WATER-LAID VOLCANIC ROCKS OF EARLY UPPER CRETACEOUS AGE IN SOUTH­


WESTEHN AHKANSAS, SOUTHEASTERN OKLAHOIVIA, AND NORTHEASTERN TEXAS 


By CLARENCE S. Ross, HUGH D.'MISER, and LLOYD W. STEPHENSON 

INTRODUCTION 

Very few persons associate volcanoes with the fiat 

land of the Gulf Coastal Plain of southwestern Arkansas, but for a number·of years geologists have known 

that the "roots" of old volcanoes were present near 

Murfreesboro, in Pike County. They found here not 

,only the rocks that ~nce composed the craters of these 

volcanoes, but also the decomposed material filling 

their necks, which carries diamonds and is almost 

identical with the diamond-bearing earth of the great 

Kimberley Inine of South Africa. Much of the material 

ejected by these volcanoes was in the form of volcanic 

ash, sand, nnd lapilli, which were thrown out by vio­

.lent explosions and then widely distributed by wind 

and water. 

, The present paper deals with these and other vol­

'canoes in Arkansas and with recent ·discoveries of 

material tha,t was ejected from them. From the character of this lnaterial it has been possible to determine 

the geologic period in which the explosions occurred, 

the localities in Arkansas whence the material came, 

nnd the agencies by which it was distributed. 

DISCOVEHV OF ROCKS OF VOLCANIC ORIGIN IN THE 

WOODBINE AND TOKIO FORMATIONS 

The igneous rocks of Arkansas were for many years 

believed to have been formed near the end of Cretaceous time.l Later evidence placed their time of intrusion between the Comanche (Lower Cretaceous) and 

Gulf (Upper Cretaceous) epochs.2 The occurrence' in 

the basal Gulf rocks in Arkansas of water-laid mtLterials that have been derived from igneous rocks has 

been described by several geologists. 3 Recently discovered evidence indicates that volcanic eruptions 

accompanied by violent explosions took place near 

I BI'IlIHWI', J, c., nud Brnckett, R. N., The I1eridotite of Pike County, Ark.:Am. 

JOUI'. Sel., 311 sel'., vol. 38, pp. 50-59, 1889. Williams, J. F., 'rhe igneous rocks of Arkansus: AI'kansas 0001. Survey Ann. Rept. for 1890, vol. 2, p. 3, 1891. 

» Glenn, L, C., Arkansns dinmond-bearing peridotite (abstract): Geol. Soc. America BulL, vol. 23, p, 726, 1912. Miser, n. D., New areas of diamond-bearing peridotite in Al'kn.nsns: U. S. 0001. SUl'vey Bull. 540, pp. 541-545, 1914. 

8 Sterl'ett" n. n., [Dilllllonds in) Arkansas: U. S. Oeol. Survey Mineral Resources 

fol' lIJOO, pL. 2, pp. ili7-7511, 1010, Miser, fl. D., op. cit. Miser, fl. D., and Purdue, 

A. n., Ol'll\'el deposit.s of the Caddo Oap and De Queen quadrangles, Ark.: U, S. 

0001. SUl'vey Bull. (iOO, pp. 22-24, 1918; l.\'[iser, fl. D., and Ross, C. S., DiamondbCllring peridotite in Pike County, Ark.: U. S. Geol. Survey Bull. 735, pp. 291-292, 

}1I23. 

Murfreesboro, Ark., early in Gulf time.4 The dialnond 

deposits near Murfreesbo~o occur in the necks of the 

Cretaceous volcanoes. Yet the discovery of unquestionable volcanic ash and tuff in the Gulf series of 

sou thwestern Arkansas was not made until 1923 . This 

discovery has led to the conclusion that much if not all 

of the water-laid igneous material previously fo'und in 

the rocks of Gulf age was originally fragmental material 

that was ejected from volcanic vents. 

The volcanic material was identified by Clarence S. 

Ross in the spring of 1923 during the examination of 

specimens submitted to the United States Geological 

Survey by J. N. Garner, of Nashville, Ark. In October, 

1923, Miser studied deposits of volcanic material in 

the Gulf series of southeastern Oklahoma; in N ovember and December, 1923, Ross and Miser made a 

field investigation of similar deposits in Arkansas; in 

1924-1926 L. W. Stephenson studied them in Red 

River, Lamar, and Fannin Counties in northeastern 

Texas; in 1925 Miser, Stephenson, and C. H. Dane 

visited many exposures of the volcanic material in 

Arkansas, andlateri.n 1926 they visited several exposures 

of it in northeastern Texas. 

To Mr., Dane the authors of the present report 

.extend their thanks for his cooperation and assistance 

both in the field and in the office. To Mr. J. N. Garner 

they wish to express their sincere appreciation of his 

cooperation in the field. He personally guided them 

to 'exposures of volcanic rocks in Arkansas that he 

had discovered both before and after he had sent the 

first specimens to the Geological Survey for identification. 

In Arkansas and Oklahoma volcanic rocks of Cretaceous age are so far as known confined to the Woodbine and Tokio formations, but in. Texas they are 

found in the Woodbine sand, Eagle Ford clay, Austin 

chalk, Taylor marl, and Navarro formation. The 

Woodbine formation is the basal formation of the 

Gulf series in southwestern Arkansas, southeastern 

Oklahoma, and northeastern Texas. In Arkansas and 

in McCurtain County, Okla., it forms the lower part 

4 Miser, H. D., and Ross, C. S., op. cit., pp. 31~312; Econ. Geology, vol. 17, pp. 

662-674, 1922; Smithsonian Inst. Ann. Rept. for 1023, pp. 261-272, 1025. Mitchell, 

G. J., Diamond deposits in Arkansas: ·r:ng. and Min. Jour.-Press, vol. 116, pp. 

285-287, 1923. 

17u 
176 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

of the "Bingen sand" of Veatch, and the Tokio 

formation is the upper part of the "Bingen." In 

Arkansas and Oklahoma the Gulf series is separated 

from the Comanche series 'by a marked unconformity, 

and in places in Arkansas the Gulf series rests upon 

the truncated edges of steeply dipping Paleozoic 

rocks. 

A short preliminary paper on the volcanic rocks in 

the "Bingen formation" of Arkansas and Oklahoma 

was recently published 5 and a brief description of the 

igneous rocks in the De Queen and Caddo Gap 

quadrangles, Arkansas and Oklahoma, is given in a 

report now in press.6 

DISTRIBUTION OF THE VOLCANIC ROCKS 

The volcanic rocks here described are exposed in an 

east-west belt of country about 150 miles long that lies 

near the northern margin of the Gulf Coastal Plain, 

in Texas, Oklahoma, and Arkansas. The exposures 

in Arkansas and in McCurtain County, Okla., occur 

in a strip of high land lying only a few miles south 

of the north boundary of the Coastal Plain. This 

strip is a southward-sloping cuesta to which Veatch 7 

has applied the name" Lockesburg," from Lockesburg, Sevier County, Ark. (Veatch used the term 

" wold" instead of "cuesta," but of these two terms 

cuesta is in more general.use at present.) The Lockesburg cuesta owes its form and altitude to the resistant 

character of the southward-dipping beds of gravel, 

tuff, and sand of the Woodbine and Tokio formations, 

and it is in general coextensive with the outcrops of 

these formations as shown on Plate 20. It ranges in 

width from several to many miles and extends from a 

point near Delight, Ark., west by south across Pike, 

Hempstead, Howard, Sevier, and Little River Counties into Oklahoma, where it descends into the bottom 

lands of Red River west of Idabel, McCurtain County. 

Within this distance of about 100 miles the cuesta is 

not continuous but is trenched by the wide alluvial 

valleys of Little, Cossatot, Saline, and Little Missouri 

Rivers, which run in a general southeasterly direction, 

and by the valleys of the small southward-flowing 

streams between the wide valleys. Owing to the 

extensive dissection of the cuesta by streams, its surface is rolling to hilly, and there are no large tracts of 

level coun try. . 

The north edge of the cuesta culminates at 600 to 

700 feet above sea level, and its northward-facing 

escarpment is conspicuous, especially in Arkansas, 

where it rises 100 to 200 feet above the land at its foot. 

& Miser, H. D., and Ross, C. S., Volcanic rocks in the Upper Cretaceous of southwestern Arkansas and southeastern Oklahoma: Am. Jour. ScL, 5th ser., vol. 9, 

pp. 113-126, 1925. 

oMiser, H. D., and Purdue, A. H., Geology of the De Queen and Caddo Gap 

quadrangles, Arkansas and Oklahoma: U.S. Geol. Survey Bull. 808, pp. 99-115, 1929. 

7 Veatch, A. C., Geology and underground water resources of northern Louisiana 

and southern Arkansas: U. S. Geol. Survey Prof. Paper 46, pp. 14-15, 1906. 

The country that is underlain by the volcanic rocks 

of the Woodbine formation is known as "red-land" 

country and lies along the northern edge of the Lockesburg cuesta. (See pI. 18, A). On it in Arkansas are 

situated Highland, Corinth, Centerpoint, Horatio, and 

Cerro Gordo; in Oklahoma, Jadie, Goodwater, Odell, 

Shults, and Idabel. 

The red-land country received its name from the 

prevailing bright-red color of its clayey soil and sub-· 

soil. In spite of its poor appearance the soil produces 

good crops, especially of peaches and other fruits. 

The red clay is derived by weathering from volcanic. 

tuff and owes its fertility to the potash and other 

mineral ingredients supplied by the tuff. 

In northeastern Texas the rocks containing the vol-· 

canic material occur in the northern parts of Red. 

River and Lamar Counties, in a belt having a maxunuln. 

width of 5 miles, and in the northwestern part of Fan-· 

nin County. The Woodbine sand, of which these rocks. 

are a part, does not form a cuesta here, for the rocks. 

have been planed off by the terrace-forming processes. 

operating in the valley of Red River. Most of the· 

exposures occur in bluffs along Red River beneath a· 

covering of terrace materials or along the sides of 

tributary valleys whose streams have cut down through 

the terrace covering. 

ROCKS ASSOCIATED WITH THE VOLCANIC MATERIAL, 

GENERAL FEATURES 

Most of the rocks in which the volcanic material is" 

expos~d are sedimentary, but some are of igneous origin~ 

The igneous rocks include the four bodies of diamondbearing peridotite near Murfreesboro, Ark.; a dike of 

ouachitite of possible Cretaceous age 7 miles east of 

Gillham, Ark.,s a diorite sill of Ordovician (?) age 4· 

miles north of Glover, in northern McCurtain County,. 

Okla. 9 ; quartz-orthoclase pegmatites of Carboniferous. 

age, also in northern McCurtain County9; and granite· 

of pre-Cambrian age on the west border of the mapped 

area (pI. 20) southwest of Atoka, Okla. Beds of 

volcanic ash and tuff found a short distance north of 

the Coastal Plain are of Silurian,lO Devonian,!l and 

Carboniferous age.l2 

The sedimentary rocks in the country adjoining the: 

Coastal Plain .on the north are of Paleozoic age, 

ranging from Cambrian to Carboniferous, though thin. 

beds of Quaternary gravel and alluvium are found 

in places, especially along the streams. (See pI. 20.) 

8 Mitchell, G. J., Antimony in southwestern Arkansas: Eng. and Min. Jour.-· 

Press, vol. 114, pp. 455-456, 1922; also letter dated Sept. 7, 1923. 

g Honess, C. W., Geology of the southern Ouachita Mountains of Oklahoma:. 

Oklahoma Geol. Survey Bull. 32, pp. 39-40, 48-49, 64-66, 210-212, 1923. 

10 Honess, C. W., op. cit., pp. 107-109. 

11 Idem, pp. 121-139. 

12 Miser, H. D., Mississippian tuff in the Ouachita Mountain region [abstract): 

Geol. Soc. America Bull. vol. 31, pp. 125-126, 1920. lioness, C. W., The Stanley 

shale: Am. Jour. ScL, 5th ser., vol. 1, pp. 63-80, 1921; Oklahoma Geol. Survey Bull. 

32, pp. 179-202, 1923. 
-----

WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 177 

The Paleozoic rOCKS consist mainly of shale, sandstone, 

limestone, novaculite, and chert and have 'a total 

thickness in west-central Arkansas and southeastern 

Oldu,homa of about 25,000 feet. They were compressed into close westward-trending folds and were 

broken by many faults near the end of Pennsylvanian 

time, so that the dips are various but generally at 

high angles. 

The sedimentary rocks of the part of the Coastal 

Plain in which the volcanic rocks here described occur 

are of Comanche (Lower Cretaceous), Gulf (Upper 

Cretaceous), and Quaternary age. They have been 

grouped into several formations, but only the Woodbine, Eagle Ford, and Tokio formations, which contain 

the volcanic deposits, are here briefly described. (See 

fig. 16.) 

Sys- Se­ Thlokness Formation and member Section Character of rocks Character of topography and soil tom rlos in feet

-- ----1--------------------1--------------1--------1----------------1------------------------------------

~IIIIIII 

Brownstown marl. 


100± 
{FOSSiliferous blue or gray }Gently rolling area Fertile black waxy soil calcareous clay. . . 

Gravel; gray crOSS-bed_)


Tokio 
 ded quartz sand; ligformation 
 nltlc material; volcanic - . (100-300+) ash light-colored and BIlly areas. ~lray sand~ and gravelly soil, suitable for (upper part dark: clays, some of general farmmg and frUIt culture. of "Blngon sand" which contain fossil 


of Veatch). 
 l
plants.

Unconformity ------1 

Woodbine 

formation GraV~I; greenis? volcanic }Rolllng southward-sloping plateau_ Gravelly clay soil \ (l~re~. Ef~~ 0-350 tuff, red clay, and dark suitable for general farming and fruit culture 

gen sand " plant-bearing clay. . 

of Veatch). 

J --. Unconformity ---­

All soils mentioned below are suitable for genera farming C,) it they are fertili?,od and properl y cared for. 

Gray cross-bedded saud } in heavy beds; some Poor gray sandy soil 

clay. 

i j

FOSSmferous limestone 

and an equal or greater De Queen lime­ (60-72) amount of green clay. stone mem bar. Gypsum and celestite Usually a yellowish-brown clay soil; in some areas fertil3 near base. but in others poor. 

! 

o 


'l'rinlty 
 70-1,000+ Variegated clays. formation. 

G) 

( .g 0-40) {pebbles less than an inch

in diameter. DiSsected southward-sloping upland. Gravelly soi suit- = gravel lentil. able for fruit culture El Ultima Variegated clays. o Thule o j Fossiliferous limestone Dierks limestone { (0-40) and a smaller amount }Fertile black clay soil. lentil. { of green clay. 

Gray cross-bedded ·sand } in heavy beds; some Sandy gray soil. 

clay. 

j

lrregularlY bedded peb-j 

(

0-100) bles and cobbles as Dissected southward-sloping upland. Gravelly soil suitmember. 

Pike gravel much as 10 inches in able for fruit culture. 

diameter. '______________________ 

Unconformity ------1 'IIiIIIII 

] Atoka formation, Jackfork Shale and sandstone. o :g sandstone, and Stanley shalo. 

-ee 

tOG) 

C,) 

FlGunE 10.-Generalized section of the oldest Cretaceous rocks exposed in Boward, Pikc, and Sevier Counties, Ark. 
178 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

Stratigraphic relations of Woodbine and Tokio formations in northeastern Texas, southeastern Oklahoma, and southwestern A1'kansal:i to 

adjacent formations of Cretaceous age 

[For a graphic representation of relations of some of the rocks see section on pI. 20] 

Northeastern Texas Southeastern Oklahoma Southwestern Arkansas 

Brownstown marl. Present in McCurtain Coun- Brownstown marl. Brownstown marl (restricted), ty but not exposed, 

Unconformity -------.--­

Blossom sand. 

Tokio formation. Present in McCurtain County. Tokio formation.a 

Bonham clay. 

--- -Unconformity? Unconformity ---.-------

Ector tongue of Austin chalk; basal 

part is shaly clay and sand with" fish- Not present. 
 bed conglomerate" at base. Thins Not present. 

out toward northeast in Fannin 


County. 

