"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

""

"

""

"

"

"

"

"

" " "

"

"

"

"

"

"

"

"

"

""

"

"

""

"

"

"

"

"

"

"

"

""

"

"

"

"

"

"

"""

"

""

"

"

"

""

"

"

"

"

"

"

"

"

"

"

"

"

"

"""

""

"

"

"

"

"

"

"

"

"

"

"

""

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

"

""

Erie

Lima

Havre

RugbyMalta

Flint UticaKeene

Omaha

Shelby

Wausau

BarrieBerlin

Bangor

Topeka

Duluth

Dayton

Toledo

London

Newark

Albany

Austin

Pierre

Peoria

Muncie

Boston

Scioto

PembinaWarroad

Glasgow

Augusta

Ashland

Lincoln

Norfolk

Yankton

Newport

Mankato

HibbingBemidji

Detroit

Saginaw

Buffalo

Rutland

Dubuque

Lansing

Chicago

Manistee

Petoskey

Escanaba

Houghton

Mitchell

Columbia

Hannibal

St. Paul

Brainerd Ironwood

Columbus

New York

Scranton

Syracuse

Waterloo

Aberdeen

MoorheadBismarck

Rockford

Madision

Portland

Big Falls

Manhattan

Concordia

Manitowoc

Green Bay

WakefieldMarquette

Williston

Rochester

St. Cloud

Cleveland

New Haven

Rochester

Watertown

Galesburg

Davenport

La Crosse

Brookings

Jamestown

Milwaukee

Champaign

Worcester

Kincardine

Owen Sound

Sioux City

St. Joseph

Montpelier

Burlington

Eau Claire

Montevideo

Evansville

Louisville

Cincinnati

Youngstown

Binghamton

Falls City

Fort Dodge

Kirksville

Des MoinesSouth Bend

Fort Wayne

Providence

Manchester

Huntington

Port Austin

Rogers City

Sioux Falls

Minneapolis

Bloomington

Terre Haute

Springfield

Springfield

Glens Falls

Worthington

Grand Forks

Jacksonville

Mount Vernon

Indianapolis

Williamsport

Poughkeepsie

Cedar Rapids

Grand Rapids

Traverse City

Thief River Falls

68°W

68°W

72°W

72°W

76°W

76°W

80°W

80°W

84°W

84°W

88°W

88°W

92°W

92°W

96°W

96°W

100°W

100°W

104°W

104°W

108°W

108°W

112°W

112°W

48°N 48°N

46°N 46°N46°N46°N

44°N 44°N

42°N 42°N

40°N 40°N

38°N 38°N

44°N44°N

>800>600 to 800>500 to 600>400 to 500>300 to 400>200 to 300>100 to 200>50 to 100>25 to 50>5 to 25>0 to 50

GIS database and digital cartography by David R. Soller and Christopher P. GarrityVector to raster conversion by David R. Soller and Susan D. PriceDigital cartographic production by Christopher P. Garrity Edited by Regan AustinManuscript approved for publication December 1, 2017

EXPLANATIONSediment thickness, in feet

CANADAUNITED STATES

UNITED STATES

MEXICO

Dallas

Denver

Houston

Phoenix

Memphis

Chicago

Detroit

Seattle

New York

DC

Los Angeles

TX

CA

MT

AZ

NV

ID

NM

MI

CO

OR

KS

UT

SD

WY

NE

IL

MN

IA

ND

WI

OK

FL

WA

MO

GAAL

AR

PA

NY

NC

LA

IN

MS

TN

VA

MDOH

KY

SC

ME

WV

VTNH

MACT

NJ

Figure 1. Map area (in gray) is the extent of Quaternary sediments in the glaciated United States east of Rocky Mountains, including the Great Lakes, part of southern Ontario, and part of the Atlantic offshore area. Colored lines depict maximum extent of glacial ice. The green line shows the extent during late Wisconsinan time; this was the most recent major advance of continental glaciers in North America, reaching its maximum in most places roughly 24,500 years ago. The red line is the maximum extent of Quaternary ice prior to that time.INTRODUCTION

