3.0 Source Data

3.1 Stream Sediment Chemistry

3.2 Surface Water Chemistry

3.3 Geologic Province

3.4 Bedrock Lithology Groups

3.5 Drainage Basin Hydrology

3.6 Population Density

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3.1 Stream Sediment Chemistry

The NURE stream sediment samples selected for re-analysis were analyzed for 40 elements by inductively coupled plasma atomic emission spectrometry (ICP-AES) following an acid-dissolution procedure (ICP40), 16 elements by ICP_AES following a lithium metaborate fusion procedure (ICP16), arsenic and selenium by hydride-generation atomic absorption spectrometry (HGAA) and mercury by cold-vapor atomic absorption (CVAA) (methods described in Taggart, 2002). Uranium and ytterbium values, from the original NURE dataset, were analyzed by instrumental neutron activation analysis (INAA) (Smith, 2001b). Table 1 lists the elements presented in this report and the methods used to determine them. Elements for which detection limits were high relative to typical stream-sediment concentrations are not presented. The stream sediment chemistry database, description of samples, and description of analytical methods is provided by the U.S. Geological Survey (2004).

Table 1. Stream sediment geochemical data presented in this report, categorized by analytical method used:

3.2 Surface Water Chemistry

Field measurements of stream water pH, alkalinity, and specific conductance determined for steam water at the sediment sample sites during the sampling for the NURE program are reported by the U.S. Geological Survey (2004) and a discussion of analytical methods is given in Smith (2000a). Water pH was determined by meter. Alkalinity was measured by field titrating drops of H₂SO₄ into the water sample until a pH of approximately 4.5 was reached. The alkalinity is calculated as (drops of H₂SO₄/water volume) expressed as millequivalents of H₂SO₄ per liter of sample. Specific conductance was measured at the sample site with a conductivity meter and is reported as micromhos/cm.

3.3 Geologic Province

The bedrock geology of the New England region has been divided into 11 geologic provinces, using geologic province categories modified from Robinson and Kapo (2003). Each province group shares common features of (1) lithology, (2) age of formation, (3) geologic setting, and (4) tectonic history.  The province groups generally occur as northeast trending belts that follow the structural fabric of the Appalachian foldbelt and faults in New England. The province boundary lines are provided in the general stream sediment and water chemistry map figures, in order to examine any association with data values and a particular province. Box-plots for stream sediment and water data grouped by province were also created to show these associations. The geologic province groups, listed in general order from west to east, are:

• Grenville Belt: Includes areas of Grenville Basement (PreCambrian Y metamorphic rocks) in western Connecticut, Massachusetts, and Vermont. Principally granitic gneiss and metasedimentary rocks. Includes some Cambrian metasedimentary rocks deposited on Precambrian basement.
• Grenville Shelf Sequence: Principally carbonate rocks and other metasedimentary rocks deposited in a carbonate shelf sequence overlying Grenville basement in western Connecticut, Massachusetts, and Vermont.
• Eugeosynclinal Sequence: Includes slates and pelitic metamorphic rocks in the Taconic Range and schists east of the Grenville Belt. Principally Cambrian to Ordovician pelitic metasedimentary rocks, including metavolcanic layers and lenses of ultramafic rocks.
• Waits River-Gile Mountain Belt: Principally Devonian variably-calcareous metasedimentary rocks in eastern Vermont and the northern Connecticut valley in Massachusetts, intruded by Devonian granite.
• Mesozoic Basin: Triassic to Jurassic age sediments and basalt flows deposited in localized rift basins in central Connecticut and Massachusetts. Intruded by Jurassic diabase and basalt dikes.
• Bronson Hill Belt: Localized along the eastern Connecticut valley from Connecticut to western New Hampshire and northern Maine. Principally Ordovician igneous and metavolcanic rocks overlain by Ordovician to Devonian metasedimentary rocks. Sulfidic schists and mafic rocks are common. Intruded by Devonian granites.
• New Hampshire – Maine Sequence: Covers eastern Connecticut, central Massachusetts, eastern New Hampshire, and central Maine. Principally Silurodevonian metasedimentary rocks and Silurodevonian and younger igneous rocks, principally granite.
• Coastal Maine: Localized along northeastern coastal Maine. Principally PreCambrian Z to Silurian metasedimentary and metavolcanic rocks intruded by Devonian granites. Large granite bodies in the Coastal Maine Province are shown separately.
• Avalon Province: Localized in eastern Massachusetts, Rhode Island, and coastal Connecticut. Principally Precambrian Z granite and granitic gneiss and metasedimentary rocks of Precambrian Z to Ordovician age. Intruded by Ordovician to Devonian granites. Cretaceous sediments and thick areas of Quaternary glacial sediments occur in southern coastal areas.
• Narragansett Basin: Permian conglomerates and other sediments deposited in fault-bounded basins in Avalon province  rocks in southeastern Massachusetts and Rhode Island.
• White Mountain Igneous Province: Permian and younger alkalic granites and related volcanics included in the White Mountain Igneous Province category of McHone and Butler (1984).

3.4 Bedrock Lithology Groups

The 16 bedrock lithology groups portray the dominant lithology of the map units shown on the bedrock geologic maps covering the states of New England. Geochemical summary maps, grouped by bedrock lithology category, provide a visual display of possible associations between elements or water chemistry characteristics and individual bedrock lithology groups. The Bedrock lithology group categories portrayed on the geochemical summary maps and box plots are derived from the rock group B category in Robinson and Kapo (2003). The Rock Group categories are listed below:

1.     Unconsolidated Sediments (areas in the south-coastal part of New England where crystalline bedrock is overlain by Cretaceous marine sediments and thick deposits of glacial sediments)

2.     Basin Sediments (2 categories)

a.     Mesozoic Basin sediments

b.     Narragansett Basin sediments

3.     Granitic Rocks (6 categories)

a.     Alkali Granites (White Mountain Igneous Province)

b.     Peraluminous Granites of late Devonian and younger age

c.     Avalon Granites in Avalon Province

d.     Grenville Granites in Grenville Province

e.     Granites in Coastal Maine Province

f.      Other Granites

4.     Felsic Volcanics

5.     Mafic Rocks (and their metamorphic equivalents)

6.     Metamorphic Rocks (5 categories)

a.     Calcareous Protolith:

                                               i.     Carbonate rocks

                                             ii.     Calcpelites

                                            iii.     Calcgranofels

b.     Sulfidic Schists

c.     Other metamorphic rocks

3.5 Drainage basin hydrology

Geochemical summary maps were created showing median stream sediment values (or water chemistry values) by drainage basin area. The drainage basin areas are derived from the Hydrologic Unit Codes (Steeves and Nebert, 1994). These figures provide geochemistry estimates for stream sediments and water chemistry at the local watershed level.

3.6 Population Density

The study area was divided into four categories based on population density. The population categories are derived from the U.S. Census Tiger files for population density in the year 2000, with population data grouped by census block (U.S. Census Bureau, 2000). The two urban and two rural categories, and the areas they cover in New England, are defined and listed below (Table 2). Geochemical summary maps and box plots, grouped by population category, are provided for Cu, Pb, Zn, Hg, factor analyses, and water chemistry data. The figures display possible associations between the data and population density, and provide a visual basis for exploring these associations in additional studies.

Table 2. Population density categories on grid maps and box plots:

      Category                         Population Density Range    Area of coverage in New England

(Continue to Section 4.0)

Direct questions and comments to:
Gilpin R. Robinson
U.S. Geological Survey
Email grobinso@usgs.gov 
Phone (703)-648-6113