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Throughout the Quaternary, glaciers have provided considerable amounts of sediments to the oceans. However, little is known concerning the physical and chemical characteristics of these sediments. Rapid recession of glaciers during the past 100 years has deposited large amounts of glacial sediments in the fiords and inlets of southeast Alaska. These mechanically weathered, rapidly deposited sediments provide and unparalleled laboratory to study sediment-seawater
interaction and the geochemical characteristics of glaciomarine sediments.
Glaciomarine sediments in southeast Alaska consist predominantly of feldspar, quartz, illite, and chlorite. Kaolinite is not a weathering product in this area. Interstitial waters from bottom grab samples showed a substantial decrease in sodium ions compared with the overlying waters. Significant variations in Na+ concentration with depth also were found in interstitial waters obtained from cores. Laboratory and field observations suggest that primary glacial clays are saturated with H+ and Ca++. During transport and early stages of burial in marine environment, cation exchange of H+ and Ca++ from glacial and fluvial sediments for Na+, K+, and Mg++ of seawater is the major process causing changes i the interstitial water. No mineralogic alterations of clay were observed from the glaciofluvial to marine environment. Cationic concentrations in interstitial waters can be related to the bulk mineralogy and particle size of sediments, the environment of deposition, and the path length the sediments follow before deposition.
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