The Aguada Limestone 

of Northwestern 

Puerto Rico

By WATSON H. MONROE

CONTRIBUTIONS TO STRATIGRAPHY

* GEOLOGICAL SURVEY BULLETIN 1274-G

Prepared in cooperation with the 

Commonwealth of Puerto Rico 

Economic Development Administration, 

Industrial Research Department
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

U.S. GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1968

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

Washington, D.G. 20402 - Price 10 cents (paper cover)
CONTENTS

Page 

Abstract- _-___--____.___-_______-_-_---_--_______-_.-_-_-_-___--_ Gl

Introduction. ..._..._____._._.___._.___..-.._________..._-._._..__ 1

Rocks exposed in northwestern Puerto Rico____-._._._.___-----___._- 4

Aguada Limestone_____---___-__-_-_-_-_--______-_-_-_-__--.--__- 6

References cited__._._____-____________----.__.___.______.____-__ 12

ILLUSTRATIONS

 

Page 

FIQUBE 1. Map of northwestern Puerto Rico showing geologic contacts

as mapped by Zapp, Bergquist, and Thomas.._____-_____. G2

2. Map of northwestern Puerto Rico showing geologic contacts

as mapped by Monroe....-_----__._.---.__-_---------. 3

3. Diagrammatic section showing rocks exposed in northwestern

Puerto Rico...-.._-___-_--________._-____--_----____. 5

m

CONTRIBUTIONS TO STRATIGRAPHY

THE AGUADA LIMESTONE OF NORTHWESTERN 

PUERTO RICO

BY WATSON H. MONEOE

ABSTRACT

Geologic mapping in 1966 and 1967 has shown that the strata exposed in the 

area near Aguada, chosen as the type area of the Aguada Limestone, are a westward extension of strata probably belonging to the Cibao Formation that underlies 

the Aguada Limestone. The closest outcrops of limestone equivalent to the 

Aguada Limestone as mapped elsewhere in Puerto Rico are approximately 5 

kilometers northeast of Aguada. As the name Aguada is firmly entrenched in 

the geologic literature for the limestone beds between the Cibao Formation and 

the Aymam6n Limestone, the name Aguada Limestone is retained, but a special 

reference section is designated on Highway 110, 2 to 3 km north of Moca. The 

new reference section is about 9 km northeast of Aguada.

INTRODUCTION

The stratigraphic sequence of Oligocene and Miocene rocks in 

Puerto Rico was described in 1948 by Zapp, Bergquist, and Thomas. 

Detailed geologic mapping in northern Puerto Rico between 1957 and 

1967 by Monroe and Briggs (Briggs, 1965; Monroe, 1962,1963a, 1963b, 

1967; Monroe and Pease, 1962) has confirmed the stratigraphic sequence of Zapp, Bergquist, and Thomas (1948), but it has resulted in 

minor differences in location of geologic contacts and in somewhat 

more precise location of contacts in stratigraphic sections. In northwestern Puerto Ricoj however, mapping of the Moca and Aguadilla 

quadrangles by Monroe in 1965-67 has shown that the upper and lower 

contacts of the Aguada Limestone diverge significantly from those 

shown by Zapp, Bergquist, and Thomas (1948) and that the type area 

of the Aguada Limestone is within the outcrop belt of the underlying 

Cibao Formation as defined farther east. Figure 1 is a generalized 

reduction of the northwestern part of the map prepared by Zapp, 

Bergquist, and Thomas (1948); figure 2 is a generalized reduction of 

the maps of the Aguadilla, Isabela, and Moca quadrangles surveyed 

by W. H. Monroe in 1965-67.

Gl
G2 CONTRIBUTIONS TO STRATIGRAPHY
AGUADA LIMESTONE OF NORTHWESTERN PUERTO RICO G3

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G4 CONTRIBUTIONS TO STRATIGRAPHY

During the preparation of this paper very helpful suggestions were 

made by H. R. Bergquist, R. P. Briggs, G. V. Cohee, and J. B. Epstein.

The paper was prepared in cooperation with the Commonwealth of 

Puerto Rico Economic Development Administration, Industrial Research Department.

