Section II --
Map Development (continued)
Local Table of Contents:
From: Influences on Wetlands and Lakes in the Adirondack Park of New York State:
A Catalog of Existing and New GIS Data Layers for the
400,000 Hectare Oswegatchie/Black River Watershed,

II.F. Bedrock Geology;
II.G. Bedrock ANC Composite Map;
II.H. Surficial Geology
OB2 Contents


One of the objectives of this study was to determine the underlying geology for the study area by incorporating the best available digital data and discuss it and the availability of more detailed data for this area. This section of the report was prepared by Dr. David Franzi, SUNY Plattsburgh.


sbedrock.jpg (12036 bytes)F. Geologic Map of New York

The bedrock digital database for the Oswegatchie and Black River watershed is derived from the Geologic Map of New York (New York State Museum and Science Service, Map and Chart Series 15). The state map consists of five sheets, the Adirondack, Hudson-Mohawk, Lower Hudson, Finger Lakes, and Niagara, all published at a 1:250,000 scale. More than 75% of the project watersheds lie within the Adirondack Sheet, including all of the watersheds of the Oswegatchie, Beaver, and Moose rivers. The southernmost portion of the Black River watershed extends into the Hudson-Mohawk Sheet.


Map Development

The Geologic Map of New York was first compiled by Broughton, and others (1962) and subsequently updated and republished by Isachsen and Fischer (1970). The latter version was reprinted in 1995. The map was compiled primarily from 15-minute quadrangle maps published by the New York State Museum and Science Service (1:62500) and published and open-file maps (various scales) from the state and federal geological surveys.


Information Sources

The principal sources of geological information pertaining to the Oswegatchie and Black River watersheds are attached to this report. Most of this information can be found in the Geologic Map of New York, the Surficial Geologic Map of New York, and Sources of Information for Preliminary Brittle Structures Map of New York, published by the New York State Geological Survey, and the Geologic Map Index of New York from the United States Geological Survey. Other sources of information were obtained from recently published literature and personal communication.

The bibliography can be used to determine the date, location, and type of geological investigations that have been conducted within the project watersheds. It is important to note that most of the significant geological quadrangle map investigations were conducted more than 30 years ago. Recent geological investigations are relatively few in number and have been more topical in nature (e.g. the analysis of brittle structures in the Adirondack Massif and evaluation of lake acidification) or related to regional geological map compilation. The most detailed bedrock information is found in the mining districts in the northwestern Adirondack lowlands near Gouverneur, some of which extends into the northwestern portion of the project watersheds.

Peer review of published information sources provides quality control for geological data used to compile the bedrock map. Open-file reports and unpublished reconnaissance maps may or may not have experienced peer review and are of uncertain quality. The Geologic Map of New York has been published twice (1962 and 1970), each time receiving its own peer review.

Published map coverage within the Oswegatchie and Black River watersheds is fairly complete, although not uniform. With the exception of the newly completed "Bedrock Geology" map (Whitney et al. in preparation), most of the detailed published information is concerned with the geology of the mining districts in the Gouverneur region or the Black River and St. Lawrence lowlands. Geological coverage for the upper regions of these watersheds is less extensive and primarily available as unpublished or open-file maps.


Database Limitations and Applications

The geological information in the electronic database appears much as it does on the paper maps, however, some information was lost or poorly represented in the digitizing process. Several of the map units on the Geologic Map of New York contain overprint patterns that relate to special rock textures or fabrics that are not represented on the electronic database. More importantly, geological faults and other structures are not included in the database map. These structures may have an important effect upon the geomorphic development and regional and local surface-water and ground-water flow.

Some discrepancies between the paper map and the electronic database occur along the southern border of St. Lawrence County near its intersection with Hamilton and Herkimer counties. These discrepancies include a polygon mislabeled as H20 (should be mu) and an under-representation of the extent of Quaternary deposits (Q) west of High Falls. Other minor errors along the county boundary lie outside the project watersheds.

The colors used on the electronic database may not be sufficiently distinct to differentiate the rock units without polygon labels. The rock units within the project watersheds that have similar color are noted in the table below.

Table II.F.1 Rock units of similar color in the electronic database.
Rock Units Database Color
ps, phqs, phgs, hqs, and ffg dark green
mug, bqpq, amg, qt, and garb blue-green
hbg, hgbo, am, and lg yellow

In some cases it may be appropriate to combine similar rock units into groups and assign a single color to the group while retaining the polygon labels for each unit. Some of the genetic groupings that are made in the explanation that accompanies the Geologic Map of New York may be used for this purpose. If it is not possible or cost-effective to alter the electronic database by grouping rock units, some effort should be made to alter the colors used or to employ overprint patterns to distinguish each rock unit.

There should be more landmarks and cultural features printed on the electronic database maps to help potential users locate specific points. A complete hydrography overlay and town locations and names would be most useful in this regard.

The 1:250,000 scale of the Geologic Map of New York may limit its application for large-scale watershed or site-specific investigations. Although more detailed geological information is available for some parts of the project watersheds this information is spotty in occurrence and its inclusion in the database will require some reinterpretation and redefinition of the regional map units. This process will be both time-consuming and expensive.

