The late Proterozoic Zig-Zag Dal Basalt Formation of eastern North Greenland

The late Proterozoic (c. 1230 Ma) Zig-Zag Dal Basalt Formationfound in the platform area of eastern North Greenland is a remnantof a sequence of tholeiitic flood basalts which once may havecovered a large part of North Greenland. The basalts can besubdivided into three main units, totalling up to 1350 m inthickness and erupted within a short interval of time. Someof the flows are more than 100 m thick and have volumes of hundredsof cubic kilometers. Most of the basalts are aphyric or containvery sparse phenocrysts of plagioclase and augite. The chemical composition of the basalts was strongly influencedby hydrothermal metasomatism (incipient spilitization) soonafter deposition. Study of less-mobile elements suggests thatthe basalts formed from increasingly depleted mantle sources.Chemical discontinuities occur between the three main unitsand are probably related to breaks in the volcanic activity.Chemical variation within each unit is mainly governed by lowpressure fractionation of olivine, augite and plagioclase, althoughsuccessive flows do not represent successively more fractionatedmagma batches. Assimilation of crustal material at depth doesnot seem to have greatly affected the basic magma.     

Census of seabird colonies on Nordaustlandet, Svalbard, and in neighbouring localities in 1978 and 1979

Seabird colonies were censused during the summer expedition of Norsk Polarinstitutt to Nordaustlandet, Svalbard, in 1978 and 1979, and to Kongsøya in 1979. An outline is given of the distribution of the species together with an estimate of the number of breeding pairs in the colonies. Twentv-five colonies were censused; seven were visited both years. Four colonies with more than 1,000 breeding pairs of the most abundant species, Briinnich's guillemot and kittiwake, were found on Nordaustlandet.     

Observations of moulting Eider and breeding Common Eider Somateria mollissima at Nordaustlandet, Svalbard, in 1979

A survey on the Common Eider Somateria mollissima in wing-feather moult and females with young was carried out in connection with Norsk Polarinstitutt's expedition to Svalbard in July and August 1979. A total of 3450 moulting eider were found on a water area of approximately 2500 km²; 18% of these were flightless. Females dominated in the population with about 82%. Of the breeding population, 109 females with 336 young were found. The average ratio of female to young has been calculated at 1:3.08. This ratio in relation to other studies of eider productivity is discussed briefly.