Geological Study Samples

The sediments dataset is a catalog of the geological samples used in a study of the physical and chemical properties of local soils. The chemical and granulometric analyses conducted on these samples contributed to an evaluation of potential for successful dry-land agriculture in the Dolores Valley. Soils in the project area are generally derived from eolian parent material and exhibit a loamy texture that indicates their suitability for agricultural production (Decker and Petersen 1987). Constraining factors on soil productivity include macronutrient and macronutrient levels, percentage of organic matter, electrical conductivity (EC), and alkalinity (pH). These variables are used to identify the quality of soils based on the relative amount of nutrients available for plant growth; they are also useful in determining which areas are unsuitable for agricultural development due to their alkalinity or salinity. The sediments dataset provides the alkalinity of each sample with a two digit number; a decimal is assumed between the digits. A logarithmic scale is used to describe sample texture; seven variables in the dataset indicate grain size at fixed percentage points on a cumulative curve, each denoted by the phi prefix. The dataset also includes each sample's Munsell color, the percent of organic matter lost on ignition, phosphate levels, and reaction to hydrochloric acid.

Variables for the sediments dataset have been described by Wilshusen et al. (1999); see especially the section "Samples" by Josh Torres in Chapter 4. In most cases, his descriptions are suitable for use as metadata and have been repeated almost verbatim here. See also Chapter 7, "Resource Studies," by Kenneth Lee Petersen, in the Final Synthetic Report. Selected resources from the collection of published and unpublished DAP reports may have been used for clarification in some cases and will be appropriately referenced.