Finally, in spite of its limitations, the Geologic Map of New York represents the best regional geological coverage for the project watersheds that is currently available. It may be best to include the bedrock geology database as received from the state survey and provide an up-to-date bibliography of geological information to those who request the information.


sbedanc.jpg (11846 bytes)G. Bedrock ANC Composite Map

An alternative to a genetic grouping or rock units may be to group rock units by their buffering capacity such as that suggested by Norton 1982. These categories are:

  1. Low to no acid-neutralizing capacity (e.g. granitic gneiss, quartz sandstones)
  2. Medium to low acid-neutralizing capacity (e.g. metamorphic felsic to intermediate volcanic rocks, intermediate igneous rocks, calc-silicate gneisses, noncalcareous clastic sedimentary rocks)
  3. High to medium acid-neutralizing capacity (e.g. slightly calcareous rocks, metamorphic intermediate to mafic volcanic rocks, ultramafic rocks)
  4. "Infinite" acid-neutralizing capacity (e.g. carbonate rocks: limestones, dolostones and marble)
  5. Areas where bedrock is obscured by thick Quaternary glacial or alluvial sediment

Dr. Phil Whitney, a geologist with the New York State Geological Survey who has mapped extensively in the western Adirondack region, recommended the following grouping for the bedrock units in the project watersheds to correspond to Norton's buffering categories (1-5):

  1. phqs, hqs, hbg, hbgo, lg, qt, ffg
  2. bqp, garb, ps, ach, Cp (Potsdam Sandstone)
  3. mu, mug, am, amg, gb, ack, a
  4. mb, cs, OCth (Theresa Fm.)
  5. Q (thick Quaternary deposits)


The bedrock units were grouped this way using ArcView. A graphic of this interpretation is provided in the poster attached at the back of this report. The bedrock ANC composite area totals (and percent of total) for the study area are:

Low to No ANC = 243,892 ha (61%)
Medium to Low ANC = 4,280 ha ( 1%)
High to Medium ANC = 124,629 ha (31%)
Infinite ANC = 2,348 ha ( 1%)
Quaternary deposits (bedrock obscured) = 20,326 ha ( 5%)
Water = 3,286 ha ( 1%)


ssurfgeo.jpg (12249 bytes)H. Surficial Geological Map of New York

The surficial geology database for the Oswegatchie and Black River watershed is derived from the Surficial Geologic Map of New York (New York State Museum and Science Service, Geological Survey, Map and Chart Series 40). The surficial map consists of five sheets, the Adirondack, Hudson-Mohawk, Lower Hudson, Finger Lakes, and Niagara, all published at a 1:250,000 scale. The surficial geology coverage within the project watersheds is the same as that for the Geologic Map of New York.


Map Development

There is relatively little published information on the surficial geology of the project watersheds. Fairchild (1912) included part of the project area in his synopsis of glacial lakes in the Black and Mohawk Valleys. The 15-minute geological quadrangle reports, published as Museum Bulletins by the New York State Museum and Science Service, often contain descriptive accounts of glacial deposits and history in the region but contain little or no specific information on the spatial distribution or thickness of the deposits. Consequently, unlike the bedrock map, most of the surficial geology that appears on the Surficial Geologic Map of New York - Adirondack and Hudson-Mohawk Sheets was generated primarily by reconnaissance survey specifically for the mapping project between 1986 and 1990. The surficial geology mapping project was designed to provide a regional map that could be of use to planners and engineers and from which an understanding of the surficial geology of the Adirondack region could evolve. The map was not intended to provide detailed, site-specific information and should not be used for that purpose.


Information Sources

Most of the sources of information for the surficial map consist of open-file reconnaissance maps at the New York State Geological Survey. A notable exception is the Surficial Geologic Map of the Black River Basin (Waller, 1976) which covers the upper Black River watershed within the Adirondack Park boundary. The reconnaissance maps received little or no peer review and are variable in quality. Some degree of quality control for the final map compilation was achieved by overlapping the areas covered by individual mappers.


Database Limitation and Applications

Given the large regional extent of the Adirondack Sheet and the relatively short time over which the surficial geologic information was gathered, little detailed surficial information is available for the project watersheds. The greatest map detail occurs in populated areas and valleys where exposures are easily accessible by road. Remote upland areas received little or no attention. A significant "border fault" occurs at latitude of 43E30' which forms the boundary between the Adirondack and Hudson-Mohawk sheets of the Surficial Geologic Map of New York. Some of the discrepancies reflect changes in the map units used (e.g. fluvial-deltaic sandplains on the Hudson-Mohawk Sheet are mapped as lacustrine deltas on the Adirondack Sheet) but others represent more serious differences in sediment types. Fortunately relatively little of the project watersheds fall within the Hudson-Mohawk sheet and most of what does is located in upland areas where no differences exist between the maps.

The textural and compositional information contained in the surficial map units is probably too generalized for most resource management or land-use applications. The variability of sediment texture within certain surficial map units, especially ice-contact stratified drift units, precludes anything but a broad textural classification. No such classification is attempted here.

The Surficial Geologic Map of New York is the best regional coverage of its type for the project watersheds. Future additions to the surficial geology database should include large scale mapping of the deposits and more detailed information on sediment texture, composition, and thickness.


References for Geological Information for the Oswegatchie and Black River Watersheds

Bedrock Geology


Surficial Geology


General Geology

Continue reading next section of OB2 Report -- Section II.I. OB2 Contents