ROCKS EXPOSED IN NORTHWESTERN PUERTO RICO

The rocks exposed in northwestern Puerto Rico consist of a basement 

of volcanic rocks largely of Eocene age, but possibly in part Cretaceous 

and Paleocene, overlain with angular unconformity by a sequence of 

sedimentary rocks ranging in age from middle Oligocene to Holocene. 

Most of the sequence of Oligocene and Miocene age is limestone, except 

in the lower part where beds of sand and gravel are present. The 

sequence is summarized in figure 3.

At the base is the San Sebastian Formation of the Rio Guatemala 

Group, which consists of 0 to about 155 meters of sand 'and gravel but 

contains thin lenses of clay and very sandy clayey limestone. Fossils 

are abundant in some beds. The San Sebastian is not present in the 

extreme west near Aguada, unless a thin unmapp'able bed of lenticular 

sand and gravel at the base of the Cibao Formation may represent it. 

In the eastern part of the area, the upper part of the San Sebastian 

Formation intertongues toward the east with the Lares Limestone. The 

San Sebastian is overlain conformably by the Lares Limestone in the 

eastern part of the area shown in figure 2 and by the Cibao Formation 

in the central part where the Lares has intertongued with the upper 

part of the San Sebastian.

The Lares Limestone, also of the Rio Guatemala Group, consists 

of 0 to 210 m of alternating beds of earthy limestone, hard coralline 

chalk, calcareous clay like the overlying Cibao, and thin lenses of 

sand and gravel similar to the underlying San Sebastian. Corals, 

oysters and other mollusks, and large Foraminifera are common.

The Cibao Formation ait the top of the Rio Guatemala Group consists of 250 to 280 m of interbedded calcareous clay, soft earthy chalk, 

and hard very fine grained calcarenite and nongranular limestone. In 

the eastern part of the area, the middle of the formation, the Guajataca Member, contains many lenses of sand and gravel as much as 15 m 

thick. The formation is generally fossiliferous; locally it contains 

many oysters, an abundance of other mollusks, a few corals, and a few 

large Foraminifera.

The Cibao is overlain conformably by the Aguada Limestone, which 

is about 90 m thick throughout the area. At the base of the Aguada is 

a bed of hard medium-grained calcarenite, 50 centimeters to several 

meters thick. At the eastern edge of the area, the lower 60 m (lower
AGUADA LIMESTONE OF NORTHWESTERN PUERTO RICO G5

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Beach, swamp, and alluvial deposits

Camuy Formation

Aymamon Limestone

Thin-bedded limestone

Aguada Limestone

Upper member

Lower member

Cibao Formation

Lares Limestone

Tuffaceous sandstone and siltstone

a 

o 

o

2

TO

FIGUEE 3. Diagrammatic section showing rocks exposed 

in northwestern Puerto Rico.
G6 CONTRIBUTIONS TO STRATIGRAPHY

member) consists of granular chalky soft limestone or marl, containing 

discontinuous beds of fine- to medium-grained f ossilif erous calcarenite. 

Although this part of the formation resembles the Cibao, it contains 

much less clay. This lower member is overlain by thick layers of 

very pale orange to pink hard calcarenite alternating with chalky 

and rubbly limestone (upper member). In the western part of the 

area of outcrop shown in figure 2, the lower member grades laterally 

into hard calcarenitic limestone like the upper member farther east. 

The Aguada is locally fossiliferous, containing the foraminifer 

Marginopora sp., some corals, and a few molluska, but fossils are much 

less common than in the Cibao. Oysters 'are very rare. At the top and 

locally at lower positions, the formation contains 1 to 9 m of orange to 

pink granular thin-bedded and cross-laminated limestone in which 

individual beds range in thickness from 1 to Y cm. This thin-bedded 

zone has proved !a useful marker for the top of the formation, as it has 

been found at or near this position in nearly all sections from Aguadilla 

to San Juan.

The Aguada is overlain sharply but probably conformably by the 

Aym'amon Limestone, which is about 195 m thick. At most places the 

Aymamon consists of white to very pale orange, very pure fossiliferous 

limestone, generally indurated at the surface into finely crystalline 

rather dense limestone. In northwestern Puerto Rico, the upper 85 m 

contains many thick lenses or beds of very pale orange to brightyellow, slightly ferruginous chalk containing many beds of large 

oysters (Ostrea haitensis Gabb) and other fossils; these beds are 

interbedded with hard white limestone like the lower part of the 

formation.

