Wyville Thomson Ridge Research Articles

Mineralogie et geochimie des sediments quaternaires de l'Ocean atlantique nord-oriental (Mer de Novege — Golfe de Cascogne) — Essais d'interpretations sedimentologiques

The mineralogical and geochemical study of sediments of 14 cores (12 Kullenberg — 2 Reineck) allows us to determine the origin and the process of transport and deposition of detritic fine-grained materials and biogenetic carbonates of the North Atlantic Ocean between the Norwegian Sea and the Bay of Biscay during the different climatic periods of the recent Quaternary. During the cold periods (Würm and Riss), we can notice a mineralogical and geochemical individualization between two types of sediments: 1. (1) One comes from erosion of acidic eruptive rocks, metamorphic rocks and silicic sedimentary rocks (all rich in quartz and illite, presence of correlation between clay minerals/trace elements and calcite/Sr). 2. (2) The other comes from the dismantling of volcanic basic rocks (poor in quartz, rich in montmorillonite, absence of correlation between clay minerals/trace elements, calcite/Sr, and association plagioclase feldspars/Fe, Ti, Ba). The geographic distribution of these two types of material shows that the fine-grained detritic deposits come directly from close-by springs. This explains the blockage of the north—south circulation of Norwegian Sea water, especially north of the Wyville-Thomson ridge. As for the light or non-existent carbonate sedimentation north of the Wyville-Thomson ridge, it develops progressively towards the south, thus permitting the localization of the southern limit of the polar front near the Wyville-Thomson ridge. During the warm periods (Holocene and Riss—Würm Interglacial) on the contrary, the fading of sedimentary differentiation appears to indicate the existence of the north—south circulation of Norwegian Sea water to the south of Rockall Bank. These currents transport the fine-grained materials to the other side of the Wyvile-Thomson ridge and deposit them preferentially south of Rockall Bank, after having taken up coarse quartz elements while crossing the Wyville-Thomson ridge north-west of the Bay of Biscay, the nordic deposits are sparse and the carbonate pelagic sedimentation predominates.

The overflow of Norwegian sea deep water across the wyville-thomson Ridge

Accumulating evidence has pointed to a source of Northeast Atlantic Deep Water in the northern Rockall Trough and prompted a re-examination of geological and hydrographic data. The first showed that the sedimentary Feni Ridge could be traced along the length of the westernRockall Through to the foot of the Wyville-Thomson Ridge, and the second that dense water frequently existed at the lowest point of the ridge crest. Collected soundings and new data suggested a path by which this might enter the Rockall Trough, and overflow of Norweigian Sea Deep Water was observed taking place from the ridge crest in a narrow layer in July 1972. The flow is probably intermittent and appears to entrain Atlantic Water from intermediate depths.

Some Factors Affecting the Extent of Ice in the Barents Sea Area

Variations in flow of the Gulf Stream system and in transport of warm Atlantic water across the Wyville-Thomson Ridge northeastwards (via the North Cape Current) affect the areal extent of ice in the Barents Sea. Theoretical considerations and data are presented relating variations in the Florida Current (southern Gulf Stream system), as indicated by mean sea level changes at Charleston, S.C., and Miami, Fla., to ice conditions in the Barents Sea three years later. Low sea level at Charleston and Miami means strong flow of the Florida Current, contraction of the North Atlantic eddy, little warm Atlantic surface water discharged into the Barents Sea and thus more ice. Conversely, high sea level at Charleston and Miami results in more Atlantic water in Barents Sea and less ice. Relationship of ice to winds in Barents Sea area is also briefly discussed. In the period 1925-1938, good agreement between sea level, ice, and wind curves occurs in 12 of the 14 years.

XX.—Report on Rock Specimens dredged by the “Michael Sars” in 1910, by H.M.S. “Triton” in 1882, and by H.M.S. “Knight Errant” in 1880

I have been entrusted by Sir John Murray, K.C.B., with the examination of some of the coarser materials, more especially the rock-fragments, obtained from the bed of the Atlantic by Sir John Murray and Dr Hjort during the recent Michael Sars Expedition in 1910, and also with the re-examination of the collections dredged from the Wyville Thomson ridge and the Faroe Banks during the former expeditions of H.M. ships Triton in 1882 and Knight Errant in 1880

4. On theCrinoideaof the North Atlantic between Gibraltar and the Faeroe Islands

This communication falls conveniently into two sections—I. dealing with the specimens obtained by H.M.SS. “Lightning” and “Porcupine,” during what may be called the pre-Challenger period of deep-sea exploration; II. concerning those dredged by the “Knight Errant” and “Triton” during the surveys of the Wyville Thomson ridge, which were conducted in the years 1880–82.

IX.—Asteroidea dredged in the Faeröe Channel during the Cruise of H.M.S. “Triton ” in August 1882

The star-fishes recorded in the present communication were dredged by Mr John Murray during the cruise of H.M.S. “Triton” (under the command of Staff-Commander Tizard, R.K), whilst investigating the nature of the Wyville-Thomson Ridge and the adjacent portions of the Faeröe Channel. All the forms, excepting these from Station 3, were obtained from deep water, and the collection, as a whole, is both rich and interesting. One species and two well-marked varieties have not hitherto been described, and two other species have only been found once previously. The series consequently forms a valuable supplement to the collections made during the cruises of H.M.S. “Porcupine” and the “Knight Errant,” and is an important addition to our knowledge of the fauna of this region of the Atlantic. I propose to reserve any remarks upon the general character of the asterid fauna of the Faeröe Channel until treating of the collections obtained during the “Porcupine” and “Lightning” cruises.