AEC Category: HEALTH AND SAFETY

AERORADIQACTIVITY SURVEY ANDAREAL GEOLOGY OF PARTS OFEAST-CENTRAL NEW YORK ANDWEST-CENTRAL NEW ENGLAND(ARMS-I1)

Th!T !3STATEMIENTA

Pete PopnoeApproved for Public ReleaseDistribution Unlimited

20050916 193Issuance Date: October 1964

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AERORADIOACTIVITY SURVEY ANDAREAL GEOLOGY OF PARTS OFEAST-CENTRAL-NEW YORK ANDWEST-CENTRAL NEW ENGLAND(ARMS-I)

By

Peter Popenoe

Approved by: Director Approved by: L. J. DEAL, ChiefU. S. Geological Survey Civil Effects Branc'

U. S. Geological Survey

and

Division of Biology and Medicine, USAEC

August 1962

ABSTRACT

An airborne gamma-radiation survey of Connecticut, Rhode Island,and parts of New York, Massachusetts, New Hampshire, and Vermont wasmade during the period from 1958 through 1960 by the U. S. GeologicalSurvey in cooperation with the Division of Biology and Medicine,U. S. Atomic Energy Commission. Results of the survey indicate thata wide range of natural radioactivity exists and that the levels areclosely related to the type of bedrock underlying glacial material,and subordinately to the glacial material. This report discusses theradioactivity and correlates the data with the areal geology of thenorthern portion of the area surveyed. The southern portion of thearea is discussed in CEX-58.4.61.

The area was traversed with parallel flight lines flown 500 ftabove the ground and spaced at 1-mile intervals. Continuous aeroradio-activity profiles were obtained with scintillation detection equipmentinstalled in a twin-engine aircraft. A map of radioactivity units wasprepared from the profiles.

Parts of four physiographic provinces are included in thesurvey area: the Appalachian Plateau province underlain by relativelyflat-lying Paleozoic shale, sandstone, and limestone; the Valley andRidge province underlain by weakly folded Paleozoic shale, sandstone,limestone, and dolomite; and the New England and Adirondack provinces,underlain chiefly by highly deformed Precambrian and Paleozoic schist,gneiss, and amphibolite. Bedrock in the survey area is mantled withunconsolidated glacial deposits that range in thickness from 0 to morethan 200 ft.

Rocks of both sedimentary and igneous origin produced high andlow levels of radioactivity. Three large areas containing rocks ofmoderate to high radioactivity are present: one is associated withclastic rocks of Devonian age in the Helderberg Plateau and foothillsof the Catskill Mountains: another is associated with phyllite andslate of Cambrian and Ordovician age in the Taconic Mountains andfoothills; and a third is associated with a broad belt of phyllite,micaceous quartzite, and intrusive igneous rock, chiefly of Devonianage, in New Hampshire and east-central Massachusetts. Low radio-activity is associated with a large massif of anorthosite in theAdirondack Mountains, large areas of the Precambrian complex of theGreen and Adirondack Mountains, a broad belt of Cambrian, Ordovician,and Devonian schist, gneiss, and amphibolite in eastern Vermont;igneous rocks of the Oliverian Plutonic Series (Devonian?) in NewHampshire and Massachusetts, and glacial lacustrine deposits alongthe Hudson and Connecticut Rivers.

5

CONTENTSPage

ABSTRACT ................... .......................... 5

1. INTRODUCTION. ................................ .. 1

1.1 Location of Area ............ .................. . 11

1.2 Purpose of Survey .... ....................... . 11

1.3 Airborne Survey Procedure ........... .............. 13

1.4 Scintillation Detection Equipment ....... .......... 13

1.5 Theoretical Considerations ...... ............. ... 15

1.6 Compilation of Aeroradioactivity Data ........... 17

2. GENERAL GEOLOGY ......... . .................... 19

3. GENERAL DISTRIBUTION OF RADIOACTIVITY .......... 25

4. GEOLOGY AND RELATED RADIOACTIVITY OF THE APPALACHIAN

PLATEAU AND VALLEY AND RIDGE PROVINCES .... ........... 28

5. GEOLOGY AND RELATED RADIOACTIVITY OF THE NEW ENGLAND

AND ADIRONDACK PROVINCES ......... ................. .. 29

5.1 Adirondack Province ........... ............... 29

5.2 Western New England Highlands ....... ............. 30

5.2.1 Taconic Mountains ............ .............. 30

5.2.2 Green Mountains ... . ........... 31

5.2.3 Berkshire Highlands ...... ......... .... 32

5.2.4 Eastern Vermont and West-central Massachusetts 32

5.3 Triassic Rocks of Central Massachusetts ....... 33

7

CONTENTS (Continued')Page

5.4 Eastern New England Highlands ............ 34

6. suviARY . . . . . . . . . . . . . . . . . . . . . . . 6

REFERENCES .... ......................... 3(

ILLUSTRATIONS

FIGURES

1. Location of the Survey Area and Nuclear Facilities

Within the Area . . . . . ............. . . . . 12

2. Diagram of Radioactivity Survey Equipment ......... 14

3. Aeroradioactivity Profile in the Keene and Brattleboro

Quadrangles, New Hampshire and Vermont, Showing

Relationship to Bedrock Geology and Effects of

Topography, Altitude, and Water..... ............... 18

4 a. Detailed Aeroradioactivity Map of Parts of the Keene

and Brattleboro Quadrangles, New Hampshire and Vermont,

Showing Radioactivity Units, Geology, and Flight Lines . 20

4b. Aeroradioactivity Profiles along Flight Lines 178

through 191 Shown in Figure 4a . . ........ .... 21

5. Physiographic Divisions of Parts of East-central New York

and West-central New England . . . . ........... 22

6. Geologic Sketch Map of Parts of East-central New York

and West-central New England . . ..... .............. . 23

7. Glacial Map of Parts of East-central New York and

West-central NewEngland . ............... 26

8

ILLUSTRATIONS (Continued)Page

8. Generalized Aeroradioactivity of Parts of East-central

New York and West-central New England ............ 27

PLATE

1. Aeroradioactivity of East-central New York and West-

central New England ..... ............... . in pocket

TABLE

1. Approximate Amounts of Uranium, Thorium, and K0 in Common

Rocks . . . . . . . . . . . . . . . .... . . . ................. 17

AERORADIOACTIVITY SURVEY AND

AREAL GEOLOGY OF PARTS OFEAST-CENTRAL NEW YORK ANDWEST-CENTRAL NEW ENGLAND (ARMS-I)

1. INTRODUCTION

1.1 Location of Area

An aeroradioactivity survey of Connecticut, Rhode Island, centraland western Massachusetts, eastern New York, and parts of southernVermont and southwestern New Hampshire was made between Oct. 17, 1958,and Aug. 31, 1960, by the U. S. Geological Survey in cooperation withthe Division of Biology and Medicine, U. S. Atomic Energy Commission,as part of the Aerial Radiological Measurement Surveys(ARMS-I) program.The surveyed area comprises about 28,000 square miles; however, onlythe northern part of the area is discussed in this report (Fig. 1).The southern part of the survey area is discussed in CEX-58..64.

1.2 Purpose of Survey

The survey is part of a nationwide program to obtain data on theexisting gamma radioactivity for areas in and adjacent to nuclearfacilities. These data provide information that can be used to detectany future variations in radioactivity which may result from nucleartesting, reactor or other Atomic Energy Commission operations, orradioactivity accidents.

