New Pb-Pb Single Zircon Age Constraints on the Timing of Neoproterozoic Glaciation and Continental Break-up in Namibia

Abstract

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Neoproterozoic iron formation: An evaluation of its temporal, environmental and tectonic significance

“…The basin evolution of the Port Nolloth Group is similar to that of the Damara orogen, with a middle Neoproterozoic (c. 750 Ma; (Frimmel et al, 1996) extensional basin, evolving into a passive margin, then ultimately deformed during late Neoproterozoic assembly of west Gondwana. Iron formation in the Gariep basin occurs in the Jakkalsberg…”

The Kalahari Craton during the assembly and dispersal of Rodinia

“…780 Ma Lekkersing granite, giving a minimum age for the lower Port Nolloth Zone sedimentary rocks (Allsop et al, 1979 in Frimmel andFrank, 1998). A Pb-Pb single zircon age from a felsic volcanic rock gave an age of 741 ± 6 Ma, which was interpreted as a crystallisation age (Frimmel et al, 1996b), therefore giving a good estimate for the onset of rifting of ca. 780-740 Ma.…”

Neoproterozoic glaciation in the Earth System

“…Do Neoproterozoic glacial deposits contain sedimentary features indicative of different dominating (Frimmel et al 1996), Idaho (Fanning & Link 2004), Oman and Australia (Kendall et al 2006). (b) Period ,660 to 635 Ma ('Marinoan').…”

“…Therefore, even the most conservative reading of the sparse information on the Sturtian shown in Figure 3a, with U-Pb dates indicating glaciation at least 40 Ma apart (667 and 712 Ma), is inconsistent with a single synchronous glacial event. If the oldest (Pb-Pb) and youngest (Re-Os) dates of .741 and 643 Ma are accepted, then it is certain that 'Sturtian' events must have been diachronous, but the older date (Frimmel et al 1996) is in a terrain with more complex geological relationships. The low error in U-Pb dating by TIMS provides the prospect of at least establishing the absolute time of an event, but it is a far more complicated stratigraphic problem to establish the duration of an event in a single local setting.…”