2013/07/31 by Clive R. Calver, James L. Crowley, M.T.D. Wingate +3 · 4 citations
Earth and Planetary Sciences · #Geological and Geochemical Analysis #Paleontology and Stratigraphy of Fossils #Geology and Paleoclimatology Research
paper · doi:10.1130/g34568.1
openalex publication_date 2013/07/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
U-Pb zircon data from the uppermost Cottons Breccia, representing the Marinoan glacial-postglacial transition on King Island, Tasmania, provide the first direct age constraint on the Cryogenian-Ediacaran boundary in Australia. Zircons in four samples from the topmost meter of the Cottons Breccia, dated by sensitive high-resolution ion microprobe, exhibit two modes ca. 660 Ma and ca. 635 Ma. The younger component predominates in the uppermost sample, a possibly volcanolithic dolomitic sandstone, apparently lacking glacially transported debris, in the transition to cap carbonate. Chemical abrasionthermal ionization mass spectrometry (CA-TIMS) U-Pb dating of euhedral zircons from that sample yields a weighted-mean age of 636.41 0.45 Ma. Equivalence to published TIMS ash bed dates from Cryogenian-Ediacaran transitional strata in Namibia (635.51 0.82 Ma, within glacial deposit) and China (635.23 0.84 Ma, 2 m above glacial deposit) supports correlation of those strata to the Australian type sections and globally synchronous deglaciation at the end of the Cryogenian Period.