The major nuclear facilities included within the surveyed areaare: Brookhaven National Laboratory, Upton, N.Y.; ConsolidatedEdison Reactor, Indian Point, N. Y.; Knolls Atomic Power Laboratory,Schenectady, N. Y.; Submarine Intermediate Reactor (Mark A) WestMilton, N. Y.; Combustion Engineering Facility, Windsor, Conn.;Electric Boat Works, Groton, Conn.; and Yankee Atomic Power Company,Rowe., Mass. (Fig. 1).

Information on radioactivity levels in the environs and outsidethe plant boundaries of Atomic Energy Commission and contractorinstallations are reported in special periodic reports from eachinstallation. These reports are published in the U. S. Public Health

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The entire area surveyed includes the overlapping areas within50 miles of the Rowe, Schenectady, Windsor, and Brookhaven facilities.Parts of the area could not be flown because of the rugged topography.These are labeled "not surveyed" on the radioactivity map (P1. 1).

1.3 Airborne Survey Procedure

Radioactivity data were obtained with scintillation detectionequipment installed in a DC-3 type aircraft. East-west flight lineswere flown at 1-mile intervals in the entire area except the partwest of Albany, N. Y., where the lines were oriented north-south. Theaircraft maintained an approximate altitude of 500 ft above theground at ah average air speed of 150 mph. Topographic maps were usedfor pilot guidance. The flight path of the aircraft was recorded by agyrostabilized continuous-strip-film camera, and the distance of theaircraft from the ground was measured by a continuously-recordingradar altimeter. Fiducial markings which provide a common referencefor the radioactivity and altimeter data and the strip film, were madewith an electromechanical edgemark system operated by the flightobserver when the aircraft passed over recognizable features on theground2 .

1.4 Scintillation Detection Equipment

The gamma radiation detection equipment used by the GeologicalSurvey was developed by the Health Physics Division of Oak RidgeNational Laboratory and has been described in detail by Davis andReinhardt 3 . Briefly, the detecting element consists of sixthallium-activated sodium iodide crystals, 4 in. in diameter and2 in. thick, each with a photomultiplier tube and connected inparallel. The signal from the detecting element is amplified andfed through a discriminator and pulse shaper that is set to acceptonly pulses originating from gamma radiation with energies greaterthan 50 thousand electron volts (kev). The signal is then fed to tworate meters. One rate meter feeds a circuit that records totalradioactivity on a graphic milliammeter. The signal from the otherrate meter is recorded by a circuit from which the cosmic backgroundhas been removed and which is app¶7oximately corrected for altitudevariations from the nominal 500-ft surveying altitude by a signalfrom the radar altimeter servomechanism. The system described isillustrated by a diagram (Fig. 2).

The range of topographic roughness handled satisfactorily by thealtitude compensator is approximately between 100 and 900 ft. Thegamma absorption of a 1000-ft-thick air layer is great enougý to makedetection of all but the largest natural sources impractical 3therefore a large percentage of the measured signal when the aircraftis more than 900 ft above the ground is supplied by the altitudecompensator. The compensator on the Geological Survey equipment was

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adequate in all areas but those having the most extreme topographicroughness. The limits of the compensator were exceeded in smallareas of Green and Schoharie Counties, N. Y.

The gamma-ray flux at 2000 ft above the ground, which comesmainly from cosmic radiation and to a much lesser extent from radio-nuclides in the air, except after nuclear tests, is measured each daybefore surveying is started, and the assumed cosmic component isremoved from the compensated circuit. A part of a regular flight line,called a test line, is flown at the beginning and end of each day'ssurveying. Through a comparison of these data, variations due toatmospheric and meteorological conditions and to equipment calibrationmay be obtained.

The effective area of response of the scintillation crystalsat an altitude of 500 ft above the ground is a circle roughly 1000ft in diameter, and the radioactivity recorded is an average of theradioactivity received within the area of response. Theoretical aspectsof the area of res onse and other considerations are discussed bySakakura5, Gregoryg, and Moxham 7 .

Several times each day the rate meter is calibrated with aresonant reed controlled oscillator, and the scintillation detectionequipment is calibrated with a Cs 1 3 7 source. A ground check of thecrystals is made several times each week with a 10-microgram radiumsource.

The detection equipment is calibrated in counts per second (cps),which may be directly related to the average equivalent uraniumcontent of the surface material. The sensitivity of the GeologicalSurvey equipment has been expressed in many ways; Davis and Reinhardt(Ref. 3, P. 717) state "with a microgram of radium at one foot fromthe crystals, the counting rate is roughly 2,000 cps" and "when flyingover a one gram radium source at 2,000 feet, an increase of 50 cpsover background was noted". Davis and Reinhardtu also state "Thecount rates at 500 ft equivalent to a ground reading of 1 micro-roentgen/hour for csl37 and C06 0 plane sources are 25 and 18 cpsrespectively". Theoretical aspects of sensitivity are also dis-cussed by Sakakura (Ref. 5).

1.5 Theoretical Considerations

The principal sources of the gamma-ray flux at 500 ft above theground are cosmic radiation, radionuclides in the air (mostly radondaughter products), and radionuclides in the surface layer of theground. It is difficult to accurately determine the contributionof each component at any particular time during the survey daylhowever certain assumptions on theory and calibration procedurepermit reasonable estimates to be made.

The cosmic background is measured at 2000 ft above the groundtwice each day and the assumed cosmic component at 500 ft above theground is removed from the altitude-compensated circuit. Variationsin this component during the survey day are difficult to separatefrom the other components, but they are believed insignificant innormal surveying.

Many variables, such as moisture content of the soil,temperature, barometric pressure, and wind velocity, affect the

15

concentration of radionuclides in the air. It is not uncommon incases of temperature inversion to have a ten-fold increase in radonconcentration. The gamma effect from radon concentration has notbeen fully evaluated, but it is believed to be insignificant innormal surveying.

The radioactivity of synthetic particles (fallout, coolingeffluent gases, etc.) in the atmosphere may cause sharp or broadradioactivity anomalies, but these conditions were not encounteredduring the survey of this area.

The ground component of radioactivity measured at 500 ft abovethe ground comes mainly from the upper few inches of surface materialand originates from natural radionuclides and radioactive fissionproducts of fallout. Although an increase in measured radioactivitybelieved to be caused by fallout was noted during the survey of thesouthern part of the area in Oct. 1958 (Ref. 1), all of the areadiscussed in this report was flown in 1959 and 1960 and does notappear to be greatly affected by the fallout. This may be a resultof the cessation of nuclear testing prior to September 1961 and therapid decay of the short-lived fission products 9 . Gustafson,Marinelli, and BrarI 0 concluded from a study of the radioactivity of,soil at Lemont, Ill., that in the spring of 1957 the activity due tofallout was less than one-tenth of the total gamma activity of thesoil. This conclusion is supported by the fact that less than 100cps due to natural radioactivity and fallout was recorded overseveral large areas in the New England and New York portions of theproject. Any fallout that may be present is assumed to be uniformover the area surveyed.

.Of the naturally occurring radionuclides in the surface layer ofthe ground only members of the uranium and thorium decay series, andK40 are sufficiently abundant to affect the measured radioactivity.Trace amounts of these elements are found in all natural materials(Table 1). The concentration of these elements in the surficialmaterial (glacial drift, soil, weathered rock, etc.) is determinedby the original composition of the parent rock from which thesurficial material was derived, and changes brought about by geologicand soil forming processes.

