2.2 The Lagoon Bottom Around BAKER GZ The following is an excerpt from Reference C-2 that describes the lagoon bottom surrounding the BAKER target area. The characteristic sediment in the target -area, prior to Test B, consisted chiefly of remains of the calcareous alga Halimeda. This alga, green when living consists of flat oval plates, 2mm. to 5mm. in diameter, joined together in series like a string of beads. When the plant dies, the green tissue decomposes and the plates fall apart, leaving a residue of small white or pale brown plates resembling uncooked rolled oats. With this Halimeda debris there usually is admixed a variable amount of mud (silt and clay-sized particles), sand, and shells. Five cores taken in the vicinity of the explosion point two weeks after Test B in the summer of 1946 showed that this sediment no longer occurred in the target area. Instead, a layer of mud covered the bottom, with coarser material below. However, the 33 cores taken during the 1947 resurvey show that the typical sequence in the target area now is as follows: A, A top layer of "target area" mud (see Figure C-3), grading through a thin transition zone into B. A layer of silt and sand, the coarseness increasing turn grades into C. fine with to coarse silty depth. This in A layer of clean, white Halimeda debris, with occasional fragments of green Halimeda. usually with a sharp contact, on - This D. Pale tan or admixed mud and sand. debris The bottom layer brownish (D) Halimeda of this sediment of the target area The layers Baker three explosion. top It usually (A, 8B, with sequence appears be the original the rests, D is not 4¢sic}) to prior to radioactive. apparently represent material that was stirred up by the explosion and subsequently settled out roughly in a sequence 9000063 C-4