GEOLOGY AND GEOHYDROLOGY 



45 



the subsurface geology of Bikini Atoll (Emery et al., 1954) 

 and Midway Atoll (Ladd ct al., 1970). 



Basement Rocks 



In 1952, two deep holes (Fig. 3) reached the volcanic 

 basement below the carbonate sediment caprock. Hole 



F-1 on Elugelab Island encountered hard basement rock at 

 1405 m depth. In hole E-1 on Medren Island, unweath- 

 ered basalt cuttings were recovered from 1267 m, and 

 solid basalt cores were taken from 1282.5 m to 1287 m. 

 The basalt was an alkali olivine basalt containing analcime 

 (Schlanger, 1963). The rock is similar to the late lavas of 



INSERTS APPROXIMATE 



PAKRY ISLAND 



180' 140- 



INDEX MAP 



J_ 



_L 



162*00' 162MO' 162'20 162-30- 



Fig. 3 Location map of three deep AEC holes drilled in 1951 and 1952. [From Ladd and Schlanger, I960.] 



