Recognition Criteria of 

Igneous and Metamorphic Rocks 

on Aerial Photographs of 

Chichagof and Kruzof Islands 

Southeastern Alaska

By J. S. POMEROY

PROCEDURES AND STUDIES IN PHOTOGEOLOGY

GEOLOGICAL SURVEY BULLETIN 1043-E

An aid in the identification of major rock 

types in a complex geologic terrane

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402
CONTENTS

	Page 

.Abstract__________-____-----_-------__-_.---.. ____________ 87

Introduction. _____________-_____-_-___-___-___--__-----_--.-__---__ 87

Purpose_______._______-_____-_-_--________------_-------_---__ 87

Geologic sketch-_-____________________-i__--___----__-_______ 89

Geography___ _______-__.______-_____-________---__---__---__ 89

Recognition elements __________________________________________ 89

Chichagof Island.--__--_-_-_-__---__---__-----------------------.- 90

Summary, of geology__-_______________-________--___-_________ ' 90

Recognition criteria of metamorphic rocks on aerial photographs. _ _ _ _ 90

' Recognition criteria of intrusive rocks on aerial photographs ________ ; 97

Kruzof Island__________.__-_____-______.______-_-_--__-_---__-____ 101

Summary of geology...-_________-____--___---__----_---______- .101

. -Recognition.criteria of rock types on aerial photographs____________ 102

Summary and conclusions__-_-_-___-_-------___--------------_--__- 104

Source and identifying data of photographs.__________________________ 109

Selected bibliography_---__--________-_____-___--__-----_--__----_- 109

ILLUSTRATIONS

Page 

FIGURE 28. Index map showing area discussed______-______---_____.__ 88

. 29. Tonal differences and drainage characteristics of metamorphicigneous terrane, Rust Mountain area, Chichagof Island. ._ 91

30. Structural features, and drainage characteristics of .igneousmetamorphic terrane north of the head of Hoonah Sound, 

Chichagof Island._________'______________________.____ 93

31. Drainage characteristics of igneous-metamorphic .terrane -

in Deep Bay-Peril Strait area, Chichagof Island..____.... 94

32. Tonal differences and structural features of igneous-metamorphic terrane north of Hoonah Sound, Chichagof 

Island________---_-_.--____-____-__--________ 95

33. Vegetation and structural features of igneous-metamorphic 

terrane northeast of the head of Hoonah Sound, Chichagof 

Island______-___-____-_____.-___-_-_____-_-___-____ 96

34.. Drainage characteristics and structural features of igneousmetamorphic terrane near Rust Mountain, Chichagof 

Island____________________________________________ -97

35. Vegetation and structural features of igneous-metamorphic

terrane in Point Mary-Shelikof Bay area, Kruzof Island._ .99

36. Drainage characteristics of igneous terrane northeast of

Emmons Island, Chichagof Island...-------------.----- 100

37, 38. Structural features.

37. Northeast of Emmons Island, Chichagof Island.______ 102

38. Metamorphic terrane on southern Chichagof Island. _. 103

in
IV CONTENTS

Page 

FIGURE 39. Tonal differences in igneous-metamorphic terrane along

coast of northwestern Chichagof Island _________________ 105

40. Tonal differences and structural features of igneous-metamorphic terrane along eastern Kruzof Island.____________ 106

41. Topographic expression of volcanic landscape, southern

KruzofIsland______________________________________ 107

TABLE

Page 

TABLE 1. Summary of recognition criteria of igneous and metamorphic

rocks on aerial photographs of Chichagof and Kruzof Islands. _ 108
PROCEDURES. AND STUDIES IN PHOTOGEOLOGY

RECOGNITION CRITERIA OF IGNEOUS AND METAMORPHIC 

ROCKS ON AERIAL PHOTOGRAPHS OF CHIGHAGOF AND 

KRUZOF ISLANDS, SOUTHEASTERN ALASKA

By J. S. POMEROY

ABSTRACT

Various aerial photographic recognition elements such as photographic tone, 

vegetation, drainage characteristics, structural features, and topographic expression can be.used to assist in the semidetailed reconnaissance field mapping 

of a complex area of regionally and thermally metamorphosed rocks intruded 

by several types of igneous rocks. Combinations of these recognition elements 

are effective in distinguishing .the igneous and metamorphic rocks of Chichagof 

and Kruzof' Islands. Drainage character is one of the most reliable criteria.