Beginning roughly 2.6 million years ago, global climate entered a cooling phase known as the Pleistocene Epoch. As snow in northern latitudes compacted into ice several kilometers thick, it flowed as glaciers southward across the North American continent. These glaciers extended across the northern United States, dramatically altering the landscape they covered. East of the Rocky Mountains, the ice coalesced into continental glaciers (called the Laurentide Ice Sheet) that at times blanketed much of the north-central and northeastern United States (see fig. 1). To the west of the Laurentide Ice Sheet, glaciers formed in the mountains of western Canada and the United States and coalesced into the Cordilleran ice sheet; this relatively smaller ice mass extended into the conterminous United States in the northernmost areas of western Montana, Idaho, and Washington. Throughout the Pleistocene, landscape alteration occurred by (1) glacial erosion of the rocks and sediments; (2) redeposition of the eroded earth materials in a form substantially different from their source rocks, in terms of texture and overall character;and (3) disruption of preexisting drainage patterns by the newly deposited sediments. In many cases, pre-glacial drainage systems (including,for example, the Mississippi River) were rerouted because their older drainage courses became blocked with glacial sediment.

The continental glaciers advanced and retreated many times across those areas. During each ice advance, or glaciation, erosion and deposi-tion occurred, and the landscape was again altered. Through successive glaciations, the landscape and the bedrock surface gradually came to resemble their present configurations. As continental ice sheets receded and the Pleistocene ended, erosion and deposition of sediment (for example in stream valleys) continued to shape the landscape up to the present day (albeit to a lesser extent than during glaciation). The interval of time since the last recession of the glaciers is called the Holocene and, together with the Pleistocene, constitutes the Quaternary Period of geologic time; this publication characterizes the three-dimensional geometry of the Quaternary sediments and the bedrock surface that lies beneath.

The pre-glacial landscape was underlain mostly by weathered bedrock generally similar in nature to that found in many areas of the non-glaciated United States. Glacial erosion and redeposition of earth materials produced a young, mineral-rich soil that formed the basis for the highly productive agricultural economy in the U.S. midcontinent. Extensive buried sands and gravels within the glacial deposits also provided a stimulus to other economic sectors by serving as high-quality aquifers supplying groundwater to the region’s industry and cities. An understand-ing of the three-dimensional distribution of these glacial sediments has direct utility for addressing various societal issues including groundwa-ter quality and supply, and landscape and soil response to earthquake-induced shaking.

Horberg and Anderson (1956) compiled, from preexisting maps and well data, the first synoptic view of bedrock topography in the glaciated central United States (from New York to the Dakotas), using a 250-foot (ft) isopach (thickness) contour interval. A more detailed map showing the thickness and character of the continental glacial deposits east of the Rocky Mountains (printed in four sections as Soller, 1993, 1994, 1997, and 1998) was later compiled using similar data and methods. That map was then published in Geographic Information System (GIS) format (Soller, Packard, and Garrity, 2012) and was used as the basis for deriving the digital, gridded data and maps of sediment thickness and bedrock topography included in this publication.

The Quaternary sediment thickness map and bedrock topographic map shown here provide a regional overview and are intended to supplement the more detailed work on which they are based. Detailed mapping is particularly useful in populated areas for site-specific planning. In contrast, regional maps such as these serve to place local, detailed mapping in context; to permit the extrapolation of data into unmapped areas; and to depict large-scale regional geologic features and patterns that are beyond the scope of local, detailed mapping. They also can enhance the reader’s general understanding of the region’s landscape and geologic history and provide a source of information for regional decision making that could benefit by improved predictability of bedrock depth beneath the unconsolidated Quaternary sediments. To enable these maps to be analyzed in conjunction with other types of information, this publication also includes the map data in GIS compatible format.

