The Nd and Hf isotopic evolution of the mantle through the Archean. results from the Isua supracrustals, West Greenland, and from the Birimian terranes of West Africa

1999 ◽  
Vol 63 (22) ◽  
pp. 3901-3914 ◽  
Author(s):  
Janne Blichert-Toft ◽  
Francis Albarède ◽  
Minik Rosing ◽  
Robert Frei ◽  
David Bridgwater
Keyword(s):  
West Africa ◽  
West Greenland ◽  
Isotopic Evolution

scholarly journals Do Nearctic Northern Wheatears (Oenanthe Oenanthe Leucorhoa) Migrate Nonstop to Africa?

The Condor ◽  
2006 ◽  
Vol 108 (2) ◽  
pp. 446-451 ◽  
Author(s):  
Kasper Thorup ◽  
Kasper Thorup ◽  
Troels Eske Ortvad ◽  
JØrgen RabØl
Keyword(s):  
West Africa ◽  
Western Europe ◽  
Great Circle ◽  
Wintering Grounds ◽  
Oenanthe Oenanthe ◽  
West Greenland ◽  
Flight Costs ◽  
Body Weights ◽  
Direct Flight ◽  
Great Circle Distance

Abstract We present data suggesting that Northern Wheatears (Oenanthe oenanthe leucorhoa) breeding in West Greenland and Canada may be able to accomplish migration to their wintering grounds in West Africa in one direct, transatlantic crossing of more than 4000 km (great circle distance). This conclusion is based on analyses of wing lengths, body weights, and timing of departure from West Greenland and arrival on an island 350 km off the coast of Morocco. Previously, it has been suggested that Nearctic wheatears migrate to Africa by a two-step journey, the first leg comprising a shorter transatlantic crossing to western Europe. A long, direct flight has previously been considered unfeasible as the predicted flight costs were considered to be too high. However, recent insights in aerodynamic theory make these long ocean crossings appear more feasible, especially when taking the use of tailwinds into account.

scholarly journals Use of Rb-Sr isotope data to constrain the time of deposition of Precambrian metasediments: an example from Hamborgerland, West Greenland

1993 ◽  
Vol 159 ◽  
pp. 95-100
Author(s):  
F Kalsbeek
Keyword(s):  
Granulite Facies ◽  
Field Investigation ◽  
High Grade ◽  
Sr Isotope ◽  
West Greenland ◽  
Relative Age ◽  
Isotopic Evolution ◽  
High Grade Metamorphism ◽  
Isotope System ◽  
Nd Model Age

In high-grade metamorphic terrains it is often not possible to determine the relative age of metasedimentary units by field investigation. However, the time of deposition of the original sediment can be constrained by consideration of the Sr-isotopic evolution of the rocks on the scale of an outcrop. An outline of the method is given, and Rb-Sr data for high-grade (granulite facies) metasediments from HamborgerIand, West Greenland, are discussed as an example. Sm-Nd model age data indicate that these rocks were derived by erosion of a 3000–3200 Ma basement. Deposition took place not long before 2700 Ma ago, and closure of the Rb-Sr isotope system after high-grade metamorphism occurred at about 2600 Ma.

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