INTRODUCTION 

'PURPOSE

Field investigations involving regional reconnaissance mapping 

were conducted on Chichagof, Baranof, and Kruzof Islands during 

the summer of 1961 (Loney and others, 1963). During the field season 

'the author,observed the usefulness of vertical aerial photographs in 

studying a geological^ complex; te-rrane. Because little has previously been written about photointerpretive aspects of specific 

igneous-metamorphic-terranes, it is the purpose of this paper to summarize the photointerpretive features of the igneous and metamorphic 

terrane of Chichagof and Kruzof Islands (fig. 28). Areas on 

Chichagof Island which were mapped by other workers (Rossman, 

1959;. Lathram and others, 1959; Loney and others, 1963; Reed and 

Coats, 1941) are not discussed here.

87
88 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

FIGDRE 28. Index map showing area discussed.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 89

GEOLOGIC SKETCH

Rocks ranging in age from. Silurian (?) and Devonian (?) to Quaternary crop out on Chichagof and Kruzof Islands. Plutonic rocks are 

abundant and constitute about 30 percent of the area discussed. Most 

of the layered rocks are older than the intrusive bodies, and although 

some of them are metamorphosed only slightly, most of them show the 

effects of either contact, regional, or dynamic metamorphism. In 

many places the rock type is a result of more than one form of 

metamorphism.

The area is complicated structurally by faulting and folding, and 

some of the layered rock units have been isoclinally folded.

During the Pleistocene Epoch, an ice sheet from the north and 

northeast covered all but the highest elevations. of Chichagof and 

Kruzof Islands. Aerial photographs indicate that the ice cover 

reached a/ninimum elevation between 2,400 and 2,700 feet over a large 

part of Chichagof Island and much less, below 1,900 feet, on Kruzof 

Island. Glaciers no longer exist in the area, but the ubiquitous 

cirques and U-shaped valleys are evidence that glaciation has occurred.

GEOGRAPHY

The area is topographically representative of southeastern Alaska. 

Mountains rise directly from the major inland waterways, and the 

only low regions are the alluvial valleys which are best developed at 

the heads of bays. Some peaks rise to elevations of slightly less than 

4,000 feet.

An annual rainfall of more than 85 inches is a major climatic feature. During the winter the climate is usually moderate along the 

shoreline, although a large amount of snow falls in the higher country. Summers are usually moist and cool; the daily temperature 

during the summer seldom exceeds 60°-65°.

Hemlock and spruce are the dominant tree growth. Brush, usually 

alder, devilsclub, and berry bushes, is thick and impenetrable in some 

places in the low areas. The elevation of the timberline varies but 

is usually between 2,000 and 2,600 feet.

RECOGNITION ELEMENTS

In studying the aerial photographs of an igneous and metamorphic 

terrane, different recognition elements photograph tone, vegetation, 

topographic expression, drainage and erosional characteristics, as well 

as the structural features of the rocks such as foliation and jointing 

can be used. Some recognition elements are more valuable than others, 

although any particular recognition element is more effective when
90 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

other criteria are used with it. Complete interpretation is prevented 

in many areas by an insufficient number of criteria.

CHICHAGOF ISLAND

SUMMARY OF GEOLOGY

The central and eastern parts of Chichagof Island are dominated 

by several plutonic bodies composed principally of granodiorite, 

tonalite, diorite, and gabbro but also containing small amounts of 

syenite, monzonite, adamellite, trondhjemite, and norite (Loney and 

others, 1963). These plutonic bodies have intruded and metamorphosed many of the Paleozoic and Mesozoic rocks. Large areas of 

mixed migmatitic rocks lie adjacent to several plutonic bodies. Most 

of the intrusive rocks are probably the same age as those of the Coast 

Eange batholith (Cretaceous), but a few may be older. Roof pendants consist principally of intensely folded hornfels, marble, amphibolite, and schist. A belt of graywacke, argillite, conglomerate, 

limestone, and marble crops out along the northeast edge of the area. 

