Ice rafting

Ruddiman, W. F. Glover, L. K. (1972). Vertical mixing of ice-rafted volcanic ash in North-Atlantic sediments. Geol. Soc. Amer. Bull, 83, 2817-36. 

Weathered fragments of continental crust comprise the bulk of marine sediments. These particles are primarily detrital silicates, with clay minerals being the most abmidant mineral type. Clay minerals are transported into the ocean by river runoff, winds, and ice rafting. Some are authigenic, being produced on and in the seafloor as a consequence of volcanic activity, diagenesis and metagenesis. 

Ice rafting is responsible for 7% of the terrigenous input of siliclastic particles to the ocean. When the ice melts, the particles settle to the seafloor to form glacial marine deposits. These are currently forming at latitudes greater than 40°N and 50° S. Most of the glacial marine sediments are poorly sorted deposits composed of relatively unweathered materials with chlorite being the dominant clay mineral. In the North Atlantic, layers... 

The dominant clay mineral at high latitudes is chlorite. In addition to ice rafting, lithogenous materials are transported in the polar oceans by rivers and winds. Polar seas are also characterized by diatomaceous oozes due to the occurrence of upwelling supported by divergence at 60°N and 60°S. 

The continental shelves cover most of the seafloor in the Arctic Ocean, making this the shallowest ocean. Thus, most of the sediments are neritic. Because of light limitation, primary production is inhibited, so river runoff and ice rafting supply most of the particles to this ocean. As a result, lithogenous and glacial marine sediments are most common. 

Ice rafting The transport of Uthogenous material by icebergs. The rafted material is rock eroded from the continents as the icebergs flowed seaward. 

Heinrich H. (1988). Origin and consequences of cyclic ice rafting in the northeast Atlantic Ocean during the past 130,000 years. Quat. Res., 29, 142-152. 

Figure 20 Nd-Sr-isotope ratios of terrigenous clastic components of Heinrich layer H3. Shown for reference are the average and 2 sigma range for the data published on Heinrich layers HI, H2, H4, and H5, and reported compositions of potential source areas of ice rafted detritus (Grousset et al., 2001, and references therein). Also included is the average of 5 unpublished analyses across H3 from V28-82, where the error bars represent the range of values measured (A. lost and S. Hemming) (somces Grousset et al., 1993 Revel et al., 1996 Snoeckx et al., 1999).

Results from studies of the ice-rafted detritus population from core V23-14 provide insights into the evolution of ice sheets of the northwest Atlantic margin since 43 ka. Between Heinrich layers H5 and H3 (MIS 3), it appears that the... 

Grousset F. E., Labeyrie L., Sinko J. A., Cremer M., Bond G., Duprat J., Cortijo E., and Huon S. (1993) Patterns of ice-rafted detritus in the glacial North-Atlantic (40-degrees-55-degrees-N). Paleoceanography 8(2), 175-192. 

Gwiazda R. H., Hemming S. R., and Broecker W. S. (1996b) Tracking the sources of icebergs with lead isotopes the provenance of ice-rafted debris in Heinrich layer 2. Paleoceanography 11(1), 77—93. 

Hemming S. R. and Hajdas 1. (2003) Ice-rafted detritus evidence from Ar-40/Ar-39 ages of individual hornblende grains for evolution of the eastern margin of the Laurentide ice sheet since 43 C-14ky. Quat. Int. 99, 29-43. 

Hemming S. R., Broecker W. S., Sharp W. D., Bond G. C., Gwiazda R. H., McManus J. F., Klas M., and Hajdas I. (1998) Provenance of Heinrich layers in core V28-82, northeastern Atlantic Ar-40/Ar-39 ages of ice-rafted hornblende, Pb isotopes in feldspar grains, and Nd—Sr—Pb isotopes in the fine sediment fraction. Earth Planet. Sci. Lett. 164(1-2), 317-333. 

Hemming S. R., Vorren T. O., and Kleman J. (2002b) Provinciality of ice rafting in the North Atlantic application of Ar-40/Ar-39 dating of individual ice rafted hornblende grains. Quat. Int. 95-96, 75-85. 

Ruddiman W. F. (1977) Late quaternary deposition of ice-rafted sand in subpolar North-Atlantic (Lat 40-degrees to 65-degrees-N). Geol. Soc. Am. Bull. 88(12), 1813-1827. 

Manighetti B. and McCave I. (1995) Depositional fluxes and paleoproductivity and ice rafting in the NE Atlantic over the past 30 ka. Paleoceanography 10, 579—592. 

Figure 35 Reconstructed variations in mean temperature of shallow low-latimde seawater during the Phanerozoic based on the data in Figure 34. Note the good agreement of the cooling episodes with the extended latitudinal dispersion of ice rafted dehris (shaded histograms). In the subsequent publication, Shaviv and Veizer (2003) showed that the proposed temperamre variations correlated with the intensity of cosmic-ray flux reaching the Earth. The pco2 (PAL— present-day atmospheric level) is that for the Geocarb model of Berner (1994).

Additional evidence for the factors that force millennial-scale climate change comes firom the study of layers of sand-sized material that are transported to the sea by ice. During the last glacial period there are six layers of ice-rafted debris (IRD) in the North Atlantic firom the Labrador Sea across to France (Fig. 7.23). The layers are tens... 

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