Precambrian (Aphebian) microfossils from Belcher Islands, Hudson Bay

1969 ◽  
Vol 6 (5) ◽  
pp. 1137-1144 ◽  
Author(s):  
H. J. Hofmann ◽  
G. D. Jackson
Keyword(s):  
Hudson Bay ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
Central Australia ◽  
First Time ◽  
Proterozoic Age

A small assemblage of primitive microscopic fossils is here reported for the first time from the lower part of the Belcher Group in Hudson Bay. The microbiota includes chains and clumps of bacteria, and filamentous and spheroidal structures of probable algal or fungal affinities. In addition, a variety of isolated and clustered spheroids and other structures of probable biologic origin is present. The structures are more than 1600 m.y. old, and occur in a black chert associated with thick dolomite beds considered to be of Aphebian (Early Proterozoic) age. Morphologically comparable Precambrian microfossils occur in the Gunflint Formation (Early Proterozoic, Ontario) and the Bitter Springs Formation (Late Proterozoic, central Australia).

scholarly journals Isotopic studies in the East Greenland Caledonides (72°–74°N) – Precambrian and Caledonian ages

1981 ◽  
Vol 104 ◽  
pp. 47-72
Author(s):  
D.C Rex ◽  
A.R Gledhill
Keyword(s):  
Crystalline Rocks ◽  
Reference Line ◽  
Published Data ◽  
East Greenland ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
Isotopic Studies ◽  
Data Points ◽  
Proterozoic Age

Rb-Sr isotopic studies on crystalline rocks from different rock units of the East Greenland Caledonides have given a number of isochron and 'errorchron' ages, as well as sets of inconclusive data. All the results are presented here as an illustration of the problems encountered, though previously published data is given in summary form. Eleven collections from Archaean - early Proterozoic rock units have given seven early Proterozoic Rb-Sr whole rock isochrons, while one set of data points plot about a 2450 m.y. reference line. Seven collections from metasediments of presumed middle to late Proterozoic age produced only one 'errorchron' of c. 1245 m.y., but data points from all the collections plot about a 1250 m.y. reference line. Six collections from a suite of 'older' granites gave four isochron ages of 1080, 1000,765 and 650 m.y. Eight collections from Caledonian granites gave four isochron ages, three 'errorchrons' and one mineral-whole rock isochron; the ages fall in the range 377-550 m.y.

New Complexities in Zoogeography and Taxonomy of the Pygmy Whitefish (Prosopium coulteri)

1972 ◽  
Vol 29 (12) ◽  
pp. 1772-1775 ◽  
Author(s):  
C. C. Lindsey ◽  
W. G. Franzin
Keyword(s):  
River System ◽  
Yukon Territory ◽  
Hudson Bay ◽  
The South ◽  
Bristol Bay ◽  
River Drainage ◽  
Bay Area ◽  
First Time ◽  
Mackenzie River

Pygmy whitefish (Prosopium coulteri) are recorded for the first time from the Peel–Mackenzie river drainage (Elliott Lake, Yukon Territory) and from the Hudson Bay drainage (Waterton Lakes, Alberta, in the South Saskatchewan–Nelson river system). The morphology of specimens from both localities contradicts the previously known pattern of a southeastern "low-rakered" and a northwestern "high-rakered" form (with the two forms occurring sympatrically in some lakes of the Bristol Bay area). Specimens from Elliott Lake, the most northerly known locality, resemble the southeastern form and those from Waterton Lakes the northwestern form. Both Waterton and Elliott lakes lie close to unglaciated refugia, suggesting that the species may have survived Wisconsin glaciation and diverged in several different watersheds.

Where are the Eburnian–Transamazonian collisional belts?

1990 ◽  
Vol 27 (10) ◽  
pp. 1382-1393 ◽  
Author(s):  
Jean Michel Bertrand ◽  
Emmanuel Ferraz Jardim de Sá
Keyword(s):  
West African ◽  
High Grade ◽  
The West ◽  
West African Craton ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
Nappe Tectonics ◽  
Pan African ◽  
Orogenic Belts ◽  
Lower Crustal

The reconstruction of Early Proterozoic crustal evolution and geodynamic environments, in Africa and South America, is incomplete if cratonic areas alone are studied. If the presence of high-grade gneisses is considered as a first clue to past collisional behaviour, 2 Ga high-grade gneisses are more abundant within the Pan-African–Brasiliano mobile belts than in the intervening pre-Late Proterozoic cratons. The West African craton and the Guiana–Amazonia craton consist of relatively small Archaean nuclei and widespread low- to medium-grade volcanic and volcanoclastic formations intruded by Early Proterozoic granites. By contrast, 2 Ga granulitic assemblages and (or) nappes and syntectonic granites are known in several areas within the Pan-African–Brasiliano belts of Hoggar–Iforas–Air, Nigeria, Cameroon, and northeast Brazil. Nappe tectonics have been also described in the Congo–Chaillu craton, and Early Proterozoic reworking of older granulites may have occurred in the São Francisco craton. The location of the Pan-African–Brasiliano orogenic belts is probably controlled by preexisting major structures inherited from the Early Proterozoic. High-grade, lower crustal assemblages 2 Ga old have been uplifted or overthrust and now form polycyclic domains in these younger orogenic belts, though rarely in the cratons themselves. The Congo–Chaillu and perhaps the São Francisco craton are exceptional in showing controversial evidence of collisional Eburnian–Transamazonian assemblages undisturbed during Late Proterozoic time.