An important consideration in any study of the radioactivity ofsurficial material is whether the material is derived from the bed-rock beneath it or whether it is derived from rock entirely differentfrom that on which it is resting. The fact that the surficialmaterial in the New York-New England area consists chiefly of un-consolidated glacial drift has an important bearing on the radio-activity of the area. It will be demonstrated later that the glacialmaterial bears a close relationship to the underlying bedrock.

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TABLE 1 - - APPROXIMATE AMOUNTS OF URANIUM, TIHIORIUM, AND K40 IN

COMMON ROCKS*

40Common rocks Uranium, ppm Thorium, ppm , ppm

Ultramafic 0.001 0.004 0.005

Basaltic 1.0 4.0 0.99

Granodiorite 3.0 8.5 3.0

Granite 3.0 17.0 5.0

Syenite 3.0 13.0 5.7

Shale 3.7 12.0 3.2

Sandstone 0.45 1.7 1.3

Carbonate 2.2 1.7 0.32

* Adapted from Turekian and Wedepohl 1 assuming the isotopic

abundance of K is 0.0119 percent of total potassium.

1.6 Compilation of Aeroradioactivity Data

Flight lines were plotted from the strip film onto base maps ata scale of I in. equals 1 mile (1:62,500). The altitude-compensatedradioactivity profiles were compared with topographic maps of the sameareas and all radioactivity lows attributable to lakes, ponds, rivers,or swamps were marked as such on the profiles (Fig. 3). This step wasnecessary because the glacial terrain is responsible for the numerouspoorly drained areas in which lakes and swamp abound. These waterbodies limit the source area by shielding the ground component, thusproducing many lows on the radioactivity profiles. The amplitudes ofthe lows are proportional to the areal extent of the water within thearea of response of the scintillation crystals. To reproduce allthese lows on the aeroradioactivity map would greatly complicate itwith numerous undesirable readings.

Adjacent aeroradioactivity profiles were then reexamined andsignificant changes or breaks in the level of radioactivity werecorrelated from line to line (Figs. 4a and 4b). The changes wereplotted on overlays of the base maps and connected by solid or dashedlines depending on the degree of correlation. As would be expected

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in a glaciated area many Qf the radioactivity boundaries aregradational, whereas others stand out quite sharply. The solid linesdenote relatively distinct changes in radioactivity level, and thedashed lines denote relatively minor or subtle changes. After therecords obtained over these specific areas had been scanned, theareas between the lines of change were assigned general ranges ofradioactivity level.

The overlays were then photographically reduced and the dataplotted on sheets of the Army Map Service, Corps of Engineers1:2501000-scale, topographic map series. The final 1:250,000 mapwas thus derived (Pi. 1). This map is also published in theGeological Survey Geophysical Investigations Map Seriesl 2 .

2. GENERAL GEOLOGY

A detailed description of the geology is beyond the purposeand scope of this report, however, a general knowledge of the regionalgeology is necessary to better interpret the radioactivity pattern.

Parts of four physiographic provinces are included in thearea (Fig. 5); the Appalachian Plateau province underlain byrelatively flat lying Paleozoic shale, sandstone, limestone anddolomite; the Valley and Ridge province underlain by weakly foldedPaleozoic shale,.dolomite, limestone, and sandstone; and the NewEngland and Adirondack provinces underlain chiefly by Precambrianand Paleozoic complexes of highly deformed schist, gneiss, andamphibolite of sedimentary and igneous origin.

Fig. 6 is a geologic sketch map Compiled from published maps anddescriptive literature. The geology of much of the area is currentlybeing restudied and there is much unpublished or only informallypublished data that contradict existing maps. Only recently havegeologists working in the region begun to have a good understandingof the complex metamorphic geology. The nature of many of theformations is poorly understood and discrepancies in origin,boundaries, names, and ages of many of the formations. exist fromstate to state, or area to area. Some of the difficulty in bedrockmapping is caused by the mantle of glacial drift, but the majordifficulties are the complex structure, high degree of metamorphism,deformation, igneous intrusion, and heterogenous lithology of theunits. Many of the metasedimentary schists and gneisses have beenintruded to such a degree that the rocks must be mapped as mixtures.In addition, reliable guide fossils on which age determinations maybe based are very scarce in NewEngland.

Most of the geologic data for Vermont are based on the newCentennial Geologic Map of Vermont by Doll, et. al. 13. In NewHampshire the State Geological Map by Billings14 is the major sourceof data. For Massachusetts detailed quadrangle maps were used whereavailable, but most of the geology is based on the PreliminaryGeologic Map by Emerson 1 5 published nearly a half century ago. ForNew York various dgta were used, primarily the Geologic Map of theSouthern Taconicsl., geologic quadrangle maps, ground-water resourcesmaps, and the 1901 Geologic Map of New York by Merrilll 7 .

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Unconsolidated glacial drift covers perhaps 98 percent of thesurface of the New York-New England area (Fig. 7) and outcrops existonly where bedrock projects through the glacial cover. Till, orboulder clay, an unsorted deposit, blankets most of the area. Severallarge lacustrine deposits of sorted silt, clay, and sand are presentin the Hudson and Connecticut River valleys. Goldthwait±b estimatesthe average thickness of the glacial deposits in New Hampshire to be37 ft. Although accurate information as to depths of glacial materialis lacking for much of the area, generally the most extensive depositsare located in the valleys, and the deposits are thin over the uplandareas or steep slopes. Composition of the deposits is extremelyvariable but is generally relatable to the nearby bedrock whichusually supplied the dominant material in the deposit. Thus depositsover shale are generally argillaceous, while those over areas ofcrystalline rock are general arenaceous.

3- GENERAL DISTRIBUTION OF RADIOACTIVITY

A summary of the radioactivity measured in the survey is shownin Fig. 8. Radioactivity levels ranged from less than 100 cps (countsper second) to 1150 cps, the average being about 500 cps.

The radioactivity map (PI. 1) of the area demonstrates that thegreat majority of the glacial drift mantling the bedrock bears a closerelationship to the underlying bedrock, except where its depth istoo great, as in areas of lacustrine deposits, or along the contactsbetween formations where material from one formation is interminglingwith that of another. Radioactivity boundaries are in most casesgradational owing to this intermingling of materials. It is surprisingthat bedrock radioactivity boundaries can be seen at all, but Nelsonand Narten 1 9 found in a radioactivity study of Maine that "the radio-activity of the glacial materials is about the same magnitude as thatof the rocks in the areas where they are found. It would thus seemthat glacial debris from the eroded rocks of Maine has not beentransported great distances". On the aeroradioactivity map many ofthe bedrock units may be traced for miles by their characteristiclevel regardless of the glacial cover.

Both sedimentary and igneous rocks show relatively high andlow radioactivity levels. In the Appalachian Plateau province theradioactivity of the carbonate rocks generally range from 300 to500 cps whereas the shale and sandstone generally range from 350 to700 cps. The shale, phyllite, graywacke and limestone underlying thefoothills of the Taconic Mountains generally range from 300 to 750cps, but levels as high as 1050 cps are associated with the shaleand phyllite underlying the Taconic Mountains. The New England andAdirondack provinces contain sedimentary and igneous rocks of variedradioactivity ranging from less than 100 to 1150 cps. Exceptionallylow radioactivity (100 to 400 cps) is associated with the schist andgneiss of the Green Mountains and eastern Vermont, the igneous rocksof the Oliverian Plutonic Series of New Hampshire and easternMassachusetts, and a large massif of anorthosite and areas of complexrock in the Adirondack Mountains of New York. Moderate to high

25

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radioactivity (400 to 1150 cps) is associated with a broad belt ofigneous and metasedimentary rocks in New Hampshire and easternMassachusetts, the Ascutney Mountain stock in Vermont, and locally inthe Adirondack Mountains.