UnconformityEagle Ford clay. Thins out toward east Eagle Ford shale present only in Bryan County. Not present. . in Lamar and Red River Counties. 

Unconformity­ -Unconformity 

Woodbine sand a in Woodbine formation a Woodbine formation.a Thins out 

Woodbine sand.a Bryan and Choctaw in McCurtain Coun- toward east. 

Counties. ty. 

Unconformity Unconformity -Unconformity----------­

Washita group. Thins out toward Washita group. Washita group. Thins toward east. east. 

Goodland limestone. Thins out to- Fredericksburg group. Goodland limestone. ward east. 

Trinity sand. Thins toward west by overlap of Trinity formation. Thins out toward 

Trinity sand.. younger beds of formation over older beds of east owing to unconformity at base 

formation. of Woodbine and Tokio formations. 

a Contains water-iaid volcanic rocks. 

WOODBINE FORMATION westward through the southern part of McCurtain, 

The Woodbine formation of the Gulf series (Upper 

Cretaceous) received its name from the village of 

Woodbine, in Cooke County, Tex. The formation consists mainly of quartz sand in northeastern 

Texas and in Bryan and Choctaw Counties, Okla., 

where it is appropriately called the Woodbine sand. 

Water-laid volcanic material is present in the Woodbine but increases in quantity toward the east in 

Texas, . Oklahoma, and Arkansas and comprises a 

large part of the formation in McCurtain County, 

Okla., and in southwestern Arkansas, where the term 

formation is more suitable than the tenn sand. In 

Arkansas the Woodbine comprises the lower part of 

the "Bingen sand" of Veatch and later authors, 

and in McCurtain County, Okla., it comprises the 

lower part of the "Bingen formation" as shown on 

the geologic map of the State published in 1926 by 

the United States Geological Survey. 

The area of ou tcrop is a belt extending from the 

valley of Little Missouri River in Pike County, 

Ark., west by south to the Oklahoma. line, thence 

Choctaw, and Bryan Counties, Okla., and the northern 

parts of Red River, Lamar, Fannin, and Grayson 

Counties, Tex., 8:,nd thence southward for many 

miles through central Texas. (See pl. 20.) In both 

southwestern Arkansas and McCurtain County, Okla., 

the Woodbine and the gravel and sand of the younger 

Tokio formation produce the southward-sloping 

Lockesburg cuesta, which i~ described on page 176. 

The formation has an estimated thickness of about 

500 feet in southern Bryan and Choctaw Counties, 

Okla., and an apparent thickness of 625 feet in Fannin 

County, Tex., but it thins toward the east so that 

the thickness at most places in Arkansas is between 

250 and 350 feet. It thins out on the west side of the 

valley of Little Missouri River, in Arkansas, and is 

not present east of this stream. 

The formation has a southerly dip of perhaps 50 

feet to the mile in most of the area shown on the accompanying map, though near the west end of the area 

it has been bent into a low anticline called the Preston 

anticline, whose axis extends southeastward through 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 18 

A. ROLLING" RED-LAND " COUNTRY ON LOCKESBURG CUESTA NEAR CORINTH, HOWARD 


COUNTY, ARK. 


Underlain by gravel and tuff ill the Woodbine and Tokio rormations. Such country is especially adapted to growing peaches and other fruils. Photograph furnished by J. N. Garner 

Cross bedding is conspicuous. Photograph by P. D. Torrey 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 19 

A 

B 

WEATHERED PERIDOTITE BRECCIA IN NECK OF CRETACEOUS VOLCANO NEAR MURFREF..sBORO, PIKE 


COUNTY, ARK. 


Contains diamonds. A shows diamonds being mined by hydraulicking. In B the hill in the distance is partly capped by a mass of Paleozoic sandstone that was lifted and carried upward during volcanic activity 
1.:. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 20 

Base compiled from U.S.Geological Geolo~ compiled by authors from pub­ SUNey 1:500,000 maps GEOLOGIC MAP OF PARTS OF ARKANSAS, OKLAHOMA, AND TEXAS, 	 lisheo and unpublished maps 

WITH GENERALIZED STRUCTURE SECTION SHOWING TIlE HELATlON8 OF THE COMANCHE SERIES AND THE LOWER PART OF THE GULF SERIES 

AND THE ]U'jLATION8 OF THE IGNEOU8 AND VOLCANIC ROCKS 

Scale 1:500,000 o 	 10 20 30 40 50 MilES 

E'""+3 e----------3 • 

EXPLANATION 

______ _ _ _A_TA~R_N Y ______ __--------------------	____________________________________________________________________________________________________~C~R~E~T~CEOUS r ______ C_-A_R_B_O_~FEROUS PRE-CARB0,!'J'FEROUS r 	 ------, 'r 	 ,.------------------------------------------------------------------------------------------------------=---~~------------------------------------------,\r , I 

Gulf series Comanche series l Upper Cretaceous) (L<ncer Cretaceous) r-------------------------------------~~~~~~~~--~~---------------------------------------------A________________________________________________________________________________________________________----,\(r--------------------------------------------~~------------------------------------------~ 

om 	 A 

Blossom sand ..-.-........- ......


Flood-plain ~ and terrace Brownstown marl Tokio formation ~ ~ ~ ~ [;J

Ector tongue of Woodbine fonnation Peridotite (tuff, breccia, Washita group Goodland limestone Trinity formation Atoka fonnation, Jackfork sandstone, Devonian to Cambrian rocks 

deposits (Contains water-laid volcanic Austin chalk 	 and Stanley shale (Include..... pre-Cambrial1 gnn, itf' soufh· (Consists mainly 0/ quarlz sand in noo-th- and intrasive rock) in 

( Partly repre!umted) malerial1'n Arkansas) eastern Texas and Bryan aM Choctaw volcanic necks Undud~l) in itQrthu:e:>t comero! area other west of Atoka) 

Bonham clay Counties, Okla., but t'olcanic material (Near Afurfreesboro, formation ... of Corbon deTow; aup) 

1°n Woodbine in these areas increa.ses Ark.) in quantity toward ea.~t and f".omprises 

"0........ 1 .... 0 1-'.... 	 Arkansas. 

large 

ta1.n 

material 

Counlll. 

part 

in 

of 

Best Texas 

Okla" 

formation 

expooures and 

and 

Oklahoma

southweatern 

in 

of volcanic

MeCur­are ~I~_ ...., u <1! 

~ ~ "'Ol~....... 

Q) C1J ~ 5 shown on map -g E o~ ~ ~ -g :i -g c- :&, 0 	 -B 5: 

~~" ~~ c~ ~~ E. ..... '.;.:..; ',,: ,;.../ '~:i ':~'.'r? .~ ·.4···P.. ·:~·.·..,. . 

~::~':'i..~:.: 4:'~.~,,> '~. '.. :.~ ...,;:'..;:~:: ~:7· t:.~j ·;,,:·::':~",:7~t -:'.~'. 

,'.. , ':.' 	 .'. ..... 

E·' 

....' " . 

Vertical scale A Tok io formation, Upper Cretaceous; contains some water·lald DeQueen limestone member K Devonian, Silurian, Ordovician, Cambrian, and 


volcaniC tuf! (mdicated by triane-ular ~attern) Ultima Thule e-ravel lentil 0E==C==l,=OOEO~===="'C=====:::E=====C=====5S,OIOO FEET
 pre-Cambrian rocks 

8 Woodbine formallon. Upper Cretaceous; contains Horizontal scale is 5ame as that of map Dierks limestone lentil L Peridotite intruded in early Upper Cretaceous time 


much water.lald volcaniC tuff Pike g-ravel member M Trachytic rock in supposed volcanic neck a few miles 


C INashlta 2"roup, Lower Cretaceous northwest of Nashville, Ark 


o Goodland I~ mestone, Lower Cretaceous 
U. S. GEOLOGI CAL SURVEY PROFESSIONAL PAPER 154 PLATE 21 

PHOTOMICROGRAPHS OF VOLCANIC ROCKS 

A, Sodalite phonolite from boulder bed in Mine Creek near Nashville, Ark. The phenocrysts that show zoning are sodalitc. Enlarged 34 diameters B, Phonolil.e pellet from phonolite arkose, Owen place, Howard County, Ark. The elongated crystals are plagioclase, and the gray groundmass is a very fine 

grained orthoclase-albite aggregate. Enlarged 34 diameters C, Orthoclase crystal partly replaced by calcite, Owen place, Howa rd County, Ark. Enlarged 48 diameters D, Orthoclase crystal pa rtly replaced hy calcite, Owen place, Howard County, Ark. The area with fingerlike extensions has the same optical orientation as the white central mass, and t he dark area between is calcite. Enlarged 28 diameters 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 22 

PHOTOM1CHOGHAPHS OF VOLCANIC ROCKS 

A, Volcanic tuff en tirely replaced by calcite but preserving the structure of glassy pumice, Owen place, Howard County, Ark , Enlarged 54 dia meters B, P a rt of a la rge glassy pumice fragmen t entirely replaced by calcite, Owen place, Howard County, Ark. C, PhonoliLe tuff from Prothro dome, Bienville Parish, La. Pure wh ite areas are feldspar; light. spotted ones are quartz or novaculite, and darker ODes with 

white elongated inclusions are phonoille. The interst.itial material is glauconite. Enlarged 33 diame t.ers D, Phonolite tufT from Prothro dome, Bienville Parish, La. WhiLe angular areas urc feldspar; rounded one, quartz; gray ones, phonolite pelle Is and partly replaced augite grains above and to the right of the center. Groundmass ca lcite. Enlarged 54 diame ters 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 179 

the village of Ector, Fannin County, Tex., and it 

has also been bent into a syncline whose axis runs 

northwestward through Yuba, Bryan County, Okla. 

The Woodbine rests upon the truncated edges of all 

the COlnanche formations-the youngest subjacent 

forn1ations to the west and the oldest to the eastand at the east edge of the area shown o~ the map 

(pI. 20) it rests upon steeply dipping beds of sandstone and shale of Carboniferous age. A marked 

angular unconformity therefore separates the Gulf 

series from the Comanche series in southwestern 

Arkansas and southeastern Oldahoma. (See section 

on pI. 20.) 

The water-laid volcanic material in the Woodbine 

consists of tuffaceous sand in northeastern Texas 

and in Bryan and Choctaw Counties, Okla., and of 

tuff in McCurtain County, Olda., and in southwestern 

Arkansas. The sand and tuff, which are described in 

detail on pages 180 to 200, occur in widespread beds that 

attain a thickness of 125 feet or n10re. These materials are mostly cross-bedded, soft, grayish and olivegray, are cOlnposed of coarse and fine grains of volcanic rocks, and are for the most part unconsolidated 

but in places cemented by calcite. The calcitecmnented Inasses are lenticular or spherical. 

Besides tuffaceous sand the Woodbine of northeastern Texas and of Bryan and Choctaw Counties, 

Okla., includes irregularly bedded quartz sand, which 

was deposited in shallow marine and brackish water. 

Interbedded with the sand are films, lenses, and layers 

of clay, whir.h in places attain a thickness of 25 feet 

or more. 

In Arkansas nnd in McCurtain County, Okla., 

there is a bed of gravel at the base of the formation 

and. beds and. lenses of gravel higher in the formation. 

(See pI. 18, B.) The gravel beds are thickest and 

most extensive in Arkansas, where the basal bed is 

continuous and attains a thickness of about '60 feet. 

The beds of gravel consist mostly of pebbles of novaculite, but in addition there are in Arkansas rather 

extensive deposits of pebbles of igneous rocks in the 

tuff, which overlies the basal gravel. Some of the 

larger igneous pebbles occur in the thick bed of gravel 

at the base of the formation, but most of then1 occur in 

thin beds and lenses of gravel interstratified in the 

tuff. Many small ppbbles are, however, disseminated 

through the tuff. Clay is found at some places in 

beds many feet thick interbedded with the volcanic 

tutL It is gray to brown, is lan1inated, and contains 

at places fossil leaves, some of which were collected at 

a locality on Mine Creek 4 miles north of Nashville, 

Ark. 

EAGLE FORD CLAY 

In western Lamar County and in Fannin County, 

Tex., the Woodbine sand is overlain, probably unconformltbly, by the Eagle Ford clay, which consists 

typically of 300 or 400 feet of dark, more or less 

bituminous clay carrying calcium carbonate con­

-cretions, in part septarian, some of which are fossiliferous. 

The Eagle Ford is represented on Plate 20 as 

extending as a rapidly narrowing band eastward from 

Lamar County into Red River County in the vicinity 

of Woodland, but the beds thus mapped are not 

typical of the Eagle Ford clay. They consist of 50 or 

60 feet of fine to coarse marine sand, a central band 

of which contains a small percentage of water-laid 

volcanic Inaterial. At the base of this sand just 

north of Woodland is a bed of conglomeratic sand, 

172 feet thick, containing many waterworn pebbles of 

novaculite reaching a diameter of 1 inch and reworked 

chunks of soft reddish sandstone. The Eagle Ford 

age of the sands near Woodland has not been satisfactorily established, and indeed there is some question 

as to whether they may not represent the basal part 

of the deposits of Austin age (Bonham clay) which 

overlie them within a mile south of Woodland. (See 

pp. 196-197.) The beds exposed within 4 or 5 miles 

north of Woodland are mostly sand and sand~.tone 

and are of Woodbine aspect, but future studies nlay 

show that they are in part of Eagle Ford age. 

TOKIO FORMATION 

The Tokio formation takes its nalne from the village 

of Tokio, at the northern edge _ot~ Hempstead Cour;tty, 

Ark. The deposits when first defined by Miser and, 

Purdue were described as the" Tokio sand member of 

the Bingen fornlation." Recent field work by Stephenson and Dane, in which Miserco~perated for short 

periods, has sho'wn that an unconformity occur,s at 

the base of a thick gravel bed immediately underneath 

the "Tokio sand member of the Bingen." I t has 

also shown that the part of the"Bingen" below' this 

gravel bed represents the vVoodbine sand of Texas. 

As a result of this work and of a study of the fossils by 

Stephenson, the following changes in names have been 

made: The name "Bingen," has been discontInued; 

the lower part of the "Bingen "-the part below the 

unconformity-is called the Woodbine formation; 

and the "Tokio sand member of the Bingen" is now 

called the Tokio formation, though the lower limit of 

the new formation is extended so as to include the 

thick gravel at whose base there is an unconformity. 

The Tokio formation as thus defined has a basal 

gravel like the Woodbine, and each formation has an 

unconformity at its base. The formation in Arkansas 

rests upon lower and lower roel\:s toward the eastfirst upon the truncated edge of the vVoodbine formation, then upon successive parts of the Trinity formation, and next upon the steeply dipping rocks of 

Paleozoic age. (See structure section on pI. 20.) 

The Tokio formation is exposed. in a belt extending 

west by south across several counties 'in southwestern 
180 SHORTE'R CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

Arkansas and thence into McCurtain County, Okla., 

at whose southern border the' belt of exposure is 

terminated by alluvium and terrace deposits of' 

Quaternary age along Red River. The belt of exposure 

is not continuous but is broken by bands of alluvium 

and terrace gravel along Little Missouri, Saline, 

Cossatot, and Little Rivers and other streams that 

cross it. The belt ranges in width from a few miles 

to about 12 miles and narrows eastward in consequence 

of the, apparent thinning of the formation in this 

direction. The thickness is about 300 feet in the area 

west of Nashville, Ark., and is less east of Nashville. 

The formation contains water-laid igneous materials 

near Murfreesboro, Pike County, Ark. These include 

thin beds that appear to be peridotite tuff and also 

include beds of kaolin that is apparen~ly altered voleanic dust. These volcanic materials are described on 

pages 186 and 187. The formation is, however, composed largely of light to dark gray clay and gray sand 

that weathers yellowish and reddish. In addition there 

is much gravel in Arkansas, the thickest bed of 

which is at the base. The gravel is composed of 

well-rounded pebbles consisting of quartz and novaculite of many colors and ranging in size from that 

of a pea to a diameter of about 6 inches. The dark 

clay contains many invertebrate fossils, and some of 

it contains identifiable fossil plants. The proportions of clay and sand change both vertically, and 

horizon tally in the formation. 

