MID-QUATERNARY VEGETATION OF THE HONOLULU PLAIN (OAHU, HAWAIIAN ISLANDS)

Pyroclastic rocks of the Honolulu Volcanic Series (Salt Lake eruption) preserve plant macrofossils dating from the mid-Quaternary (250,000-470,000 BP). Ashfall and pyroclastic surge deposits contain leaves and other plant parts documenting the existence of two lowland communities, a shrubland of Hawaiian cotton (Gossypium tomentosa) and a dry forest community with Kanaloa kahoolawensis (a nearly extinct woody legume); Sapindus oahuensis (soapberry); Prichardia sp. (loulu palm); and other dryland taxa. Fossil material in an associated lahar deposit shows that nearby slopes supported forests of Cordia subcordata (kou), Sapindus oahuensis, Pritchardia, and other taxa. These assemblages are a record of the vegetation of the dry lowlands of the Hawaiian Islands at least a hundred thousand years before the advent of humans.