To the west is a thick section of nonplutonic rocks mapped as several 

distinct units which range in age f rojn Permian (?) and Triassic (?) 

to Early Cretaceous. These units, some of which are nearly monolithologic, consist of greenstone, marble, greenschist, phyllite, and 

graywacke.

Marble is one of the major metamorphic rock types in the region. 

Because marble is lighter in tone on the photographs than any other 

metamorphic rock, it can be distinguished from other rock types 

wherever it is fairly homogeneous (fig. 29) ; marble is also generally 

lighter in tone than intrusive rock. Depending on the scale of the 

photographs or the magnification of the lens of the stereoscope, karst 

features may be observed. In a few places where massive nonfoliated 

marble occurs, it can be distinguished from other metamorphic rocks 

which usually have conspicuous foliation traces. Also, joints appear 

to be less developed in marble than in greenschist, phyllite, and 

hornfels.

Marble usually supports a stand of forest that is denser than that 

most characteristic of intrusive terranes. On eastern Chichagof 

Island a wide belt of nearly homogeneous marble crops out along 

Chatham Strait; a thick stand of forest obscures the area between 

the shoreline and the few ridge crests above timberline where the 

marble is exposed. Elsewhere in southeastern Alaska, marble supports a denser stand of evergreen forest than do other metamorphic
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 91

FIGURE 29. Tonal differences and drainage -characteristics of metamorphic-igneous

 terrane, Rust Mountain area, Chichagof Island. Light-toned marble (A), can 

easily be differentiated from adjacent metamorphic rocks. Extensive gullying as 

at B is diagnostic of terrane underlain by plutonic rock. Greenstone (C) has 

been intruded by granodlorite which crops out along mountain flank and along 

ridge at D. A thin veneer of greenstone masks the granodiorite in places. Note

 drainage in greenstone at B and probable fault scarp at F.

708-385 O 63
92 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

and intrusive rocks (Condon, 1961, p. 9, 14, 19; Ray, 1960, p. 135). 

In the eastern part of the island, the small number of rills along the 

ridge slopes indicates a low surface-drainage density in the marble, 

where there is much greater subterranean drainage through solution 

channels.

Fine-grained mafic igneous rocks and metamorphic derivatives of 

politic sedimentary rocks such as phyllite usually have a fine-textured, 

or high, drainage density (fig. 30), but the drainage density of coarser 

grained derivatives such as gneisses or quartzofeldspathic schists and 

amphibolites is often much less (fig. 31). When discussing gully 

characteristics associated with the erosion of different materials, 

Lueder (1959, p. 69) writes about one type of gully which develops in 

very small grained cohesive materials that are low in porosity. These 

gullies have long and wide channels, a moderate to large number of 

branches, and a fairly uniform gradient. This type of gully is typical 

of many of the fine-grained metamorphic rocks.

Practically all the observed drainage of both metamorphic and 

igneous terranes is imposed upon a thin regolith. Research workers 

at Purdue University (1953, p. 16) found that gully characteristics 

of the major soil textural groups become nondistinctive and also that 

combinations are found when the soil has a "strong" or well-developed 

profile. Conversely, a thin soil mantle would have definite gully 

characteristics.

On the photographs, most metamorphic rocks show not only a conspicuous foliation but also an equally well developed joint system 

(figs. 32, 33). These "checkerboard" or grid patterns usually indicate an area of metamorphic rocks. Gneisses or quartzofeldspathic 

schists, however, do not have these characteristics in this region.

The metamorphic rocks of the average roof-pendant area cannot 

be divided on the photographs. Owing to the complexity of these 

rocks, field mapping of any particular lithology, even at a semidetailed scale, is often practically impossible. In these areas, particularly, any metamorphic unit tends to be thin and of short lateral 

extent.