SOURCE DATA AND METHODSIn a digital format, map information may be stored either as a raster (grid) or a vector format. Maps in raster format have a unique value

(for example, elevation or thickness) at every location on the map, whereas the information on maps in vector format is contained only in the isopach (thickness) or contour (elevation) lines. On vector maps, areas between isopach or contour lines do not have actual values—they only can be inferred by interpolation between the lines.

The bedrock topographic map was created from two source maps: (1) the elevation of the land surface, in raster format, and (2) the thickness of the glacial sediments, in vector format. The thickness of glacial sediment map was converted to raster format according to the process described below. The bedrock topographic map then was derived by a process based on subtracting the glacial sediment grid values from the land-surface grid values.

LAND-SURFACE TOPOGRAPHY AND BATHYMETRYLand-surface elevations were obtained from the USGS National Elevation Dataset (https://lta.cr.usgs.gov/NED). Great Lakes bathymetric

data were from the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information (https://ww-w.ngdc.noaa.gov/mgg/ greatlakes/greatlakes.html). Bathymetric data for the Atlantic offshore area were from GEBCO (General Bathymetric Chart of the Oceans, http://www.gebco.net/data_and_products /gridded_bathymetry_data/gebco_30_second_grid/). Resolution of data both within and across these three sources varied, generally between 1/3 arc-second (about 10 meters [m]) and 30 arc-second grids (about 1,000 m). The data from these three sources were resampled to the resolution used for the Quaternary sediment data (1,000 m), and merged into a single grid file.

MAP OF QUATERNARY SEDIMENT THICKNESSThe source map (Soller, Packard, and Garrity, 2012) shows Quaternary sediment thickness beneath most submerged areas, but certain areas

(notably the northern half of Lake Michigan) were not mapped. Using a bathymetric map and a general understanding of the bedrock geology in those areas, for the purposes of this study we extrapolated sediment thickness contour lines into the previously unmapped areas. The map data then were converted to raster (gridded) format, matching the grid spacing and projection of the land-surface topographic map, as described here.

The goal was to produce a Quaternary sediment thickness map in raster format that is as similar as possible to the pattern of information on the original vector map of sediment thickness. Conversion to raster format can be a complex task, especially where contour lines are irregularly spaced. Such was the case with this source map because Quaternary sediment thickness can vary greatly across small distances (resulting in closely spaced contours) and because the contour interval was different in areas of relatively thin and thick sediment. Where sediment is thicker, the depth to bedrock is less certain, and the contour interval is greater than for areas of thin sediment cover (the source map’s sediment thickness contours were 0, 50, 100, 200, 400, 600, 800, 1,000, and 1,200 ft). Also, the source map included a contact between areas of continuous and discontinuous till cover, which was assigned a thickness value of 5 ft.

Further challenges to successful data conversion are raised by the computer algorithms employed to rasterize a vector map. Gridding algorithms that use kriging, splining, or inverse-distance weighting each can produce distinctly different results depending on the nature of the source data and the parameters selected. Owing to the nature of our map data, which in many places is similar in configuration to topographic contours, we found that the Esri ArcGIS “TopoGrid” command produced results superior to other gridding options in ArcGIS and to those offered by software packages specializing in three-dimensional rendering of geologic surfaces. All isopach contours were converted to point data (densified to 500 m) and processed with the TopoGrid command.

The raster map then was compared to the vector source map, and locations were identified where the source map’s pattern of thickness information was not adequately reproduced. In those areas, additional representative data points were added to permit the algorithm to interpo-late more precisely, and to produce a more faithful copy of the original vector map. After these data were added to the map, the algorithm was run again, the results were compared to the source map, and additional data points were added as needed. Through these many iterations, the raster map of Quaternary sediment thickness was produced.

REFERENCESHorberg, Leland, and Anderson, R.C., 1956, Bedrock topography and Pleistocene glacial lobes in central United States: Journal of Geology,

v. 64, no. 2, p. 101–116.Kempton, J.P., Johnson, W.H., Cartwright, K., and Heigold, P.C., 1991, Mahomet Bedrock Valley in east-central Illinois—topography, glacial

drift stratigraphy, and Hydrogeology, in W.N. Melhorn and J.P. Kempton, eds., Geology and Hydrogeology of the Teays-Mahomet Bedrock Valley System: Geological Society of America Special Paper 258, p. 91–124.