The Aymamon is overlain near Isabela by the lower part of the 

Camuy Formation, which in this area consists of about 30 m of thinbedded and cross-laminated to massive ferruginous chalk and calcarenite varying in color from very pale orange to pale reddish 

brown.

Resting unconformably on all the rocks described above are discontinuous deposits of sand, clay, and sandy gravel of late Tertiary 

to Holocene age. In figures 1 and 2, only those deposits believed to be of 

Quaternary age are shown; most of these are alluvium and various 

kinds of beach deposits.

AGUADA LIMESTONE

The Aguada Limestone was named by Zapp, Bergquist, and Thomas 

in 1948:

The Aguada limestone is named from prominent exposures in the vicinity 

of the town of Aguada, near the west coast of the island. The Aguada limestone 

consists of the transitional beds between the underlying Rio Guatemala group
AGUADA LIMESTONE OF NORTHWESTERN PUERTO RICO G7

and the overlying Aymam6n limestone. It rests conformably on the Rio Guatemala 

group where present, but southwest of Aguadilla and east of Bayam6n, the 

Aguada limestone overlaps the [Cibao Formation of the] Rio Guatemala group 

and rests unconformably on the Cretaceous rocks. The Aguada limestone is 

overlain conformably by the Aymam6n limestone with which it is, in general, 

coextensive.

Geologic mapping in northern Puerto Rico by W. H. Monroe and 

R. P. Briggs between 1957 and 1967 has confirmed in general the 

mapping of the Aguada Limestone by Zapp, Bergquist, 'and Thomas 

(1948) in most areas except in northwestern Puerto Rico. Mapping in 

1965-67 by W. H. Monroe has shown that in the Moca and Aguadilla 

quadrangles the contacts drawn by Zapp, Bergquist, and Thomas 

(1948) for the top and bottom of the Aguada become progressively too 

low toward the west and that the area near Aguada, chosen as the 

type area by Zapp, Bergquist, and Thomas, is entirely within the 

Cibao Formation as mapped elsewhere by them. Figures 1 and 2 show 

graphically the difference in the maps.

The distinctive thin-bedded limestone at the top of the Aguada 

Limestone is readily traceable throughout northern Puerto Rico. It 

is roughly at the top of the Aguada as mapped by Zapp, Bergquist, and 

Thomas as far west as the eastern part of the area shown in figures 

1 and 2; still farther west it occurs at progressively higher stratigraphic positions than the upper contact shown on the 1948 map. 

It is obscurely exposed at two places near Highway 112 in the eastern 

part of the Moca quadrangle, well exposed at several places on Highway 110 in the western part of the quadrangle, and well exposed 

ait several places in the eastern part of the Aguadilla quadrangle and 

on the new cute of Highway 2 just east of Aguadilla; it can be followed 

down the face of the sea cliff north of Aguadilla and reaches sea 

level near the small U.S. Military Reservation about 3 km north of the 

center of Aguadilla. (The places mentioned above can be found on the 

topographic maps of the Moca and Aguadilla quadrangles.)

The lower two-thirds of the Aguada Limestone in the eastern part of 

the area shown in figure 2 contains much earthy limestone and some 

calcareous clay; at the base is a bed of medium-grained calcarenite 

l/2 to 1 m thick that is characteristic of the base of the formation 

farther east. This part of the Aguada, designated "lower member" on 

detailed maps (Monroe, 1967), resembles the underlying Cibao Formation, except that it contains much less calcareous clay. It seems probable 

that Zapp, Bergquist, and Thomas (1948) did not recognize the continuity of the thick bed of calcarenite at the base of the sequence, and 

farther west they correlated the upper part of the Cibao as defined 

herein with this lower member of the Aguada. In the western part of 

the area, the lower member grades laterally into hard limestone very
G8 CONTRIBUTIONS TO STRATIGRAPHY

much like the upper member. In the eastern part of the area shown in 

figures 1 and 2, Zapp, Bergquist, and Thomas (1948) correlated outliers of the harder upper member of the Aguada, as herein denned, 

with the Aymamon Limestone. In the area near Aguadilla, almost the 

entire Aguada was mapped with the Aymamon.