On southwestern Chichagof Island where the units are nearly 

monolithologic, few criteria are available to distinguish the metamorphic rocks (other than marble), with but one exception. In massive greenstone foliation is commonly obscure or nonexistent both 

on the photographs (figs. 29, 34) and in the field; conversely, adjacent 

bodies of greenschist "and phyllite have a pronounced foliation. In 

places the phyllite reproduces a lighter photographic tone than the 

greenschist, but this distinction is probably due to the abundant 

siliceous laminae which are associated with a particular phyllite unit.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 93
94 PROCEDURES AND STUDIES IN PHOTOGEOLOGY
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 95

\4

FIGURE 32. Tonal differences and structural characteristics of igneous-metamorphic 

terrane north of the head of Hoonah Sound, Chichagof Island. A, gabbro; B, 

marble ; C, interbedded hornfels, schist, amphibolite, and minor marble ; D, foliation ; and E, joints. Although the tone of the marble exposures (B) is lighter 

than that of the gabbro (A), the tone of the vegetation is darker (F). Marble 

usually shows less well-developed joints than do most other metamorphic rocks. 

Note checkerboard (grid) pattern at C.
96 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

f f)

FIGUKE 33. Vegetation and structural features of igneous-metamorphic terrane northeast 

of the head of Hoonah Sound, Chichagof Island. Gabbroic terrane (A) is comparatively 

sparsely wooded even at elevations as low as 900 feet. Higher country (B) Is underlain 

mostly by hornfels. C represents joints, and D is the strike of the foliation in the 

metamorphic rocks.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 97

FicDKK M4. Drainage characteristics and structural features of igneous-im'tamorphic 

terrane near Rust Mountain, Chichagof Island. A deeply incised'drainage system 

is developed on granodiorite at A. Metamorphic area (B) is underlain by massive 

greenstone. Note absence of foliation traces in the greenstone.

A thick unmetamorphosed graywacke unit borders the metamorphic 

rocks to the west, but on the photographs the graywacke cannot be 

distinguished from the metamorphic rocks.

RECOGNITION CRITERIA OF INTRUSIVE ROCKS ON AERIAL

PHOTOGRAPHS

Aerial photographs are of little value in differentiating intrusive 

rock types. As shown by field mapping, individual plutons on Chichagof Island are usually very complex and may include diverse rock
98 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

types. Also, migmatitic areas cannot be recognized on the aerial 

photographs.

Tonal variations, for example, between a granodiorite or tonalite 

and a gabbro outcrop are either nonexistent or very weakly reproduced 

on the same photograph. Although tonal distinctions would logically 

result from the predominance of light- or dark-colored minerals in 

the rock type and from the tone of the weathered surface, only occasionally is this criterion reliable. Likewise, tonal variations between 

intrusive rock types mapped by the author in other areas of southeastern Alaska are not well reproduced on the aerial photographs.

Vegetational differences are sometimes more useful than tonal 

contrast in distinguishing plutonic rock types. Residual soils developed on silicic rocks are usually fertile and support a great variety 

of vegetation. Mafic rocks and their residual soils, however, contain 

a less well balanced supply of nutrients and support a more restricted type of vegetation. Soils derived from ultramafic rocks 

are infertile and frequently lack vegetation (Eardley, 1942, p. 159- 

160).

The silicic plutonic rocks of the eastern half of Chichagof Island 

as well as the granodiorite of Kruzof Island (fig. 35) tend to support 

a dense forest. In contrast, the gabbroic area northeast and northwest of the head of Hoonah Sound has a low timberline and a scanty 

brush growth. (See figure 33.) Admittedly, some terranes underlain by silicic plutonic rock do not support a dense stand of vegetation; for example, in some areas of central and western Chichagof 

Island, a scant tree growth is typical. Local climatic factors and the 

effect of glaciation on soil cover and drainage possibly cause these 

differences.

An area, however, of ultramafic rocks along the eastern shoreline 

of nearby Baranof Island has a vegetation-rock-type relation unaffected by other influences. The boundary of the Red Bluff Bay 

chromite-bearing body as mapped in detail by Guild and Balsley 

(1942) coincides with the vegetational boundary. Although it is 

near sea level, the ultramafic area has almost no vegetation. Robinson and others (1935) state that large quantities of chromium and 

nickel in soils cause infertility.

