GEOLOGICAL CONTEXT
The geology at the Harroun Site may be summarized in tabular form as follows:
Zone II. A stratum of sand forming the surface of the floodplain, varying from about 5 to 12 feet thick. Zone II was divided into three parts, IIa, IIb, and IIc.
Zone IIc. Humus-stained topsoil, the superficial portion of the Zone II sand member, 0.6 to 1.1 feet thick.
Zone IIb. Grayish to whitish sand with irregular-shaped patches of brownish sand. The brown patches probably represent subsurface staining of the gray-white sands by iron salts carried by percolating water. Zone IIb was 2.0 to 3.1 feet thick where exposed.
Zone IIa. Grayish to whitish sand similar to IIb, but without the patches of brown sand. This zone was heavily saturated with subsurface water wherever encountered, and the presence of the water may have kept the iron salts in solution, thereby explaining the absence of the stains. The thickness of Zone IIa was not determined since seeping ground water prevented excavating down to its base.
Zone IIc. Humus-stained topsoil, the superficial portion of the Zone II sand member, 0.6 to 1.1 feet thick.
Zone IIb. Grayish to whitish sand with irregular-shaped patches of brownish sand. The brown patches probably represent subsurface staining of the gray-white sands by iron salts carried by percolating water. Zone IIb was 2.0 to 3.1 feet thick where exposed.
Zone IIa. Grayish to whitish sand similar to IIb, but without the patches of brown sand. This zone was heavily saturated with subsurface water wherever encountered, and the presence of the water may have kept the iron salts in solution, thereby explaining the absence of the stains. The thickness of Zone IIa was not determined since seeping ground water prevented excavating down to its base.
Zone I. A reddish clay member observed in natural exposures along the edge of the creek channel. The top of Zone I was undulating, and it lay at a depth of approximately 5 to 12 feet below the surface of the floodplain in the exposures examined. The thickness was not determined, but was in excess of 10 feet. The top of Zone I was not reached in any of the excavated squares because seeping ground water prevented carrying the excavations deeper than 4 to 5 feet.