TESTING SUPERCONTINENT-SUPEROCEAN CYCLE PREDICTIONS WITH QUANTITATIVE COMPARISON OF BIVARIATE KERNEL DENSITY ESTIMATES OF THE GLOBAL ZIRCON RECORD

Paired U-Pb geochronologic and Hf-isotope analysis of zircon is a powerful tracer of plate tectonic processes. The global zircon record is commonly interrogated to understand the growth and evolution of continental crust and the supercontinent cycle. However, the extent to which the global zircon record is itself modulated by the supercontinent cycle is debated. Recently, a ca. 1.0-1.3 Ga long cycle of superoceans has been proposed to cause alternating introversion and extroversion of supercontinents. This hypothesis posits that an introverted supercontinent should inherit a global-scale subduction girdle from the previous supercontinent, and result is less continental recycling. To evaluate this hypothesis, we employ the newly developed method of quantitative comparison via bivariate kernel density estimates to examine the transition from the Nuna/Columbia to Rodinia supercontinents throughout the Proterozoic. Using a spatially referenced global database, we compared data from thirteen cratonic blocks during the Nuna/Columbia-Rodinia transition from 2200-900 Ma. Bivariate Cross Correlation, Likeness, and Similarity metrics consistently group cratons together according to their relative position in the Nuna/Columbia supercontinent. Laurentia, Proto-Australia, and Baltica form a close association according to all metrics. Further, the global record is dominated by grains from these cratons from 2200-900 Ma. The zircon records of Laurentia, Proto-Australia, and Baltica are characterized by a near continuum of primarily juvenile magmatism throughout the transition from Nuna/Columbia to Rodinia, characteristic of protracted accretionary orogenesis and crustal growth. This juvenile Hf-isotope signature dominates the global zircon record throughout the Proterozoic and persists into the Phanerozoic detrital zircon record. These results are consistent with the prediction that supercontinents assembled by introversion involve less continental recycling. However, long-lived subduction-related processes appear to be compartmentalized within the Nuna/Columbia supercontinent.