Surface drainage patterns in the intrusive rock of Chichagof Island 

are less dense than those in most metamorphic rocks. (See figures 30, 

33, 34, 36.) Such wide spacing of streams results in a coarse-textured 

drainage system. The channels tend to be curvilinear although a few 

are nearly straight where slopes are steep. As previously mentioned 

(p. 92), the fine-grained metamorphic rocks have fine-textured or high 

drainage densities. Ray and Fischer (1960) discuss the drainage 

density of different rock types.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 99
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FIGURE 36. Drainage characteristics of igenous terrane northeast of Emmons Island, Chichhagof Island. Deeply 

incised drainage system has developed on tonalite. Eapid disintegration of rock accounts for light-colored 

tone of hillside ravines. This characteristic is usually reliable in differentiating plutonic from metamorphic 

rock in areas largely covered by vegetation.
101

One of the best criteria for distinguishing plutonic from metamorphic rocks is the recognition of the steeply incised heads of hillside 

ravines characteristic of many areas of intrusive rock. (See figs. 

29,31,34,35,36.) This criterion is helpful and reliable in areas where 

outcrops are sparse and where ridges are covered by trees or brush. 

Lueder (1959, p. 69) discusses one type of gully which develops in noncohesive material that has appreciable grain size and porosity; it is 

characterized by "* * * comparatively short length; simple and 

direct plan with few or no short simple branches, steep, uniform 

gradient with sharp knickpoint at head end, and a descriptive short 

steep gash or nick." Such a description fits most areas underlain by 

silica-rich to intermediate plutonic rocks on Chichagof Island.

Kesidual soils developed from rocks of gabbroic composition sometimes will have gullies of the type mentioned by Lueder. Gabbroic 

rock, however, even though it is usually coarse-grained, more often 

produces a somewhat clayey and impermeable soil, the soil composition depending on the amount of hornblende or other mafic minerals 

in the parent rock. Characteristics of the drainage system will likely 

include features of gullies developed both in silicic intrusive rocks 

and in pelitic and other fine-grained metamorphic rocks.

A large part of the plutonic rock on Chichagof Island is directionless 

or nonfoliated. Occasionally, however, an intrusive mass is foliated, 

and traces of the foliation are sometimes distinct in the photograph 

if the area is large enough. This feature can be confused with the 

conspicuous steep joint set that prevails in some plutons (fig. 37). 

Joint systems are more common and as easily distinguished in areas 

partly covered by sparse vegetation as they are in areas of good 

outcrop.

In the higher areas of Chichagof Island, igneous and metamorphic 

rocks can often be distinguished by the topographic expression of the 

ridges. Plutonic ridge crests are somewhat rounded or much less 

rugged than the characteristic sharp-crested serrate ridges of 

metamorphic rocks such as marble, phyllite, greenschist, and hornf els. 

Gneissic ridges are much less rugged than those ridges underlain by 

most metamorphic rocks.

Dikes intruding metamorphic rock are usually discernible on the 

photographs (fig. 38). As they are more resistant than the country 

rock in this area, the dikes occasionally have some relief.

KRUZOF ISLAND

SUMMARY OF GEOLOGY

Rocks ranging in age from Triassic and (or) Jurassic to Eecent 

crop out on Kruzof Island. The oldest rocks, which constitute only
102 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

a very small part of the island, consist of greenstone, greenschist, graywacke semischist, metachert, and phyllite. Graywacke, metamorphosed in places, overlies and is transitional with these rocks. A 

granodioritic plutoii was emplaced after the deposition of the graywacke and has caused contact metamorphism in the adjacent rocks. 

Post-Pleistocene basaltic flows erupted over what is now southern 

Kruzof Island.

RECOGNITION CRITERIA OF ROCK TYPES ON AERIAL 

PHOTOGRAPHS

Aerial photographs are useful in distinguishing intrusive rock from 

the graywacke and its metamorphic equivalents. Pronounced contrast in tone is found along the shoreline on both the east and the west 

sides of the island (figs. 35, 39, 40) where plutonic rock is light in tone 

when compared to the medium-toned graywacke and graywacke horiifels. As only a few parts of the ridges are above the timberline, tonal

FIGURE 37. Structural features northeast of Emmons Island, Chlchagof Island. 

