ABSTRACT Large igneous provinces and associated silicic magmatism can have a significant global climatic effect, so we explored the relationship between the large igneous province record and the ca. 580 Ma Gaskiers glaciation. The late Ediacaran glaciation exists on at least 14 different paleocontinental blocks, and assuming synchroneity, this Gaskiers glaciation was likely of short duration, with estimates ranging from 1.6 m.y. to 340 k.y. The Central Iapetus magmatic province event found in Laurentia, Baltica, and West Africa consists of multiple pulses in the range 620–520 Ma, with the ca. 580 Ma pulse particularly well developed in North Africa. Based on the age matches of 580–570 Ma Central Iapetus magmatic province pulses and the Gaskiers glaciation, and taking into consideration that there is no robust evidence for a major meteorite impact at the time of the Gaskiers onset, we propose that: (1) the initial silicic ca. 580 Ma pulse of the Ouarzazate event (Anti-Atlas of Morocco) helped to trigger the Gaskiers glaciation, and (2) global warming associated with the subsequent ca. 579–570 Ma continental flood basalts, marking the second stage of the Ouarzazate event, helped to end the ice age.

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 +3.7/–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 δ 13 C values.

Abstract The Neoproterozoic diamictite-bearing Squantum Member is located in the Boston Basin in eastern Massachusetts, USA. The Boston Basin forms part of the Avalonia island arc terrane ( c. 650 Ma), and appears to have originated as a rift-type basin in an extensional setting along the northern margin of Gondwana, although its exact position is debated. Inferred palaeoenvironmental reconstructions of the Boston Basin have alternated between a fluvial basin where ice played a major role in transporting much of the coarse material and an evolving marine basin dominated by non-glacial subaqueous mass flow, submarine fans and turbidity-current deposition. The age of the Squantum is bracketed between c. 595 and 570 Ma, and is correlated by some to the glaciogenic diamictite succession of the Gaskiers Formation (eastern Newfoundland) as part of the putative global Gaskiers Glaciation c. 582–585 Ma. However, the Squantum Member consists of diamictite, graded sandstone and siltstone units, and fine-grained laminated argillite/mudstone units typical of debris flow and turbidite facies that accumulate in a submarine setting. A glacial influence is not readily identified and revolves around early interpretations of the diamictite as being ‘till-like’, the presence of laminated horizons that resemble glaciolacustrine ‘varvites’ and the disputed recognition of ice-rafted dropstones. There are no associated carbonates and, consequently, no geochemical data are available in connection with the Squantum Member.

ABSTRACT Ediacaran sediments record the termination of Cryogenian “snowball Earth” glaciations, preserve the first occurrences of macroscopic metazoans, and contain one of the largest known negative δ 13 C excursions (the Shuram-Wonoka). The rock record for the transition between the Proterozoic and Phanerozoic in North America is also physically distinct, with much of the continent characterized by a wide variety of mostly crystalline Proterozoic and Archean rocks overlain by Lower Paleozoic shallow-marine sediments. Here, we present quantitative macrostratigraphic summaries of rock quantity and type using a new comprehensive compilation of Ediacaran geological successions in North America. In keeping with previous results that have identified early Paleozoic burial of the “Great Unconformity” as a major transition in the rock record, we find that the Ediacaran System has greatly reduced areal extent and volume in comparison to the Cambrian and most younger Phanerozoic systems. The closest quantitative analogue to the Ediacaran System in North America is the Permian–Triassic interval, deposited during the culminating assembly and early rifting phases of the supercontinent Pangea. The Shuram-Wonoka carbon isotope excursion occurs against the backdrop of the largest increase in carbonate and total rock volume observed in the Ediacaran. The putatively global Gaskiers glaciation (ca. 580–579 Ma), by contrast, has little quantitative expression in these data. Although the importance of Ediacaran time is often framed in the context of glaciation, biological evolution, and geochemical perturbations, the quantitative expressions of rock area, volume, and lithology in the geologic record clearly demark the late Ediacaran to early Cambrian as the most dramatic transition in at least the past 635 m.y. The extent to which the timing and nature of this transition are reflected globally remains to be determined, but we hypothesize that the large expansion in the extent and volume of sedimentation within the Ediacaran, particularly among carbonates, and again from the Ediacaran to the Cambrian, documented here over ~17% of Earth’s present-day continental area, provides important insights into the drivers of biogeochemical and biological evolution at the dawn of animal life.

