The data type and an unique ID are included for each point. Also included for a subset of points are data fields that were used to contour the clay content of the Glasford Formation and the percentage of illite in the clay mineral fraction of the Glasford, as well as fields for magnetic susceptibility and the soil horizon sampled. A companion word processing document named data_pt.doc provides further details.
The data were published in 1999 on an ISGS Illinois Geologic Quadrangle entitled Surficial Geology Map, Alton Quadrangle (Illinois Portion) Madison County, Illinois by David Grimley. These data do not include all the information on the published map. Refer to the published map for a complete explanation of the Quaternary geology of the Alton quadrangle.
The nominal scale is 1:24,000.
Any hardcopies utilizing DNR data sets shall clearly indicate their source. If the licensee has modified the data in any way they are obligated to describe the types of modifications they have performed on the hardcopy map. Licensee specifically agrees not to misrepresent DNR data sets, nor to imply that changes they made were approved by DNR.
These data are not to be used for commercial profit.
These data should not be used at scales greater than 1:24,000.
Mapping contributions: E.D. McKay, J.A. Devera, B.F. Denny Clay mineralogy: H.D. Glass Data automation: J. Schoen, C. Abert, T. McTighe GIS processing: C. Abert, D. Nelson Documentation: D. Nelson QA/QC: D. Nelson, C. Abert, R. Krumm
Data set was DESCRIBED and coverage files listed to determine the feature types present. In this data set, the following feature types were found and checked: points. The presence of spatial indices was also checked.
For PAT files, each ITEM was checked for the following:
- DOMAIN of allowable values - adherence of values to the DOMAIN - definition of ITEMS - requirement of all UNIQUE values for an item - logic of ITEMS REDEFINED over other ITEMS - length of ITEM name as regards conversion to shape fileBUILD statuses of data sets were checked, as were LABELERRORS and NODEERRORS (where appropriate), and PROJECTION definition.
The presence of a DBLBND file was verified.
The presence and location of TICS were checked.
Point topology present. Boundary values appropriate for map projection and map units. "Fuzzy" tolerance is zero and therefore meaningless. AAT items with long name were renamed and tics were replaced. COVER-ID values were recalculated to be unique. There are no attribute values outside the appropriate domains.
Points derived from the ISGS borehole database and previously collected ISGS field note descriptions are generally accurate to 100 feet, however, it is possible that some points could have inaccuracy on the order of 2500 feet. Refer to the companion word processing document entitled data_pt.doc for more detailed location information for data points.
Relatively, locations of outcrops and stratigraphic test holes have higher accuracy and locations of water wells and previous field notes have a greater possibility of error.
Polygon attributes:
PTCODE: The type of data point 1 = stratigraphic test hole 2 = outcrop examined 3 = ISGS field note description 4 = water well/engineering boring ID: An unique identifier for the point. Stratigraphic test holes have a prefix of "ALT", for example "ALT-1" Outcrops examined have a suffix of "f", for example "1f" ISGS field note descriptions are prefixed with "FN", for example "FN1" Water wells and engineering borings are a 5-digit number. This number can be related to the ISGS borehole database and to records in the ISGS Geological Records Unit using the COUNTY NUMBER segment of the API number field.Laboratory data were determined on many samples of calcareous and relatively unaltered glacial till. Data from till deposited during the Illinois Episode (Glasford Formation) are recorded in the items CLAY_PCT, ILLITE_PCT, MAG_SUS, and HORIZON, and were used for contouring the illite and clay mineral data. During our mapping, we became interested in lateral trends of the lithology of the Glasford Formation which may have resulted from the incorporation of various bedrock and surficial materials as glacial ice advanced towards the Mississippi Valley. Since weathering is also an important factor, the horizon sampled is noted.
HORIZON: The horizon from which the sample was obtained. B = fairly weathered, B horizon of the soil profile C = calcareous and oxidized, C horizon of soil profile D = calcareous and unoxidized, D horizon of soil profile avg = indicates an average of several samplesCLAY_PCT: Clay percentage (<4 µm fraction) was measured by hydrometer methods and are of the <2 mm fraction. A value of zero indicates no data were acquired.
ILLITE_PCT: Illite percentage is that estimated by X-ray diffraction in the <2 µm clay mineral fraction . Peak intensities were determined after glycolation of clay mineral slides. Peak intensity factors of 3x for illite [10 Å peak], 2x for kaolinite plus chlorite [7 Å peak], and 1x for expandable clay minerals [17 Å peak] were applied to samples. Clay mineral analyses are courtesy of Herb Glass, Illinois State Geological Survey. A value of zero indicates no data were acquired.
MAG_SUS: Magnetic susceptibility (MS) were measured with a Bartington MS2 meter and probe in the field or on samples in the laboratory. The measurements are a ratio of the induced field to the applied magnetic field. The two-digit numbers are in 10 exp -5 (SI units). Higher numbers generally mean a greater content of magnetite. A value of zero indicates no data were acquired.
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