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