The sequence of rocks near the town of Aguada consists principally 

of somewhat lenticular, irregularly bedded, slightly ferruginous chalk 

and calcareous clay interbedded, especially at the base, with hard 

medium-grained calcarenite. The sequence is well exposed in a quarry 

and on building sites north of the quarry just west of the intersection 

of Highways 439 and 115 at marker km 26 hm 0, Highway 115 (62,100 

m N.; 74,900 m E.),1 2.5 km northeast of the church in the plaza at 

Aguada. This site is marked B in figure 2. Although Zapp, Bergquist, 

and Thomas (1948) did not designate a type locality for the Aguada 

Limestone, this quarry is within the type area.

Section of Ciltao Formation exposed in quarry and on building sites on hill north 

of quarry 2.5 km northeast of Aguada

Thickness 

(meters)

10. Limestone, vuggy, fossiliferous, very finely crystalline, very pale 

orange; interbedded with rubbly chalk containing concretionary 

masses of limestone as much as about 5 cm in diameter. To top of 

hill ____________________________________i 7. 0

9. Chalk, very finely crystalline, fossiliferous; containing scattered .concretions of limestone as much as about 4 cm in diameter______ 4. 8 

"8. Limestone, compact, very fine grained, chalky_______________ 1.0 

7. Chalk, moderate orange-pink________:_________________ 1.5

6. Chalk, compact, rubbly, very pale orange; grading down into rubbly 

chalky, very finely crystalline limestone, locally cemented into compact limestone. Upper part very poorly exposed on hill north of 

quarry _______________________________ 9.0

5. Chalk, recrystallized into brown vuggy limestone; dendrites of

MnO2 _________ .__________________________ 1. 0

4. Marlstone, compact; interbedded with white chalk___________ 6. 5 

3. Clay, chalky ; containing oysters________________________ 1. 7 

2. Calcarenite, fine-grained; alternates with compact silty chalk; beds

20-50 cm thick__________________________________ 3. 3 

1. Limestone, compact, rubbly, chalky; to bottom of quarry road_____ 2. 0

Total thickness___________________:_________ 37. 8

1 The kilometer and hectometer markers along highways are renumbered from time to 

time, so that locations in this paper are also referred to the Puerto Rico metric grid which 

is shown on the borders of U.S. Geological Survey topographic maps of Puerto Rico. The 

numbers show the meters north and east of an arbitrary reference point south of Isla 

Mona and southwest of Puerto Rico.
AGUADA LIMESTONE OF NORTHWESTERN PUERTO RICO G9

Although the strata in the vicinity of Aguada resemble the strata 

in the lower part of the Aguada Limestone in the eastern part of the 

area shown in figure 2, they are much more like the strata in the upper 

part of the Cibao Formation in that area and farther west. Furthermore, they contain several oyster-bearing beds, as does the Cibao, 

whereas oysters are very rare in the Aguada elsewhere in Puerto Rico. 

The thickness of the Aguada throughout most of northern Puerto Rico 

is about 90 m, except downdip in the valley of the Rio Grande de 

Manati and the Rio Grande de Arecibo, where Briggs (1961) reported thicknesses of as much as 140 m. In order to include the strata 

near Aguada in the Aguada Limestone, the"thickness of the Aguada 

would have to be at least 150 m, probably as much as 180 m..

Limestone is fairly common, in the lower .part of the sequence near 

Aguada. This limestone resembles the limestone beds in the Cibao, but 

conceivably could be limestone of the Lares Limestone deposited west of 

the area in which thick masses of gravel were deposited during Lares 

time. This gravel generally has been included in the upper part of the 

San Sebastian Formation. The limestone does not look like any of that 

in the Lares in the eastern part of the area in figure 2, however, and 

it has not been feasible to map it separately from the gradationally 

overlying chalk, calcareous clay, and earthy limestone. Hubbard (1923, 

p. 43-44) mapped all the limestone, chalk, and calcareous clay near 

Aguada in the Lares Limestone.

The fossils found in the rocks near Aguada are mostly long-ranging species and are of little value in solving the problem. The presence 

of oysters suggests a correlation with either the Cibao or the Lares, 

for oysters are common in both of these formations and are very rare 

in the Aguada. H. R. Bergquist (written commun., probably 1945) 

collected Lepidocyclina (USGS colln. 17171; loc. A in fig. 2) from an 

outcrop of weathered buff limestone at the north end of an isolated 

hill 360 m south of Aguada; Lepidocyclina is common in the lower 

two-thirds of the Cibao and in the Lares but : has not been reported 

from the Aguada.

