Globally synchronous Marinoan deglaciation indicated by U-Pb geochronology of the Cottons Breccia, Tasmania, Australia

被引:101
作者
Calver, C. R. [1 ]
Crowley, J. L. [2 ]
Wingate, M. T. D. [3 ,4 ]
Evans, D. A. D. [5 ]
Raub, T. D. [6 ]
Schmitz, M. D. [2 ]
机构
[1] Mineral Resources Tasmania, Rosny Pk, Tas 7018, Australia
[2] Boise State Univ, Dept Geosci, Boise, ID 83725 USA
[3] Geol Survey Western Australia, East Perth, WA 6004, Australia
[4] Univ Western Australia, Sch Earth & Environm, Crawley, WA 6009, Australia
[5] Yale Univ, Dept Geol & Geophys, New Haven, CT 06520 USA
[6] Univ St Andrews, Dept Earth & Environm Sci, St Andrews KY16 9AL, Fife, Scotland
基金
英国自然环境研究理事会;
关键词
KING ISLAND; NEOPROTEROZOIC GLACIATION; LOW PALEOLATITUDE; SOUTH-AUSTRALIA; GRASSY GROUP; TIME-SCALE; EDIACARAN; CONSTRAINTS; DEPOSITS; CONTEXT;
D O I
10.1130/G34568.1
中图分类号
P5 [地质学];
学科分类号
0709 ; 081803 ;
摘要
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 abrasion-thermal 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.
引用
收藏
页码:1127 / 1130
页数:4
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