WAS THE AREQUIPA MASSIF THE CONJUGATE RIFTED MARGIN OF NORTHEASTERN LAURENTIA?

Previous Neoproterozoic tectonic reconstructions of the supercontinent Rodinia have placed the Arequipa Massif between the Newfoundland margin of NE Laurentia and Amazonia after Mesoproterozoic accretion of an allochthonous Arequipa. To fully test this model, we compare Arequipa to both the NE margin of Laurentia and to the peri-Laurentian Dashwoods terrane. New metamorphic, geochronological, geochemical and stratigraphic constraints from these terranes inspire a reinterpretation of the tectonic history of both Arequipa and the NE margin of Laurentia. The oldest sedimentary sequence on Arequipa is the Neoproterozoic San Juan Fm. LA-ICPMS detrital zircon geochronology from the San Juan Fm yields peaks at 2.0-1.7, 1.4-0.9, and 0.8-0.7 Ga. Carbon isotope chemostratigraphy and newly discovered trace fossils further constrain basin formation of the San Juan Fm between the 635 Ma Marinoan glaciation and the early Cambrian. Although 2.0-1.7 and 1.4-0.9 detrital zircon ages are common in the northern Appalachians and throughout Rodinia, 0.95-0.55 Ga ages are rare. Moreover, rift volcanism and siliciclastic sedimentation on the NE margin of Laurentia are initiated in the late Ediacaran to early Cambrian while the onset of rifting is much earlier on Arequipa, and sedimentation is dominated by carbonate facies. Data to be presented from Dashwoods will further test whether Arequipa was the conjugate rifted margin of NE Laurentia. Alternative conjugate rifted margins for Arequipa are evaluated, including the southern Appalachians and Kalahari.