Miocene bentonites in the White Limestone Group of Jamaica formed from volcanic ash that settled to the sea floor between 25 and 8.5 Ma. Trace element data, especially the Nb/Y ratios less than 0.5, suggest a subalkaline volcanic source, and the low Nb and Zr values suggest eruption from a volcanic arc setting. Similarities between the bentonites of the White Limestone Group and altered ash beds in ODP cores (Leg 165) suggest a source region in Central America, but variations between different ash beds suggest derivation from more than one volcanic centre during the Miocene.