Excavations at the Alamo Shrine [page 23]Post holes were noted in Units 1, 3, and 12 (Fig. 9). In Unit 1, the outline of a post hole of 23 cm diameter filled with brown soil was exposed at the top of the level. It is located 24 cm away from the building wall and was found to penetrate to a depth of 50 cm. The post hole in Unit 3 was basically of the same description and was located 1.16 m from the building. The post hole found in Unit 12 was located 1 m from the building, off the southwest corner and in line with the hole in Unit 3. These holes possibly had been dug by the U.S. Army under the direction of Major E. B. Babbitt, Acting Quartermaster U.S.A., in 1849 to install scaffolding posts for the repair of the building.
Just below the packed caliche level was a deposit of light gray to brown clayey soil averaging about 4 cm in depth with thin lenses of light gray earth. On top of this level were many fist-sized and larger stones. Recovered from the level were potsherds of majolica, Good, and plain wares; bottle glass fragments animal bones; fragments of charcoal; and a flagstone fragment. This level appears to date to the Spanish Colonial period of occupation.
Below the gray brown soil was a deposit of off-white calcareous earth (caliche) roughly 10 to 15 cm in depth. This is a packed caliche fill similar in color and composition to the upper level. Artifacts recovered from this deposit include sherds of majolica, Goliad, and plain wares; square nails; bottle glass fragments; and animal bones. This level evidently dates to the Spanish Colonial mission period.
The caliche level lies on top of firmly packed dark brown clay which appears black when first exposed. It extends roughly 20 cm below the caliche level to where it gradually changes to a dark reddish-brown clay. There is no clear level distinction, as the color changes with depth when viewed in sunlight.
This soil is a component of the Patrick series, a member of the Venus-Frio-Trinity soils association as described by the U.S. Department of Agriculture (Taylor, Hailey, and Richmond 1966:26-27). It is a dark brown calcareous clay loam, almost black in appearance when moist. It has a substratum of red-brown clay loam overlying calcareous soil known locally as caliche. The calcium carbonate in this subsoil increases with depth.
In the upper few centimeters of the dark brown clay, the excavations recovered majolica, Tonolá, and Goliad pottery fragments; chert flakes; tool forms and arrow points; and numerous animal bones. Below the thin deposit of artifacts, the clay was culturally sterile. In the upper part of this level, where the artifacts and bone were concentrated, there were many snail shells (including Rabdotus, Practicolella and Helicina species). 'Below the cultural level, the number of shells rapidly diminish with depth. The top of the dark brown clay, which lies about 40 cm below the upper white caliche level, appears to have been the early mission period ground surface.