|This map has been superseded by USGS Open-File Report 97-852. This database of the Rifle 7.5 minute quadrangle, Garfield county, Colorado originally released as U.S Geological Survey Open-File Report 95-52, has been updated to include a digitized database
|Shroba, Ralph R.; Green, Morris W.; and Fairer, George M.
|U.S. Geological Survey Open-File Report 95-52
From their origin in ArcInfo and the Alacarte package, each coverage contains topological and bookkeeping attributes of little or no scientific interest; only the attributes of scientific significance are described in detail here. The other attributes are AREA, PERIMETER, LENGTH, FNODE#, TNODE#, LPOLY#, RPOLY#, cover#, cover-ID, SEL, and SYMB. The primary layer is the geology layer (marlm-geo), which consists of both polygon features and arc features that describes map units (polygons), and depositional contacts, faults (which may or may not be polygon bounding features) and map boundaries. Map units (polygons) are described in the polygon attribute table (marlm-geo.pat). The identities of the map units are recorded in the PTYPE field by map label (i.e. Ts). For a description of the map units, consult the PostScript or PDF explanation pamphlets in this report. Geologic lines (arcs) are recorded as strings of vectors and are described in the arc attribute table (marlm-geo.aat). They define the boundaries of the map units, the faults, and the map boundaries. These distinctions, including the geologic identities of the unit boundaries, are recorded in the LTYPE field. Attributes for geologic lines generally follow a scheme of the type of geologic line (i.e. fault), followed by a locational and/or scientific modifier (i.e. approx. located or queried). The geologic structure layer (marlm-str) consists of point features that describe geologic structures such as strike and dip of beds. Point features, typically structural measurements, are described in the point attribute table ( marlm-str.pat) and are used to represent locations of structural measurements such as strike and dip, and foliation. The type of structural measurement of points is attributed in the PTTYPE field, and the measurements taken at that location are attributed in the STRIKE and DIP fields. Features representing location of samples (marlm-smp) discussed in the original report, are described in the point attribute table (marlm-smp.pat). Attributes of features in this dataset are recorded in the PTTYPE field, and the sample number from the map is recorded in the SAMPNO field.
|Description of the type of geologic line
Geologically-significant polygonal map features such as rock units
|Geologic map unit attribute
|Description of the type of sample
|The sample number or designator, as depicted on the map and in the report.
Geologically-significant points (field observations of geologic structure)
|Description of the structural measurement
|The dip value of the structural measurement, indeterminated dips contain a value of 99, assumed or inferred dip values are negative
|The strike of the structural measurement, based on the 'right hand rule'