722 EIGHTH PACIFIC SCIENCE CONGRESS 



The topography of the Puget Sound area is due primarily to glacial 

 action by a lobe of the Cordillerian ice sheet. The shore line is bordered 

 by deposits of clay, sand, gravel and till, reminiscent of the glacial con- 

 trol. These glacier-derived sediments often form shore line cliffs 200 

 or more feet high. 



Glacial till is a prominent source of sediments in Puget Sound and 

 may become a part of the marine sediment in various ways. (1) The 

 slopes may be in part composed of glacial deposits "in situ". (2) The 

 erosion of cliffs and beaches will also be a supply of glacial sediments. 

 (3) the streams are imposed on glacial till and will transport this ma- 

 terial to the marine environment. (4) Slumping of the cliffs, Avhich are 

 composed of glacial deposits, will add to the marine sediments. 



Chemically and mechanically weathered material from the basement 

 rocks of the Cascade and Olympic Mountains contributes to the sedi- 

 ments as they are carried to the Sound by the numerous streams and 

 rivers. Volcanics, from direct dust-falls and from inland erosion, pro- 

 bably account for some sediment supply in the Sound. 



In the area of sampling (Fig. 1), between President Point on the 

 west shore and Point Wells on the east, the bottom configuration is 

 analogous to the steep shore bluffs. The eastern underwater slope is 

 generally steep and continuous with a value of 1:3.5 from a single 

 break at about 20 feet below sea level to the base of the slope which 

 is approximately 700 feet below sea level. A few localities have slopes 

 of 1:1. The western slope is not as continuous, being divided into areas 

 with different slope angles. Some portions are exceedingly steep with 

 values as great as 1:3, others have gradual slopes with an average value 

 of 1:15. This suggests that bathyraetrically the two slopes are different 

 (See Fig. 3). In this region the slope areas account for about one-hall 

 of the total Sound width of 3.7 miles. The mid-channel region, repre- 

 senting the remaining one-half, is relatively flat \vith a maximum reliel 

 of about 75 feet. 



Method of Sampling and Analysis 

 Initial examination of core samples from Puget Sound indicated 

 that extreme variability in particle size existed. It was suspected that 

 this variability occurred over exceedingly small horizontal distances. In 

 order to study the variability both horizontally as well as vertically, over 

 small horizontal distances, a device Tvas designed to simultaneously ob- 

 tain three cores spaced in a triangular pattern, 1 foot apart (Fig. 2). 

 The cores obtained by this method were cut into sections 1 cm. in length 

 from the surface down. Thus three approximately equal surface samples 

 and three samples for every subsequent 4 cm. in depth were obtained 