A, dominant joint set in tonalite. Persistent linear features represent dominant 

vertical joint set in nonfoliated tonalite. These trends could be mistaken for 

foliation in a metamorphic (or igneous) rock.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 103

FIODRB 38. Structural features of metamorphic terrane on 

southern Chichagof Island. Altered gabbroic bodies (A) cut 

n sequence of greenstone, greenschist, and metachert. Note 

light tone of A. Linear trend at B represents foliation of the 

metamorphic rocks. At C thin beds of light-toned metachert 

could be mistaken for felsic sills. Light-toned linear bodies 

at D are dikes that have filled joints in the metamorphic 

rocks.
104 '-' PROCEDURES AND STUDIES IN PHOTOGEOLOGY

variations cannot be used here. The metagraywacke ridges; however, 

tend to be sharper crested than the less rugged ridges of intrusive rock 

that lie at similar elevations.

The photographs show that the structural patterns in the two rock 

types are dissimilar. Fairly to moderately, well defined northeastward-trending joints are common in the granodiorite. Conspicuous 

northwestward-trending bedding and: foliation^ traces are found in 

the. gray wacke and gray wacke hornf els.

The contact between the gray wacke and its metamorphic equivalent 

is gradational; so neither-unit can be distinguished on the photo- 

, graphs, nor can a- contact be delineated between the gray wacke and 

the older rocks which are transitional, with it.

The basaltic-flows and their associated cones of southern Kruzof 

Island are obvious features on the aerial photographs (fig. 41). The 

landscape is. characterized both by a radial and by a dendritic drainage pattern having, more dense-vegetation growing along the creeks 

and shoreline and by an absence'of structural trends (fig. 40). Although the photographic tone of the basalt-and metagraywaeke along 

the shoreline is similar^ closely spaced persistent northwest foliation 

traces in the metagraywacke contrast with the. featureless and flatly ing basalt.

SUMMARY AND.CONCLUSIONS

Recognition criteria of the major igneous and metamorphic rock 

types on-the aerial,photographs of. Chichagof and Kruzof Islands are 

summarized in table 1. The author believes that most of these recognition, elements- are applicable elsewhere in southeastern Alaska, 

and that a few can be used in almost any- region. While photointerpretation techniques can seldom be used as a- substitution for field 

mapping, they can greatly assist an experienced field ^mapper even 

in a complex geologic terrane. The author certainly cannot subscribe 

to any suggestion that rocks, particularly those of igneous-and metamorphic origin, might be best differentiated by using aerial survey instead of field and laboratory, methods (Lueder, 1959, p. 269, 272, 274).

Aerial photographs ior the discussed area are chiefly valuable for 

the help they give in the differentiation of igneous from metamorphic 

rocks. Aerial photographs are of limited value when distinguishing 

the complexly -folded and varied metamorphic lithologies from one 

another or when identifying intrusive rock types. Various recognition .elements such, as-outcrop tone, vegetation, topographic expression, drainage and erosional characteristics, and structural features of 

the rocks themselves are used in .the demarcation of the major rock 

types. Of these criteria, drainage character is one of the more reliable 

recognition elements.
RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 105

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RECOGNITION CRITERIA, ROCKS ON AERIAL PHOTOGRAPHS 109

SOURCE AND IDENTIFYING DATA OF PHOTOGRAPHS

[Project code SEA (Southeastern Alaska)]

Figure

29__._. -_--_.__ ..__... ....

30.. __...--.__..-.. .......

31. _--___--___.-__-____ ...

32.. .-...--.._.-.... ....._

33.. ._....-_...._... ......

34__. _ ___ --- ____

35.. ---..--__-.---.. ------

36..------.. .._-_--.---.--

37.. ________________ ------

38 ---_----------------.

39.. _____________________ .