CHARACTER OF VOLCANIC ROCKS 

GENERAL FEATURES 

Most of the tuff occurs in the Woodbine formation. 

The main bed of volcanic material overlies the basal 

gravel of the formation and attains a thickness of 125 

feet or more in the area lying between Center Point 

and Nashville, Ark. It consists of mineral grains, 

rock fragments, and pebbles in a claylike matrix. 

The best exposures of volcanic material in Arkansas 

are on and near Mine Creek, Blue Bayou, and other 

streams near Center Point and Nashville. (See fig. 

'17.) Near Blue Bayou Church, 4 miles south of 

Center Point, the principal mineral in the sand bars 

of Blue Bayou is orthoclase in glistening transparent 

grains that have been derived from near-by exposures 

of tuff. The best exposures in Oklahoma are ~ear 

Odell and Garvin; there the tuff is characterized by 

the occurrence of "black sand" and limonitic "buckshot" in the gullies. In Arkansas and Texas these 

minerals are not abundant enough to be conspicuous 

in gullies. 

In northeastern Texas water-laid tuffaceous material, the westward extension of the tuffaceous beds of 

the Woodbine of Arkansas, forms a considerable part 

of the sand of the Woodbine formation, especially in 

the upper beds. 

Coarse tuffaceous sand containing notable amounts 

of volcanic materials has been ~examined at six 

localities (pI. 20), which are alined in an approximate 

east-west direction in the northern parts of Red River 

and Lamar Counties, as follows: At Silver City Ferry, 

17 miles north of Clarksville, at a locality 2 miles east 

of Kanawha, and at Pine Bluff Ferry, 472 miles north 

of Woodland, in Red River County; at Golden Bluff, 

3 miles east of Arthur City, at the bluff near Arthur 

City, and at Garretts Bluff, 13 miles west of Arthur 

City, in Lamar County. Similar coarse tuffaceous 

sand in approximately the same stratigraphic position 

has been observed at Hyatts Bluff, 5 miles northwest 

of Ravenna, Fannin County. The locality east of 

Kanawha in Red River County has yielded large 

typical specimens of Ostrea soleniscus Meek, a characteristic Woodbine species. Smaller, less typical 

specimens, probably belonging to the same species, 

occur at Golden Bluff, in Lamar County, at a horizon 

30 feet above the top of the main bed of tuffaceous 

sand. (See pIs. 25-27.) 

Volcanic material makes up a small percentage of a 

sandstone of questionable Eagle Ford age in the vicinity of Woodland, in the northwestern part of Red 

River County, and a similar slightly tuffaceous sandstone occurs at MediII, in the northeastern part of 

Lamar County. These localities are between 4 and 5 

miles south of the main east-west belt of tuffaceous 

sandstone,and on the assumption that the regional dip 

of the beds toward the south is not less than 50 feet to 

the mile, this upper tuffaceous bed should be 200 feet 

or more stratigraphically above the main tuffaceous 

bed. Other beds of tuffaceous material may occur between the main bed and the uppermost bed, but this 

has not yet been demonstrated. At Woodland and 

Medill the tuffaceous sandstone is immediately overlain by the Bonham clay, which belongs stratigraphically above the Eagle Ford clay. 

A sandstone containing a small percentage of tuffaceous material was observed in a bluff on Red River, ] Y2 

miles north of Ragtown, in the northwestern part of 

Lamar County. This sandstone lies near the top of 

the Woodbine formation about 12 feet stratigraphically 

below the base of the Eagle Ford clay, which is well 

developed in this area. 

The tuffs and tuffaceous sands of southwestern 

Arkansas, southeastern Oklahoma, and northeastern 

Texas were for the most part deposited in shallow 

water and under the influence of strong currents. 

They are mixed in various proportions with detrital 

material derived from the Paleozoic rocks on the north, 

and parts of the tuffs themselves were reworked and 

redeposited. All this has resulted in a very intimate 

mixing of the various types of volcanic and detrital 

materials and an obscuring of the volcanic history. 

The geologic study is still further complicated by an 

intense alteration of the glassy tuffs, which has left 
WATER":'LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 181 

'them in the forn1 of clay beds. Nevertheless some 

layers in the tuffs, especially in the vicinity of N ashville, Ark., are composed of volcanic debris that shows 

little mixing of the volcanic rocks, and this has made 

possible a recognition of the principal rock types and 

rock textures that have contributed to the formation 

-of the volcanic beds of the region. 

The volcanic material that occurs in greatest volume 

.and with the widest distribution IS ill the form of 

are probably a finely crystalline phase derived from 

the same magma that formed the glassy tuff. Accompanying these materials are crystal grains, which 

represent the phenocrysts that were ejected along with 

the tuff. 

LI~HIC PHONOLITE TUFF AND SAND 

The most widely distributed volcanic material occurs 

1n the form of small rounded rock pellets that average 

19ze 

FIOURE 17.-Map of part of Howard County, Ark., showing the surface distribution of the volcanic deposits of the Woodbine formation 

rounded lithic rock grains that average between 0.5 

and 1 millimeter in diameter. Interbedded with the 

tuff are beds of gravel and boulders, which are composed predominantly of quartz and novaculite but 

which locally contain well-rounded boulders of the 

same volcanic rock types as the material in the lithic 

tuff. 

Near N ash,ville are extensive beds of material that 

was originally glassy pumiceous tuff. Associated with 

this are angular lithic tuff and rock fragments that 

0.5 to 1 millimeter in diameter. The color of the 

unweathered rock is dark olive-green to dark graygreen. On weathering the material assumes various 

shades of yellow and brownish red. Beds made up 

almost wholly of fragments of volcanic rock have been 

recognized in a few localities, and this material may 

be called lithic tuff, but more commonly the fragments 

of volcanic rock are mixed with some grains of quartz 

and novaculite, and this material is more correctly 

described as tuffaceous sand. (See pI. 22, 0, D.) 
182 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

The volcanic rock structure is clearly recognizable in 

all thin sections, even in .the rocks that have completely lost their original minerals through kaolinization. The rounded rock pellets are characterized by 

a single volcanic rock type, and the only difference is 

a slight one in texture and mineral proportions. (See 

pI. 21, B.) They all show a trachytic structure, and 

many have a parallel arrangement of the slender plagioclase crystals of the ground mass. The rock of the 

pellets is all of very fine grain, and the crystals of the 

groundmass range from 0.02 to 0.3 millimeter in greatest length. Anhedral orthoclase is abundant; and nephelite is often recognizable despite the fineness of grain. 

The rock grains rarely carry phenocrysts, as these were 

not abundant and were usually set free by the explosive violence that pulverized the rock. 

The mineral grains associated with the lithic phonolite tuff and sand are orthoclase, plagioclase, augite, 

hornblende, zircon, apatite, and magnetite. Titani te, biotj te, and black spinel are found in some beds, 

but it seems probable that these mine~als were derived 

from the admixed pumice tuff and not from the phonolite. Brown tourmaline, garnet, and staurolite, which 

are characteristic of metamorphic rocks, are present in 

small amounts and are associated with the typical 

minerals of igneous rocks in the tuff. Secondary minerals that have developed in the beds after their 

deposition are siderite, calcite, pyrite, glauconite and 

phosphatic granules. 

PHONOLITE COBBLES 

Well-rounded cobbles and pebbles are found locally 

in the beds and lenses of gravel associated with the 

tuff and are especially abundant on Mine Creek, near 

Nashville, Ark. (See fig. 17.) Few pebbles in the 

tuff are more than 2 or 3 inches in diameter; but the 

cobbles in the gravel reach 9 or 10 inches in diameter. 

The rock type that makes up 75 per cent or more ,of 

the cobbles is the same as that forming the phonolite 

pellets and is represented by the analysis on page 187. 

The rock structure is shown in Plate 21, B. The rock 

is dark gray with a very fine grained groundmass and 

phenocrysts of sodic plagioclase and orthoclase forming 

less than 5 per cent of the mass. Augite is still rarer 

and is seldom seen in a hand specimen. The microscope shows a rock with trachytic structure and groundmass crystals which range from 0.02 to 0.3 millimeter 

in length and many of which have a common orientation. The range in mineral composition of the phonolite is as follows: 

Mineral composition of phonolite 

Per cent 

Plagioclase______ - - __ - - - - - __ - - - - - - - - - 50-65' 

Orthoclase _________________________ _ 30-40 

Nephelite__________________________ _ 5-15 

Pyroxene or hornblende______________ _ 2-15 

Magnetite_______________ - ____ ----- -- 3 

Apatite _________ - - __ :- - - - - - - --- - - - - -- 0.5 

The orthoclase forms anhedral crystals between 

the euhedral plagioclase crystals .. The nephelite is 

in part anhedral and in part euhedral and forms very 

small interstitial crystals. Augite occurs as phenocrysts and in the groundmass, but forms less than 3 

per cent of the rock in the predominant type of phonolite. In a few specimens· it is more abundant and may 

reach 15 per cent. Green or brown hornblende is a 

rare constituent. One specimen examined was similar to the predominant type of rock but contained a, 

small proportion of sodalite. (See pI. 21, A.) 

N early all the phonolite from the gravel and most 

of the rock pellets in the tuff are very fine grained and 

commonly show flow structure or orientation of the 

feldspar grains and so have a structure characteristic 

of volcanic rocks, but a rare rock type that occurs 

in the boulders has the texture of an intrusive. This 

is a fourchite With abundant augite and nephelite. 

PUMICE TUFF 

In the vicinity of Nashville, Ark., are extensive 

beds composed partly or almost wholly of materials' 

that originally formed a tuffaceous volcanic pumice. 

This pumice has completely lost its glassy texture 

and is most commonly represented by bentonitic c1aylike material, but locally concretionary calcium carbonate has cemented the pumice fragments into 

boulderlike forms that have escaped this type of 

alteration. . 

The predominant color in the claylike rnaterial is. 

gray to light blue-gray where unweathered; after 

oxidation it is yellow. The boulders with calcite 

cement are pale buff. The punlice fraglnent.s differ 

widely in size, ranging from 0.1 to 50 millimeters in 

diameter. The pumice has .a fibrous structure that 

resulted from the presence of very fine, closely spaced 

elongated or flattened vesicles separated by very thin 

glass walls. In the claylike beds consolidation has 

slightly compressed and flattened the altered pumice 

fragments and eliminated the vesicles, but the fiberlike pumiceous texture has been periectly retained. 

(See pI. 22, B.) In hand specimens the clay has little 

resemblance to tuff, but thin sections exhibit the tuff 

structure as perfectly as the original glass. 

The pumice beds contain mineral grains representing phenocrysts that were set free fronl their glassy 

matrix by the explosive force of the eruptions I that 

produced the pumice itself. Most of these crystals 

are euhedral or have one end perfect and the other 

fractured, but in some beds the crystals are strongly 

etched, though none of them are well rounded by 

transportation and abrasion. . 

The minerals are orthoclase, biotite, titanite, magnetite, zircon. apatite, and black spinel. Augite and 

hornblende possibly occur in very small amount but 

are probably derived from the phonolite and not from 

the trachyte. Orthoclase is very abundant and may 
WATER-LA.ID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 183 

form as much as 25 per cent of the rock, but the other 

minerals are rare and form less than 1 per cent. The 

metamorphic rock minerals tourmaline, garnet, and 

staurolite occur in small proportions in tuff of all 

types. Phosphatic grains and glauconite were probably formed during deposition, and siderite, calcite, 

and pyrite have developed after deposition. 

LITHIC TRACHYTE ROCK FRAGMENTS 

Crystalline rock fragnlents are associated with the 

pumice tuff and in sonle localities fornl as much as 

50 per cen t of the nlaterial. The puniice and the 

trachyte always occur together and carry the same 

Inineruls, and it seeIns evident that one is the glassy 

and the other the crystalline phase of the same igneous 

magnu},. They show little sorting, large and small 

rock fragnlents occurring together. In this they 

differ frOll1 the phonolite rock fragments, which are 

well rounded and usually well sorted. The pumice 

and orthoclase trachyte show much less miAmg with 

foreign Inaterial than the phonolite, and some beds 

are conlposed of pure igneous nlaterial. 

The orthoclase trachyte rock fragments range from 

1 to 20 Inillilneters in dianleter and are angular or 

knotted. They are white or light gray and are composed of phenocrysts of orthoclase in a groundmass 

that is a very fine grained aggregate of anhedral 

feldspar. Euhedral orthoclase phenocrysts are abundant in sonle fragments and nearly absent in others. 

Biotite, titanite, and black spinel in fine euhedral 

crystals are very sparsely present. 

DETAILED DESCRIPTION OF MINERALS 

IGNEOUS ROCK MINERALS 

Orthoclase.-The pumice and lithic tuff of trachytic 

composition contain abundant orthoclase, and the 

lithic phonolite tuff and sand contain small proportions. The orthoclase crystals range from 0.3 to 3 

milliIneters in dianleter but average about 1.5 lnillimeters. Most of the crystals have been fractured, 

probably by the explosive eruptions, but nlOst of 

thenl show one or more perfect crystal faces, and 

Carlsbad, Manebach, and Beveno twins are not rare. 

SOlne crystals have been etched, as described on 

page 185 and pictured in Plate 21, 0, D, and there is 

practically no rounding of the fragments of tuff near 

N ashville, Ark., 'but iIl other areas there is slight 

rOlmding of some of .the crystals. N early all the crystals show great clearness, but a few have inclusions of 

glass. The optical axial angle is small in most crystals 

and nearly uniaxial in many, and ..these characters 

indicate that the nlineral is the sanidine variety of 

orthoclase. 

Augite.-In the phonolite tuff augite is the second 

11lOSt abundant Inineral, but in the pumice and trachyte 

tuff it is rare or absent. Most of the crystals are pale 

bottle-green in millimeter-sized grains and colorless in 

thin section, but a few are faintly lavender in thin 

section. Nearly all have the peculiar cocksconlb termination shown in Plate 24, A. The origin of these 

forms is discussed on page 184. 

Biotite.-Dark-brown euhedral flakes of biotite are 

present in the pumice and trachyte tuff but fornl less 

than 1 per cent of the rock. 

Hornblende.-Many separations of heavy nunerals 

have been made by means of heavy solu.tions, and 

slender hornblende crystals are always present, but 

they form only a fraction of 1 per cent of the tuff. 

They are brilliant black in millimeter-sized grains 

and usually olive-green in thin section,'but a few have 

the reddish-brown. color of basaltic hornblende. The 

crystals reach 3 or 4 millimeters in length and most of 

them are euhedral, but some of those separated from 

the tuffaceous sand of Oklahoma and Texas are slightly 

rounded by abrasion, although none of them show 

etching. 

Titanite.-All the igneous rocks of the region contain 

titanite, but it is especially abundant in the pumice and 

trachyte tuff. It forms brilliant golden-yellow crystals 

that average less than 1 millimeter in diameter. Most 

of them are perfectly euhedral and show almost no 

fracturing or rounding by attrition, but a few are 

slightly etched. 

Magnetite and spinel.-Magnetite is present in all 

the tuffs, and black spinel is most abundant in the 

pumice and trachyte tuff. Both have very sharp 

euhedral faces, but the crystals are usually pitted or 

incompletely developed. The magnetite can be separated from the spinel with a hand magnet, and then 

it is noticed that the spinel has much more brilliant 

black faces than the nlagnetite. The spinel is opaque 

except in exceedingly fine grains. 

Apatite and zircon.-Apatite and zircon ate present 

in all the heavy minerals that have been separated. 

The apatite is usually colorless, but a few grains are 

a fine blue. The zircon is colorless to deep lavenderpink. 

