SURFICIAL GEOLOGY – GLACIAL MARGIN AND SCARPS

DODGE COUNTY, MINNESOTA

Field | Description
Main ID Information | Metadata Updated 2007
Title | Dodge County Aggregate Evaluation – Glacial margin and Scarps (lines)
Filename | Sgeoxln3 (ArcView Shapefile)
Abstract | This dataset consists of information about the types of landforms and features that are best represented on a map by a line (or arc). These landforms include channel scarps and glacial margins.
Place Keywords | Dodge County, Minnesota
Theme Keywords | Landforms, geologic features
Time Period of Content | Fall 2001 – Spring 2002
Parent Theme | NA (Agg02py3)
Spatial Extent of the Data | Dodge County, Minnesota
Contact Person | Aggregate Resources Mapping Program
Contact Person Organization/Division | Department of Natural Resources, Division of Lands and Minerals
Contact Person Position | Geologist or GIS Specialist
Contact Address | 500 Lafayette Road, Box 45
Contact City | St. Paul
Contact Zip Code | 55155-4045
Contact Voice Phone | 651-296-4807
Contact Fax Phone | 651-296-5939
Additional ID Information |
Originator | Department of Natural Resources, Division of Lands and Minerals, Mineral Potential Section
Purpose | To represent small, linear, surficial geologic landforms and features on a map as lines, because they are too small to be represented by a polygon.
Progress | Complete
Currentness Reference | All data was gathered in the late fall of 2001 and compiled in the fall of 2001 through the spring of 2002.
Maintenance Frequency | None planned
Access Constraints | NA
Use Constraints | NA
Associated Data Sets | County Aggregate Mapping Program datasets for Dodge County, including data on sand and gravel potential, crushed stone potential, field observations, rock piles, and test pit quality data.
Data Quality |
Attribute Accuracy |
Logical Consistency |
Completeness | The mapping units were delineated by aerial photograph (at a scale of 1:40000) interpretation and digitized onscreen, using Arcview with 1:12000 USGS DOQs and 1:24000 USGS DRGs as the spatially registered backdrops.
Horizontal Positional Accuracy | 1:50000
Vertical Positional Accuracy | NA
Lineage | Color infrared and black-and-white aerial photographs were used to delineate geological landforms and aggregate resources. Stereoscopic pairs of color infrared aerial photographs (NAPP, 9"x9" at 1:40,000 scale, April 1991 and 1992) were used along with reconnaissance-level, high-altitude, black-and-white photographs (1:80,000 scale). Aerial photographs (DOQs at 1:12000) were also available digitally and used within ARCVIEW. Aerial photographic interpretation was completed with a glacial mapping technique known as the landsystems approach. This technique relies on the principle that depositional glacial landforms are composed of a predictable range of sediments, some consisting of sorted sand and gravel and others consisting of silts, clays, or unsorted materials. In addition to the landsystems approach, several other general characteristics helped determine the nature of the material, such as tonal contrasts, texture, context, shape, size, trend, association, and patterns. These characteristics can help determine the properties of the surface material (e.g., certain vegetation grows on well drained soils such as sand and gravel, which on an aerial photograph has a distinctive texture, tone, pattern, etc.). The landform recognition approach (part of the landsystems approach) was also used when interpreting the topography within Dodge County; glacial landforms have distinct and unique shapes and patterns that can be observed in their topographic expression. Topographic maps (USGS 1:24,000), digital elevation models, and shaded relief maps were all used to help delineate these sand and gravel bearing features. The topographic expression of a feature can also be observed by looking at the distribution of lakes and wetlands. For example, a string of lakes and/or wetlands may be the signature of a glacial outwash channel or collapsed channel, which may host sand or gravel deposits. Several aggregate bearing features were located using this technique (outwash channels, collapsed channels, glaciofluvial fans, eskers, and terraces).
Source Scale Denominator | 1:50000
Spatial Reference |
Horizontal Coordinate Scheme | UTM
Ellipsoid | GRS80
Horizontal Datum | NAD83
Horizontal Units | Meters
Distance Resolution | NA
Altitude Datum | NA
Altitude Units | NA
Depth Datum | NA
Depth Units | NA
UTM Zone Number | 15E
Raster only |
Cell Width | NA
Cell Height | NA
Spatial Data Organization |
Geographic Reference for Tabular Data |
Native Dataset Environment | ArcView 3.1 / ArcInfo 8.0.2
Vendor Specific Object Type | Point
Tiling Scheme | Dodge County
Spatial Object Type | Point
Transfer Size | 10 kb
Entities -- Attributes |
Entity-Attribute Overview | The lines represent geologic landforms that are too small to be mapped as polygons. Note: some of these lines are also found in the agg02ln3 shapefile, because they form the boundary between two polygon mapping units.
Entity-Attribute Detailed Citation | ArcView specific fields include shape (i.e., feature type - polyline), fnode_ (id of beginning node of line), tnode_ (id of ending node of line), lpoly_ (id of polygon to the left of the line - “0" if a line feature, not a line defining a polygon), rpoly_ (id of polygon to the right of the line - “0" if a line feature, not a line defining a polygon), Length (length of line segment), sgeoxln3_ (unique id for line, assigned by Arc/INFO software), sgeoxln3_i (an id usually assigned during theme creation). The scarp line attributes are described in the table below.

Table Name | Field Name | Begin Column | Definition | Valid Values | Descriptions
Sgeoxln3.shp | Uniqln_id |  | Number,3,0 | 265 | Channel Scarp - well defined
|  |  |  | 266 | Channel Scarp - inferred
|  |  |  | 270 | Glacial margin – well defined
|  |  |  | 271 | Glacial margin – inferred
| Sgeolntype |  | Text, 33 | Channel scarp – well defined | Channel Scarp - well defined
|  |  |  | Channel scarp - inferred | Channel Scarp – inferred
|  |  |  | Glacial margin – well defined | Glacial Margin – well defined
|  |  |  | Glacial margin - inferred | Glacial Margin - inferred