.... The C- and Sr-isotopic abundances of lower Keele Formation carbonates approximate those for other pre-Varanger samples, confirming that the simple disc-like fossils of the underlying Twitya Formation predate all known diverse Ediacaran faunas. "Tepee" and Sheepbed carbonates record strong post-glacial...

...H. J. Hofmann; G. M. Narbonne; J. D. Aitken Abstract A turbidite sequence within the Twitya Formation (Windermere Supergroup) in the ackenzie Mountains, northwestern Canada, has yielded an assemblage composed of simple centimetric annuli and discs, which are interpreted as biogenic and referred...

... in the June beds; (D) Fractofusus , a deep-water rangeomorph from the June beds; (E–F) discoidal “Twitya discs”; (G) hemispherical “Twitya discs” showing partial overfolding due to current flow. Figure 3. Trace fossils from Blueflower Formation at Sekwi Brook: (A) Helminthoidichnites...

...Figure 1. Inset: Location of study area. Left: Stratigraphic column, lower part of Windermere Supergroup. Right: Stratigraphic column at 64°40′30″N, 129°54′15″W, upper part of Twitya Formation (Twitya-Keele transition) showing lithologies and location of glendonite pseudomorphs (stars) ...

... places the Twitya Formation immediately over Paleozoic carbonate units. The Twitya Formation hosts the emerald-bearing quartz–carbonate veins and is comprised of a lower shale-dominated package with layers of thin-bedded limestone turbidites and an upper package of ankeritic and dolomitic turbidite...

...Figure 4. Selected photographs from the Nadaleen River area, Yukon, Canada. (A) Upper part of the Twitya Formation and lower portion of the Ice Brook Formation, including the yellow-weathering limestone unit near its base. The location of section K1 ( Fig. 5 ) is indicated. Elevation difference...

...Peter Laznicka Abstract Conspicuous spherical and subspherical barite nodules occur in Devonian(?)/Mississippian carbonaceous shales and argillaceous dolomitic limestones in Twitya river area (western foothills of the Backbone Ranges, Mackenzie Mountains, N.W.T.).The majority of barite nodules...

... stratiform copper mineralization and fluid convection in Coates Lake basin. The transition from localized rift sedimentation to areally extensive basins of the Twitya Formation resulted in the formation of lithological seals over pre-Twitya rift faults. “Cu” marks the formation of stratiform copper...

... formation roughly with the start of the Varanger glaciation, to which Grotzinger et al. (1995) assign a maximum age of 600 Ma. The possibility that the Twitya forms are prokaryotic aggregates cannot be ruled out ( Hofmann et al. 1990 ). If excluded on that basis, they would be replaced as the first...