Precambrian zircons from the Florida basement: a Gondwanan connection

A Gondwanan origin for the pre-Cretaceous basement of Florida is suggested by U-Pb ages of 515 to 2860 Ma for single zircons separated from subsurface samples of lower Paleozoic sandstone of the Suwannee basin and Neoproterozoic Osceola granite. Forty individual grains analyzed by SHRIMP ion microprobe yielded ages from 515 to 2860 Ma; ages >1000 Ma were predominantly concordant. Two principal populations are evident: 1) 515 to 637 Ma and 2) 1967 to 2282 Ma. Only six zircons were recovered from the granite; four are Pan-African and two are Archean. For the sandstone, the similarity between the Sm-Nd model age (1245 Ma) and the average of the single zircon ages (1326 Ma) suggests that these zircons are chronologically representative of the aggregate provenance of the sandstone. The presence of detritus from rocks of two orogenic cycles clearly places the basement of Florida in Gondwanaland proximal to the West African and/or Trans-Amazonian-San Luis cratons in the early Paleozoic, a location it probably shared with other circum-Atlantic exotic terranes. -from Authors