SECONDARY MINERALS 

S:iderite.-Small grains of siderite have been formed 

in most of the tuff beds, probably before the calcite, 

for small crystals of siderite are completely inclosed 

in calcite. Siderite is found in the calcite concretions 

in the phonolite, in uncemented phonolite tuff and 

tuffaceous sand, and in the bentonitic material derived 

from the pumice. It most generally forms small euhedral rhombs, but also some knotlike pellets and a few 

well-rounded radially fiorous grains similar to grains 

of sphaerosiderite. A few boulder-like masses several 

inches in diameter are composed almost entirely of 

siderite. The color is yellow to reddish brown, and 

the index of refraction indicates that much of the 

material is nearly pure iron carbonate. 
184 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

The siderite grains weather out of the tuff and b~­

come oxidized to limonite. These grains become concentrated by flowing water and form accumulations 

of shotlike grains in the steam beds throughout the 

region. 

Oalcite.-The tuff and tuffaceous sand of Arkansas 

contain concretions cemented with calcite that re,sch 

a maximm;n diameter of several feet. In the Texas 

and Oklahoma areas some beds are completely cemented with calcite, and the same relation is shown 

in the Louisiana localities that contain tuff identical 

in character with that of Arkansas, Oklahoma, and 

Texas. T~e calcite commonly forms large crystals, 

some of them 4 to 5 centimeters in diameter, that 

inclose large numbers of mineral and rock grains. 

Pyrite.-8mall rounded crystalline aggregates and 

octahedrons of pyrite have been formed abundantly 

in some of the tuff beds subsequent to their deposition. 

Phosphatic grains.-Small rounded grains of phosphatic material were probahly formed together with 

the marine type of glauconite on the sea bottom 

during the deposition of the beds. 

GZauconite.-The tuff jn some localities, especially 

that from the Prothro salt dome, Bienville Parish, La., 

contains rounded glauconite grains. These are bluish 

green, are composed of the usual aggregate of overlapping crystal plates, and were probably formed on 

the sea bottom. Most of the tuff beds of the phonolite type contain some proportion of a yellowish-green 

mineral, with a habit entirely dissimilar to that of the 

normal glauconite. This mineral has developed in the 

tuff since its deposition, as it has replaced augite and 

phonolite grains with various degrees of completeness 

and has slightly replaced calcite. It forms narrow 

zones around all mineral and rock grains in many beds 

of the phonolite tuff and is the cause of the green color 

in most of these beds. It forms radial zones of a 

micaceous mineral with a high birefringence and a 

mean index of refraction of about 1.62. Qualitative 

chemical tests show the presence of essential potash 

and indicate that the material is glauconite or possibly 

celadonite. 

MINERALS CHARACTERISTIC OF METAMORPHIC ROCKS 

N early all crops of heavy minerals separated from 

the tuff contain very small proportions of minerals 

that are characteristic of metamorphid rocks. [The 

most generally distributed of these is brown tourmaline, but pale-pink garnet and staurolite are occasionally seen. Some fragments of these minerals are 

rounded, but many are sharply angular, and much of 

the tourmaline is enhedrai. There is no direct evidence as to the source of these minerals, but it is 

possible that deeply buried metamorphic rocks were 

shattered and small quantities of their mineral components carried to the surface together with the normal. 

volcanic material by the violence of the volcanic 

eruptions. This supposition is supported by the 

presence at the diamond mines near M urfrees boro, 

Pike County, Ark., of rather large blocks of Paleozoic 

sandstone that are believed to have been blasted from 

their position and carried to the surface, and fragments 

of norite that must have been derived from some deepseated source have also been recognized in rock from 

the same locality. (See pI. 19.) 

REPLACEMENT OF MINERALS SUBSEQUENT TO. SEDIMENTARy DEPOSITION. 

The augite grains from all the tuff beds show multiple 

terminating pyramids that produce the cockscomblike habit shown in Plate 24, A. Calcite-cemented 

concretions have been formed in the tuff bedsof Arkansas subsequent to their deposition, and in parts of 

Texas and at the Prothro salt dome, La., the beds are 

completely cemented by calcite. Thin sections of tuff 

from the Owen place, Ark. (fig. 17), and the Prothro 

dome give a clue to the mode of formation of the 

augite crystals with the cockscomb habit. In many 

localities of the region a fihn of glauconitic material 

was deposited around each grain of rock or mineral 

soon after its deposition. Thus the original form of 

the augite crystals was preserved. Later the augite 

was partly replaced by calcite or etched by solutions 

that permeated the beds. In their present form the 

augite grains show each a dark zone of glauconitic 

material that marks the original boundary of the 

crystal; within that is a zone of calcite that represents 

replaced augite; and the core is perfectly fresh augite 

. with cockscomb habit.o (See pI. 23, 0.) Not uncommonly the replacement has progressed so far that two 

or more completely isolated augite areas that are in 

uniform optical orientation have developed from a 

single original grain, as shown in Plate 23, B. The 

multiple terminations were not present on the original 

augite grains and have developed entirely as a result 

of secondary processes. Most of the tuff beds in the 

Arkansas area do not have an interstitial cement of 

calcite, but'in these the augite grains also show the 

cockscomb habit. It is evident that carbonate-bearing 

waters were present in all the beds of the Woodbine 

formation, and it seems probable that these were 

capable of corroding and etching augite. In ·many of 

the Texas and Oklahoma localities the replaceluent of 

augite is complete, and the characteristic form of the 

replaced crystal is all that remains to indicate that 

augite was once present. The pyroxene has been 

altered to glauconite after partial repla.cement by 

calcite, and interstitial glauconite and films of glauconite· around mineral grains are characteristic of several 

localities. One of these grains is pictured in Plate 

24, D. All these changes took place only after the 

deposition of the material, and they present abundant 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 185 

evidence that glauconite is not necessarily formed on 

the sea bottom but can result from the replacement of 

preexisting minerals. 

Augite crystals with the cockscomb habit have 

been observed in material from northern New Mexico 

and Montana and are illustrated in Plate 24, B, O. 

Those from Montana were slightly rounded before 

the secondary crystal faces were developed. 

110st of the orthoclase crystals show euhedral faces, 

but a few have been embayed and replaced by calcite, 

as shown in Plate 21, 0, D. 

All the other minerals of igneous rocks are unaltered 

and unreplaced by calcite. Hornblende is unetched, 

and the original crystal faces are often brilliant and 

perfect. Thus it is ev:dent that augite was not stable 

under the conditions that controlled the deposition of 

these sediInentary beds and was subject to solution or 

replacement, whereas under the same conditions hornblende was stable. 

ALTERATION AND WEATHERING OF TUFFS 

The volcanic tuffs throughout the region are composed largely of materials that were not stable under 

the physical conditions that promoted solution and 

hydration (in the zone of katamorphism) and so have 

undergone very extensive alteration. Some of these 

changes were pr<?duced by ordinary weathering, but 

others are more profound. . 

Fresh phonolite tuff and tuffaceous sand are greenish 

gra.y or dull olive-green. They are very porous, and 

their easy perIneability has resulted in rather deep 

weathering in much of the region. Where weathering 

is complete they have assunled a red or reddish-brown 

color, but the less deeply weathered material is rusty 

brown. 

The crystalline materials have resisted alteration 

much lllore than those with glassy texture, and so 

many of the individual phonolite grains are little 

affected by even the nlore intense alteration processes. 

In some beds, however, the feldspar of some of the 

rock fragments has been kaolinized and the original 

minerals have been more or less replaced by secondary 

ones. 

As the phonolite cobbles are all very well rounded 

they must have been transported and eroded prior to 

deposition in their present situation. Many of them 

have been weathered and show an outer kaolinized 

zone an inch or more in thickness. Fresh and weathered pebbles are found side by side, in places below 

the pernlanent water level of the creek beds. This 

indicates that the kaolinization of the pebbles took 

place before deposition. As the glassy tuff was altered 

to bentonite after deposition, kaolinization and the 

fOrInation of bentonite are two processes that took 

place at different times and probably under different 

conditions. 

BENTONITE 

Throughout most of the Arkansas area the glassy 

pumiceous tuff of the Woodbine formation has been 

altered to a bentonite that contains a large proportion of igneous-rock phenocrysts and detrital rock 

fragments, but locally calcite concretions have formed 

in the pumice tuff soon after deposition and prevented 

the formation of bentonite. 

Bentonite is a rock composed predominantly of 

clay and formed by the alteration and devitrification 

of glassy 'volcanic material, usually a tuff. It generally contains differing porportions of igneous-rock 

phenocrysts and admixed detrital debris. Most 

bentonites contain montmorillonite as their characteristic clay nlineral, but the bentonite of southwestern Arkansas is composed of, beidelliteY This 

mineral has been found in one other sample of bentonite 14 and in gouge clays from mineral veins/5 

and it is an abundant soil and clay forming mineral, 

which has the chemical formula (AlzOa, Fe20a). 

3Si02.nH20, where n is about 4. The mineral is 

plastic and has a micaceous habit and high birefringence. An analysis of Arkansas bentonite has 

been made by Earl V. Shannon, of the United States 

National Museum, who, together with C. S. Ross, 

has been engaged.in a study of bentonite. The igneous 

rock from which the Arkansas bentonite has been 

derived has been analyzed by George Steiger, of the 

Geological Survey. 

The conditions that promote the change of volcanic glass to bentonite have not been well known, 

but mineral relations in the Arkansas area pernlit 

some deductions as to the physical environment 

that favored the change. The development of bentonite was not due to surface weathering but to 

causes that affected all glassy materials at all observable depths, and in the same beds feldspar, all ferromagnesian minerals, and fragments of lithic tuff 

are commonly unaltered. The lime concretions that 

were formed in the tuff beds have preserved very 

delicate pumice fragments with uncollapsed bubble 

wans, as shown in Plate 22, A, B, and evidently the 

infiltrating calcium carbonate was introduced before 

the formation of the bentonite. The calcium was no 

doubt transported as bicarbonate, and it is quite 

probable that the water was bicarbonate bearing 

throughout the period of alteration. The ash fell 

in a marine embayment, and the entrapped wat.er 

may have remained saline during alteration, but it 

13 Larsen, E. S., and Wherry, E. T., Leverrierite from Colorado: Washington 

Acad. Sci. Jour., vol. 7, pp. 208-217, 1917; Beidellite, a new mineral name: Idem, 

vol. 15, pp. 465-466, 1925. Ross, C. S., and Shannon, E. V., The chemical composition and optical properties of beidellite: Washington Acad. Sci. Jour., vol. 15, 

pp. 467-468, 1925; The minerals of bentonite and related clays and their physical 

properties: Am. Ceramic Soc. Jour., vol. 9, pp. 77-96, 1926. 

14 Ross, C. S., and Shannon, E. V., Am. Ceramic Soc. Jour., vol. 9, pp. 77-96, 1926. 

13 Larsen, E. S., and Wherry, E. T., Leverrierite from Colorado: Washington 

Acad. Sci. Jour., vol. 7, pp. 208-217, 1917. 
186 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

is impossible to determine the degree of dilution with 

fresh water. The ash fell in water, and calcite concretions were present when the alteration took 

pla,ce, and therefore volcanic gases and acids stronger 

than the dissolved carbon dioxide were not present and 

could have had no part in the alteration. It. seems 

equally certain that organic or so-called humic acids 

were absent, for no extensive plant relnains are associated with the beds, and a very great thickness of material has been affected by the processes of alteration. 

The known factors of the alteration were the absence 

of oxidizing conditions, the presence of water for 

hydration, the removal of excess chemical constituents, 

and the probable presence of bicarbonates, sodium 

chloride, and possibly of magnesium salts from the sea 

water. Calciul11 carbonate and iron carbonate leave 

a record of their transportation probably as bicarbonates, but soluble alkaline bicarbonates would leave no 

such record and so mayor may not have been present. 

The absence of sulphate minerals like gypsum indicates 

that sulphates were absent or practically absent from 

the solutions. No other factors suggest themselves 

that are likely to have contributed to the formation of 

bentonite. Thus it seems iInprobable that the alteration of volcanic glass to bentonitic clay was brought 

about by unusual chemical conditions. On the other 

hand, it seems to have been the result of hydration and 

solution of an unstable glass that was perhaps nlore or 

less aided by the presence of chlorides and bicarbonates, 

the latter probably in very weak concentration. 

Analyses of the trachyte that is believed to have 

approximately the same composition as the pumice, 

of the bentonite from Mine Creek, and of other related 

clay lninerals are given in the following table: 

Analyses of trachyte, bentonitic clay from Mine Creek, Howard 

County, Ark., and related clays 

Si0 _________________ _ 2 62. 97 45. 1'2 47. 28 48. 80

Ab0 3-- - - - - - - - - - - - - - - -­ 19. 00 28.24 20.27 21.08 Fe20 3 _________________ 


FeO_________________ _ 

} 

1. 13 


MgO______ -"' __________ _ {--:~~:- ---~~~~- -----~~: .26 2. 32 . 70 4. 84 ·CaO _________________ _ .54 . 88 2. 75 1. 36 N a 0 ________________ _ 2. 86 K 0 . 97} (a) 2 _________________ _ _ _ _ _ _ _ _ _ Trace 

H 20 - -- - - - - - - - - - - - - - -- .72 2 10. 80 

18. 72 19.72 20. 92 

H20+---- ---- ______ .- -- 1. 26 Ti02 _____ ~ ___________ _ .26 

P20s------------------ .10 

99. 90 99. 40 100. 37 97. 92 

a About 2 per ;ent alkalies. 

1. Trachyte, Coleman Creek, Howard County, Ark. GeorgG 

Steiger, analyst. 

2. Bentonitic mineral concentrated from bentonite derived 

from trachytic pumice, Mine Creek, Howard County, Ark. 

Earl V. Shannon, analyst. 

3. Clay mineral from Beidell, Colo. Edgar T. Wherry, 

ana~yst. Larsen, E. S., and Wherry, E. T., Washington Acad. 

Sci. Jour., vol. 7, p. ·213, 1917. 

4. Bentonitic mineral concentrated from bentonite, Ardmore, 

Nebr. Earl V. Shannon, analyst. 

The analyses given above show the chemical relations of the bentonitic mineral to the rock from which 

it was derived. Analysis 1 represents the porphyritic 

trachyte with a very fine crystalline groundmass, but 

the relation of pumice to trachyte and the identity of 

the associated phenocrysts indicate that one was the 

glassy and the other the crystalline phase derived from 

the same magma. The norm of the trachyte given on 

page 187 shows that it was a highly alkalic rock with 

less than 4 per cent of quartz and indicates that the 

Arkansas bentonite was derived from a rock low in 

quartz and high in alkalies. No analyses have previously been available of material that was known to 

have altered to bentonite, but the presence of the 

igneous rock minerals has led to the belief that bentonite was .derived from glassy rocks high in alkalies 

and less silicic than normal rhyolites. 16 

Analyses 1 and 2 sho~ the chemical changes involved 

in the alteration ofglass to bentonite. It"is probable 

that there has been little addition or abstractiol1 of 

Al20 a during the alteration of the glass, but the alkalies 

have been almost completely abstracted. This indicates that it has taken about 1Y2 parts of the trachyte 

pumice to produce each part of the resulting bentonite, 

which would require the removal of about half the 

original silica to give a final product with 47.23 per 

cent of silica. There appears to have been a moderate 

addition of iron, and a rather large' addition of magnesium was probably derived from the sea water that 

was present during alteration. The other great 

change was the addition of water and the production 

of hydrated minerals. 

KAOLINIZED VOLCANIC MATERIAL 

One or more beds of kaolinized volcanic material 

having a thickness of 5 feet occur in the Tokio formation between Murfreesboro and Delight, Ark. (See 

p1. 20.) The material is chalky white to creamy, but 

the lowest layer of one bed has a lavender color. It is 

nonplastic, is very fine grained, and breaks with a 

conchoidal fracture. .The volcanic material is known 

locally as kaolin and has been so designated by all 

geo19gists 17 who have heretofore written on the region. 

A description of the kaolin deposits and a discussion of 

their economic value are given on pages 201 and 202. 

