NEW LOOK AT THE SIBERIAN CONNECTION: NO SWEAT

Abstract

The Proterozoic connection between northeastern Siberia and western Laurentia that we proposed in 1978 is strongly supported by several new lines of evidence. New age data and refined structural trends in predrift basement rocks improve the resolution of the fit between the cratons. The mouth of the large river that is inferred to have provided the point source for the lower part of the Mesoproterozoic Belt-Purcell Supergroup in western Laurentia aligns with the Mesoproterozoic Udzha trough of Siberia. The elbow bend in the Udzha trough bypasses the Archean Wyoming Province to link the Belt-Purcell basin with Paleoproterozoic regions in southwest Laurentia having appropriate Nd crustal-residence ages and zircon crystallization ages to have provided sources for much of the sediment. The Grenville and Granite-Rhyolite provinces of southwest Laurentia provide sources for detrital zircons and felsic volcanic fragments in the east-derived Mesoproterozoic Mayamkan Formation of Siberia. The ages of mafic sills in the Sette-Daban region of Siberia overlap those in southwest Laurentia. Ediacara occur in off-shelf environments on both margins. The two margins have very similar latest Neoproterozoic earliest Cambrian rift-drift signatures, including a breakup unconformity and Tommotian shelf assemblages that record the onset of thermally driven subsidence. Two possible submarine volcanoes with archeocyathan caps may confirm the establishment of Early Cambrian seafloor spreading. The Siberian west Laurentian connection provides better correlations among prerift terranes than does the southwest United States East Antarctic connection (SWEAT), and is more compatible with the overall geologic history of Laurentia and Gondwana.