T52 Detrital Zircons on the North American Continental Interior I

Sunday, 25 September 2016
1:30 PM - 5:30 PM
Room 402

TECTONIC AND CLIMATIC IMPLICATIONS OF CLASTIC DISPERSAL PATHWAYS IN THE PERMIAN MID-CONTINENT

Paper number: T52-7
Program: Technical Sessions
Time: 3:05 PM – 3:25 PM

Authors

Abstract

Over 30 new and previously acquired detrital-zircon analyses from silt- and sandstones of mid-continent North America record sediment dispersal during Permian time. These data are from units interpreted to record eolian-transported sediment ultimately deposited in either continental or shallow epeiric environments, and subordinate fluvial environments, and provide a comprehensive view of spatial and temporal changes in source regions during the Permian.

Data were collected by LA-ICPMS at the University of Arizona from randomly picked detrital zircon grains (n ranges from <100-200 per sample) from both outcrop and core. The U-Pb ages range from Archean to Permian (the approximate depositional age of the corresponding unit). The older Archean grains compose a small but consistent percentage of grains in the samples, and likely reflect either reworking of lower Paleozoic strata or erosion of emergent cratonal areas. The rare young grains (<300 Ma) appear to be volcanic zircons reflecting either coeval eruptions or reworking of penecontemporaneous ash beds. However, three age groups dominate (44-74%) the U-Pb spectra of zircons in all samples: 1) 1300-900 Ma (Grenville); 2) 790-570 Ma (Neoproterozoic); and 3) 480-360 Ma (early to mid Paleozoic). Finally, zircons with ages between 1600-1800 Ma, which likely represent the Yavapai-Mazatzal basement of the southwestern U.S., compose <15% of the total zircons in most samples.

The data suggest that the Central Pangaean Mountains were a dominant source of sediment to the mid-continent region during the Permian, which seems to be a pervasive conclusion from research on Permian strata ranging from the Appalachian basins to the western Pangaean margin. The Ancestral Rocky Mountains— cored by Yavapai-Mazatzal basement— were less important sources during Permian time.

Although the Central Pangaean Mountains, and in particular the Grenville-age basement rocks were a dominant source of sediment to the mid-continent, changes in the relative proportions of Neoproterozoic and Paleozoic grains relative to the Grenville-aged grains vary through time and space, presumably recording docking and uplift of various Appalachian terranes, overprinted by paleoclimatic controls through the Permian.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-282227

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