SUPPLEMENTAL MATERIAL
Methods
Sensitive High Resolution Ion Microprobe-Reverse Geometry (SHRIMP-RG) zircon U-Pb sample preparation and analysis by the United States Geological Survey (USGS)The general methods used to obtain zircon U-Pb dates from samples reported in Tables S1, S2, and S6 is as follows. Rock samples were pulverized and sieved to select material sized about 75-600 microns. Density separation via methylene iodide (3.32 g/cm 3 density) and
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