Because of the doubt as to the assignment of the strata near Aguada, 

a special:reference section for the Aguada Limestone is established 

about 9 km northeast of Aguada on Highway 110 between markers 

km 15 hm 6 and km lT-lim 0 from 2 to 3 km north of Moca. The dips 

in the area are generally north and range from 3 ° to 4°.

The top of the Aguada Limestone is very well and characteristically 

exposed in a roadcut on Puerto Rico Highway 110 at Escuela Centro, 

marker km 16 hm 6 (E in fig. 2; 65,325 m N.; 80,790 m E.). This outcrop is on a hill capped by an outlier of Aymamon Limestone.
G10 CONTRIBUTIONS TO STRATIGRAPHY

Section in cut on Puerto Rico Highway 110 at Escuela Centro

Aymamdn Limestone: (meters) 

5. Limestone, massive, very pale orange, finely porous, very finely

crystalline. To top of hill______________ _______ 2.0

Aguada Limestone:

4. Calcarenite, thin-bedded, cross-laminated, grayish-orange-pink to 

moderate-orange-pink, fine- to medium-grained; in beds 3-5 cm 

thick. Marffinopora sp_________________________ o. 0 

3. Calcarenite, hard, moderate-reddish-orange to grayish-orange fineto medium-grained; containing some solution cavities. No fossils 

seen ____________________________________ 0. 7 

2. Clay, plastic, light-gray______________________________ 0. 3

i. Calcarenite, hard, pinkish-gray, fine-grained. Marginopora sp. From

road level 0. 5

Total thickness________________ 8. 5

Cuts on Highway 110 farther south expose lower parts of the 

Aguada. In the next deep cut at km 16 hm 4.5 (F in fig. 2), the thinbedded limestone of bed 4 of the section described above is underlain 

by 2 m of massive orange-pink to light-reddish-brown Calcarenite perforated by abundant solution cavities. The calcarenite rests on about 

5 m of a solution breccia of very finely crystalline limestone that closely 

resembles the Aymamon Limestone. This is underlain by medium- to 

coarse-grained, hard chalky calcarenite. No fossils were observed in 

any of these beds. A spring near the northern end of the cut flows out 

of a small cavern in the brecciated beds. The presence of gray clay at 

the bottom of the spring but not in the adjacent limestone suggests that 

bed 2 in the section at Escuela Centro may be a secondary deposit.

At km 16 hm 2 (G in fig. 2), still lower strata consist of very paleorange and grayish-orange-pink unfossiliferous limestone containing 

many black grains, probably MnO2 . Similar rock is exposed at several 

other cuts farther south, one of which is at the bottom of a cliff of 

limestone about 15 m high. One small coral head was observed in a cut 

at km 15 hm 9.

The hard generally unfossiliferous limestone exposed in the series 

of roadcuts described above is underlain by about 5 m of coarsely 

rubbly, compact but not recrystallized, orange-pink chalky limestone that contains a few Kuphm tubes at km 15 hm 7 (H in fig. 2; 

64,500 m N.; 80.600 m E.). This material is characteristic of the lower 

part of the Aguada as exposed in the eastern part of the area shown 

in figure 2.

At km 15 hm 6 (J in fig. 2; 64,400 m N.; 80,540 m E.), hard crystalline cavernous limestone stratigraphically below the chalky limestone 

of km 15 hm 7, and at the bottom of the Aguada, is exposed. The contact 

with the underlying Cibao Formation is covered by heavy forest
AGUADA LIMESTONE OP NORTHWESTERN PUERTO RICO Gil

growth here, but it is exposed on several hills farther south, where 

the basal bed of the Aguada consists of 1 to 2 m of medium-grained 

calcarenite that rests on calcareous clay. The Cibao is exposed on the 

west side of the highway at km 15 hm 4 (K in fig. 2; 64,200 m N.; 

80,510 m E.), where it consists of pink and yellowish-gray rubbly 

chalk containing Pecten sp., Kuphus sp., and Foraminif era.

