SYSTEMATIC REGIONAL PATTERNS IN DETRITAL-ZIRCON POPULATIONS FROM CRYOGENIAN, EDIACARAN AND CAMBRIAN SANDSTONES, BRIGHAM GROUP AND TINTIC QUARTZITE, NORTHERN UTAH THRUST BELT

Three end-member detrital-zircon provenance patterns (“barcodes”) are found in 14 new detrital zircon samples from the Brigham Group near Huntsville, in the Sheeprock and San Francisco Mountains of the northern Utah thrust belt, and from the Tintic Quartzite of the parautochthon east of Provo, Utah. We obtained U-Pb age data using the LA-ICP-MS at the University of Arizona. Although the rocks are <660 Ma, zircons younger than 950 Ma are sparse to absent, obviating attempts to constrain depositional ages.

Above glaciogenic diamictites of the Perry Canyon and Dutch Peak formations, lower Brigham Group strata (Caddy Canyon, Mutual and Inkom formations) contain mixed Laurentian provenance, with Grenvillean (950 to 1250 Ma), A-type granite (1400 to 1500 Ma), Yavapai-Mojave-Mazatzal (1650 to 1800 Ma) and Neoarchean (2500 to 3000 Ma) grain populations. Grenvillean grains are most common (up to 80% of sample) in lower strata, with the 1650 to 1800 Ma population becoming more important upward.

A marked provenance change is present at the base of Ediacaran and Cambrian Prospect Mountain, Geertsen Canyon, and Tintic formations, as a sharp and unimodal 1770 Ma composes up to 85% of the grains. The other populations are variably present, but in subordinate sizes (>15% each).

These results are consistent with trends from southeast Idaho and are interpreted to reflect transcontinental Laurentian drainage during post-glacial lowstand which was choked off during the Sauk I transgression. Zircon populations in Ediacaran and Lower Cambrian Sauk I strata were sourced from proximal Paleoproterozoic terranes possibly uplifted on the rift shoulder near the onset of the final rift-drift transition of the Cordilleran miogeocline. Transcontinental Grenville-sourced drainages must have been diverted or flooded by Sauk I transgression.