Chapter 42 The deep-marine glaciogenic Gaskiers Formation, Newfoundland, Canada

Abstract

In eastern Canada, the Neoproterozoic Gaskiers Formation (Fm.) consists of a thick diamictite-turbidite succession (250-300 m thick) that occurs within the deep-marine predominantly volcaniclastic turbidite units of the Conception Group (4-5 km thick). These rocks are well exposed on the coast of the Avalon Peninsula in eastern Newfoundland. The thick succession is considered by some to represent the final Neoproterozoic glacial event, known as the Gaskiers Glaciation c. 582-585 Ma. The Gaskiers Fm. appears to have accumulated in a volcanically-influenced arc-related basin within the confines of the Proterozoic peri-Gondwanan Avalon terrane, before rifting away from the Gondwanan margin in the early Palaeozoic, but it is not clear whether it was adjacent to the West African Craton or the Amazon Craton. It has also been argued that Avalon had already rifted from Gondwana by the late Proterozoic.Glacially striated clasts, dropstones, and chatter-marked garnets identify a glaciated source area, and clasts and matrix are of volcanic origin; pyroclastic flows and volcanic bombs are also present. As a result, there is a growing consensus that the Gaskiers Fm. records local glaciation of a high relief volcanic topography, owing its origin to the episodic downslope reworking of volcanic and glacial debris into a deep, rapidly subsiding basin. The volcanic nature of these deposits implies that local volcanic activity was coeval with deposition. A minimum age of the Gaskiers Fm. is constrained by a diverse assemblage of Ediacaran-type fossils in the upper Conception Group dated at c. 565 + 3 Ma and in the lower St. John's Group, which overlies the Conception Group. A maximum age for the Gaskiers is provided by a U -Pb date of 606 þ3.7/ -2.9) Ma in the Harbour Main volcanic rocks underlying the Gaskiers Fm. A thin limestone bed has also been identified at two localities in Conception Bay directly overlying the diamictite yielding strongly negative d 13 C values.

Chapter 43 The Squantum Member of the Boston Basin, Massachusetts, USA

“…in Newfoundland, Canada (Carto & Eyles 2011), but the case for a glacial setting for the Boston Basin strata is tenuous, unlike for the Gaskiers Fm., where undoubted glacially striated and faceted clasts, as well as dropstones, are found. The extent of glaciation around the outer Gondwanan margin (the so-called Gaskiers Glaciation c. 580 Ma) was probably limited to topographically controlled small glacier complexes on higher standing, arc-related volcanoes.…”

Volcanosedimentary paleoenvironments of Ediacaran fossils in Newfoundland

“…4C), is comparable with a volcanic bomb (Tsuya, 1939). This could be a dropped cobble from fl oating ice (as noted in the Gaskiers Formation of Newfoundland by Williams and King, 1979;Carto and Eyles, 2011;Retallack, 2013b), and its penetration of volcanic ash could be a coincidence, but there is no other evidence for ice rafting in the Mistaken Point Formation. As a 15-cm-long volcanic bomb, this spindle of basalt would have come from a vent no more than 5 km distant, judging from sizes of observed volcanic bombs around Japanese volcanoes (Minakami, 1942).…”

“…2). Conglomerate and tillite of the Conception Group include clasts of granite, diorite, granophyre, basalt, basaltic scoria, chert, sandstone, siltstone, and shale derived from uplands of continental crust (Williams and King, 1979;Carto and Eyles, 2011;Retallack, 2013b).…”

Revisão estratigráfica das unidades superiores da faixa paraguai norte : litoestratigrafia, quimioestratigrafia (C e Sr) e geocronologia (U-Pb). Mato Grosso, Brasil

“…A Formação Serra Azul, em termos litoestratigráficos e isotópicos (Figueiredo, 2006, é comparável à Formação Gaskiers (Newfoundland, Canadá - Carto & Eyles, 2011) que possui valores de δ 13 C entre -6‰ e -1,5‰ (Myrow & Kaufman, 1999 Figueiredo et al, 1974;Alvarenga & Saes, 1992;Figueiredo et al, 2004Figueiredo et al, , 2008Alvarenga et al, 2007;Bandeira, 2006Bandeira, , 2011Bandeira et al, 2007).…”