40_ -_-_--__-_- _ --..._

41

Roll

135

139

128

139

128

135

135

128

128

135

135

128

135

Exposures

22-23

38-39

90-91

39-40

80-81

75-76

39-40

39-40

39

70

35

103

57-58

Topographic quadrangle 

(1:63,360)

Sitka C-6

D-6

B-5

D-6

D-5, D-6

C-6

A-6

C-5

C-5

C-6

B-6

A-5

A-5, A-6

Other data:

Approximate scale of photographs is 1:40,000. 

Photographs were taken by U.S. Navy during July 1948. 

Focal length of lens of camera was 6 inches. 

Photographs may be purchased from:

U.S. Geological Survey

Map Information, Office

Washington, D.C. 20235

SELECTED BIBLIOGRAPHY

Allum, J. A. E., 1961, Photogeological interpretation of areas of regional metamorphism: [LondonJ Inst. Mining and Metallurgy Bull. 655, p. 521-543.

Condon, W. H., 1961, Geology of the Craig quadrangle, Alaska : U.S. Geol. Survey 

Bull. 1108-B, p. B1-B43 [1962].

Eardley, A. J., 1942, Aerial photographs their use and interpretation: New 

York, Harper & Bros., 203 p.

Guild, P. W., and Balsley, J. R., Jr., 1942, Chromite deposits of Red Bluff Bay 

and vicinity, Baranof Island, Alaska: U.S. Geol. Survey Bull. 936-G, p. 

171-187.

Lathram, E. H., and others, 1959, Progress map of the geology of the Juneau 

quadrangle, Alaska: U.S. Geol. Survey Misc. Geol. inv. Map 1-303, scale 

1:250,000.

Loney, R. A., Berg, H. C., Ponieroy, J. S., and Brew, D. A., 1963, Reconnaissance 

geologic map of Chichagof Island and northwestern Baranof Island, Alaska: 

U.S. Geol. Survey Misc. Geol. Inv. .Map 1-388, 1 p.

honey, R. A., Condon, W. H., and Dutro, J. T., Jr., 1963, Geology of the Freshwater Bay area, Chichagof Island, Alaska: U.S. Geol. Survey Bull. 1108-C, 

C1-C54.

Lueder, D. R., 1959, Aerial photographic interpretation principles and applications : New York, McGraw-Hill Book Co., 462 p.

Miller, Y. C., and Miller, C. F., 1961, Photogeology: New York, McGraw-Hill 

Book Co., 248 p.

Purdue University, 1953, A manual on the airphoto interpretation of soils and 

rocks for engineering purposes: Purdue Univ. School of Civil Engineering 

and Engineering Mechanics, 206 p.
110 PROCEDURES AND STUDIES IN PHOTOGEOLOGY

Ray, R. G., 1960, Aerial photographs in geologic interpretation and mapping:

U.S. Geol. Survey Prof. Paper 373, 230 p.

Ray, R. G., and Fischer, W. A., 1960, Quantitative photography a geologic research tool: Photogramm. Eng., v. 26, no. 1, p. 143-150. 

Reed, J. C., and Coats, R. R., 1941, Geology and ore deposits of the Chichagof

mining district, Alaska: U.S. Geol. Survey Bull. 929, 148 p. 

Robinson, W. O., Edgington, Glen, and Byers, H. G., 1935, Chemical studies of 

-infertile soils derived from rocks high in magnesium and generally high

in chromium and nickel: U.S. Dept. Agriculture Tech. Bull. 471. 

Rossman, D. L., 1959, Geology and ore deposits of northwestern Chichagof

Island: U.S. Geol. Survey Bull. 1058-E, p. 139-216. 

Smith, H. T. U., 1943, Aerial photographs and their interpretation: New York,

Appleton-Century-Crofts, 372 p. 

Tator, B. A., and others, 1960, Photo interpretation in geology, Chap. 4 in

Manual of Photographic Interpretation: Am. Soc. Photogramm., p. 169-342. 

Turner, F. J., 1952, "Gefugerelief" illustrated by "schist tor" topography in

central Otago, New Zealand: Am. Jour. Sci., v. 250, no. 11, p. 802-807. 

Twenhofel, W. S., and Sainsbury, C. L., 1958, Fault patterns in southeastern

Alaska: Geol. Soc. America Bull., v. 69, no. 11, p. 1431-1442.