Soller, D.R., 1992, Text and references to accompany “Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains”: U.S. Geological Survey Bulletin 1921, 54 p., available at https://pubs.usgs.gov/bul/1921/.

Soller, D.R., 1993, Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains—Northeastern states, the Great Lakes, and parts of southern Ontario and the Atlantic offshore area (east of 80°31′ west longitude): U.S. Geological Survey Miscellaneous Geologic Investigations Map I-1970-A, scale 1:1,000,000, available at http://ngmdb.usgs.gov/Prodesc/proddesc_10047.htm.

Soller, D.R., 1994, Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains—Northern Plains states (west of 102° west longitude): U.S. Geological Survey Miscellaneous Investigations Series Map I-1970-D, scale 1:1,000,000, available at http://ngmdb.usgs.gov/Prodesc/proddesc_10048.htm.

Soller, D.R., 1997, Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains—Northern and Central Plains states (90° to 102° west longitude): U.S. Geological Survey Miscellaneous Investigations Series Map I-1970-C, scale 1:1,000,000, available at http://ngmdb.usgs.gov/Prodesc/proddesc_13020.htm.

Soller, D.R., 1998, Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains—Northern Great Lakes states and central Mississippi Valley states, the Great Lakes, and southern Ontario (80°31′ to 93° west longitude): U.S. Geological Survey Miscellaneous Investigations Series Map I-1970-B, scale 1:1,000,000, available at http://ngmdb.usgs.gov/Prodesc/proddesc_13019.htm.

Soller, D.R., Packard, P.H., and Garrity, C.P., 2012, Database for USGS Map I-1970—Map showing the thickness and character of Quaternary sediments in the glaciated United States east of the Rocky Mountains: U.S. Geological Survey Data Series 656, available at http://pubs.usgs.gov/ds/656/.

DATA SOURCESU.S. Geological Survey, 2016, National Hydrography Dataset: U.S. Geological Survey database, accessed October 2016, at http://nhd.usgs.gov.U.S. Geological Survey, 2016, Geographic Names Information System: U.S. Geological Survey database, accessed October 2016 at

https://geonames.usgs.gov.U.S. Geological Survey, 2016, 3D Elevation Program (3DEP) products and services: U.S. Geological Survey, The National Map database,

accessed October 2016 at http://nationalmap.gov/3DEP/3dep_prodserv.html.U.S. Geological Survey, 2016, The National Map Small-Scale Collection: U.S. Geological Survey, The National Map database, accessed

October 2016 at https://nationalmap.gov/small_scale/.

Map of Quaternary Sediment ThicknessQuaternary Sediment Thickness and Bedrock Topography of the Glaciated United States East of the Rocky Mountains

ByDavid R. Soller and Christopher P. Garrity

2018 ISSN 2329-132X (online)https://doi.org/10.3133/sim3392

Base modified from U.S. Geological Survey digital data, 1:1,000,000-scaleWeb Mercator projection, World Geodetic System of 1984

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government

This map or plate is offered as an online-only, digital publication. Users should be aware that, because of differences in rendering processes and pixel resolution, some slight distortion of scale or color may occur when viewing it on a computer screen or when printing it on an electronic plotter, even when it is viewed or printed at its intended publication scale.

Digital files available at https://doi.org/10.3133/sim3392

Suggested citation: Soller, D.R., and Garrity, C.P., 2018, Map of Quaternary sediment thickness, sheet 1 in Quaternary sediment thickness and bedrock topography of the glaciated United States east of the Rocky Mountains: U.S. Geological Survey Scientific Investigations Map 3392, 2 sheets, scale 1:5,000,000. https://doi.org/10.3133/sim3392.

U.S. Department of the InteriorU.S. Geological Survey

Scientific Investigations Map 3392Sheet 1 of 2