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Click here for ordering information for the new map.

Bedrock Geologic Map of Vermont
by Nicholas M. Ratcliffe, Rolfe S. Stanley, Marjorie H. Gale, Peter J. Thompson and Gregory J. Walsh
With contributions by Norman L. Hatch Jr., Douglas W. Rankin, Barry L. Doolan, Jonathan Kim, Charlotte J. Mehrtens, John N. Aleinikoff and J. Gregory McHone

Cartography by Linda M. Masonic
USGS Scientific Investigations Map 3184

What is a bedrock map?
A bedrock geological map shows the type of intact, solid bedrock at or near the earth's surface. The map is used to predict the nature of the bedrock at depth or where it is obscured by surficial material (sand, clay, till etc). Geologists observe the exposed rock types and structures (folds, faults, fractures) in the field, sample the rock for microscopic(petrographic), chemical, and geochronological studies, then use this information to develop a three dimensional model of the underlying bedrock and to understand the depositional and deformational history of Vermont. A bedrock map generally includes rock descriptions, age relationships (stratigraphic sequence), and major and minor structural data used to portray a three dimensional model of the rock on a two dimensional topographic base map.

How was the map made?
The Vermont Geological Survey (VGS) directed by Laurence Becker at the Agency of Natural Resources (ANR), the United States Geological Survey (USGS), University of Vermont geologists and students, and geologists affiliated with other New England colleges have participated since the early 1980's in a cooperative venture to produce the new bedrock geological map of Vermont at a scale of 1:100,000. The bedrock map will make available to the public a geological map based on work which incorporates the understanding of plate tectonic theory. The new map incorporates field mapping studies at scales of 1:5,000 to 1:250,000 conducted over 25 years by more than 60 geologists.(Click here to see the map crew at work) In 1984 the plan was for northern VT to be mapped by UVM and students of Doolan, Stanley and Mehrtens; southern and eastern VT was to be mapped by USGS geologists. The proposed method in the north was to complete three east-west traverses then connect lines between the traverses. Most mappers began heading east then took some serious right or left hand turns (see map status in 1997)! Mapping was done by pace and compass on a variety of base mapsand there was no use of GPS or digital mapping in 1984. Maps were hand drafted in ink on mylar, then hand colored ( a fine art using all the available prismacolor pencils). The entire process from field work to map publication was (and still is) labor intensive. To see how progress was made from field work, to digital maps, to the new compiled publication, glance through the table below.

1861 Geologic Map of Vermont,
scale 1:400,000
1961 Centennial Map of Vermont,
scale 1:250,000
- A hand drafted and colored map of the Newport area (scale 1:12,000) is representative of the contributions to the new State map
- As the digital world evolved, maps were submitted on mylar and digitized. Here is a copy of the contacts layer (scale 1:24,000) prepared for digitization.
- The first digitally created maps were somewhat coarse with angular linework and a poor topographic base. The maps improved over the next 10 years.
- Status of the Montpelier one-degree sheet in 1997 shows large areas which need to be completed through mapping and compilation of data.
Status of the Mt. Mansfield one-degree sheet in 1997 is shown on the hand drafted and colored mylar.
Draft of the complete Mt. Mansfield sheet
Draft of the complete Montpelier sheet
A (before) - Granville and Mt. Abe on the 1961 map 2004-
A (after) - Granville and Mt. Abe on a hand colored draft
B (before)- A portion of northern VT on the 1961 map 2004
- B (after) - A portion of a hand colored draft map

2006-2011 found the map in the good hands of the USGS technical editors and cartographic group (Estabrook, Masonic and Stettner) and with GIS data to be completed by Walsh. The hand-drafted/colored maps, correlation chart and description of map units were digitized in in Adobe Illustrator. Cross-sections and a tectonic map were completed in 2008, in time for scientific peer review by Hatcher and Tucker. The geologic names were reviewed and final corrections were made, with Walsh also reviewing the work as part of the GIS conversion. The map will be published as three 76"x52" sheets.

- Map room at USGS, Reston, VA
Preliminary one-degree sheets were produced from 1997-2001. During 2001-2006 we compiled and edited the complete map, unit descriptions, and correlation chart, conducted reconnaisance and new mapping in order to meld the one-degree sheets, and prepared the map and cross-sections for scientific review.
- A hand-colored/drafted map of the entire state was presented at the NE/SE GSA meeting in Virginia in 2004.

We presented the map and a series of talks at The New Bedrock Geologic Map of Vermont: New Answers, New Problems, and New Uses of Bedrock Geologic Data, a symposium at NE/SE GSA in March 2010 (view abstracts)
The map was printed by USGS in CO on 2.22.2012.

USGS Scientific Investigations Map 3184
Hear about the map on Vermont Edition

The map is on permanent display in the Perkins Museum, Delehanty Hall, Geology Dept., University of Vermont, Burlington ,VT  

Generalized Geologic 
	Map of Vermont - 1970 - click for larger map image

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