Geochemistry of Subsea Permafrost at Prudhoe Bay, Alaska.

Abstract : The analytical data from sediment, interstitial water, and seawater analyses of samples collected near Prudhoe Bay, Alaska, during the period from March to May 1977, are presented. Analyses include determinations of moisture, calcium carbonate, and organic carbon contents in the sediment samples and pH, electrical conductivity, alkalinity, and concentrations of sodium, potassium, calcium, magnesium, chloride, and sulfate in the interstitial water and seawater samples. Salinity, ionic balance, and freezing point of the water samples were calculated. The marine sediments in Prudhoe Bay generally contain more calcium carbonate, organic carbon, and interstitial water than the underlying glacial and fluvial gravels. On land, a surficial layer of peat also had high organic carbon and moisture contents. The salinity of the seawater samples varied from concentrated brines near the shore where sea ice is frozen directly to, or is located near, the sea bottom to water which was 1.0 to 1.5 ppt less saline than normal seawater at a distance of approximately 10 to 15 km from shore. Potassium, calcium, sulfate, and alkalinity concentrations all showed significant variations from those of normal seawater. The interstitial water samples from sediments taken from the marine boreholes generally contained water whose overall composition was close to that for normal seawater, suggesting that seawater had either infiltrated into, or had been deposited with, the sediments. Potassium, calcium, alkalinity, sulfate, and magnesium concentrations showed significant variations from those of normal seawater.