Newly found fossils in the Conception and St. John's groups of the Bonavista Peninsula considerably extend the known geographic distribution of the Ediacaran fossils in Newfoundland. They occur in deepwater sediments and are preserved as epireliefs, forming census populations underneath volcanic ash layers throughout a more than 1 km thick turbiditic sequence. the exposed fossiliferous units comprise the Mistaken Point, Trepassey, Fermeuse, and Renews Head formations. the remains are tectonically deformed, with long axes of elliptical discs aligned parallel to cleavage strike; shortening of originally circular bedding surface features is on the order of 30-50% (averaging ~35%).The assemblage includesAspidella, Blackbrookia, Bradgatia, Charnia, Charniodiscus, Fractofusus, Hiemalora, andIvesheadia.These occur throughout the succession, withAspidellabeing the most common genus, followed byCharniaandCharniodiscus.Four new taxa are described, with candelabra-like fossils with aHiemalora-like base referred toPrimocandelabrum hiemaloranumn. gen. and sp., bush-like fossils toParviscopa bonavistensisn. gen. and sp., ladder-like fossils toHadryniscala avalonican. gen. and sp., and string-like fossils with basal disc toHadrynichorde catalinensisn. gen. and sp. the remains also include dubiofossils. The stratigraphic ranges of some taxa on the Bonavista Peninsula are longer than previously reported from the Avalon Peninsula, withFractofususspindles present in the Trepassey Formation,Bradgatia, Charnia, Charniodiscus, andIvesheadiareaching as high as the Fermeuse Formation, andAspidellaextending into the middle of the Renews Head Formation. the spindles in the Trepassey Formation are comparable to those found mainly in the stratigraphically older Briscal Formation on the Avalon Peninsula.
Concentrations of U, Th, 231pa and 1°Be were measured in Holocene sediments from two cores collected off the west coast of South America, two cores from the East Pacific Rise, two from the equatorial Pacific and one from the south Pacific central gyre. Our results, together with data from 5 cores reported in the literature, show that boundary scavenging plays a major role in the removal of 1°Be from the Pacific Ocean. Deposition rates of 1°Be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central Pacific. Deposition of 231pa is 4 to 5-fold greater at the margin sites. The residence time of 1°Be with respect to chemical scavenging, defined as its inventory in the water column divided by its rate of removal to the sediments, varies regionally from > 1000 years at the red-clay sites in the deep central Pacific to -100 years at the margin sites. Different factors control boundary scavenging of Pa and Be. For example, scavenging of 231pa is enhanced by metal-oxide coatings of particles, whereas this seems to have little influence on the scavenging of l°Be.
Organic-walled microfossils are reported from the Borden Rift Basin of northern Baffin Island and Bylot Island. The diverse assemblage, obtained by palynological acid maceration, comprises 39 taxa and occurs in fine-grained siliciclastic and carbonate units from all but the two lowermost formations of the Bylot Supergroup; their age is bracketed between 1,270 and 750 Ma. Of 307 samples analyzed from all parts of the basin, 133 yielded identifiable remains. The microbiota comprises the following taxa: Siphonophycus septatum, S. robustum, S. rugosum n. comb., S. kestron, S. capitaneum, Pellicularia tenera, Polythrichoides lineatus, Obruchevella valdaica, Karamia? sp., opaque filaments, Oscillatoriopsis spp., Palaeolyngbya sp., Arctacellularia tetragonala n. comb., A. ellipsoidea, Chlorogloeaopsis contexta n. comb., C. kanshiensis n. comb., Navifusa bacillaris n. comb., N. majensis, N. actinomorpha n. comb., Leiosphaeridia minutissima, L. tenuissima, L. crassa, L. jacutica, L. ternata, Lophosphaeridium granulatum, Valeria lophostriata, Pterospermopsimorpha insolita, Eomicrocystis elegans, E. malgica, Symplassosphaeridium spp., Synsphaeridium spp., Satka squamifera, Satka spp., Coneosphaera arctica n. sp., Coneosphaera sp., Spumosina rubiginosa, and Fabiformis baffinensis n. sp. The taxon Palaeocalothrix divaricatus, present in some macerates, is possibly a modern fungal contaminant. Abundance and taxonomic diversity varies considerably between formations and environments, with the Arctic Bay Formation exhibiting the greatest productivity and species diversity of the seven formations studied, and the transgressive muddy shelf deposits being the most productive of the 11 environments recognized. This microfossil assemblage of predominantly planktonic species has distinctive taxa in common with Middle to Late Riphean sequences in Siberia (Lakhanda and Miroedikha Groups, ca. 950 to 850 Ma), the lower part of the Thule Group (< 1,270 Ma) in northwest Greenland, the Fury and Hecla Group in western Baffin Island, and taxa reported from the upper part of the Bushimay Supergroup in Zaire. On the other hand, some elements in the Bylot Supergroup are more characteristic of Vendian beds on the Russian Platform, indicating longer stratigraphic ranges for such taxa than previously thought. The compositional similarity between the Borden Basin and Siberian sequences supports palinspastic reconstructions juxtaposing Siberia and Laurentia during the middle to late Proterozoic, and the opening of the Poseidon Ocean.
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