Abstract Neoproterozoic glaciogenic outcrops are mostly limited to the southwestern and northwestern margins of the Tarim basin and the Tianshan Mountains. Only two glaciogenic diamictites are recorded in the Neoproterozoic successions from the Tielikeli and Aksu-Wusi areas of the Tarim basin. The lower diamictite from the Polong Formation in the Tielikeli area is c. 800 m thick. The upper diamictite in the area is very thin (Yutang diamictite, 10 m; Yulmeinak diamictite, 51 m). In contrast to the Tarim basin, the Neoproterozoic successions along the northern margin of the Tarim Block in the Tianshan Mountains record three or four glaciogenic diamictites, which are well developed and crop out in the Qurugtagh area. Although the glaciogenic nature of the oldest Beiyixi diamictite remains questionable, all other diamictites (Altungol, Tereeken and Hankalchough) exhibit distinct glaciogenic sedimentary features. SHRIMP zircon U–Pb dating demonstrate that the Bayisi diamictite was deposited between 740±7 Ma and 725±10 Ma, the Altungol and Tereeken diamictites between 725±10 Ma and 615±6 Ma, respectively, and the Hankalchough diamictite between 615±6 Ma and c. 542 Ma. Carbonates atop the Altungol, Tereeken and Hankalchough diamictites show distinct C-isotopic values that are typical for those recorded in ‘cap carbonates’ on other continents. The striking similarity between the cap carbonate of the Tereeken and Marinoan-age Nantuo diamictites further support a 635 Ma ‘Marinoan’ age for the Tereeken glaciation. Unlike the 582 Ma Gaskiers glaciations of Newfoundland, the Hankalchough diamictite is possibly <551 Ma, as suggested by C-isotope chemostratigraphy and biostratigraphy, indicating that post-Marinoan glaciations on different continents may be diachronous. Supplementary material Data are available at: http://www.geolsoc.org.uk/SUP18469 .

Abstract The Infracambrian is a term for mostly Neoproterozoic successions in North Africa and areas to the east. Its base lies within the middle Neoproterozoic period, or Cryogenian, includes the youngest Neoproterozoic period, or Ediacaran, and continues into the early Cambrian to the level at which trilobites first appear. The Cryogenian lacks any biostratigraphic zonation; and no global biostratigraphic schemes exist for the Ediacaran. The formal classification of the Neoproterozoic is currently under review. The Cryogenian–Ediacaran (CE) interval includes at least three prominent diamictite horizons that are clearly linked to penecontemporaneous glaciations. The oldest is ‘Sturtian’, next oldest is ‘Marinoan’ (probably the most extensive), both names are Australian in origin but are used internationally. The Gaskiers glaciation is the youngest and probably the least extensive. There are important unresolved problems of the precise number, age, extent and nomenclature of the Neoproterozic glaciations in Australia. Several palaeomagnetic poles in the age range 600–550 Ma place glacial deposits of that age range in Australia in tropical latitudes. These data, together with older poles from Laurentia, gave rise to the notion of the Snowball Earth, in which the Earth froze over completely, but the profound refrigeration required appears to have had very little effect on biological evolution. Biostratigraphic zonation with the precision attainable throughout the Phanerozoic does not appear possible for the CE interval. Thus, most correlations are based on about 40 U–Pb and Re–Os dates. These confirm the existence of at least three glacial sequences (sequence is used here as an informal term), but it is possible that the Sturtian and Marinoan were essentially one glacial unit. Deglaciation was accompanied by the unique ‘cap carbonates’. The glacial sequences all show a characteristic δ 13 C pattern, but present knowledge is inadequate to use these patterns for detailed global correlation. The most reliable chemostratigraphic correlations are likely to be based on strontium isotope variations. Black shale horizons commonly follow deglaciation. A few basins produce Neoproterozoic hydrocarbons; others are potential producers. As a whole, the Neoproterozoic represents both a scientific and an exploration frontier.

Abstract Neoproterozoic glacial successions have been described in South America, but the glacial deposits of the Río de la Plata Craton have been neglected in previous studies addressing the global distribution of glacially influenced successions. The Río de la Plata Craton contains Neoproterozoic glacial deposits in the Sierra del Volcán Formation (Tandilia System, Argentina), glacial influenced deposits in the Playa Hermosa and Zanja del Tigre formations (Dom Feliciano Belt, Uruguay) and suspected glacially influenced deposits in Passo da Areia (São Gabriel block, Brazil). The Tandilia System glacial record includes diamictites, dropstones and rhythmites deposited in glaciomarine conditions in a tectonically stable depositional setting. The Dom Feliciano Belt includes a thin section with ice-rafted clasts in carbonates and a thicker section containing diamictites, rhythmites, outsized clasts and deformed beds in a volcano-sedimentary succession. The São Gabriel block occurrence deserves more attention to confirm any glacial influence in the fine-grained part of the succession. Glaciation is considered to be contemporaneous with the Gaskiers glaciation (580 Ma), with the exception of the carbonates with dropstones that may represent a previous event correlative with one of the glaciations described in the Kalahari Craton, prior to Kalahari–Río de la Plata assembly in the proto-western Gondwana margin.

This volume covers new developments and research on mass extinctions, volcanism, and impacts, ranging from the ancient Central Iapetus magmatic province linked with the Gaskiers glaciation to thermogenic degassing in large igneous provinces, the global mercury enrichment in Valanginian sediments, and the Guerrero-Morelos carbonate platform response to the Caribbean-Colombian Cretaceous large igneous province. This section is followed by a series of end-Cretaceous studies, including the implications for the Cretaceous-Paleogene boundary event in shallow platform environments and correlation to the deep sea; the role of wildfires linked to Deccan volcanism on ecosystems from the Indian subcontinent; rock magnetic and mineralogical study of Deccan red boles; and factors leading to the collapse of producers during Deccan Traps eruptions and the Chicxulub impact.