Strata characteristic of the upper part of the Cibao Formation in 

this area are exposed in the cuts of Highway 110 near the top of the 

bluff north of Moca, from about km 14 hm 8 to about km 15 (L in fig. 2; 

63,840 m N.; 80,480 m E.). The top of this section is about 35 m 

below the top of the Cibao Formation.

Section of Cibao Formation on Highway 110 at top of bluff 1.3 km north of Moca

Thickness 

(meters)

Limestone, very chalky, rubbly. To top of cut about 5.0

Calcarenite, hard, grayish-orange, fine-grained; resembling Aguada Limestone _ ________ _ 1. 4

Marl, moderate orange-pink to pale-yellowish-orange, fine- to mediumgrained, chalky; crudely stratified into beds 2-15 cm thick_______ 4.0

Clay, very light bluish gray (generally weathered to tan), silty, calcareous; 

containing impressions of fossils; abundant large pelecypods and gastropods in lower part; crudely bedded to massive_________ __ 3.3

Clay, similar to above; crudely stratified in layers about % m thick; gastrojpods and Marginopora sp__________________:______ __ 1. 5

Limestone, crudely bedded, marly, less distinctly bedded than above; 

abundant fragments and molds of pelecypods, gastropods, corals, and 

one echinoid; base very sharp, forming small overhang__________ 5. 0

Siltstone, soft, calcareous, fossiliferous__ _____________ ____ 0.3

Breccia of calcareous nodules 1 to 2 cm in diameter, a few as large as 5 cm 

grading down into massive slightly rubbly marlstone; Orthaulaa sp__ 10.0

Total thickness______________________________ 30.5 

Concealed below by landslide debris.

The new cuts on the long north-south slope of Highway 2 just east 

of Aguadilla, 5 km northeast of Aguada, include the entire sequence of 

the Aguada Limestone, but at most places the strata are broken except 

for short distances, because at least two north-northwest-trending 

fault zones cut through the formation. These exposures are suitable 

as another reference locality where the rocks have many of the characteristic lithologic features of the Aguada Limestone. The base of the 

formation consists of thick beds of medium- to coarse-grained calcarenite and is exposed east of the southern edge of Aguadilla at 

marker km 128 hm 9.5 (D in fig. 2; 64,650 m N.; 76,400 m E.). The 

thin-bedded limestone, 9 m thick, at the top of the formation is typically exposed at km 126 hm 0 (C in fig. 2; 67,510 m N.; 76,890 m E.).
G12 CONTRIBUTIONS TO STRATIGRAPHY 

REFERENCES CITED

Briggs, R. P., 1961, Geology of Kewanee Interamerican Oil Company test well 

No. 4CPR, northern Puerto Rico, in Oil and gas possibilities of northern 

Puerto Rico : San Juan, Puerto Rico Mining Comm., p. 1-23.

 1965, Geologic map of the Barceloneta quadrangle, Puerto Rico: U.S.

Geol. Survey Misc. Geol. Inv. Map 1-421. 

Hubbard, Bela, 1923, The geology of the Lares District, Porto Rico: New York

Acad. Sci., Scientific Survey of Porto Rico and the Virgin Islands,' v. 2

pt 1,115 p. 

Monroe, W. H., 1962, Geology of the Manati quadrangle, Puerto Rico: U.S.

Geol. Survey Misc. Geol. Inv. Map 1-334.

 1963a, Geology of the Vega Alta quadrangle, Puerto Rico: U.S. Geol. 

Survey Geol. Quad. Map GQ-191.

 1963b, Geology of the Camuy quadrangle, Puerto Rico: U.S. Geol.

Survey Geol. Quad. Map GQ-197. 

 1967, Geologic map of the Quebradillas quadrangle, Puerto Rico: U.S.

Geol. Survey Misc. Geol. Inv. Map 1-498. 

Monroe, W. H., and Pease, M. H., Jr., 1962, Preliminary geologic map of the

Bayam6n quadrangle, Puerto Rico: U.S. Geol. Survey Misc. Geol. Inv.

Map 1-347. 

Zapp, A. D., Bergquist, H. R., and Thomas, C. R., 1948, Tertiary geology of the

coastal plains of Puerto Rico: U.S. Geol. Survey Oil and Gas Inv. Prelim.

Map 85, 2 sheets.

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