Miocene bentonites in the White Limestone Group, Jamaica

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.