The altered volcanic material is very pure clay, and 

microscopic studies indicate that it is composed of 

pellet-like fragments, the largest of which are less than 

1 millimeter in diameter. The internal structure of 

the pellets resembles that of altered feldspar, but the 

same structure seems to be characteristic of some 

clay minerals. The structure therefore does not give 

clear evidence of the origin of the kaolin. Kaolin is a 

16 Ross, C. S., and Shannon, E. V., The minerals of bentonite and related clays 

and their physical properties: Am. Ceramic Soc. Jour., vol. 9, p. 84, 1926. 

17 Branner, J. C., The clays of Arkansas: U. S. Geol. Survey Bull. 351, pp. 147-153, 

1908. Miser, R. D., and Purdue, A. R., Gravel deposits of the Caddo Gap and De 

Queen quadrangles, Ark.: U. S. Geol. Survey Bull. 690, p. 24, 1918. 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 23 

PHOTOMICROGRAPHS OF VOLCANIC ROCKS 

A, Thin section of bentonitic volcanic tuff from Coleman Creck near ashville. Ark. The large fra~ment was orilrinally glassy pumice of ortho­ clase trachyte composition but. is now compleLeiy altered to the clay mineral heidellite. Groundmass is finc-grained material of the same type. Enlarged 62 diameters B, Phonolile sand from Owen place, belween Cenlcr Poinl and Corinth, Howa rd CounlY. Ark. The cenlral grain is augite parCly replaced by calcite. R eplacement has left. two residual areus of augite that ex lin ui h simultalleously under crossed nieols aod have saw-tooth secondary terminal faces on the lower border. The upper left grain is phonolite and the others quarlz and orthoclase. Groundmass is calcite. Enlarged 100 diameters C. Augite grains from Owen place partly rcpaced by calcite with the development of saw-tooth faces. Original outline of crystal fragment marked by zone of glauconite lhal appears black. Enlarged 100 diamelers 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 24 

PHOTOMICROGRAPHS OF VOLCANIC ROCKS 

A, Augite grains from phonolite tuff, Owen place, near Nashville, Ark. Secondary saw-tooth crystal faces have developed through corrosion and replacement by calcite. E nlarged 34 diameters B, Etched augite grains from San Antonio Creek , Rio Arriba County, N. Mex. Enlarged 34 diameters C, Etched augite gra ins from the Lebo shale member of the Fort Union f ormation, Montana. Enlarged 54 diameters 

D, Augite grains partly replaced by glauconite and calcite, I)rothro dome, Bienville Parish, La. Grains at left are phonolite. Gronndmass is calcite. Enlarged 

100 diameters 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE 25 

A. TUFFACEOUS SANDSTONE OF THE WOODIIlNE FORMATION AT SILVER CITY FERRY, 


RED RIVER, RED RlYER COUNTY, TEX. 


• 

B. 	IRREGULARLY BEDDED SAND AND CLAY OF THE WOODBINE SAND IN ROAD CUT 

LEADING DOWN TO THE LOWER FERRY AT ARTHURS BLUFF, RED RIVER, LAMAR 

COUNTY, TEX. 

Most of the fossil leaves from this locality described by E. W. Berry were obtained in tbe lower partoftbe 

section shown in the picture 
U. S. GEOLOGICAL SURVEY 	 PROFESSIONAL PAPER 154 PLATE 26 

A. 	LENS OF TUFFACEOUS SAND IN LAMINATED SANDY CLAY OF THE WOODBINE FORMATION, ABOVE THE LOWER FERRY AT ARTHURS BLUFF, RED RIVER, LAMAR COUNTY, 

TEX. 

B. TUFFACEOUS SANDSTONE OF THE WOODBINE FORMATION, BELOW THE LOWER FERRY 


AT ARTHURS BLUFF, RED RIVER, LAMAR COUNTY, TEX. 


• 

U. S . GEOLOGICAL SURVEY PROFESSIONAL PAPER 154 PLATE Z1 

A. TUFFACEOUS SANDSTONE OF THE WOODBINE FORMATION AT HYArrS BLUFF, RED 


RIVER, FANNIN COUNTY, TEX. 


B. TUFFACEOUS SAND OF THE WOODBINE FORMATION, PARTLY INDUHATED TO CONCHETIONAHY MASSES, NEAR THE UPPER END OF HYATTS BLUFF, RED RIVEH, 

FANNIN COU TY, TEX. 
------

------- ------- ------- ------- ------- ------- ------- ------- ------- ------- ------- ------- _______ 

-------

------- ------- ------- -------

-------- _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _____ _ 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

________ 

WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 187 

mineral that is normally derived from feldspathic nlaterial, and snlall proportions of augite, hornblende, 

zireon, and tourmaline that are characteristic of the 

volcanic rocks are present. It is therefore probable 

tha t the l(aolin in these beds was derived fronl feldspathic volcanic nlaterial that had been reworked and 

deposited. 

PERIDOTITE TUFF (?) 

The lower beds of the Toki'o formation on the Riley 

plaee and on the Twin Knobs, near Murfreesboro, 

Pike County, Ark., consist in large part of altered 

serpentine grains and peridotite fragments. Although 

the beds are water-laid, showing lamination and pronounced cross bedding, the igneous material may have 

been ejected into the air fronl the near-by vents and 

then falleri to or near its present position. There is, 

however, no evidence yet known that would preclude 

the derivation of the lnaterial from adjacent peridotite exposures by erosion. 

Peridotite tuff (?) is present in small areas around 

the IntXSses of peridotite, though it appears to be 

absent at two localities where exposures show the 

Tokio formation resting directly upon the peridotite. 

CHEMICAL RELATIONS OF VOLCANIC ROCKS OF 

ARKANSAS 

The following analyses show the chemical composition of the volcanic rocks and their relations to other 

igneous rocks of Arkansas: 

Analyses of volcanic rocks of Arkansas and related intrusive ro~k8 

1 2 3 4 5 6

SiO - _______ 58. 77 62. 97 60.13 60. 20 53.09 38. 78 AI 0

2 _______ 2 s 20. 60 19.00 20. 03 20. 40 21. 16 6.85

Fc2

0s __ - ___ 1. 74. 1. 89 8. 83 f 1. 40 2. 36 l;'eO________ } 1. 13 1. 36 l 1. 33 1. 88 2. 04 1. 99

1\1gO _______ .54 .26 .76 1. 04 .32 26.34

·CaO.. _______ .79 .54 .87 . 2. 00 3. 30 3. 88

Na O _______ 7. 16 2. 86 6. 30 6. 30 6. 86 .78 2 

K 5. 71 10. 80 5.97 6. 07 8. 42 2.56 20-- - - --'-­ H .89 .72 .16 10 .24 1. 95 20-· -----­ 2.19 1. 26 1.41 .23 1. 13 7.85 1:120+ - - ---­ Ti02 _______ .37 .26 1. 15 .14 .l1 .89

P20 5 - - - - _ -­ .03 .10 .06 .15 .15 SO _________ .04 .08

1\1110__ - ____ .24 Tra.ce. Trace. .20

BaO _______ Trace. SrO ________ .01

nc None. None. .82 .14 CO2- - - - - - -­ Zr(L _______ _ .05 Trace. .04

S03 ___ - - _ - ­ ~_~~~ r:o:: :: .14 .13 None.

BaO _______ I .61 -------1------­ CL ___ -- ___ .09 .02

100. 18 100. 72 100. 47 100.48 100. 84 I

9Q. 90 

1. Phonolite boulder, IVIine Creek, Howard County, Ark. 

George Steiger, analyst. 

2. Orthoqase trachyte, Coleman Creek, Howard County, 

Al'k. George Steiger, analyst. . 

3. Foyaite, Braddock's quarry, Fourche Mountain, Little 

Rock, Ark. H. S. Washington, a.nalyst. Washington, H. S., 

100874: 0 -:2D--13 

The foyaite-ijolite series of Magnet Cove [Ark.]: Jour. Geology, 

vol. 9, pp. 609, 611, 1901. 

4. Pulaskite, Fourche Mountain, Little Rock, Ark. H. S. 

\Vashington, analyst. Idem.. 

5. Foyaite, Diamond Joe quarry, Magnet Cove, Ark. H. S. 

Washington, analyst. Idem. 

6. Peridotite (probably hypabyssal) from Prairie Creek area, ~~_, 

Ark. R. N. Brackett, analyst. Williams, J. F., Igneous rocks ~_,J~ 

of Arkansas: Arkansas Geol. Survey Ann. Rept. for 1890, 

p. 	383, 1891. 

~ / 

N m'ms oj voZr:anic rocks of Arkansas and related intnlsiue rocks. / 

[The numbers correspond to those in the preceding table; analysis 6 represents an \ 

altered rock, and no norm has been calculated] 

Q------------­ Z___ _ _ _ _ _ _ _ _ _ _ _ O. 24 

C_____________ 1. 10 1. 80 1.53 ______________ _ 

01'_____________ 33.92 63.94 35.58 36.14 49.48 

ab_____________ 44.44 24.10 49.26 42.44 8.12 

an__ _ _ _ _ _ _ _ _ _ _ _ 3. 89 1. 95 4. 45 9. 17 2. 22 

ne__ _ _ _ _ _ _ _ _ _ _ _ cc_ 8. 80 L 99 5. 96 27. 12 

1. 80 

SaL___________ 92.49 95.39 I 92.81 93.71 88.74 

hy_____________ ~~i~ ~ = = = = = = = = = = = = === = = = = = = = = = 1. = 13= = = = = = = = = I= ______________________ = = = = = = = 5: ~~_ oL __ .:._________ 1. 80 ________ 1. 33 3.15 ______ _ 

mt. _ _ _ ________ 2. 09 _ _ _ _ _ _ _ _ . 93 2. 55 2. 78 

hln____________ ________ ________ 1.76 ---- ____ --- ___ _ 

il______________ .74 .46 2.13 .30 .15 

ap_____________ ________ .34 ________ .34 .34 

Fem__________ _ 4. 65 1. 93 6.15 6. 34 9. 53 

a Washington, H. S., U. S. Oeo!. Surrey Prof. Paper 99, pp. 271, 287, 305, 1917. 

1. 1.(4) 5.1".'4. 4. 1".5"."2.3(4). 

2. 1.5.1.2. 	 5. I(II).6".1.3. 

3. 1.5.1".3(4). 

The analyses just given and the norms calculated 

from them show that two distinct types of rock have 

contributed material to the Arkansas tuffs. The most 

striking quality that these rocks have in common is the 

high percentage of the alkalies and the low percentage 

of iron and magnesia that go to produce ferromagnesian 

nlinerals. The phonolite boulder from l\1ine Creek, 

Howard County, Ark. (analysis 1), contains 92.49 per 

cent of salic minerals, of which 78.46 per cent consists 

of alkalic feldspars. It is low in fernie minerals, low 

in anorthite, and very low in magnesium. It is therefore an alkalic phonolite rather rich in potassium, and, 

as would be expected in a rock of this type, the structure is trachytie.. In normative composition it is very 

similar to the foyaite from Braddock's quarry, Fourche 

Mountain, Little Rock, Ark., and to the pulaskite from 

Fourche l\10untain. . 

The rock from Coleman Creek, Howard County, Ark. 

(analysis 2), has a very unusual chemical composition. 

Only two rocks that fall in the groups.I.5.1.1 and 

1.5.1.2 of the quantitative system are listed by Washington. 1s One of these is orthoclasite, an orthocl&seis Washington, H. S., U. S. Oeo!. Survey Prof. Paper 99, p. 269, ]917. 
188 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY. 1928 

rich dike rock from Alaska, and the other a pegmatite. 

The rock from Coleman Creek is closely related to the 

rock from Fourche Mountain (analysis 3) but is very 

much higher in potassium. With nearly 64 per cent 

of orthoclase, 88 per cent of alkalic feldspar, and only 

1.93 per cent of femic minerals in the norm, it constitutes a new rock type for Arkansas and a type that 

has not heretofore been reported among volcanic rocks. 

It can be best described as an orthoclase trachyte. 

/ 	 The analysis of the massive hypabyssal peridotite 

is given to show the dissimilarity between the diamondbearing rock of Pike County, Ark., and the volcanic 

tuffs of the same area. 

AGE OF THE VOLCANIC ROCKS 

The Woodbine and Tokio formations, both of which 

contain water-law volcanic rocks, have yielded fossils 

from which the age of the formations may be determined. Fossil plants have been obtained from the 

Wood bine fornla tion on Mine Creek 3 nliles north of 

N ashville, Ark., and from the Tokio formation in the 

"Big" railroad cut, 2% miles east of Tokio, Ark., and 

in the Adanls kaolin pits, in sec. 24, T. 8 S., R. 25 

W., 5 nllies east-southeast of Murfreesboro, Ark. 

The plants at the Adams pits occur in a 5-foot bed of 

kaolin which is probably altered volcanic material; 

the plants on Mine Creek are in a lens of clay in a 

thick bed of tuff; and the plants at the railroad cut are 

in a dark gumbo clay that is overlain by sand and lightcolored clay. 

No fossil invertebrates have been found in the Woodbine fonnation in Arkansas, but the Tokio formation 

has yielded small collections from five or six localities, 

mostly of poorly preserved prints and molds. 

The fossil plants from the Woodbine and Tokio 

formations in Arkansas have been studied by Berry.19 

Also a fossil flora composed of 43 species from the 

Woodbine sand at Arthurs Bluff, on Red River in 

Lamar County, Tex., has been studied by Berry.zo 

The fossil plants there occur "in coarse sandstone containing a considerable percentage of tuffaceous material 

and in more or less sandy cross-bedded clay interbedded with and overlying the sandstone. Berry says: 

I can therefore only state the well-known fact that the Woodbine and Bingen formations are at least partly contemporaneous. 

I am of the opinion, which is based on the range of the Woodbine 

plants in other formations, that Arthurs Bluff is approximately 

on the boundary between the lower and upper members of the 

Bingen as recognized by Miser in Arkansas in the specific area 

where he collected the plants. 

Since the publication of Berry's papers on the fossil 

floras of the "Bingen fornlation" of Arkansas and the 

Woodbine sand at Arthurs Bluff in Texas much has 

been learned in regard to the age and stratigraphic 

10 Berry, E. W., Contributions to the Mesozoic flora of the Atlantic Coastal 

Plain, XII-Arkansas: Torrey Bot. Club Bull. 44, pp. 167-190, 1917. 

20 Berry, E. W., The flora of the Woodbine sand at Arthurs Bluff, Texas: U. S. 

Geol. Survey Prof. Paper 129, pp. 153-181, 1922. 

relations of these and other formations of the Gulf 

series in Arkansas and northeastern Texas. Miser and 

Purdue z1 in 1919 divided the "Bingen sand" of Veatch, 

in Howard and Pike Counties, Ark., into the lower or 

main part of the formation and an upper "Tokio sand 

member." The distribution of the "Tokio sand member" as represented on the map accolllpanying the 

paper cited shows that it overlaps the main part of 

the "Bingen" and finally conceals the "Bingen" 

completely from west to east. The unconformity 

beneath the gravel bed at the base of the Tokio formation of the present report has since been traced by 

Dane southwestward as far as Little River, where it is 

concealed by the river alluvium. From northeast to 

southwest the Tokio, according to Dane,2z becomes 

interstratified with beds of clay of increasing thickness, until in Sevier County the clay predominates over 

the sand. 

The lower part of the "Bingen sand" of Veatch 

contains the thickest beds of volcanic tuff already 

mentioned, and thin beds of volcanic material are 

present in the overlying Tokio formation. The beds 

of volcanic tuff of the lower part of the "Bingen sand" 

have been traced westward from Arkansas through 

McCurtain, Choctaw, and Bryan Counties, Okla., and 

through the northern parts of Red River, Lamar, and 

Fannin Counties, Tex., where they form a continuous 

and characteristic deposit connecting directly with the 

upper part of the Woodbine sand. The tuffaceous beds 

are interbedded with the fossil plant bearing beds 

a~ Arthurs Bluff. In Lamar and Fannin Counties the 

volcanic tuffs have been definitely identified beneath 

the Eagle Ford clay, showing that the lower part of 

the "Bingen" is in reality the eastward extension of 

the upper part of the Woodbine sand. 

