to Maastrichtian and that the area of core F1‐533 probably was adjacent to an eroding vegetated land mass.