Glacial lacustrine deposits in the vicinity of Albany, N. Y.,and scattered along the Connecticut River in Massachusettsgenerally have low associated radioactivity (200 to 400 cps). In manyareas recent river or stream alluvium differs in radioactivity fromthe bedrock.

Several radioactivity highs were measured at or near Springfield,Mass. (1050 cps) and Schenectady, N. Y. (900 and 1000 cps). Thesemeasurements (P1. 1) have no obvious geologic explanation and arebelieved not due to natural effects.

4. GEOLOGY AND RELATED RADIOACTIVITY OF THE APPALACHIAN PLATEAU

AND VALLEY AND RIDGE PROVINCES

The sedimentary rocks of the Appalachian Plateau and Valley andRidge provinces within the survey area range in age from Late Cambrianto Late Devonian. The rocks are relatively flat lying in theAppalachian Plateau, and become weakly folded and metamorphosed in theValley and Ridge province before they disappear under the rocks of theTaconic thrust sheets.

The Upper Cambrian section resting unconformably on Precambrianrocks and cropping out at the margins of the Adirondack Mountains,consists of sandstone and conglomerate overlain by several formationsof dolomite. A great thickness of massive gray Ordovician limestoneoverlies the Cambrian section. The Mohawk River valley is underlainby Ordovician black bituminous shale and gray calcareous shale withinterbedded sandstone and limestone. Resistant Silurian and LowerDevonian limestone with lesser amounts of sandstone and thin beddedshale uphold the Helderberg escarpment, a prominent topographicfeature to the south of the Mohawk River valley. Middle Devonianrocks, which are exposed at the surface in the Helderberg Plateau,consist predominantly of black bituminous shale in the west, gradingeastward to bluish-gray sandy shale.

The Upper Devonian section exposed in the Catskill Mountains andfoothills, is characterized by arkosic sandstone, siltstone, graywacke,some conglomerate, and greenish to reddish clay. The Upper Devoniangenerally consists of marine shale near its base and grades upwardto continental red beds.

Radioactivity levels range from 200 to 1050 cps. The level ofthe Cambrian and Lower Ordovician carbonate section generally rangesfrom 300 to 500 cps, but in many areas that section is not separableby radioactivity from the Ordovician shale sequence. The radio-activity of the Ordovician shale exposed along the Mohawk Valleyranges from 300 to 750 cps. Generally the shale is higher in radio-activity (500 to 650 cps) in the western part of the area, and lower(350 to 500 cps) west of Schenectady, N. Y., where the section containsabundant sandstone.

The resistant Silurian and Lower Devonian limestone sequencealong the Helderberg escarpment forms what is perhaps the best

28

exposure of bedrock in the project area. The carbonate sequence ismarked by a distinct radioactivity low (generally 300 to 500 cps).

Radioactivity of the Middle Devonian marine shale exposed on theHelderberg Plateau generally is from 400 to 600 cps in level, butseveral large areas in Schoharie and Otsego Counties, N.Y., average500 to 700 cps. The Upper Devonian Catskill red beds generally rangefrom 450 to 600 cps in level.

Locally, in Green and Schoharie Counties, radioactivity levelsrange from 700 to 1050 cps in steep-sided valleys. Comparison of theradioactivity profiles and altimeter records over these areas indicatethat these anomalous values are due to overcompensation by thealtitude-compensated circuit in the Geological Survey equipment,rather than to natural radioactivity.

Analyses of the Paleozoic rocks of the Hudson and Mohawk valleysby Narten and McKeown 2 0 indicate that "In the Paleozoic rocks theaverage radioactivity of the most strongly radioactive rocks is 0.003percent equivalent uranium".

In the Hudson River valley low radioactivity levels averaging250 to 400 cps are associated with lacustrine sand, gravel, andclay deposited in the glacial Lake Albany (Fig. 7). A significantradioactivity break occurs along a north-south line in the centerof the lake deposits. It is interesting that northeast of SaratogaSprings, N. Y., where the change in level is particularly pronounced,the break occurs near the location of a fault mapped by Cushing andRuedemann 2 1 . On the east side of the fault the Snake Hill Formation,a unit lithologically similar to the rocks of the Taconic sequenceis present, and on the west side the Canajoharie Shale, a black shale,is present. The Snake Hill Formation is now thought to be a faciesof the Canajoharie Shale. The fault shown by Cushing and Ruedemanncorresponds closely to the place where the cleaved rocks merge intouncleaved rocks 2 2 . It seems that the change in level is not due to adifference in the bedrock, but may be due to a difference in sourcearea for the lake sediments, those on the west derived from thePrecambrian Adirondack region, and those on the east derived fromthe Taconic Mountains.

5. GEOLOGY AND RELATED RADIOACTIVITY OF THE NEW ENGLAND AND

ADIRONDACK PROVINCES

5.1 Adirondack Province

The Adirondack Mountains of New York are underlain by a complexof Precambrian metasedimentary and meta-igneous rocks. The meta-sedimentary rocks, known as the Grenville Series. are dominantlymarble, quartzite, amphibolite, and biotitic, garnetiferous, andsillimanitic gneiss. These rocks are moderately to highly deformed,and injected with anorthosite, gabbro, diorite, syenite, and agranitic complex, which have interacted with the metasediments toproduce hybrid rocks and skarns. Paragneisses were injected lit-par-lit with magma and partially granitized by magmatic fluids whichpermeated the rocks. Some granites are not separable from granitizedsediment or migmatite 2 3 .

29

Radioactivity levels of the Precambrian rocks are generallyb~low 500 cps, except near the western boundary of the project wherethey are slightly higher (up to 700 cps). A large massif ofanorthosite exposed mainly in the Thirteenth Lake quadrangle innorthwestern Warren County, N. Y., is exceptionally low in level(150 to 350 cps). Large areas of rocks of anomalously low radio-activity are also found at the intersection of Herkimer, Fulton, andHamilton Counties, N. Y., where quartz-feldspar-garnet gneiss andmixed granite, syenite, and Grenville rocks are 200 to 400 cps inlevel; and at the southeastern extension of the Adirondack Precambriancomplex in Saratoga County, N. Y., where Grenville rocks and syeniteare 100 to 400 cps in level. High levels are scattered throughout thearea, the highest just west of the anorthosite massif (1150 cps), andanother sharp high of 1050 associated with a known uranium-richpegnatite located just north of the Sacandaga Reservoir in FultonCounty, N. Y. Investigations by Narten and McKeown (Ref. 20, p. 23)in the Adirondack Mountains indicate that '"although there are manyabnormally radioactive rocks and glacial materials, particularly nearthe contacts of igneous and metamorphic rocks, pegmatites are the onlyknown sources of concentrations of radioactive elements".

5.2 Western New England Highlands

5.2.1 Taconic Mountains

Underlying the Taconic Mountains and the foothills to the westis a sucession of Cambrian and Ordovician clastic rocks, primarilymicaceous and quartz-silt shale, purple and green shale and slate,red slate, quartzite, graywacke, and interbedded black shale andlimestone. Dikes of diabase, albite basalt, and tuffs are presentin the Taconic clastics indicating eugeosynclinal deposition. Theseclastics have relatively great north-south extent, relatively smalleast-west extent, and are surrounded by and rest discordantly oncontemporaneous miogeosynclinal carbonates and orthoquartzites 2 5.The Taconic rocks are bounded on the west by a fault, or zone offaults known as "tLogan's Line'", but the nature of the easternboundary is in doubt, for the Taconic rocks rest against and aremetamorphosed with similar Ordovician argillaceous rocks that obscurethe character of the contact.

