Seasonal Variation in Texture of Beach and Nearshore Sediments 



The study of the seasonal variation in texture and composition of 

 the beach and shelf sediments in the la Jolla area is being continued. The 

 textural analysis of the series of periodic bottom samples taken along a 

 predetermined grid in 19i;9 and 1950 has been completed, and it is anticipated 

 that the laboratory work on the heavy mineral composition and mica counts 

 will be completed by summer. 



The results of the variation in texture were presented at the 

 March meeting of the Society of Economic Paleontologists and Mineralogists 

 in Los Angeles., 



Multi-Sock Sediment Trap 



Golletiore of suspended sediment at different elevations above the 

 bottom and at various positions on the shelf in the La Jolla area, using 

 the mul'5i-sock sediment trap described in Progress Reports Nos. 2 and 10, 

 have been continued. The traps are lowered and recovered from a DUKW, and 

 oriented on the bottom by divers equipped with self-contained diving gear 

 (Aqua-lungs) , 



Most of the collections have been made from the surf zone out to 

 depths of about 85 feet and in general show that the amount of sand in 

 suspension decreases with increasing depth and distance from shore, and 

 decreases logarithmically with increasing height above the bottom. 



The deepest station mentioned previously was at 85 feet. On 29 

 February 1952 a successful observation was made in l50 feet of water 

 on the eon'iinental shelf one mile from shore, and a short distance north 

 of Scrippfi Submarine Canyon. The observation was made during a north- 

 westerly vStorm to determine the amount of material in suspension in the 

 presence of relatively large waves (height approximately 51 feet and 

 period 9 seconds). All of the socks, including the highest, at 81^ cm 

 above the bottom had trapped sediment, and the lowest socks, at a height 

 of l5 cm, contained from 3 to l6 grams of sediment. The divers observed 

 well-formed, symmetrical ripple marks in the vicinity of the trap. 



WAVES AMD CURRENTS 



Sea-Surface Roughness from Photographs of Sun's Glitter 



Investigation of the high-frequency portion of the ocean wave 

 spectrum was initiated about a year ago. One phase of the study is the 

 determination of sea-surface roughness from photographs of the sun' s 

 glitter. 



About 30 photographs have been selected for slope -frequency dis- 

 tribution analysis. These photographs cover a range of wind speed from 

 zero to 30 knots. Five photographs were taken over slicks. One of the 



16 



