SHRIMP AND LAICPMS DETRITAL ZIRCON GEOCHRONOLOGY OF MESOPROTEROZOIC TO EARLY CAMBRIAN SAMPLES FROM SE SIBERIA AND SW LAURENTIA; IMPLICATIONS FOR RODINIA RECONSTRUCTION

The Mesoproterozoic position of Siberia with respect to Laurentia in the supercontinent Rodinia has been a topic of debate for over 30 years. To test the hypothesis that east Siberia was connected to west Laurentia, we performed 1,071 U-Th-Pb analyses on individual detrital zircon grains from seven SW Laurentia samples and 14 SE Siberia samples. Our results show that Siberian sedimentary assemblages collected detrital zircons from provenance sources that are absent in SE Siberia but present in SW Laurentia. Likewise, Laurentian sedimentary assemblages collected detrital zircons from sources absent in SW Laurentia but present in SE Siberia.

These data, combined with previously published detrital zircon data, strengthen several proposed Mesoproterozoic to Neoproterozoic stratigraphic correlations between the two continents. The results also lead to a three-stage tectono-sedimentary evolution model during Mesoproterozoic through Middle Cambrian time in which sedimentary successions in SE Siberia and SW Laurentia may have developed in a single basin that collected sediments during multiple stages of tectonic activity. During the Early through Middle Mesoproterozoic, each half of the basin collected sediment primarily from its respective continent in what was likely a failed intracratonic rift. During the Late Mesoproterozoic through Middle Neoproterozoic, the entire basin was flooded with sediments carrying zircons of Grenville age in the Grenville Orogeny’s foreland basin. During the Late Neoproterozoic through Early Cambrian, the supply of Laurentian zircons to the Siberian continent ceased, reflecting the rift that separated the two continents during the breakup of Rodinia.

The east Siberia-west Laurentia Rodinia reconstruction is supported by stratigraphic correlations and detrital zircon data. East Siberia and west Laurentia each contain other Precambrian features that, if studied in light of this reconstruction, could lead to important discoveries, including: 1) the evolution of the enigmatic Laurentian Belt-Purcell Supergroup and its possibly correlative Siberian Udzha Group, and 2) the evolution of the earliest trilobites that are found on the east Siberian and west Laurentian margins.