Provenance of the Old Red Sandstone: Pb isotope evidence from Arran, western Scotland

1984 ◽  
Vol 75 (2) ◽  
pp. 239-241 ◽  
Author(s):  
A. P. Dickin
Keyword(s):  
Significant Contribution ◽  
Strike Slip ◽  
Pb Isotope ◽  
Early Proterozoic ◽  
Red Sandstone ◽  
Boundary Fault ◽  
Crustal Block ◽  
Isotope Evidence ◽  
Strike Slip Movement ◽  
Proterozoic Age

ABSTRACTOld Red Sandstone sediments from Arran in western Scotland yield an array of Pb isotope compositions whose slope corresponds to an age of 1830 ± 400 Ma. These compositions are not consistent with a significant contribution of material from the Southern Highlands, Midland Valley, or Southern Uplands, but are similar to the Torridonian sandstones of NW Scotland. Bearing in mind the probable Laxfordian provenance of the Torridonian assemblage, this points to a source for the Old Red Sandstone in a crustal block of early Proterozoic age corresponding to the age of the Laxfordian episode. Since such a source is not presently in a position to yield the Old Red Sandstone, strike-slip movement along the Highland Boundary fault is a strong possibility.

A hydrothermal clay mineral assemblage at the Late Proterozoic unconformity in the Buenos Aires Complex – La Tinta Formation, Barker area, Tandilia Ranges (Argentina)

Clay Minerals ◽  
2010 ◽  
Vol 45 (2) ◽  
pp. 209-224 ◽  
Author(s):  
J. C. Martínez ◽  
J. A. Dristas ◽  
H.-J. Massonne ◽  
T. Theye
Keyword(s):  
Clay Mineral ◽  
White Mica ◽  
X Ray Diffraction ◽  
Aluminium Phosphate ◽  
X Ray ◽  
Late Proterozoic ◽  
Eu Anomaly ◽  
Rapid Changes ◽  
Mineral Assemblages ◽  
First Time

AbstractA general alteration pattern of two transitional clay mineral assemblages was determined by petrography and X-ray diffractometry studies at the Tandilia Late Proterozoic unconformity zone, around the Barker locality: (1) K-white mica + chlorite + calcite ± anatase-rutile ± secondary quartz (farther from the unconformity) and (2) pyrophyllite + K-white mica + Ti-rich hematite ± aluminium phosphate-sulphate minerals ± tourmaline ± anatase-rutile (closer to the unconformity). The local occurrence of Na in K-white micas and K-Na in pyrophyllite is described for the first time. Possible interlayering with intermediate K-Na mica and paragonite is indicated by detailed X-ray diffraction analyses. A negative Eu anomaly (Eu/Eu* = 0.24), strongly positive Eu anomaly (Eu/Eu* =11.7) and positive Ce anomaly characterized rapid changes from an unaltered basement to the most altered basement and sedimentary rocks at the unconformity. Aluminium phosphate-sulphate minerals dominate patterns of LREE. A model of hydrothermal alteration comparable to that of unconformity-related uranium deposits is presented.

Thecate Hydroids from the Shelf Waters of Northern Canada

1970 ◽  
Vol 27 (9) ◽  
pp. 1501-1547 ◽  
Author(s):  
Dale R. Calder
Keyword(s):  
North America ◽  
New Records ◽  
High Arctic ◽  
Common Species ◽  
Hudson Bay ◽  
Northern Canada ◽  
Foxe Basin ◽  
First Time

Based largely on collections from the Calanus–Salvelinus expeditions, 54 species of thecate hydroids were identified from the shelf waters of northern Canada between northeastern Newfoundland and the Alaska–Yukon border. Common species included Halecium muricatum, Calycella syringa, Campanularia integra, C. speciosa, C. volubilis, Gonothyraea loveni, Filellum serpens, Lafoea gracillima, Sertularella polyzonias, S. tricuspidata, Sertularia schmidti, and S. similis. Halecium groenlandicum, H. scutum, Cuspidella procumbens, Calycella gracilis, and Sertularia schmidti are new records for North America; Ptychogena lactea is previously known from this continent only as the medusa. Twenty-two species are reported in northern Canada for the first time, bringing to 71 the number of thecate species recorded from the region. Nearly half of the 71 species recorded are circumpolar in distribution, and over two-thirds transgress both arctic and subarctic zones.Most samples had a paucity of hydroids, particularly those from the high arctic. Collection records indicate that the most favourable regions for hydroids in northern Canada are the Strait of Belle Isle, eastern Ungava Bay, eastern Hudson Strait, northern and southeastern Hudson Bay, Foxe Channel, and northern Foxe Basin.

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