Many hypotheses have been proposed to explain the apparentanomalous position of the Taconic rocks. Those of the north arethought to be a number of klippen, which have been thrust into theirpresent position from a source area to the east (Ref. 25, P. 326).The emplacement of the rocks of the southern Taconics is controversialin nature with several hypotheses proposed to explain their structureand lithology (Ref. 16).

The miogeosynclinal rocks bounding the eastern edge of theTaconic sequence are equivalent with and lithologically similar tothe Cambrian and Ordovician sequence of the Hudson and ChamplainValleys. Resting on the Precambrian rocks of the Green Mountainsand Berkshire Highlands are Lower Cambrian quartzites andconglomerates. Cambrian and Ordovician carbonate rocks that overlie

30

the clastic sequence are described as gray, pinkish, and browndolomite, white to gray marble, and calcareous sandstone andquartzite (Ref. 13). At the top of the section are blackcarbonaceous and pyritic slate and phyllitewhich correspond to theSnake Hill Formation of the Champlain Valley (Ref. 22).

Radioactivity levels over the rocks of the Taconic sequencerange from 300 to 1050 cps. The highest levels of radioactivity,averaging 500 to 800 cps, are associated with the variegated slateand phyllite underlying the Taconic Mountains along the New York-Vermont state line. Medium high levels of 450 to 700 cps are alsoassociated with the shale and slate in the foothills of the TaconicMountains in Washington County, N. Y. In Rensselaer and ColumbiaCounties, N. Y., medium low levels of 300 to 500 cps are associatedwith the Rensselaer Graywacke and the Cambrian clastic rocks of theTaconic sequence.

Radioactivity levels of the quartzite-carbonate sequence rangefrom 100 to 950 cps, but generally are below 600 cps. In Vermont alarge area of the sequence is exceptionally low (100 to 300 cps) inlevel. The level increases in Massachusetts to an average of 300 to500 cps. In many localities the bedrock in the valleys is mantledwith a thick blanket of talus, glacial drift, and alluvium, whichis the source of the gamma radiation.

5.2.2 Green Mountains

The Green Mountains of Vermont within the surveyed area areunderlain by a complex of Precambrian metasedimentary and meta-igneous rocks similar to those of the Adirondack Mountains. Themetasedimentary rocks, known as the Mount Holly Complex, consistdominantly of biotitic, muscovitic, and chloritic gneiss, hornblendegneiss, quartz mica schist, calcite and dolomite marble, micaceousquartzite, and amphibolite.

The metasedimentary rocks are intruded by both mafic and felsicigneous rock. At the southern tip of the Green Mountains the MountHolly Complex is intruded by the Stamford Granite Gneiss, a graycoarse-grained, porphyritic granite gneiss with megacrysts ofperthitic microcline. Elsewhere intrusions of gneissic biotitegranite, quartz monzonite, granodiorite, and "white gneiss" withquartz, microcline, albite, and biotite are present. A small stock,mainly nepheline syenite and pulaskite, intrudes the complex nearCuttingsville, Vt.13,2 6 ,27.

East of the Green Mountains several large areas of Precambrianrocks crop out in the cores of dome and nappe structures. Theserocks are largely banded gneisses of granodioritic or quartz dioriticcomposition with minor ounts of biotite amphibolite and a few lensesof schist and quartziteT2.

Radioactivity. levels associated with the rocks of the GreenMountains are generally low. That of a large central area of theMount Holly Complex is exceptionally low (100 to 300 cps) and mostof the complex is generally below 500 cps. Locally, the Mount HoliyComplex has zones of rock displaying higher radioactivity. Northeastof Bennington, Vt., several zones strike north-south, and haveassociated radioactivity varying from 200 to 1000 cps. The

31

Cuttingsville, Vt., stock has a small "high" of 700 cps associatedwith it. A large portion of the Green Mountains could not be flownbecause of the rugged topography, and it is possible that some of theradioactivity values recorded over the complex are incorrect becauseof the limitations of the altitude-compensated circuit of thescintillation equipment.

The Precambrian rocks exposed in the dome and nappe structuresto the east of the Green Mountains are uniformly low in radioactivity(generally 150 to 400 cps and rarely more than 500 cps).

5.2.3 Berkshire Highlands

South of the Green Mountains a complex of Precambrian age gneissand schist of sedimentary and igneous origin forms the core of theBerkshire Highlands. The metasedimentary sequence includes quartzitegneiss, actinolite-epidote gneiss, muscovite-biotite-epidote schist,biotite amphibolite, garnetiferous gneiss, quartzite, and marble. Asin the Green Mountains to the north, the closely folded sedimentaryrocks have been invaded and altered by mafic and felsic igneous magma,locally with considerable absorption of material. The commonorthogneiss is a medium-to fine-grained, light-colored biotite-(orbiotite-muscovite) microcline-oligoclase gneiss. Locally there aresmall areas of light-colored porphyritic granite1 5, 2 9, 3 0 .

Radioactivity levels over the Berkshire Highlands generallyrange from 300 to 500 cps. Higher levels are found locally but noneof these exceed 800 cps.

5.2.4 Eastern Vermont and West-central Massachusetts

The remainder of the western New England Highlands is underlainchiefly by a broad belt of mica schist and quartzite, interstratifiedwith green schist, amphibolite, and gneiss, all of Paleozoic age.The mica schist and quartzite are metamorphosed shale and sandstoneand the green schist, amplibolite and gneiss are largely metamorphosedvolcanic rock. Igneous rocks ranging in composition from serpentinizeddunite to granite are intrusive into the metasedimentary andmetavolcanic rocks. Several large granodiorite and quartz dioriteintrusions are present in Massachusetts, and these are similar to theintrusive rocks of the Eastern Highlands.

On the geologic sketch map (Fig. 6), the Western Highlands hasbeen divided into three metasedimentary units, based primarily onage; the Cambrian, the Ordovician (separated into two units, onechiefly of sedimentary origin and the other chiefly volcanic origin)and the Devonian. The Silurian section, which is of small arealextent, is included with the Devonian section.

The Cambrian section is characterized by schist, phyllite, andgneiss, with interbedded amphibolite, greenstone, quartzite anddolomite (Ref. 13). The radioactivity over the sequence generallyranges from 200 to 500 cps. Locally, particularly over Lower Cambrianschists, the level reaches 600 cps. Radioactivity of most of theCambrian formations of Massachusetts is 300 to 500 cps in level.

32

The Ordovician rocks, particularly the volcanic rocks, areamong the best defined by radioactivity lows on the map. The BarnardVolcanic Member of the Missisquoi Formation, mainly biotite gneiss,hornblende gneiss, and amphibolite (Ref. 13) shows a low of 100 to300 cps that can be traced across Vermont to'the vicinity of WestCummington, Mass. Similarly, a low occurs east of Ascutney Mountain,over volcanic members of the Partridge Formation, and around themargins of the Oliverian Plutonic Series of New Hampshire (AmmonoosucVolcanics). Most metasedimentary rocks in the Ordovician section,consisting of quartzite, granulite, schist, and phyllite, are below400 cps in radioactivity in Vermont and northern Massachusetts andbelow 500 cps in southern Massachusetts. Several ultramafic bodiesintrude the Ordovician rocks. The largest ultramafic intrusion nearEast Dover, Vt., is represented by a low of 150 to 250 cps.

