ZIRCON GEOCHRONOLOGY OF CAMBRIAN CLASTIC AND CRYSTALLINE ROCKS FROM THE CARBON SAFE WABASH #1 WELL, INDIANA, USA

The Wabash #1 well, drilled for the Carbon Safe Wabash Project and located in West Terre Haute, Vigo County, Indiana, was drilled in early 2020 as a stratigraphic test well to characterize and evaluate the basal Cambrian Mt. Simon Sandstone for carbon dioxide storage (TD=8750 ft). The Wabash #1 well is located along the eastern flank of a newly defined Cambrian aulocogen that occurs in western Indiana and eastern Illinois. Here we present 892 new detrital zircon U-Pb ages (LA-ICPMS) from three samples of lower Cambrian Strata (Mt. Simon and Argenta Formations). A basal dike or lava flow was penetrated at ~8530 ft, and has an ⁴⁰Ar/³⁹Ar age of 526.03 +/- 1.09 Ma, which represents the first known Cambrian crust beneath the Illinois Basin. A side wall core of sandstone beneath the basalt at a depth of 8680 ft has prominent age peak of 1477 Ma, which represents local basement, and lesser peak at 1203 Ma, which were distally sourced in the Grenville Orogen. Two Cambrian zircons are present, which verifies an early Cambrian age for this unit. Zircons also were analyzed from a sidewall core at a depth of 8500 ft. Here the detrital zircon age spectrum is more variable with age peaks at 1461, 2692, 1122, and 1789 Ma, which reflects both proximally sourced sediment as wells as distal sources from the north and east. A full core of sandstone was collected at a depth of 7972 ft; this sample has age peaks of 1366, 1457, 1644, 1183, 2703, and 532 Ma, which again records a complex combination of locally and distally derived sediment. Our detrital zircon age spectra for these rocks is consistent with those obtained for lower Cambrian strata from three other Carbon Safe wells in Illinois. Deeper Cambrian sands reflect only local sediment sources areas in Mazatzal, MCGR, and Cambrian crust. Once the local source areas are buried, sediment from distal sources begin to dominate.