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Surficial geologic map of the Steamboat Springs 30' x 60' quadrangle, Grand, Jackson, and Routt counties, Colorado

IMAP 1825

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Abstract

This map is one of a series of four 30' x 60' surficial geologic maps (1:100,000 scale) intended to provide basic geologic information for planning for energy resource development and growth in northwestern Colorado. An effort is made to characterize all surficial materials, regardless of origin. Hence, residuum is given much more emphasis than is customary, and this results in several departures from conventional geologic maps: bedrock geology is deemphasized; the part of the map symbol denoting geologic age is omitted for surficial units because all surficial units shown are believed to be of Quaternary age; and faults are not shown because none in this map area was observed to displace surficial materials.

Few exposures of most map units exist, except in manmade excavations, such as gravel pits and road cuts. Consequently, thicknesses usually are estimated, and data on stratification, clast size, and relative proportions of matrix and framework clasts are limited to a few localities for each map unit. The Wentworth scale is used to describe grain sizes.

Mapping was done chiefly on aerial photographs taken in 1953. Hence, landslides and modifications resulting from gravel mining since 1953 may not show on this map. The scales of the aerial photographs (about 1:60,000) and the map (1:100,000) governed the minimum size of the deposits mapped. The minimum thickness of the depostis mapped is about 1.5m in most places. Deposit thickness, although not a mapping criterion, influences the topographic expression of many landforms, and landform is the basis for delineating the surficial deposits shown.

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Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Surficial geologic map of the Steamboat Springs 30' x 60' quadrangle, Grand, Jackson, and Routt counties, Colorado
Series title:
IMAP
Series number:
1825
Year Published:
1991
Language:
English
Publisher:
U.S. Geological Survey
Description:
55.72 x 30.11 inches
Country:
United States
State:
Colorado
County:
Grand County, Jackson County, Routt County
Scale:
100000
Online Only (Y/N):
N
Additional Online Files (Y/N):
N