The Tokio in Arkansas has been found by Dane 

to contain fossils at several stratigraphic positions, 

the lowest within 70 feet of the base, which according to 

Stephenson indicate with reasonable certainty that 

this division is younger than the Eagle Ford clay. 

Inasmuch as the lower part of the "Bingen "-that is, 

the Woodbine sand-passes beneath the Eagle Ford 

in Texas, and the upper part of the "Bingen "-that 

is, the Tokio formation-is younger than the Eagle 

Ford, it follows that the Eagle Ford is represented in 

Arkansas by the unconformity between the Woodbine 

and Tokio. 

MANNER OF DEPOSITION OF VOLCANIC MATERIALS 

The lithic tuffs of the Woodbine formation were 

water-laid, as is shown by the rounded pebbles of 

large and small sizes, the assortment of the larger 

pebbles into lenses at some places, the local occurrence 

of glauconite, and conspicuous cross-beddIng, which 

21 Miser, Hugh D., and Purdue, A. H., Gravel deposits of the Caddo Gap and 

De Queen quadrangles, Ark.: U. S. Geol. Survey Bull. 690, pp. 22-24, 1918. 

n Dane, C. H., U. S. Geol. Survey press notice, Sept. 10, 1926. 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 189 

is revealed in all exposures. Yet in spite of the waterlaid character of these tuffs the orthoclase, augite, 

titanite, and spinels found in them, especi[1,lly in the 

N ashville area, show very perfect crystal faces with 

little evidence of attrition. 

The pumiceous orthoclase trachyte tuffs of the Woodbine fonnation display little or no evidence of bedding, 

but SOlne of thCln contain leaf fragnlents suggesting 

that they, like the lithic tuffs. were deposited-in 

\\r,ater. 

The' tuffaceous sand of the Woodbine contains 

invertebrate fossils in some of the exposures in OklahOllla and Texas. The fossils together with £he 

character of the sand indicate that the Woodbine was 

there deposited in marine and brackish waters. 

The cross-bedding and assortlnent of the materials 

in peridotite tuff of the Tokio fonnation indicate that 

the tuff was water-laid. The kaolin beds that appear 

to be derived fr0111 Inaterial of volcanic origin in the 

Tokio forlnation were also water-laid, as is shown by 

the occurrence of horizontal laminae, an occasional 

grain of glauconite, and 'fossil plant leaves and stems 

lying parallel with the lanunae. 

VOLCANIC VENTS OF CRETACEOUS AGE IN ARKANSAS, 

OKLAHOMA, AND NORTHEASTERN TEXAS 

The location of the vents that supplied the volcanic 

111aterial in the Woodbine and Tokio formations may 

be inferred fr0111 the different kinds of volcanic Inaterial, 

from the thickness of the water-laid volcanic deposits, 

fr0111 their distribution, and fronl their change in 

character fronl place to place. 

Of the known deposits of tuff in Texas, Oldahoma, 

n,nd Arkansas, the thickest lie in Howard, Pike, and 

Sevier Counties, Ark. This fact, combined with the 

well known occurrence of volcanic activity at Murfreesboro, Pike County, suggests that the vent or vents 

through which the enonnous quantity of tuff and ash in 

southwestern Arkansas, southeastern Oldahoma, and 

northeastern Texas was ejected were situated in these 

three counties. The areas of Lower Cretaceous and 

older rocks in these and adjoining counties have been 

carefully studied by many geologists, but thus far no 

volcanic vents active in Cretaceous time except the 

peridotite vents near Murfreesboro have been discovered. If the Cretaceous vents supplying the other 

kinds of volcanic lllaterial were situated in the southern parts of the counties they are now concealed by 

beds of Upper Cretaceous and Quaternary age. 

The volcanic center a few nriles southeast of Murfroesboro, Ark., consisted of three or more volcanoes, 

here nl1l11ed the 11urfreesboro volcanoes. (See fig. 18 

and pI. 19.) The rocks that fill these old vents are 

exposed. Another vent that erupted volcanic material 

of a trnchytic type was apparently a few miles northwest of Nashville, Ark., and a second was apparently 

half to three-quarters of a nlile south of Lockesburg, 

Ark. These two vents are here named the Nashville 

and Lockesburg volcanoes. They supplied the tuffaceous material in the Woodbine formation. Neither 

of the vents is exposed. How many other centers, if 

any, there may have been in southwestern Arkansas, 

southeastern Oldahonla, and northeastern Texas is 

not known. The exhaustive studies by different geologists of the syenites and related types of igneous rocks 

near central Arkansas have not suggested to theIn that 

the intrusion of these rocks was accompanied by volcanic explosions. The evidence for the assumption 

that volcanic vents were located near Lockesburg 

and Nashville is given in the several succeeding paragraphs. 

The locatIOn of the three volcanoes mentioned above', 

as well as the location of distant volcanoes of Cretaceous age in these and adjacent States, is shown on 

Figure 18. The Monroe, Thrall, and Lytton Springs 

volcanoes were discovered by means of deep oil and gas 

wells. 

The peridotite material at the base of the Tokio 

formation near Murfreesboro, Ark., is believed to be 

peridotite tuff. Its occurrence near the Murfreesboro 

volcanoes indicates that they were its source. The 

necks of these volcanoes are filled with three kinds of 

peridotite-porphyritic rock, breccia, and tuff. The 

breccia is diamond bearing and has yielded diamonds 

in small comlnercial quantities. The volcanic activity 

apparently took place in early Upper Cretaceous time, 

as is indicated by the upward extension of the .necks 

through beds of the Trinity formation (Lower Cretaceous) and by the occurrence of deposits of waterlaid peridotite material (peridotite tuff?) in the lower 

part of the Tokio fornlation (Upper Cretaceous). 

The Murfreesboro volcanoes did not yield more 

than a small quantity of ejected material to the thick, 

widespread deposits of volcanic rocks in the Woodbine and Tokio formations, for no positive identification of peridotitic material has been made in the 

formationR except at localities near Murfreesboro. 

The volcanic rocks represented in the Woodbine 

and Tokio formations other than peridotitic material 

include two kinds whose sources will be considered 

separately. One kind is an orthoclase trachyte, 

characterized by pumice now largely altered to bentonite, and the other is characterized by beds of lithic 

phonolite pellets. 

The fragments of orthoclase trachyte associated 

with the pumice tuffs are not rounded, and the crystal 

grains are all very sharply euhedral or angular where 

fractured. Some of the pumice beds contain no 

foreign detrital material of any kind, even where the 

beds above and below contain large proportions. 

Much of the pumice was composed of lenticular 

vesicles bordered by exceedingly thin walls that made 

it an unusually fragile material. There was no sort.. 

ing or sizing of pumice, and sharply angular frag-· 
190 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

ments are discernible In every thin section examined. 

The fragile nature of the pumice and its relations seem 

to preclude any extensive transportation. The purest 

pumice and trachyte tuffs are found on Coleman and 

Pleasant Valley Creeks (fig .17), and the tuffs become 

less pure with distance from that locality. These 

circumstances seem to indicate rather clearly that the 

volcanic centers that supplied the pumice and trachyte 

tuffs were situated not more than a few miles from a 

point about 3 miles northwest of Nashville, Ark. 

MEXICO 

o 100 I ! ! , I 

EXPLANATION 

show crystal faces but are more rounded than in the 

N ashville area. Fresh augite is very rare but appears 

to have been abundant prior to replacement by calcite; magnetite, spinel, and other minerals that resist 

replacement are just as abundant as near Nashville. 

Pyrite and siderite have developed, augite has been 

replaced by calcite, and glauconite has formed filIns 

around and replaced mineral and rock grains. 

These results make it seem possible that the easternmost parts of the tuffaceous beds of the phonolite 

type were nearest to the volcnnic center that supplied the material. On 

the other hand, the cobbles of phonolite found on Mine Creek near N ashville, Ark. (fig. 17), were exceedingly 

well rounded and possibly sonlewhat 

weathered before they became incorporated in the tuffs and associated 

gravel beds. The small rock pellets 

that are characteristic lllaterial of the 

phonolite tuffs and sands are rounded 

and rather well sorted and l110re or 

less mixed with quartz and novaculite 

grains. This suggests that the phonolite material had been transported 

some distance, even in the Arkansas 

part of the region, though it could 

hardly have been carried by streall1S 

from the areas of igneous rocks neRr 

the center of Arkansas, the nearest of 

which is between 50 and 60 nliles northeast of Murfreesboro. The evidence 

in favor of transportation is sonlewhat 

opposed by the euhedral shape and lack 

of rounding of the· phenocrysts fronl the 

phonolite tuffs. On the whole, however, 

there seems to be no evidence that excludes considerable transportation of .. 


~ .. :.: :. :.. 
 W!}fj B the phonolite volcanic material or that

Quaternary and Sedimentary rocks Paleozoic and Igneous rocks suggests a very exact location of the 

Tertiary rocks of Cretaceous age Pre-Cambrian rocks of Cretaceous age volcanic center or centers from which 

VOLCANOES ACTIVE IN CRETACE.OUS TIME. it came. Probably, however, the east­ ~ ~¥~ . Rocks filling the necks of these Rocks that compose the necks and ern tuff beds were nearer the source of 

volcanoes are exposed at surface cones of these volcanoes are eon; cealed by rocks of Cretaceous and supply than those in the Texas-Okla­ later age homa region, where there is greater FIGURE IS.-Map of Arkansas and adjacent States showing the location of volcanocs that were active in mixing with other materials find a Cretaceous time and the exposures of igneous rocks of Cretaceous age 

The volcanic ma.terials of the phonolite type are 

fresher and less nlixed with foreign detrital debris in 

the area near N a.shville, Ark., than in the Oklahoma 

and Texas a.reas. As the tuff beds are followed west 

into Olda.homa and southwest into Texa.s there appears 

to be an increase in the avera.ge proportion of quartz 

and other nonvolcanic detrital material. Phonolite 

is the characteristic volcanic rock material, but minor 

amounts of orthoclase and rock fragments of the 

trachyte type are present. The orthoclase crystals 

greater rounding of mineral grains. 

That a volcanic center was situated in the vicinity 

of Lockesburg, Sevier County, Ark., is suggested by 

natural phenomena there. Three-quarters of a nlile 

south of Lockesburg broken and bent beds of the 

Trinity are revealed in a small exposure by the roadside. 23 No post-Cretaceous faulting and certainly no 

close Cretaceous folding has affected the Trinity at 

any other place in Arkansas, Oklaholl1a, or the adjacent 

part of Texa.s with which t.he writers are familar. The 

23 Dane, C. H., letter of Jan. 20, 1926. 
WATER-LAID VOLCANIC HOCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 191 

steep dips and fractures in the Trinity are perhaps 

attributable to displacelnent in connection with vol:.. 

('.anic ac.tivity. 'Veight is added to this suggestion by 

the oc.eurrence of numy large angular blocks of Paleozoic sandstone at the locality three-quarters of a 

mile south of Lockesburg. The blocks, measuring as 

lnuch as 15 feet in length, 4 feet in width, and 3 feet 

in thickness, could not have been transported very 

fa,r by streams that deposited the known gravel beds 

of Cretn.eeous age in Arkansas. 23 The nearest exposures 

of Paleozoic sandstone are in the Ouachita Mountains 

10 Iniles north of Lockesburg. ~10reover, the great 

abundanee of the sandstone blocks at the Lockesburg 

loeality indicates that they were probably not transported fr0111 the Ouachita ~10untains. Their source 

was thus appn.rently near by. Possibly t4ey came 

from a high ridge of Paleozoic sandstone that may have 

extended upward ~ntirely through the Trinity, about 

1,000 feet thiek, or fronl blocks of sandstone brought 

upward by volcanic explosions. Ridges of so great 

height on the Cretaceous floor are not known in Arkansas, though ridges several hundred feet high are known 

near Spencerville, Choctaw County, Okla. At the volcanic neck near Murfreesboro, Ark., on which the 

Ozark, ~1n.uney, and Arkansn.s dialnond nunes are 

located, there are masses of Paleozoic quartzite hundreds of feet in their longest dimension: These have 

all been lifted upward by the forces accompanying 

the volcanic activity, and it seelllS probable that the 

same explanation applies to the tilted Paleozoic. blocks 

ncar Lockesburg. 

WIDESPREAD VOLCANIC ACTIVITY DURING CRETACEOUS PERIOD 24 

Volcanic materials are widespread in the Woodbine 

forlnation, not only on the outcrop but in the deposits 

away frolll the outcrop, also in equivalent and overlying beds of Upper Cretaceous a$e. Furthermore, 

they are present not only in Arkansas and Oklahoma 

bu t also in Louisiana, Texas, and Alabama. The 

occurrences are briefly lllentioned below. 

Bentonite has been found in the "Bingen fornlation" 

OVoodbine and Tokio fornlations) in wells in Union 

County, Ark., as identified from samples sent to the 

Geological Survey by H. D. Easton. 

Bentonite occurs in Louisiana in beds that appear 

to be the equivalent of the Arkadelphia clay or .the 

~1arlbrook 111arl (Upper Cretaceous), which are 

younger than the Woodbine and Tokio formations. 25 

n Danc, ('. n., personal communication, Jan. 20, 1926. 

tl Since the present papcr was written a comprehensive report, by J. T. Lonsdale, 

on the igneolls rocks of the Dalconcs fault region of Texas, was issued Nov. 22, 1927, 

as Bulletin 2744, by the Bureau of Economic Geology of the University of Texas. 

Lonsdale dcscribcs not only the exposed igneous rocks but also those that have been 

found in wclls. Brief references are made in the present paper to occurrences of 

of igneous rocks In 'rexas. 'l'he rocks of all the occurrences cit.ed, as well as others, 

are dcseribcd hy Lonsdale. He describes their form, distribution, and petrographic 

character and also discllsses the age and nature of the igneous activity. 

26 Bramlette, M. N., Bentonite in the Upper Cretaceous of Louisiana: Am. Assoc. 

Petroleum Geologists Bull., vol. 8, pp. 342-344, 1924. 

Bentonite of exceptional purity which shows very 

perfect volcanic-ash structure occurs in the Eutaw 

fonnation, of Upper Cretaceous age, near Montgonlery, Ala. Material fr0111 this deposit was collected by 

,Doctor Carver, of the Tuskegee Institute, and submitted to Clarence S. Ross by Henry M. Payne for 

identification. The age of the bed is "inferred by L. W. 

Stephenson 26 from the geographic location of the bentonite occurrence. Material fr0111 the saI11e deposit has 

been submitted to the United States Geological Survey by E. M. Graves, of Montg01nery.26 

An unusually pure bentonite near Aberdeen, Monroe County, Miss., is reported by the State geologist 27 

to be part of the Eutaw formation. The Eutaw formation is porrelated by Berry 28 with the Tokio fOl'lnation 

(" upper Bingen "). 

Volcanic ash is found in the Eagle Ford clay in wells 

in northeastern Texas. 2

!l This clay is regarded by 

Stephenson as occupying part of the hiatus represented by the unconformity between the Woodbine and 

Tokio formations. 

Thin layers of bentonite reaching a nlaximum thickness of 1.5 feet, interbedded with shaly clay and platy 

limestone, have been observed by Stephenson and 

others in the lower part of the Eagle Ford clay in Texas 

as follows: In the vicinity of Austin, Tdl,vis County; 30 

northeast of Georgetown, "Villianlson County; between Belton and Temple, Bell County; at several 

places along the strike of the formation in McLennan 

County; 31 near Grand Prairie, Dallas County;32 and 

west of PottsQpro, Grayson County. These localities 

may prove to be parts of a continuous zone in the lower 

part of the Eagle Ford clay extending at least from 

Travis County to Grayson County. 

Pilot Knob, 8 miles southeast of Austin, Tex., 

(fig. 18), marks the site of an ancient volcanic eruption, 

which probably took place late in Austin time and 

early in Taylor time.33 Beds of tuff that are related 

to the central mass extend outward from it for 6 

miles. The typical Austin chalk, according to Stephenson, is apparently represented by the Tokio forlnation. The lower part of the typical Taylor marl, 

also according to Stephenson,34 is apparently equivalent to the Brownstown marl, which overlies the 

Tokio formation. If these correlations are correct, 

~ Stephenson, L. W., The Mesozoic rocks, in Geology of Alabama: Alabama 

Geol. Survey Special Rept. 14, p. 236, 1926. 

