Cultural Chronology - Soils and Stratigraphy - Artifacts - Faunal Remains - CA-MNT-910 Home
Soils and Stratigraphy
Soils and Stratigraphy - Features
Soil in the vicinity of CA-MNT-910 belongs to the Gaviota Series, which is made up of excessively drained soils on uplands formed in areas underlain by sandstone (Soil Conservation Service 1978). The heavy sand content in the sediments exposed during excavation conforms well with this description although the typical Gaviota soil is described as brown (10 YR 4/3) sandy loam in the upper 2 inches giving way to brown (10 YR 5/3) sandy loam between 2 and 12 inches. The soil at CA-MNT-910 had a low clay content and seemed better classified as a silty sand rather than a loam.
Soil within the site was an anthropomorphic version of the Gaviota series. While the site area had been originally characterized as a lithic scatter, excavation showed that it was marked by a midden deposit with darker soil and faunal remains within the matrix along with flaked stone artifacts and debris. The midden was relatively shallow, extending to depths of only 40 cm in most units. Because of extensive activity by ground burrowing animals, however, the transition between the midden and sterile substrate beneath it was very uneven, and pockets of midden occurred at depths greater than 40 cm. The midden was designated Stratum I and two relatively insignificant variants were defined: Strata Ia and Ib. Stratum Ia was a brown (10 YR 5/3) silty sand midden in the upper 3-5 cm of the deposit with a high root content and other organic debris derived from the surface. Stratum Ib had the same basic color and texture but was beneath the root zone. Stratum Ib was underlain by the natural silty sand which was reddish yellow in color (7.5 YR 6/6) and appeared to be derived from a sandstone parent rock beneath it. .
A total of 37 soil samples collected from a range of vertical and horizontal proveniences were analyzed for pH using a Poly-D pH reagent kit from the California Polytechnic State University Soil Science Department. The surface pH values ranged from 5.5 to 6.6 or medium to very slightly acidic. Patterning was apparent with depth, however, as samples below 10 cm consistently produced values between 7.0 and 8.0 (neutral or very slightly alkaline). Two conclusions are suggested from this pattern. First, soil acidity in this areas probably caused by organic debris deposited on the surface including pine needles. Pines are generally associated with acidic soils and poor archaeological preservation in California, and gray pines were part of the vegetation present on site. Second, the shift from acid to alkaline soils with depth is so exaggerated that it suggests an alteration to the natural soil. The addition of marine shells to the midden as a result of prehistoiric dietary practices probably contributes to soil alkalinity.
|
|
|
| Cal Poly student, Angela Barrios, drawing a sidewall profile | Sidewall profile from Unit 4 | Cal Poly student, Allyson Schwartzenberger taking a column sample |
Features at CA-MNT-910 included a single BRM outcrop (Feature A) situated
on the southern edge of the site and two subsurface rock concentrations. The
mortars were present on a sandstone outcrop situated in a small feeder drainage
on the southern edge of the site. Six cups were documented. Measurements are
presented below. The first rock concentration was encountered in Unit 3, 20-32
cm below surface in the central eastern portion of the unit. The rocks were
mostly reddened quartzite between 5.0 and 12.0 cm in diameter. Some were clearly
fire-affected while others were not. No ash or significant charcoal was noted.
A recent rodent run nearly circled the concentration. The second concentration
was discovered in Unit 4 between 20 and 30 cm below surface. This was a similar
circular concentration of fist-sized rocks in the western central portion of
the Unit. Again, no significant ash or charcoal were noted. The functions or
other significance of these features are unclear.
 |
| Feature A, bedrock mortars 1, 2, 3, 4, 5 and 6, CA-MNT-910 |
References Cited
Soil Conservation Service; 1978; Soil Survey of Monterey
County, California. United States Department of Agricluture in cooperation
with the University of California Agriclutural Experiment Station. United States
Government Printing Office, Washington DC.