PROVENANCE IMPLICATIONS OF DETRITAL ZIRCONS IN JURASSIC EOLIANITES AND ASSOCIATED STRATA OF THE COLORADO PLATEAU

U-Pb ages of detrital zircons (DZ) in Jurassic eolian (Aztec, Bluff, Entrada, Navajo, Nugget, Page, Wingate) and associated fluvial (Kayenta, Springdale) and marine (Curtis) sandstones of the Glen Canyon and San Rafael Groups on the Colorado Plateau set constraints for sediment delivery to Jurassic ergs and related depositional systems. Approximately 100 individual grains from each of 16 samples yielded ~940 reliable DZ ages from eolian sands (n=10) and ~530 from fluvial and marine sands (n=6) after rejection of ages with >20% discordance or >10% uncertainty. Grains <300 Ma derived potentially from the coeval Cordilleran magmatic arc form only ~1% of DZ in pre-mid-Jurassic (pre-Bajocian) eolianites, but 10%-25% in post-Bajocian eolianites deposited in part when winds blew from the WSW off the arc. The dominant >300 Ma grains fall into age groups reflecting mixed provenance including nearly all non-Cordilleran granitoid belts of North America (age groups in Ma denoted by main inferred source): (a) 15% Appalachian Paleozoic (310-505); 12% Appalachian peri-Gondwanan Neoproterozoic (510-735); 40 % peri-Appalachian Grenville orogen (910-1295); 9 % anorogenic Mesoproterozoic granite (1300-1545); 11 % Yavapai-Mazatzal belt (1550-1860); 4% older Paleoproterozoic belts (1890-2425); 9 % Archean craton (2500-3200). We infer westward transport of sand by paleorivers crossing the craton from headwaters along the relict Appalachian orogen, followed by transfer of sand to Colorado Plateau ergs by winds blowing toward southerly azimuths. Percentages of zircon grains cannot be converted directly into volumetric percentages of different source rocks eroded because of the enhanced zircon fertility of Grenville plutons. Lower Jurassic (Kayenta) fluvial sands interbedded with eolianites contain minor arc-derived DZ (10%-15%; 195-290 Ma) admixed with recycled eolian sand that is dominant, but DZ in sub-erg Springdale fluvial sand implies derivation mainly from the Cordilleran arc (42 %; 200-240 Ma) and underlying basement of southwest Laurentia. DZ grains in marine Curtis sands (n=2) were apparently reworked from immediately underlying Entrada eolianite. In combination, Jurassic depositional systems of the Colorado Plateau record transcontinental dispersal of sediment followed by intraregional recycling.