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Digital Geodata Series
DGS09-2 Coastal Plain Sediments with Potential to Form Acid (Sulfate) Soils

IMAGEMETADATA (502 KB) uodated 06-26-2010


Abstract

The New Jersey Department of Agriculture, Division of Agricultural and Natural Resources, State Soil Conservation Committee requires that plans for controlling erosion during land disturbances (such as construction) must be designed in accordance with a comprehensive set of erosion control practices known as the Standards for Soil Erosion and Sediment Control Act (P.L. 1975, chapter 251, N.J.S.A. 4:24-39 et seq.).  This map is intended to provide Federal and State agencies, and the public with fundamental geologic information on potential acid-producing (sulfate) sediments for use in natural resource planning and environmental analyses.

Soil pH is the measure of the pH of soil water, which depends on the hydrogen ion (H+) activity in solution. Soils become naturally acidic for three major reasons: rainfall and leaching, acidic parent material, and decay of organic matter which produces hydrogen ions. Sulfide-bearing (pyritic) Cretaceous and Paleogene (formerly the Tertiary period) marine and estuarine sediments, depicted on this map, are potential acid-soil producers. The development of acid-sulfate soils occurs when sulfide minerals, such as pyrite and/or elemental sulfur, in reduced sulfidic sediments oxidize upon air exposure through drainage or earth-moving operations. The overall acid-sulfate, soil-forming process involves a complex chain of reactions that connect the oxidation of iron sulfides to the release of iron oxyhydrates (+ hydronium jarosite, H3OFe3+3(SO4)2(OH)6 ) and sulfuric acids. For pyrite and marcasite, the overall reaction is:

FeS2    +     3.75O2 + 3.5 H2O   -- >    Fe(OH)3       +     2H2SO4
(pyrite/marcasite)                             (iron oxyhydrate)    (sulfuric acid)

Acid-sulfate soil formation occurs if the reduced sulfur components exceed the acid-neutralizing capacity of adsorbed bases and easily weatherable silicate and carbonate minerals. Natural Resource Conservation Service reports (see for example Soil Survey of Monmouth County) demonstrate that soils developed on these sulfidic, non calcareous, marine sediments are strongly (pH < 5.5) to extremely acid (pH < 4.5).

Depicted in the GIS data are the sedimentary units with the potential to produce acid (sulfate) soils: Kirkwood (Tkl), Sandy Hook Member of the Red Bank (Krbsh), Navesink (Kns), Marshalltown (Kmt), Englishtown (Ket), Woodbury (Kwb), Merchantville (Kmv), Magothy (Kmg), and Raritan Formations (Kr).

Owens and Others, 1998, subdivided the Magothy formation into two separate formations, the Cheesequake Formation (upper part of Magothy of Lewis and Kummel 1912-1914, 1950 revision) and the Magothy Formation (the rest of the Magothy of Lewis and Kummel). Therefore users of this Acid Soils data set should be aware when comparing this map to either the Bedrock Geology of New Jersey (DGS 04-6) or i-MapNJ Geology since the Cheesequake Formation shown on those data sets is part of the Magothy Formation on this data set.

The NRCS classifies all soils developed on the glauconite formations as extremely to very strongly acidic. In addition, NJGS obtained pH results on several other glauconite bearing formations Currently there is not enough pH data on all the glauconite formations to rule any out as non-acid producing. The plans are to continue to collect samples from other areas in these formations to develop a better database. Should future data indicate certain glauconite formations produce a low pH on exposure, they will be added to future editions of the map.

References:

Geology of New Jersey, Cook, George H., 1868, Geologic Map of New Jersey, Lewis, J. V. and Kummel, H. B., 1910-1912, revised by Kummel H. B., 1931 and Johnson, M. E., 1950.

Bedrock Geologic Map of Central and Southern New Jersey, Owens, James P., Sugarman, Peter J., Sohl, Norman F., Parker, Ronald A., Houghton, Hugh F., Volkert, Richard A., Drake, Avery A., Jr., and Orndorff, Randall C., 1998. Scale 1 to 100,000, 8 cross sections, 4 sheets, each size 58x41, I-2540-B

This map is for illustration purposes only.


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