| Abstract: |
Temper sands in prehistoric potsherds of the Mariana Islands include terrigenous detritus derived from Paleogene volcanic bedrock and calcareous grains derived chie.y from modern fringing reefs, but also in part from uplifted Neogene limestones overlying volcanic bedrock. Calcareous sands are nondiagnostic of island of origin, but volcanic sands and the terrigenous component of hybrid sands composed of mixed terrigenous and calcareous grain types can be traced to geologic sources on Saipan and Guam, the only occupied islands where volcanic bedrock is extensively exposed. Quartzose tempers of several types were derived exclusively from dacitic volcanic rocks on Saipan. Nonquartzose tempers of andesitic parentage derive from both Saipan and Guam, but abundance of orthopyroxene as well as clinopyroxene is diagnostic of Saipan andesitic tempers, the presence of olivine is diagnostic of selected tempers from Guam, and placer temper sands rich in heavy ferromagnesian minerals occur only in sherds on Guam. Temper analysis documents widespread ceramic transfer from Saipan to other islands throughout Mariana prehistory, and more restricted ceramic transfer from Guam to nearby Rota, although the origin of some andesitic temper types is petrographically indeterminate.
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