The Devonian metasedimentary formations of the Western Highlandshave been grouped into two units on Fig. 6; the Littleton Formation,discussed later under the Eastern Highlands section, and the GileMountain and Waits River Formations. The Waits River Formation (whichis Silurian and Devonian in age) is chiefly gray quartzose andmicaceous marble interbedded with gray quartz-muscovite phyllite orschist. The Gile Mountain Formation is chiefly gray quartz-muscovitephyllite or schist interbedded and intergradational with graymicaceous quartzite, calcareous mica schist, and locally quartzoseand micaceous marble (Ref. 13). Both formations have volcanic members.Radioactivity of the two formations is generally below 450 cps inlevel in Vermont and increases in level toward the southern part ofthe belt in Massachusetts, where it attains a level of 450 to 650cps near Huntington, Mass. Several large igneous bodies occur withinthe Devonian belt, but these generally are not discernible by radio-activity measurements.

A consistent change in radioactivity level occurs between theDevonian rocks of the Western Highlands (Waits River, Gile MountainFormations) and those of the Eastern Highlands (Littleton Formation,etc.). The break occurs just west of the Connecticut River and canbe traced to where the formational boundaries disappear beneath theTriassic rocks of Massachusetts. The rocks of the Western Highlandsarea are generally low whereas those of the Eastern Highlands arenoticeably higher in level.

The most highly radioactive rocks in the area occur at AscutneyMountain in the northeastern part of the belt. Here a large stockcontaining comagmatic intrusions of gabbro diorite, syenite, andgranite has invaded the schist and gneiss31. The rocks are similarto, and classed with, the White Mountain Plutonic-Volcanic Series ofNew Hampshire. The granite at Ascutney Mountain has a radioactivitylevel of 1100 cps, the gabbro diorite has a low level of 200 to 300cps.

5.3 Triassic Rocks of Central Massachusetts

In central Massachusetts continental clastic rocks of Triassicage consisting chiefly of unmetamorphosed arkose, sandstone,conglomerate and shale underlie the Connecticut River Valley andextend southward into Connecticut. Basaltic lava flows are inter-

33

bedded with the clastic rocks and crop out in a narrow belt in thewest-central part of the area. The coarser clastics were depositedas alluvial fans by streams which dumped their load of gravelly washinto a structural trou h; the finer clastics are largely lacustrineor palustrine deposits52 . The beds strike north and dip toward theeast.

The radioactivity level of the Triassic rocks is a fairlyuniform 300 to 500 cps. Locally the radioactivity level reaches600 cps, possibly owing to a different source area for the sedimentaryor glacial material. The basaltic lava flows generally have aslightly lower level (250 to 400 cps), but in most areas they do nothave sufficient areal extent for their effect to be noticeable.Glacial lacustrine deposits with low radioactivity (200 to 400 cps)are present along the Connecticut River (Fig. 7). The contact ofthe Triassic rocks with the surrounding Paleozoic rocks is notdiscernible by radioactivity except in the southwest corner of thearea where the Paleozoic rocks are slightly higher in level.

5.4 Eastern New England Highlands

East of the Connecticut River the bedrock of the New EnglandHighlands is extremely complex. These rocks generally consist ofphyllite, micaceous quartzite, and interstratified volcanic rocks,or their higher-grade metamorphic equivalents, which have beenintruded by numerous types of igneous rocks (chiefly granite,quartz monzonite, quartz diorite, and granodiorite). The meta-sedimentary rocks are mainly of marine origin, originally arenaceousshales and argillaceous sands, mostly of Paleozoic age. At manyplaces the sedimentary rocks are intricately intruded, both lit-par-lit and by granitization. All of the rocks have been regionallymetamorphosed, chiefly to the sillimanite grade, and deformed (Ref.14, p. 28).

On the basis of radioactivity the eastern New England Highlandswithin the project boundaries can be roughly divided into zones fromwest to east: a western zone of medium radioactivity, a zone of lowradioactivity associated with the Oliverian Plutonic Series, a centralzone of relatively high radioactivity, and an eastern zone of low tomedium radioactivity.

The western zone of medium radioactivity is present mainly inMassachusetts and contains Devonian and older sedimentary rocks, andPaleozoic igneous rocks. On the geologic sketch map (Fig. 6), itincludes the unit marked as Dry Hill Granite Gneiss, WilliamsburgGranodiorite, Dana Diorite, and Belchertown Tonalite, and thesurrounding metasedimentary rocks. The zone generally ranges from300 to 600 cps. There is no difference in the radioactivity of theigneous or sedimentary rocks, and the belt is not distinguishable byradioactivity from the Triassic rocks to the west.

The second zone, of low radioactivity, is comprised of adiscontinuous series of domes, collectively called the BronsonHill anticline. These domes have cores of igneous intrusive rocksand are surrounded by metamorphosed Ordovician volcanic rocks. InNew Hampshire, where the domes are extensively developed, the granite,quartz monzonite, and granodiorite that make up the domes have

34

collectively been assigned to the Oliverian Plutonic Series becauseof their lithologic similarity and structural position. Theboundaries of the various rock types within the domes cannot beprecisely located because they are transitional into one another.The rocks of the series are generally pink, medium- to coarse-grained,characteristically foliated, and commonly found near the top of theAmmonoosuc Formation, a series of Ordovician metavolcanic rocks. Mostof the rocks of the series are older than or contemporaneous withdeformation (Ref. 14, p. 52).

The volcanic rocks surrounding the domes are of two principalkinds: dark-green chlorite and chlorite epidote schist, and buffto white soda rhyolite that is massive to schistose. Some dark slateand impure gray quartzite are mixed with the volcanic rocks. Thebedding, as well as the fragmental texture, indicates that most ofthe metavolcanic rocks are of phyroclastic rather than flow origin.These volcanic rocks are similar to, and have been correlated withthe Ordovician volcanic rocks of the Western Highlands, which includethe Barnard Member of the Missisquoi Formation, and volcanic membersof the Partridge Formation (Ref. 13).

The granite, quartz monzonite, granodiorite, and the volcanicrock surrounding the domes have strikingly low radioactivity. Mostof the Oliverian plutonic rocks are characteristically low in radio-activity (generally 150 to 400 cps) and can easily be traced acrossthe project area by this associated low radioactivity. The exceptionis at one locality in the Sunapee quadrangle, near the north edge ofthe area, where the quartz diorite and quartz monzonite in the Croydondome ranges from 500 to 700 cps with a small high of 900 cps. Wherethe individual rock types are mapped separately on geologic quadranglemapsJ, there appears to be a slight difference in the associatedradioactivity. The quartz diorite, where mapped separately, generallyranges from 150 to 350 cps, and the quartz monzonite, granodiorite,and surrounding volcanic rocks generally range from 300 to 400 cps(Fig. 4 a).

The central area of the Eastern Highlands contains as a wholethe highest levels of radioactivity in the northern New Englandproject area. The bedrock is generally metamorphosed shale andsandstone of Devonian age (mainly Littleton Formation), into whichhave been intruded many igneous bodies. Some gneiss, schist,quartzite, and igneous rocks of Carboniferous and Precambrian ageare present in Che eastern part of the zone. Most of the centralarea is metamorphosed to andalusite or sillimanite grade. Many ofthe metasedimentary rocks are highly migmatized and metasomatized,and some of the igneous rocks contain inclusions of metasedimentaryrock. 1

Billings has classed the Devonian(?) igneous rocks that intrudethe central zone in New Hampshire into the New Hampshire PlutonicSeries, and rocks unassigned to series, but probably New HampshirePlutonic Series. The dominant rock types are quartz monzonite,granodiorite, granite, biotite gneiss, and quartz diorite.

