The observation by Heinrich (1988) that, during the last glacial period, much of the input of ice‐rafted detritus to the North Atlantic sediments may have occurred as a succession of catastrophic events, rekindled interest on the history of the northern ice sheets over the last glacial period. In this paper, we present a rapid method to study the distribution of these events (both in space and time) using whole core low‐field magnetic susceptibility. We report on approximately 20 cores covering the last 150 to 250 kyr. Well‐defined patterns of ice‐rafted detritus appear during periods of large continental ice‐sheet extent, although these are not always associated within their maxima. Most of the events may be traced across the North Atlantic Ocean. For the six most recent Heinrich layers (HL), two distinct patterns exist: HL1, HL2, HL4, HL5 are distributed along the northern boundary of the Glacial Polar Front, over most of the North Atlantic between ≈40° and 50°N; HL3 is more restricted to the central and eastern part of the northern Atlantic. The Nd‐Sr isotopic composition of the material constituting different Heinrich events indicates the different provenance of the two patterns: HL3 has a typical Scandinavia‐Arctic‐Icelandic “young crust” signature, and the others have a large component of northern Quebec and northern West Greenland “old crust” material. These isotopic results, obtained on core SU‐9008 from the North American basin, are in agreement with the study by Jantschik and Huon (1992), who used K‐Ar dating of silt‐ and clay‐size fractions of an eastern basin core (ME‐68‐89). These data confirm the large spatial scale of these events, and the enormous amount of ice‐rafted detritus they represent.

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Coarse-fraction sediment (>63 µm) studies for Leg 151 Sites 908 and 909 have enabled us to reconstruct the paleoclimate since the early Miocene (18.0 Ma) of the Fram Strait, in order to better understand this gateway between the North Atlantic and the Arctic Ocean. Study of the grain-size distribution patterns (subfractions 63-125 µm, 125-250 µm, 250-500 µm, 500-1000 µm, and >IOOO µm plus the coarse-component composition) suggests possible seasonal ice-rafting starting as early as 14.0 Ma. Also shown is a clear signal of ice-rafting events between 10.8 and 8.6 Ma, 7.2 and 6.8 Ma, 6.3 and 5.5 Ma, and since 5.0 Ma. Evidence indicates that the initiation of the East Greenland Current took place at 10.8 Ma and is related to the reorganization and shutdown of deep-water connections in the Middle and Central American Seaways during the latest middle to late Miocene. During the Pliocene-Pleistocene, the polar front moved over Site 908, covering the area with sea ice and pack ice during the Pleistocene (between 1.9 and 1.2 Ma). The West Spitsbergen Current episodically reached the Fram Strait during the Pliocene-Pleistocene, suggesting that the Norwegian Sea was never completely covered by sea ice and pack ice in that era.

In two feeding trials conducted with juvenile Atlantic cod Gadus morhua (initial mean weight ¼ 87.9 or 15.92 g), soy protein concentrate (SPC) was used to replace fish meal in isonitrogenous, isocaloric diets. In the first trial, five experimental diets (47% protein, 15% fat; calculated gross energy ¼ 5,059 kcal/kg) were formulated to replace 28, 60, 80, and 100% of dietary fish meal. In the second trial, three diets were formulated with SPC to replace 0, 25, and 50% of the fish meal in a modified commercial diet for marine finfish (50% protein, 15% fat; calculated gross energy ¼ 4,900 kcal/kg; calculated digestible energy ¼ 3,570 kcal/kg). Upon conclusion of the studies, no differences in survival, growth, hepatosomatic index, or viscerosomatic index were found among the treatment groups. The fish attained mean weights of 162.7 and 39.1 g in the first and second trials, respectively, with specific growth rates of 0.76% and 1.12% and feed conversion ratios of 1.28 and 1.29, respectively. No consistent pattern of enteritis was observed in the histological sections taken from fish in either study. These results indicate that SPC can entirely replace fish meal in diets of juvenile Atlantic cod or can be combined with other common feed ingredients to replace up to 50% of dietary fish meal.

Comparisons between a Greenland ice core isotopic record and marine sediment grey level records of the North Atlantic Ocean show that rapid temperature variations witnessed by the ice core (Dansgaard‐Oeschger events) during the last glacial period can also be detected in marine sediments. This shows that the resolution obtained in marine cores can be sufficiently high to record rapid climatic fluctuations. Several spectral analyses of those grey level marine records consistently indicate that significative fluctuations of the climatic response exist with periodicities of 5 to 1 kyr in addition to orbital forcing. These high frequencies are close to those predicted by various dynamic ocean models.