Age models of sediment cores from the North-West African continental margin

A statistical analysis ol 15 deep sea cores in the eastern North Atlantic off NW Africa revealed the typical fluctuation pattern of distinct species proups as has been described from various parts of the world ocean. Only the "WBF-group" appears to be correlated with global climatic changes, i.e. warmer periods as the Eemian and the Atlanticum. A partly antagonistic "High Productivity group" (HPR-group) is in general not linked with global changes but times of increased fertility in the surface water and the resulting flux of organic matter reaching the bottom. The groups were extracted from cluster analysis of more than 150 surface samples (HPR-group) and a factor analysis of selected cores (WBF-group). In contrast to previous studies the observed fluctuations can not be explained by drastic changes in bottom water masses, but by the pulsation of a distinct "High Productivity Patch" in space and time. At present, this patch is located below the well known upwelling area between 22° and 12° northern latitude. It shifted to the north (up to 27 °N) during the latest glacial period ( 18 ky), indicating an equivalent shift of upwelling productivity caused by advection of nutrient rich upwelling SACW-waters, probably during most of isotopic stages 2 and 3.

Quantitative composition and distribution of the silt fraction in surface sediments of the North-West African continental margin

Surface sediments from the continental slope and rise of North-West Africa between the Canary lslands and the Cape Verde Islands are mainly composed of silt-sized material (2-63 µm). A number of sampling profiles were run normal to the coast and the composition of the silt fraction was determined quantitatively by scanning electron microscope analysis. The carbonate portion of the sediment was found to be nearly exclusively of biogenic origin. The most important contributors are planktonic foraminifers and coccoliths with minor contributions derived from pteropods. Plankton-produced biogenic opal such as diatoms and radiolarians play a very minor role. The high production rates of opal-silica plankton which exists in the surface waters of the NW-African upwelling system does not give rise to corresponding increases of opal accumulation in the bottom sediment. Benthic producers consist mainly of foraminifers and molluscs but the entire input from benthic producers is extremely small. An exception to this occurs in the prodelta sediments of the Senegal river. Downslope particle transport is indicated by the occurrence of shallow-water coralline algae, ascidian sclerites and cliona boring chips and can be traced as far down as the continental rise. The non-carbonate silt fraction mostly consists of quartz which is derived as eolian dust from the Sahara desert by the Harmattan and the NE-Trade-wind system. The percentage of carbonate in the surface sediments directly indicates the relative proportions of autochthonous biogenic components and terrigenous allochthonous quartz particles.

From the Black Mountain to Waziristan, being an account of the border countries and the more turbulent of the tribes controlled by the North-west frontier province, and of our military relations with them in the past.

Mode of access: Internet.

The three voyages of Martin Frobisher in search of a passage to Cathay and India by the north-west, A.D. 1576-8 /

Mode of access: Internet.

The geological structure of the north-west Highlands of Scotland.

Plates XL-LII each accompanied by leaf with descriptive letterpress.

Journals of the Council of the North West Territories, from 1877 to 1887.

Title taken from binder's title.

The remarkable history of the Hudson's Bay Company : including that of the French traders of North-western Canada and of the North-west, XY, and Astor Fur Companies /

"The Cree syllabic characters": p. 497.

Journal of a tour on the north west coast of America in the year 1829, containing a description of a part of Oregon, California and the north west coast and the numbers, manners and customs of the native tribes,

"No. 64 of 150 copies printed. Also 10 copies printed on Japan vellum."

An exploration of the Tazin and Taltson rivers, North west territories,

Mode of access: Internet.

The Punjaub and North-West frontier of India;

Mode of access: Internet.