The average radioactivity of the central belt of rocks in NewHampshire is 400 to 700 cps. A large intrusion of quartz monzonitein the southwestern part of the state (500 to 700 cps) stands out insharp contrast to the surrounding rocks of lower radioactivity(Fig. 4). Elsewhere there appears to be little difference in radio-

35

activity between the igneous and sedimentary rocks. Local highreadings are found throughout the state over both igneous andsedimentary rocks. Several of the highest readings (up to 950 cps)occurred over Mount Monadnock, N. H.,which is underlain bysedimentary rocks, and over and around a body of quartz diorite nearLyndeboro, N. H.

To the south in Massachusetts the average radioactivity of thecentral zone increases to 550 to 750 cps. The Paxton Quartz Schistof Massachusetts is slightly lower with an average level of 400 to600 cps. Levels of 900 cps are present over rocks of both igneous andsedimentary origin. In the southeastern corner of the zone the North-bridge Granite Gneiss, a gneissoid porphyritic microcline-biotitegranite of Precambrian age, ranges in radioactivity from 400 to 1000cps. This rock is generally higher near its western margin and loweralong its eastern margin. The radioactive zoning may be due tomagmatic segregation, but it is possible that detailed geologic mappingwill show several distinct rock types within the unit.

Johnson 3 3 and McKeown3 4 have studied the central zone of highradioactivity in Massachusetts and New Hampshire and have concludedthat "The radioactivity of the rocks of the central New Englandprovince is considered to be due mainly to thorium, as uraniumanalyses to date have not shown more than 0.001 percent uranium"(Ref. 34, p. 24).

Although the southeastern extension of the project justtouches a zone of low to medium radioactivity, the rock types presentare characteristic of a broad area in eastern Massachusetts and inRhode Island. Two major bodies of igneous rock are present in thesurvey area; the Dedham Granodiorite, and the Milford Granite. TheDedham Granodiorite is typically a pale pink, coarse-grained biotiticgranodiorite composed essentially of microcline, plagioclase, quartz,and biotite altered to chlorite. The Milford Granite is typicallycoarse-grained, alkalic pink granite containing biotite as its darkconstituent and rounded blue quartz1 5.

Radioactivity levels over these plutonic rocks are generally low.Over the greater portion of the Milford Granite the level is auniform 300 to 400 cps. The southern end of the Milford Granite andthe greater portion of the Dedham Granodiorite range from 350 to 600cps. A stock of porphyritic riebeckite granite which has relativelyhigh radioactivity (850 to 950 cps) intrudes the Dedham Granodioriteat the tip of the southeastern project extension.

Clastic rocks of Pennsylvanian age are exposed in the extremesoutheastern corner of the project area. These rocks consist ofslightly metamorphosed conglomerate, arkose, sandstone, and shale ofnonmarine origin. Radioactivity levels range from 350 to 500 cps.

6. summARY

The natural gamma radioactivity in the project area ranges fromless than 100 cps to 1150 cps, averaging about 500 cps. Comparisonwith geologic maps indicates that the level of radioactivity isclosely related to the type of bedrock underlying soil or glacial

36

L.

deposits and subordinately related to the glacial deposits. Theassociation of radioactivity level with bedrock type is locally sogood that some geologic units may be traced for miles by theircharacteristic level.

Rocks of both sedimentary and igneous origin produced high andlow levels of radioactivity. Three large areas containing rocks ofmoderate to high radioactivity are present: one associated withclastic rocks of Devonian age in the Helderberg Plateau and foothillsof the Catskill Mountains; another associated with phyllite and slateof Cambrian and Ordovician age in the Taconic Mountains and foothills;and the third associated with a broad belt of phyllite, micaceousquartzite, volcanic material and intrusive igneous rock, chiefly ofDevonian age, in New Hampshire and east-central Massachusetts. Lowradioactivity is associated with a massif of anorthosite in theAdirondack Mountains, a large part of the Precambrian complex of theGreen and Adirondack Mountains, the Cambrian, Ordovician, andDevonian sedimentary sequence of eastern Vermont, the igneous rocksof the Oliverian Plutonic Series and surrounding volcanic rocks, andglacial lacustrine deposits along the Hudson and Connecticut Rivers.

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1. Peter Popenoe, Aeroradioactivity Survey and Areal Geologyof Parts of Southern New York and Southern New England (ARMS-I),U. S. Atomic Energy Comm. Report dEX-58.4.6 (in preparation).

2. Fred Keller, Jr., J. R. Balsley, Jr., and W. J. Dempsey, FieldOperations and Compilation Procedure Incidental to thePreparation of Isomagnetic Maps, Photogram. Eng., 13: 644-647(1957).

3. F. J. Davis and P. W. Reinhardt, Instrumentation in Aircraftfor Radiation Measurements, Nuclear Sci. and Eng., 2 (6):713-727 (1957).

4. Henry Faul, Nuclear Geology, John Wiley and Sons, New York,414 pp. (1954).

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6. A. F. Gregory, Geological Interpretation of Aeroradiometric Data,Canada Geol. Survey, Bull. No. 66, 29 pp. (1960).

7. R. M. Moxham, Airborne Radioactivity Surveys in GeologicExploration, Geophysics, 25 (2): 408-432 (1960).

8. F. J. Davis and P. W. Reinhardt, Radiation Measurements overSimulated Plane Sources, Health Physics, 8: 233-243 (1962).

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10. P. F. Gustafson, L. D. Marinelli, and S. S. Brar, Natural andFission-produced Gamma-ray Emitting Radioactivity in Soil,Science, 127 (3308): 1240-1242 (1958).

11. K. K. Turekian and K. H. Wedepohl, Distribution of theElements in Some Major Units of the Earth's Crust, Geol. Soc.America, Bull. No. 72 (2): 175-192 (1961).

37

12. Peter Popenoe, Aeroradioactivity of Parts of East-centralNew York and West-,central New England, U. S. Geol. SurveyGeophys. Inv. Map GP-358 (1964).

13. C. G. Doll, W. M. Cady, J. B. Thompson, Jr., and M. P. Billings,Centennial Geologic Map of Vermont, Vermont Geol. Survey(1961).

14. M. P. Billings, The Geology of New Hampshire, Part 2-BedrockGeology, New Hampshire State Plan. and Devel. Comm., 200 pp.(1956).

15. B. K. Emerson, Geology of Massachusetts and Rhode Island, U. S.Geol. Survey, Bull. No. 597, 289 pp., map 1:250,000 (1917).

16. D. W. Fisher, Stratigraphy and Structure in the SouthernTaconics (Rensselaer and Columbia Counties, New York), N. Y.State Geol. Assoc. 33rd Ann. Meeting, Guidebook to Field Trips,Sec. D, p. 1-22 (1961).

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18. J. W. Goldthwait, Lawrence Goldthwait, and R. P. Goldthwait,The Geology of New Hampshire, Part 1-Surficial Geology, NewHampshire State Plan. and Devel. Comm., 83 pp. (1951).

