SEA SURFACE 



-120 a 



— a. 



I 



0.1 



MILES 



I 



0.2 



This reflection profile shows an erosional bedrock surface (dark green) 

 situated about 60 feet beneath the sea floor at the tower. This surface 

 slopes gently seaward with a subbottom high approximately 1/2 mile 

 west of the tower. The bedrock is probably cretaceous sandstone, 

 conglomerates, and shales like those cropping out on nearby Point 

 Loma. The records show deep reflecting structures, indicating that the 

 bedding is nearly horizontal in the vicinity of the tower. Overlying 

 the bedrock is sand-silt-clay (loam) 30 to 70 feet thick. This section 

 has layers of shells interbedded with sandier zones, which probably 

 represents an ancient low sea level deltaic or bay deposit. Overlying 

 this section of ancient bay or deltaic deposits of the San DiegoRiver 

 is a zone of transgress ive marine sands (light green). This occurred 

 during the Holocene period as the glaciers melted. The uppermost 

 parts have been modified by present-day currents and wave action. 

 In the subbottom profile (above) the depth to subbottom reflectors is 

 approximate due to variations in sound travel time through sediments. 



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