NEOPROTEROZOIC RODINIAN EPICONTINENTAL STRATA IN SONORA, MEXICO

Neoproterozoic Rodinian epicontinental strata in central Sonora consist mainly of the 2,400-m-thick Las Viboras Group composed of fluvial, tidal, and eolian arenite, and minor conglomerate, siltstone, and dolomite, and of the El Aguila Group composed of fluvial, tidal, and shallow-marine dolomite, arenite, and siltstone. The Las Viboras Group cover 5,000 sq.km of central Sonora. The El Aguila Group covers a smaller area, but it and other possible Rodinian units may have originally covered a much larger area. Paleocurrent directions in the Las Viboras Group are generally to the north and in the El Aguila Group to the north-northwest. The widespread Rodinian strata of Sonora are analogous to widespread Neoproterozoic epicontinental strata in the Adelaide and Centralian basins of Australia. Although no unit for unit correlations are known between the two regions, the fragmentary record in Sonora of arid-climate deposits (halite casts and eolian deposits) in the Las Viboras Group and of a younger Sturtian glacial event (Corsetti et al., 2001) is similar to the succession in Australia from arid-climate deposits containing evaporites and eolian deposits in the Warrina Supergroup to glaciogenic deposits of Sturtian age. The north-northwest paleocurrent directions in the Rodinian strata in Sonora suggest a source to the south, perhaps from a part of the proposed supercontinent of Rodinia that has been rifted away from Sonora and now forms Australia.