19. J. M. Nelson and P. F. Narten, Reconnaissance of RadioactiveRocks in Maine, U. S. Geol. Survey TEI-68, 43 pp., Reportprepared for U. S. Atomic Energy Comm. (1951).

20. P. F. Narten and F. A. McKeown, Reconnaissance of theRadioactive rocks of the Hudson Valley and Adirondack Mountains,New York, U. S. Geol. Survey TEI-70 54 pp., Report preparedfor U. S. Atomic Energy Comm. (19525.

21. H. P. Cushing and Rudolph Ruedemann, Geology of SaratogaSprings and Vicinity, New York State Museum, Bull. No. 169,170 pp. (1914).

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Northwest Adirondack Mountains, New York, Geol. Soc. America,Bull. No. 64 (9): 1013-1097 (1953).

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25. E-an Zen, Stratigraphy and Structure at the North End of theTaconic Range in West-central Vermont, Geol. Soc. America,Bull. No. 72 (2): 293-338 (1961).

26. W. F. Brace, The Geology of the Rutland Area, Vermont, VermontGeol. Survey, Bull. No. 6, 120 pp. (1953).

27. J. A. MacFadyen, Jr., The Geology of the Bennington AreaVermont, Vermont Geol. Survey, Bull. No. 7, 71 pp. (1956).

28. M. P. Billings, J. B. Thompson, Jr., and John Rodgers, Geologyof the Appalachian Highlands of East-central New York, SouthernVermont, and Southern New Hampshire, Geol. Soc. America, 65thAnn. Meeting, Guidebook for Field Trips in New England, p. 14-31 1952).

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30. Norman Herz, Bedrock Geology of the Cheshire Quadrangle,Massachusetts, U. S. Geol. Survey, Map GQ-108 (1958).

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31. R. W. Chapman and C. A. Chapman, Cauldron Subsidence atAscutney Mountain, Vermont, Geol. Soc. America, Bull.iNo. 51(2)':".. 191-212 (i04o).

32. P. D. Krynine, Petrology, Stratigraphy and Origin of theTriassic Sedimentary Rocks of Connecticut, Connecticut StateGeol. and Nat. Hist. Survey, Bull. No. 73, 239 pp. (1950•.

33. D. H. Johnson, Reconnaissance of Radioactive Rocks ofMassachusetts, U. S. Geol. Survey TEI-69, 16 pp., Reportprepared for U. S. Atomic Energy Comm. (1951).

34. F. A. McKeown, Reconnaissance of Radioactive Rocks of Vermont,New Hampshire, Connecticut, Rhode Island, and SoutheasternNew York, U. S. Geol. Survey TEI-67, 46 pp., Report preparedfor U. S. Atomic Energy Comm. (1952).

35. G. E. Moore, Jr., The Structure and Metamorphism of theKenne-Brattleboro Area, New Hampshire and Vermont, Geol.Soc. America, Bull. No. 60 (l0): 1613-1669 (1949).

36. N. M. Fenneman, Physical Divisions of the United States,U. S. Geol. Survey Map, scale 1:7,000,000 (1946).

37. R. F. Flint (chr.), Glacial Map of the United States East ofthe Rocky Mountains, Geol. Soc. America (1959).

38. G. R. Webber, P. M. Hurley, and H. W. Fairbain, Relative Agesof Eastern Massachusetts Granites by Total Lead Ratios inZircon, Amer. Jour. Sci., 254 (9): 574-583 (1956).

39

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The effective area of response of the products. Locally the amount of fallout mustscintillation'equipment at an elevation of 500 be small as the lowest totalradiation measuredfeet is a circle approximately 1, 000 feet in over several areas in New York and New Englanddiameter, and the radioactivity recorded is was less than 100 counts per second in areas notan average of the radioactivity received from affected by absorption of gamma energy by water.within the area. The scintillation equipment The distribution of fallout in the area surveyed isaccepts only pulses originating from gamma assumed to be uniform.radiation with energies greater than 50 kev In compiling the radioactivity data, all(thousand electron volts). A cesium-137 source radioactivity lows attributable to bodies ofis used during periodic calibrations to assure water were deleted to facilitate the reading ofuniformity of equipment response. the map. The aeroradioactivity profiles were

The gamma radiation at 500 feet above examined and significant changes or breaks inthe ground has three principal sources: cosmic level were correlated from profile to profile.radiation, radionuclides in the air (mostly The changes were then plotted on overlays ofradon daughter products), and radionuclides in the base maps and connected by solid or dashedthe surficial layer of the ground. The cosmic lines depending on the degree or correlation.component is determined twice daily by cali- The areas between the lines of change werebrations at 2,000 feet above the ground and is assigned general ranges of radioactivity levelremoved from the radioactivity data. by scanning the records obtained over these

The component due to radionuclides in specific areas.the air at 500 feet above the ground is difficultto evaluate. It is affected by meteorological Davis, F. J., and Reinhardt, P. W., 1957,conditions, and a tenfold change in radon con- Instrumentation in aircraft for radiationcentrations is not unusual under conditions of measurements: Nuclear Sci. and Eng., v. 2,

no. 6, p. 713-727.

"400-

EXPLANATION

f

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i~dai30-0135

Radioactivity boundarySolid where well defined, dashed where transitional or not well defined.

0(0 Numbers indicate general range of radioactivity levels in counts per~faawn 20second

ke Qwn iga

3050

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fl Q~zfto

aed with extreme temperature inversion. However, ifis and inversion conditions are avoided, the air com-igine ponent may be considered to be fairly uniformre on a given day in a particular area, and willwest of not affect the discrimination of the radioactivityLted levels that reflect changes in the groundervals component.e the The ground component comes from the-ompen- upper few inches of the ground. It consistsg eleva- of gamma rays from natural radionuclides,

it. The principally members of the uranium andi by a thorium radioactive decay series and potassium-amera. 40, and fallout from radioactive nuclear fissionf the products. Locally the amount of fallout mustof 500 be small as the lowest total radiation measuredet in over several areas in New York and New Englandded is was less than 100 counts per second in areas not)d from affected by absorption of gamma energy by water.[pment The distribution of fallout in the area surveyed isamma assumed to be uniform.) kev In compiling the radioactivity data, all37 source radioactivity lows attributable to bodies ofassure water were deleted to facilitate the reading of

the map. The aeroradioactivity profiles wereabove examined and significant changes or breaks in

;: cosmic level were correlated from profile to profile.)stly The changes were then plotted on overlays ofclides in the base maps and connected by solid or dashedcosmic lines depending on the degree or correlation.

y calf- The areas between the lines of change wered and is assigned general ranges of radioactivity level

by scanning the records obtained over thesedes in specific areas.

difficultlogical Davis, F. J., and Reinhardt, P. W., 1957,ion con- Instrumentation in aircraft for radiationtions of measurements: Nuclear Sci. and Eng., v. 2,

no. 6, p. 713-727.

EXPLANATION

I\S300-400

Radioactivity boundaryd, dashed where transitional or not well defined.neral range of radioactivity levels in counts per

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Numbers indicate general range of radioactivity levels in c

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Map obtainable from U.S. Geolog.pri c

31

EXPLANATION

/ \

Radioactivity boundary-here well defined, dashed where transitional or not well defined.bers indicate general range of radioactivity levels in counts perd

750-900 650-800 550-700

350-500 250-400 50-300

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O' INTERIOR--GEOLOGICAL SURVEY, WASHINGTON. D. C.-I1964--W63265

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Map obtainable from U.S. Geological Survey, Washington, D.C. 20242price 75 cents

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