27 Lowe, E. N., personal communication. 

28 Berry. E. W., Contributions to the Mesozoic fiora of the Atlantic Coastal Plain, 

XII-Arkansas; Torrey Bot. Club Bull., vol. 44, pp. 167-190, 1917. 

29 Waite, V. V., oral communication to H. D. Miser. 

~o Dr. J. A. Udden (oral communication) has recognized bentonitic clay in Eagle 

Ford shale, in exposures on a small southern tributary of Colorado River, just south 

of Austin, Tex. 

31 Adkins, W. S., Texas Univ. Bull. 2340, p. 107, 1923. 

32 Stanton, T. W., oral communication. 

33 Hill, R. T., and Kemp, J. F., Pilot Knob. a marine Cretaceous volcano: Am. 

Geologist, vol. 6, pp. 286-294, 1890. Deussen, Alexander, Gcology of the Coastal 

Plain of Texas west of Brazos River: U. S. Geol. Survey Prof. Paper 126, p. 120, 1924. 

3l Stephenson, L. W.,· A contribution to the geology of northeastcrn Texas Bnd 

southern Oklaboma; U. S, Geol. Survey Prof. Paper 120, P. 154, 1919. 
192 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

the eruption at Pilot Knob occurred during and soon 

after Tokio time. Intrusive igneous rocks are present 

farther southwest in Texas, particularly in Uvalde 

County. The volcanic activity in that county took 

place in Tertiary time.35 

A buried sill of decomposed basalt, or possibly a bed 

of volcanic tuff, occurs in the Taylor marl near Thrall, 

Williamson County, Tex.36 (See fig. 18.) As the 

lower part of the Taylor marl is equivalent to the 

Brownstown marl, the sill of basalt or bed of tuff may 

have been formed soon after Tokio time. Concerning 

the body of igneous rock Deussen 37 says: 

The body is evidently either a sill connected with some 

near-by volcanic neck or a tuff similar to those exposed near 

Austin, deposited by a submarine volcano that was active in 

this vicinity in early Taylor time. In any event the rock is 

closely related structurally and historically to the Pilot Knob 

disturbance near Austin. 

At Lytton Springs, Caldwell County, Tex., a body. 

of igneous rock 38 has been found in deep wells to 

project upward through the Austin chalk into the 

Taylor marl. The rock, which is now largely serpentine and chlorite, was originally volcanic ash, lava, and 

intrusive basalt and probably represents an old buried. 

volcanic cone. The igneous rock here, like the serpentine rock at Thrall, yields oil in commercial quantities. 

Beds of bentonite occur in the Navarro formation 

at a locality 3% miles northwest of Macdona, Bexar 

County, Tex. The purer layers retain perfectly the 

characteristic structure of the glassy volcanic tuffs 

from which the bentonite was. deriv~d. Specimens 

collected by J. A. Udden and M. 1. Goldman were 

examined. This deposit, previously referred to the 

Taylor marl, is believed by Stephenson to belong to 

the Navarro formation. 

A succession of volcanic tuffs and flows underlies a 

part of the Monroe gas field of Louisiana. It is 1,100 

to 1,200 feet thick and "seems to include the interval 

.between the N acatoch, Marlbrook, or Annona, and 

the Washita (of Comanche age)." 39 The differences 

in the thickness of the tuffs and flows and their distribution strongly suggest that they form a part of a 

volcanic cone which is buried in Cretaceous sediments. 

(See fig. 18). The inclosing sediments above and those 

below, being both of Cretaceous age, indicate that the 

volcano was active in Cretaceous time. 

Volcanic tuff from the Prothro salt dome, in T. 14 N., 

R. 6 W., Bienville Parish, La., is identical in appearance and composition with some of the lithic tuffs in 

36 Deussen, Alexander, op. cit., p. 121. 

36 Udden, J. A., Oil in an igneous rock: Econ. Geology, vol. 10, pp. 582-585, 1915. 

37 Deussen, Alexander, op. cit., p. 120. 

38 Bybee, H. P., and Short, R. T., The Lytton Springs oil field: Texas Univ. 

Bull. 2539, Oct. 15, 1925. Collingwood, D. M., and Rettger, R. E., The Lytton 

Springs oil field, Caldwell County, Tex.: Am. Assoc. Petroleum Geologists Bull., 

vol. 10, pp. 9i3-975, 1926. 

39 Bramlette, M. N., Volcanic rocks in the Cretaceous of Louisiana: Am. Assoc. 

. Petroleum Geologists Bull., vol. 8, pp. 344-346, 1924. Spooner, W. C., and Bell, 

H. W., The Monroe gas field: Louisiana Dept. Conservation Bull. 12, pp. 5-6, 

figs. 1,2, 1925. Easton, H. D., Oil and Gas Journal, Mar. 24 and Oct. 13, 1927. 

the Woodbine formation of Arkansas and Oldahoma ; 

.	but, according to Stephenson, the fossils from the tuff 

at Prothro dome indicate that it is younger than the 

Eagle Ford clay and is probably of the age of the Tokio 

formation and the typical Austin chalk. The tuff, 

according to J. P. D. Hull/owho examined the locality in 

1922, and also according to W. C. Spooner,41 who has 

recently examined the locality, is exposed in almost 

vertical ledges 110 feet in total thickness. Mr. 

Spooner says he has found an outcrop of the same kind 

of rock in beds of the same age in the Rayburn salt 

dome, in T. 15 N., R. 5 W., Bienville Parish, La. 

The tuffaceous sand of the Prothro dome contains 

phonolite with the same unusual and significant 

composition that characterizes the phonolite tuffs of 

Arkansas, and trachyte and pumice of the Arkansas 

type are present in minor quantities. Also the entire 

list of minerals associated with the tuffs is the same. 

The volcanic rocks in the two areas thus have the same 

lithologic character. Siderite has formed, calcite has 

replaced augite, and an unusual type of glauconite has 

been deposited in films q,round and has replaced augite 

crystals and phonolite grains in both areas. 

Thus in the Prothro dome and in Arkansas, OIdahoma, and Texas the volcanic materials are the same 

(see table on p. 194), their relations are the same, and 

very peculiar and unusual secondary replacement 

processes affected the beds in both regions in the same 

way. The peculiar lithologic characters suggest in 

themselves that the beds in the Prothro dome represent 

the same formation that crops out in Arkansas, but 

the fossils discussed by Stephenson on page 200 seem 

to afford conclusive evidence that the Prothro dome 

and Woodbine beds are not of the same age. 

The volcanic activity that produced the peridotite 

. of Pike County and the nephelite syenites and associated types in other parts of Arkansas probably 

accompanied the" down-warping of the Mississippi 

embaymentinUpperCret.aceoustime. The tuff and ash 

falls in the Woodbine and Tokio formations of southeastern OIdahoma and Arkansas probably took place 

at.this time. As has been pointed out by Branner,42 

the igneous rocks of Arkansas occur near and parallel 

with the old Cretaceous-Tertiary shore line, which 

extended northeastward across the State. He believed 

that this shore line was affected by faulting or other. 

weakness and that the igneous rocks of Arkansas had 

sonle possible connection with t,his line of disturbance. 

The similarity of the peridotite and lanlprophyre dikes 

of western ICentucky and southern Illinois and the 

peridotite breccia of Riley County, Kans. 43 (fig. 18), 

40 Letter dated Aug. 1, 1924. See also Hull, J. P. D., Prothro salt dome, Bienville Parish, La.: Am. Assoc. Petroleum Geologists Bull., vol. 9, pp. 905-906, 1925. 

41 Letter dated Aug. 2, 1924; also Interior salt domes of Louisiana: Am. Assoc. 

Petroleum Geologists Bull., vol. 10, pp. 229-230, 248, 262-263, 1926. 

42 Branner, J. C., The former extension of the AppalaChians across Mississippi, 

Louisiana, and Texas: Am. Jour. ScL, 4th ser., vol. 4, p. 365, 1897. 

43 l\ioore, R. C., and Haynes, W. P., An outcrop of basic igneous rock in KansaS: 

Am. Assoc. Petroleum Geologists Bull., vol. 4, pp. 183-187, 1920. 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 193 

suggests that the intrusion of the peridotite in those 

States occurred during Upper Cretaceous time. 

Although this is a lnere suggestion, the writers know 

of no facts that. would nlilitate against this view. 

Plugs of volcanic breccia of acidic rocks occur in the 

same region as the dikes of southern Illinois (fig. 18) 

and "may represent an explosive phase of the region's 

igneous phenolnena." 44 

VOLCANIC ACTIVITY IN GULF COASTAL PLAIN AND 

ADJOINING REGION IN PALEOZOIC AND TERTIARY 

TIME 

Volcanic activity that affected the Gulf Coastal 

Plain and the adjoining country has taken place not 

only in the Upper Cretaceous epoch but at several 

other times. Bentonite occurs in the Ordovician rocks 

of Kentucky, Tennessee, and Alabama.46 Bentonite 

and slightly metalllorphosed tuff also occur in Ordovician rocks in Virginia 46 and PennsylvaniaY Volcanic ash is reported by C. W. Honess in the Missouri 

IV[ountain slate (Silurian), in McCurtain County, 

Okla. 48 Also volcanic ash and breccia are reported by 

lIoness from two horizons in the Arkansas novaculite 

of Devonian age in McCurtain County, Olda.,49 and 

he suggests that at least some of the Arkansas novaculite is silicified and devitrified volcanic ash. Volcanic 

tuff occurs in a bed 90 to 100 feet thick and in several 

thinner beds in the Stanley shale (Carboniferous) in 

Polk County, Ark., and McCurtain County, OIda.50 

Beds of Tertiary bentonite of different ages are 

reported by IIenry lvL Payne 51 to occur at several 

localities jn Mississippi and Alabama. The age of the 

bods is inferred by C. W. Cooke from the geographic 

location. The localities together with the age of the 

bentonite beds are as follows: In beds of probable 

Miocene age on the outskirts of Mobile, Ala.; in the 

Clayton fOrIlIation, of Midway (Eocene) age, at Houlka, 

Chickasaw County, l\1iss.; in the Porters Creek clay, 

of Midway (Eocene) age, west of Woodland, Chick a44 Currier, L. W., Igneous rocks [of Hardin County, Ill.]: Illinois Geol. Survey 

Bull. 41, pp. 237-244, 1920. 

4& Nelson, W. A., Volcanic ash bed in the Ordovician of Tennessee, Kentucky, 

and Alabama: Geol. Soc. America Bull., vol. 33, pp. 005-615, 1922. Butts, Charles, 

'1'he iPaleozoic rocks, in Geology of Alabama: Alabama Geol. Survey Special Rept. 

14, pp. 113-114, 131-133, 1926; U. S. Gcol. Survey Geol. Atlas. Bessemer-Vandiver 

folio (No. 221), pp. 7, 16, pIs. 10, 17, 1927. 

40 'l'aber, Stephen, Geology of the gold belt in the James River basin of Virginia: 

Virginia Geol. Survey Bull. 7, p. 43, 1913. Powell, S. L., letter dated March 24, 

1925. Nelson, W. A., Volcanic ash deposit in the Ordovician of Virginia: Geol. 

Soc. America Dull., vol. 37, pp. 149-150, 1926. Giles, A. W., 'l'he origin and occurrence in Rockbridge County, Va., of so-called "bentonite": Jour. Geology, vol. 35, 

pp. 527-541, 1927. Ross, C. S., Paleozoic volcanic materials and criteria for their 

lecognition: Am. Assoc. Petroleum Geologists Dull., vol. 12, pp. 143-164,1928. 

47 Bonine, C. A., Researches in sedimentation in 1925 and 1926, pp. 4-5, National 

Research Council, 1926. Stose, G. W., and Jonas, A. I., Ordovician shale and associated lava in southeastern Pennsylvania: Geol. Soc. AmericaBull., vol. 38, pp. 

505-536, 1927. 

48 Honess, C. W., Geology oC the southern Ouachita Mountains of Oklahoma: 

-Oklahoma Geol. Survey Bull. 32, pp. 107-lO9, 1923. 

4g Idem, pp. 121-139. 

&0 Miser, n. D., Mississippian tuff in the Ouachita Mountain region (abstract): 

Oool.~Soc. America Dull., vol. 31, pp. 125-126, 1920. Honess, C. W., The Stanley 

shale of Oklahoma: Am. Jour. Sci., 5th ser., vol. 1, pp. 63-80, 1921; also op. cit. 

A! P~rsonal communication. 

saw County, Miss., and hear Maben in Webster and 

Oktibbeha Counties, Miss.; and in the Clayton formationor the Porters Creek clay in western Union County, 

across Pontotoc County, and along the Gulf, Mobile 

& Northern Railroad in Tippah County, Miss. 

An unusually pure bentonite occurring near Aber-' 

deen, Monroe County, Miss., is reported by the State 

geologist 52 to be part of the Eutaw formation. 

A bed of glassy volcanic ash probably of Jackson 

(late Eocene) age occurs in the northeast part of La 

Salle Parish, La.53 The ash bed is 4 feet thick at the 

outcrop and is reported to be 35 feet thick in a drill 

hole near by. This material is nearly pure white and 

very fine grained and contains from 10 to 15 per cent 

of crystalline quartz, feldspar, etc. 

Tuff of Oligocene or lower Miocene age is widely 

distributed in Live Oak and McMullen Counties, 65 to 

90 miles south of San Antonio, Tex.54 

Volcanic ash of several different ages in Arkansas 

and Louisiana is briefly described by Crider,55 who 

says: "Volcanic ash has been discovered in a number 

of * * * localities in Louisiana and Arkansas 

ranging in age from Lower Cretaceous to .the Jackson 

formation of the Eocene." 

Volcanic ash is mentioned by Dumble 56 as occurring in Texas in the Fayette, Yegua, and Jackson 

formations (Eocene), in beds ·of upper Oligocene age, 

and in the Oakville sandstone (Miocene). 

Volcanic ash from the Hayes district of Calcasieu 

Parish, La., has been described recently' by Hanna,57 

though the age of the ash is not lmown to him. The 

core he examined came from a depth of l,510 feet in 

the Duhig et al. No. 1 Levey well. \ ­

DISTRIBUTION OF THE TUFF TYPES 

The general distribution of the tuff beds has been 

stated, but for the purpose of petrographic description 

it is convenient to take them up in five rather distinct 

groups of occurrences. One of these comprises the 

region north and northwest of Nashville, Ark., where 

the orthoclase trachyte pumice tuffs are the thickest 

and composed most largely of igneous material. 

Another is the area of Arkansas where the phonolite 

tuffs occur. Over part of the area the beds of the first 

group overlie those of the second, but from Blue 

Bayou west to the State line the pumice tuffs are not 

well developed so far as known. A third group of occurrences is in Oklahoma, and a foutth includes the 

62 Lowe, E. N., personal communication. 

63 Personal communication from W. M. Weigel, mineral tcchnologist oC the Mis· 

souri Pacific Railroad. 

&4 Bailey, T. L., Extensive volcanic activity in the middle Tertiary of the south 

Texas Coastal Plain: Science, new ser., vol. 59, pp. 299-300, 1924. 

6& Crider, A. F., Volcanic ash in northern Louisiana: Am. Assoc. Petroleum 

Geologists Bull., vol. 8, pp. 524-525, 1924. 

&a Dumble, E. T., A revision of the Texas Tertiary section with spccial refcrence to 

the oil-well geology of the coast region: Am. Assoc. Petroleum Geologists Bull., 

vol. 8, pp. 424-444, 1924. 

&7 Hanna, M. A., An interesting volcanic ash from Calcasieu Parish, La.: Am. 

