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Methodology for Construction of a Three-Layer Geologic Model of the Conterminous United States Using Land Surface, Top of Bedrock, and Top of Basement

Data Report 1220
National Cooperative Geologic Mapping Program
By:
https://doi.org/10.3133/dr1220

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Abstract

This report describes the methodology used for the construction of a digital three-layer geologic model of the conterminous United States by mapping the altitude of three surfaces: land surface, the top of bedrock, and the top of basement. These surfaces are mapped through the compilation and synthesis of published stratigraphic horizons from numerous topical studies. The mapped surfaces create a three-layer geologic model with three geomaterial-based subdivisions: unconsolidated to weakly consolidated sediment; layered consolidated rock strata that constitute bedrock; and crystalline rocks that are described as “basement,” consisting of either igneous, metamorphic, or highly deformed rocks. The data compilation and synthesis are highly dependent on the definition of the informal terms “bedrock” and “basement,” which may describe different ages or types of rock in different parts of the conterminous United States. This report presents the conceptualization of the three mapped layers, describes the datasets used, and summarizes the decisions made while compiling the three-layer model from the various sources. This digital dataset was created as part of efforts by the U.S. Geological Survey to develop subsurface geologic data in geospatial form as part of a broad directive to develop two-dimensional and three-dimensional geologic information at detailed, national, and continental scales. This digital dataset partly fulfills the goal of the U.S. Geological Survey’s National Cooperative Geologic Mapping Program to construct a national-scale three-dimensional geologic model.

Plain Language Summary

This report is a companion to a digital dataset created as part of U.S. Geological Survey National Cooperative Geologic Mapping Program efforts to develop subsurface geologic data in geospatial form at regional to national scales. The report describes data sources and methods used to construct a digital three-layer geologic model of the conterminous United States by mapping the altitude of three surfaces: land surface, top of bedrock, and top of basement.

Suggested Citation

Sweetkind, D.S., 2026, Methodology for construction of a three-layer geologic model of the conterminous United States using land surface, top of bedrock, and top of basement: U.S. Geological Survey Data Report 1220, 43 p., https://doi.org/10.3133/dr1220.

ISSN: 2771-9448 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Plain Language Summary 
  • Abstract
  • Introduction  
  • Purpose and Scope
  • Previous Studies
  • Methods
  • Results
  • Discussion
  • Limitations of the Model and Method
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Methodology for construction of a three-layer geologic model of the conterminous United States using land surface, top of bedrock, and top of basement
Series title Data Report
Series number 1220
DOI 10.3133/dr1220
Publication Date May 19, 2026
Year Published 2026
Language English
Publisher U.S. Geological Survey
Publisher location Reston VA
Contributing office(s) Geosciences and Environmental Change Science Center
Description Report; vii, 43 p.; Data Release
Country United States
Other Geospatial conterminous United States
Online Only (Y/N) Y
Additional publication details