Age and Provenance of Cambrian Strata in Southeastern Arizona, U.S.A.

ABSTRACT New trilobite biostratigraphy, chemostratigraphy and tandem detrital zircon U–Pb geochronology from the Bolsa Quartzite and Abrigo Formation provide insights into Cambrian depositional systems of Arizona, Laurentian tectonics and the geologic time scale. In the Whetstone Mountains, we establish the Ehmaniella Biozone in the lowermost Abrigo Formation and the Aphelaspis Biozone in its upper member. Maximum depositional ages constrain Bolsa Quartzite deposition to ≤ 2 m. y. (502.40 ± 0.55 Ma to ~500.7 Ma) during the Topazan (Wuliuan) and the uppermost Abrigo Formation to Sunwaptan (Stage 10) or younger (≤ 488.34 ± 0.59 Ma). Primary δ 13 C chemostratigraphic signals in the succession appear to correspond to the global record. Cambrian detrital zircons are derived from known (Florida Mountains granite, NM; McClure Mountain syenite, CO) and unknown Laurentian igneous sources. Geochronologic results require that the Drumian Age began at ≤ 502.40 ± 0.55 Ma and that the Sauk II transgression reached southeastern Arizona ~3–7 m. y. after passing northern Arizona (Grand Canyon).