CA-MNT-1748/H

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Soils and Stratigraphy

Soils and Stratigraphy - Features

The natural soil in the vicinity of CA-MNT-1748/H is classified as stony fluvents which occur on level areas in flood plains and on alluvial fans that are subject to flooding, deposition, and scouring during high intensity storms (Soil Conservation Service 1978). This soil type is most common in small narrow areas adjacent to creeks where it is manifested by a light brownish gray or grayish brown sandy loam.

Sidewall profile from Unit 1, CA-MNT-1748/H

Soil exposed within site boundaries was best characterized as a rich midden deposit with an underlying sandy silt loam that also contained cultural constituents. The uppermost portion of the midden marked by a dense concentration of organics including roots was designated stratum I. It extended to a depth of approximately 10 cm. The midden beneath the organic zone was dark gray brown in color (10 YR 4/2) and was characterized as a soft sandy silt loam. It extended to a maximum depth of approximately 100 cm although the transition from the midden to non-midden substrate was very gradual. Below 100 cm, the midden gave way to a brown (10 YR 5/3) sandy silt loam (Stratum III). Stratum IIIa (the upper portion of stratum III) produced some marine shell and significant quantieies of debitage. The lowermost soils encountered during the excavation were at the bottom of Unit 1 (120-150 cm below surface) where shell was no longer found and debitage counts were low. The midden and underlying soils all showed signs of heavy turbation from ground burrowing animals, and much of the debitage and shell recovered from the deeper levels seems to have been transporrted downward by this activity. The deep soils at this site seem to reflect alluvial deposition from the adjacent San Antonio River.

Sixteen soil samples were subjected to pH analysis. The resulting readings showed an overall range between 6.7 and 7.9 or very slightly acidic to slightly alkaline. Three readings from Stratum I, the organic zone on the top of the midden, all were 7.0 or neutral. Five readings from Stratum II were between all between 6.9 and 7.6, which are effectively neutral. Five readings from Stratum III (a and b variants) were between 6.8 and 7.9. One additional reading from a small pocket of ash in Unit 6 (109 cm) produced a value of 7.5. For all intents and purposes, soil at this site was essentially neutral, providing a good environment for preservation.

Unit 2

Features

Sidewall profile Unit 2, CA-MNT-1748/H showing features 2 and 3 and location of flotation sample 3 (floor sample).

Four subsurface features were identified and numbered by unit. Unit 6 Feature 1 was an ash concentration 19-26 cm below datum. A total of 9.0 liter of ash was collected from this sample and subjected to flotation analysis (see flotation sample 1, Appendix VI). All other features were found in Unit 2. Unit 2 Feature 1 consisted of a large concentration of ash 53 to 58 cm below surface in. This large concentration of ash was collected in its entirety as flotation sample 2 (27.25 liters), and a sample of charcoal from this feature was submitted for radiocarbon analysis. As described in more detail below, this sample produced a calibrated date of ca. A.D.1800, suggesting that this ash related to the time of the structure’s abandonment. This feature was sitting directly on a house floor which was defined as Unit 2 Feature 2. The floor was first encountered at a depth of 52 cm in Unit 2, and was later found to extend into adjacent Unit 5. The floor’s surface was relatively even, but it dipped to a low point 57 cm below datum in Unit 2. It was distinguished by an extremely hard surface that was whiter in color than the overlying dark brownish gray midden. A few rounded cobbles were present on the surface of the floor, but these probably originated in the midden. The indurated floor was about 8 cm thick, and its depth below the Unit 2 datum ranged from 41-57 cm. Edges of the feature were identified in both Units 2 and 5 showing that this portion of the floor exposed in these units was about 4.5 m wide. Orientation of the edges suggested that the overall configuration of the floor was probably oval-shaped as opposed to round. If the structure associated with the floor was indeed oval-shaped, it probably would have been about 4.5 x 6.0 m in size when it was in use. This suggests a residential structure rather than a ceremonial or communal dance house which would probably have been bigger. Flotation sample 3 was taken from the floor itself. The sample was 0.5 x 0.5 m in dimension and was taken whole from the floor. It represented a volume of 14 liters. A piece of charcoal recovered from this sample was used to date the floor. Discussed in more detail below, the calibrated date from this sample was A.D. 1280. We believe this sample represents a terminus post quem for the house floor; it must have been constructed sometime after A.D. 1280. Other than the 0.5 x 0.5 m sample, excavation was terminated at the floor, and plastic sheeting was placed over it before it was backfilled. An additional flotation sample was recovered from the matrix beneath the floor (flotation sample 4). A dense concentration of cobbles on the lip of the floor was defined as Feature 3.

Picture of Unit 6 Feature 1, CA-MNT-1748/H showing edge of housefloor

References Cited

Soil Conservation Service
1978 Soil Survey of Monterey County, California. United States Department of Agriculture in cooperation with the University of California Agriculture Experiment Station. United States Government Printing Office, Washington D.C.