Appendix 1. Terms and Definitions for the GeoMaterial and GeoMaterialConfidence Fields

Overview

Much of the benefit from a defined database schema depends on use of clearly defined vocabularies. On the basis of many discussions within the geoscience community over the past three decades, it seems to be the consensus (and a logical conclusion) that users of geologic map databases are best served if certain terminology, particularly for lithology, is consistent from one database to another. Such a list of terms commonly is referred to as a controlled-term list or a vocabulary.

The terms that populate the GeoMaterial and GeoMaterialConfidence fields in the DescriptionOfMapUnits table constitute such a controlled-term list. These terms are defined below, and they are encapsulated in a database table (see table 17) generated by the script GeMS_CreateDatabase_Arc10.py (or its replacement), available at the GeMS Toolkit site on GitHub (https://github.com/usgs/GeMS_Tools or https://github.com/usgs/gems-tools-pro). The table is also available as an Excel spreadsheet under the Resources heading at the GeMS website (https://ngmdb.usgs.gov/Info/standards/GeMS/); the spreadsheet also includes the field HierarchyKey to facilitate sorting.

Scope and Intent

This classification of materials is intended to characterize a map unit by means of a generalized category (GeoMaterial) based on lithologic and genetic criteria; it applies to the map unit as a whole. The purposes of this classification are to provide a basis for quickly integrating map data from different sources and to convey to the public a simple, general sense of each map unit’s lithology and genesis. We recognize that such a classification cannot completely address the immense variety of map units present across the Nation, and we expect that other regionally specific classifications of map units will be developed that are more appropriate to local conditions. The appropriateness of a selected GeoMaterial term for describing a map unit is specified by values in the GeoMaterialConfidence field (see table 1–1), which provide the map user with a potentially useful qualifier term (please refer to the Geologic Materials discussion in the “Design Considerations” section, above).

Table 1-1. Values (and their definitions) that populate the GeoMaterialConfidence field in a DescriptionOfMapUnits table.
[Note that, when creating a new database, the script GeMS_CreateDatabase_Arc10.py (available at https://github.com/usgs/GeMS_Tools) or its replacement inserts these GeoMaterialConfidence terms and definitions into Glossary table. See also, table 14]

Term Definition
High The selected term in the GeoMaterial field (and its definition) adequately characterizes1 the overall lithologic nature of rocks and (or) sediments in the map unit
Medium The selected term in the GeoMaterial field (and its definition) generally characterizes the overall lithologic nature of rocks and (or) sediments in the map unit, but one or more significant but minor lithologies are not adequately described by the selected term
Low Either (1) the overall lithologic nature of rocks and (or) sediments in this map unit is not adequately classifiable using the available list of GeoMaterial terms (and their definitions), but the selected term is the best available, or (2) this map unit is not sufficiently known enough to confidently assign a GeoMaterial term

GeoMaterial Terms

The lithologic terms in the GeoMaterial field and their definitions are provided below, and their hierarchy is represented by an indented format for clarity. Documentation of this classification, including rationale for its development, was provided in Soller (2009); some terms and definitions in that classification were updated for version 1.1 of GeneralLithology (see “Archive of Previous Versions and Related Information” section at https://ngmdb.usgs.gov/Info/standards/GeMS/). In the nine years of test implementation among the state geological surveys and USGS, this classification was slightly modified for GeMS, and renamed as “GeoMaterial”. The current version of this classification is maintained at the GeMS website.

The following is GeMS’ vocabulary of GeoMaterial terms (shown in bold type) and their definitions:

GeoMaterialConfidence Terms

The appropriateness of a selected GeoMaterial term for characterizing a map unit is described by values in the GeoMaterialConfidence field, which provide the map user with a potentially useful qualifier term. Please refer to the “Scope and Intent” section (in the introductory material of this appendix) before assigning confidence values. Table 1–1 describes the terms (and their definitions) that populate the GeoMaterialConfidence field in a DescriptionOfMapUnits table.

Reference Cited in Appendix 1

Soller, D.R., 2009, A classification of geologic materials for web display of national and regional-scale mapping, in Soller, D.R., ed., Digital Mapping Techniques ’08—Workshop Proceedings: U.S. Geological Survey Open-File Report 2009–1298, 216 p., https://pubs.usgs.gov/of/2009/1298/pdf/usgs_of2009-1298_soller4.pdf.

Published and Unpublished Sources for Terms and Definitions (Modified as Needed) in the GeoMaterial Field, as Listed in Appendix 1

Blatt, H., Tracy, R.J., and Owens, B.E., 2006, Petrology—Igneous, sedimentary, and metamorphic (3d ed.): New York, W.H. Freeman and Company, 530 p.

Hyndman, D.W., 1985, Petrology of igneous and metamorphic rocks (2d ed.): New York, McGraw-Hill, Inc., 576 p.

National Geologic Map Database Project, 2007, Science vocabulary to support the National Geologic Map Database project— Lithology terms: U.S. Geological Survey unpublished document, 218 p.

Neuendorf, K.K.E., Mehl, J.P., Jr., and Jackson, J.A., eds., 2005, Glossary of geology (5th ed.): Alexandria, Va., American Geological Institute, 779 p.

North American Geologic Map Data Model Steering Committee Science Language Technical Team, 2004, Report on progress to develop a North American science-language standard for digital geologic-map databases, in Soller, D.R., ed., Digital Mapping Techniques ’04—Workshop Proceedings: U.S. Geological Survey Open-File Report 2004–1451, p. 85–94, 4 appendixes, https://pubs.usgs.gov/of/2004/1451/nadm/.

Soller, D.R., and Reheis, M.C., compilers, 2004, Surficial materials in the conterminous United States: U.S. Geological Survey Open-File Report 2003–275, scale 1:5,000,000, https://pubs.usgs.gov/of/2003/of03-275/.

U.S. Geological Survey Volcano Hazards Program, 2008, Glossary: U.S. Geological Survey Volcano Hazards Program website, https://volcanoes.usgs.gov/vsc/glossary/.

Citation

U.S. Geological Survey National Cooperative Geologic Mapping Program, 2020, GeMS (Geologic Map Schema)—A standard format for the digital publication of geologic maps: U.S. Geological Survey Techniques and Methods, book 11, chap. B10, 74 p., https://doi.org/10.3133/tm11B10.

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