Assoc. Petroleum Geologists Bull., vol. lO, pp. 93-95, 1926. 
194 SHORTER CON'l'RIBUTIONS TO GENEHAL GEOLOGY, 1v28 

Orthoclase 

trachyte

tuffs 

Phonolite tuffs 

____________1__2__3_1__4__5_ 

tuff-bearing beds of Texas. • The fifth comprises the 

occurrences in the Prothro dome and the Rayburn, 

salt dome. 

The nlinerals and their relative proportions differ 

greatly from place to place, and no single specimen is 

entirely characteristic of a locality, but tuffs from a 

locality in each of the above five groups were unsually 

fresh and have been studied in detail. The material 

was prepared for study by washing, and the heavy 

minerals were concentrated by heavy solutions. The 

results of thjs study are given in the table below. 

Where mineral or rock grajns were present in essential 

anlOunts the approximate proportions were determined 

and are given in figures. If a mineral formed less than 

1 per cent of the material, its presence but not its proportion was determined and is indicated by an X. 

The purer specimens of all the tuffs were selected for 

study, and the figures given do not imply that all the 

specimens from a given locality had the high content 

of volcanic nlaterials indica,t,ed. 

Rocks and mine'/'als of the tuffs 

Phonolite_ _ __ _ _ _ _ _ _ _ _ _ _ _ X 78 65 70 38 


Trachyte________________ 31 X 2 X X 


Pumice __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ 45 X X X 


Quartz________ .. _________ 2 2 27 10 47 


Novaculite ______________ -1 X 3 6 2 


Orthoclase_______________ 20 X 1 11 9 


Plagioclase __ .! _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 


Augite_ __ __ __ _ _ __ __ _ _ __ _ X X X X X 


Hornblende______________ X X X X X 


Biotite__________________ X X X X X 


,Magnetite_______________ X X X X X 


Black spineL _ _ _ _ _ _ _ _ _ _ _ _ X X X X X 


Apatite_ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X X X X X 


Zircon __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X X X X X 


Tourmaline______________ X X X X X 


Staurolite_______________ X X X X X 


Garnet. __________________________ .: __ X X 


Glauconite (marine)______ ______ X ______ ______ X 


Glauconite (replacement)_ ______ 12 X X X 


Pyrite_ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X X X ___ - _______ _ 


Siderite_________________ X X X X 1 X~ Calcite___ -______________ X X X X 


Phosphatic grains________ ______ X X X 


1. From Blue Bayou, Ark., representing orthoclase trachyte 

tuffs. 

2. From Owen Place, Ark., unusually pure phonolite tuff. 

(See fig~ 17.) 


3, From Garv,in, Okla. (See pI. 20,) 


4, From Arthur City,' Tex. (See pI. 20.) 


5. From the Prothro salt dome, La. 

The last four columns of the table show a great 

variation in the proportions of volcanic and detrital 

sedimentary rock debris, but the igneous-rock minerals 

show practical identity, even though the localities 

from which they came were widely separated. The 

metamorphic-rock minerals and the minerals that 

developed subsequent to deposition are also identical. 

The orthoclase is all sanadine, the augite crystals all 

show the cockscomb habit, and the hornblende is 

similar in color and habit. Black spinel, which is a 

very unusual nlineral in volcanic rocks, is present in 

every sample studied. The gla,uronite that formed 

films around rock and nlineral grains was later than 

deposition in all the specinlens. 

THE TUFF BEDS OF ARKANSAS 

MINE CREEK, HOWARD COUNTY, ARK. 

The tuffs, tuffaceous sands, and associated grn.vel 

and boulder beds crop out for about 1 Illile along ~1ine 

Creek, 3 Iniles north of Nashville, Ark. (Sec fig. 17.) 

The beds change greatly in character within short 

distances, and there is locally a very large adlllixture 

of nonvolcanic detrital rock. For this reason the tuff 

beds on Mine Creek are hard to describe systematically, 

but the chief types of material will be ITlentioned. 

The . tuff beds contain 111any beds and lenses of 

gravel and boulders, and the rock materials are predominantly quartz and novaculite, but locally there 

are many pebbles and cobbles of igneous rock of the 

same type that fOrIns the small rounded rock pellets 

of the lithic phonolite tuffs. The most abundant 

igneous material on ~1ine Creek is composed of rounded 

grains of phonolite mixed with quartz and novaculite 

grains and with various proportions of pumice and 

trachyte fragnlen ts. 

The bentonitic beds derived fronl glassy pUlnice 

~sually contain large proportions of other rock nlaterials, but one mass of unusual purity crops out at water 

level on the west side of the creek. It is cream-white 

and is composed of clay grains derived from pumice, 

a very little finely crystalline trachyte, and about 25 


per cent euhedral orthoclase. The clay·grains retain 

perfectly the fibrous pumice structure. The clay 

portion is of unusual purity and was separated and 

analyzed. (See p. 186.) At the base of the pUlllice 

lnass is a layer of small phonolite pebbles that are 

almost completely kaolinized. 

A t nearly the same horizon are beds of deep-red 

sandy clay that are composed of orthoclase, PUI~lice 

fragments altered to clay, and altered trachyte fragnlents. The red layer is in sharp bedded contact above 

and below with beds of normal color, and it is evident 

that oxidation occurred during or before deposition and 

is not the result of recent weathering. 

Pebbles of red clay were noted by C. H. Dane 58 in 

the tuff three-quarters of a nlile south of ' Lockesburg. 

They were apparently derived fronl a bed of red clay 

older than the tuff, and they were oxidized before they 

were deposited in their present position, which is about 

20 feet above the base of the vVoodbi!le. 

. 68 Oral communication, 
WATER'-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 195 

COLEMAN CREEK, HOWARD COUNTY, ARK. 

The tuff layer crops out for about three-quarters of 

a luile along the banks and in the bed of Coleman 

Creek, locally called Teluperanceville Creek, about 3 

miles northwest of Nashville. (See fig. 17.) The total 

thickness of the exposed beds is about 12 to 15 feet, 

and two sJllall prospect pits have penetrated the tuffs 

some feet below water level. The beds are all claylike, for they are all derived frOln punuce tuff, and they 

contain nccessory grains and fragnlents of lithic trachyte. Phonolite tuff beds are not exposed on Coleman 

Creek. The pmnice contains abundant orthoclase, but 

other phenocrysts luake less than 2 per cent of the 

rock. 

The minerals identified after concentration by heavy 

solutions are biotite, titanite, lllagnetite, and black 

spinel. Augite is present but it was possibly derived 

1'rOlu phonolite fragnlents and not frOlu the pumice 

tuffs. A little tourlualine and garnet are occasionally 

seen aI110ng the heavy Ininerals. I 

The predOlninant Inaterial is the gray bentonitic clay 

derived frOl11 angular altered grains of glassy pumice. 

These bgds contain many calcite concretions that form 

luasses with a IllaAinlulll dialueter of several feet that 

are especially abundant in the creek bed. It was one 

of these Inasses of calci te-cmllen ted tuff from Colenlan 

Creek, sublIlitted to the Geological Survey by Mr. J. N. 

Garner, that led to the recognition of volcanic nlaterial 

in the region. 

The rock fragl11ents in the pumice tuffs are angular or 

subrounded, not well rounded like the phonolite rock 

fragments. The trachyte fragments have resisted 

weathering better than the phonolite and are fresh 

for the J1lOst part, and these heavy luinerals are identical with those found in the pmnice tuffs. The analysis 

of the orthoclase trachyte given on page 186 was made 

on fresh grains that were picked by hand from the 

tuffs on Colmnan Creek. These ranged fl:om 1 to 10 

nUllinleters in dianleter and were nearly white. They 

were cOlnposed of euhedral orthoclase in a very fine 

grained aphani tic groundnlass of alkalic feldspar without characteristic crystal forIll. The rock was ahnost 

without dark Ininerals, but an occasional grain of 

biotite, titanite, luagnetite, or blaek spinel could be 

observed. 

PLEASANT VALLEY CREEK: HOWARD COUNTY, ARK. 

Pleasant Valley Creek drains eastward into Mine 

Creek, and along its bed the tuffs are well exposed. 

(Sec fig. 17.) flere there is a smaller adnlixture of 

nonvoleanic rock debris than on Mine Creek, and claylike material, derived from glassy volcanic tuffs, and 

ungular lithic fragments are the most conspicuous 

Inaterials of the beds. Small fragments of trachyte are 

especially abundant in the creek bed but do not differ 

frolll those on Coleman Creek. 

BLUE BAYOU, HOWARD COUNTY, ARK. 

Some of the 11l0St extensive exposures of volcanic 

tuff in the entire region are found on Blue Bayou, ex~ 

tending from a point a short distance west of Forgy 

almost to Center Point. The best of these are near 

Blue Bayou Church, where about 40 feet of the tuff 

is exposed. (See fig. 1 7 . ) 

All types of volcanic debris are represented, but the 

gray and blue-gray claylike material is probably the 

predominant component. With this are Inixed trachyte pumice fragments and angular orthoclase 

trachyte fragments, rounded rock pellets of the phonolite tuff, and various proportions of nonvolcanic rock 

material. The beds are lens-shaped and show very 

marked cross-bedding, and the size and character 

of the material at a particular horizon change laterally 

within a few rods. 

The most abundant form of tuff at Blue Bayou 

Church is a loosely coherent material of light bluishgray color. It is made up of claylike pellets that have 

been derived from glassy pumice fragments, trachyte 

grains, igneous-rock phenocrysts, and a small amount 

of quartz and other detrital material derived from 

sedimentary rocks. The grains range in diameter 

from about 1 millimeter to 15 millimeters. 

The minerals are largely orthoclase, but biotite, 

titanite, and black spinel form less than 2 per cent of 

the rock. The orthoclase is very perfectly euhedral for 

the most part, but a few crystals are etched, and many 

are fractured so that only one end of the crystal is complete. Biotite is the most abundant dark mineral and 

occurs in flakes with euhedraloutline. The black spinel 

has euhedral form and very brilliant crystal faces. 

Pale-brown shotlike pellets of siderite with radial 

structure and a little pyrite are secondary minerals 

that developed subsequent to the deposition of the ash. 

Another specimen from Blue Bayou Bluff represents 

material that is composed of lithic and vitric tuffs in 

about equal parts. It is light bluish gray and is composed of fragments that reach a maAimum length of 

about 5 millimeters. These are angular fragments of 

finely crystalline trachyte, flattened fragments of 

pumice, and mineral grains that represent igneousrock phenocrysts. 

A microscopic study of thin sections shows that the 

pumice has been altered to a bentonitic clay mineral, 

many grains of which have a len:; shape, which is due 

to flattening by compression and loss of the original 

pumiceous porosity. The nucroscope shows that many 

of these clay grains are made up of a micaceous mineral with high birefringence. Each pmnice fragment 

appears to be a single distorted individual crystal 

of clay material. It is evident that during alteration 

the porous individual grains became flattened and 

accommodated themselves to the contour of the contiguous grains and thus assumed a distorted shape. 
196 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY) 1928 

Of the mineral grains that represent phenocrysts 

from the igneous rock, orthoclase is the only one that 

is abundant. Rare dark minerals are augite, biotite, 

titanite, green and brown hornblende, apatite, magnetite, black spinel, and pink garnet. The rock differs 

from the phonolitic tuff on the Owen place, described 

below, in having abundant biotite hut little augite. 

OWEN PLACE, HOWARD COUNTY, ARK. 

The basal part of the tuff beds, where the phonolite 

tuffs are exposed in unusual perfection, crops out along 

the northern border of the tuff area at many points 

betweenCenter Point and Corinth,HowardCounty,Ark. 

One of the best sections is found on the Owen place, 

about 3 miles west of Corinth, in the valley of a 

small northward-flowing stream. (See fig. 17.) 

Boulders, some of which reach a lllaximum diameter 

of several feet, are scattered over the surface and 

locally they are very abundant. These are indurated 

masses of pumiceous tuff that were originally cemented 

with calcium carbonate. The carbonate has since been 

partly or wholly leached away in the boulders that 

have long been lying on the surface, but others that 

have not been subjected to prolonged weathering still 

contain much calcium carbonate. 

The delicate structure of very porous, almost 

feather-like pumice fragments is to be seen in many of 

the boulders where the pumice has been exposed by the 

leaching away of the inClosing calci1+m carbonate. In 

other boulders the pumice glass itself has been partly 

or wholly replaced by calcium carbonate, and in these 

the pumice structure has been completely preserved 

and is recognizable under the microscope even where 

the rock is all calcium carbonate. (See pI. 22, B.) 

The calcium carbonate boulders occur embedded jn 

the bentonitic clay. beds derived from tuffs, and as the 

structure is the same in both types of material, it 

seems evident that both are derived from the same 

glassy pumice bf.lds. The local cementation of the 

glassy pumice into the boulderlike masses must have 

taken place before the tuffs were altered, for the delicate tuff structure and the thin-walled vesicular cavities are perfectly preserved. The greater part of these 

beds remained uncemented, and underwent the normal 

devitrification process by which glassy volcanic tuff was 

altered to a bentonitic clay mineral. 

Outcrops of clay beds derived from pumice tuff are 

not numerous in the area, but these beds do not form 

good outcrops, and it is probable that deposits of 

pumice tuff are more numerous and thicker than the 

exposures would indicate. I 

The phonolite tuffs on the Owen place, 3 miles west 

of Corinth, are among the best examples of this type 

of material in the entire region. Large masses have 

been completely indurated by the infiltration of calcium and iron carbonates. The color of phonolite tuff 

is gray-green or dark olive-green. The material is 

rather well sorted, as only a small portion of the grains 

range between 0.2 and 0.4 millime tel' in diameter and 

most of them are between 0.5 and 1 millimeter. All 

the grains are surrounded by a film of gray-green 

glauconitic material about 0.01 millimeter in thickness, and the igneous rock and minerals have been 

partly replaced by it. Weli-rOlmded fragments of 

phonolite rock form one-third to two-thirds of the 

pellet-like grains that make up the rock and are the 

most abundant single material present. The finegrained groundmass feldspar of the phonolite appears 

to be fresh, although there has probably been some 

kaolinization, and the associated ferromagnesian minerals are fresh. All rock grains retain the texture of a 

trachytic phonolite, and some are so fresh that nephelite can be recognized. Novaculite grains are present 

but are not abundant, quartz in well-roUnded grains 

is the next most abundant material present, and red 

grains of iron oxide form several per cent of the rock. 

Volcanic-rock ;minerals that represent phenocrysts 

make up about 5 per cent of the grains. These in the 

order of their abundance are orthoclase, pale-green 

augite, dark-green hornblende, titanite, magnetite, 

black spinel, biotite, red-brown basreltic hornblende, 

apatite, and zircon. Most of these crystals are perfectly euhedral. A few show a very little rounding, 

but the greater part have sharp, brilliant crystal faces. 

This is er::;pecially true of spinel, magnetite, hornblende, 

titanite, and orthoclase. The pale-green augite has 

the cockscomb-like multiple terminations shown in 

Plate 24, A. 

Carbonate completely fills the spaces between the 

grains in the indurated boulderlike masses. The 

presence of these nodular masses and the manner in 

which some of the mineral grains have been replaced 

indicate that the calcium carbonate was brought in 

by solution. This inference is confirmed by the presence of the glauconitic films around the grains that 

must have been formed in place find prior to the deposition of the calcium carbonate. 

THE TUFFACEOUS SANDS IN TEXAS 

The tuffaceous sands of the Woodbine formation in 

northeastern Texas occur InainlY in a well-defined 

zone 200 or 250 feet below the top of the formation 

as it is defined in Red River and Lamar Counties. 

The sands of this zone have been exanlined at seven 

localities, six of which are alined in a nearly direct 

east-west line in the northern part of Red River and 

Lamar Counties and the seventh is in the northwestern 

part of Fannin County. (See pI. 20.) A snlall percentage of volcanic material has been found also in 

sands of questionable Eagle Ford or basal Austin' age 

near Woodland, in Red River County, and near Medill, 

in Lamar County, but these sands can hardly be 

called tuffaceous, and their small content of volcanic 

material may have here been derived by reworking 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 197 

fr01ll older tuffaceous beds. The rocks at this locality, 

though they resemble the Woodbine formatiop. contain the species Ostrea sannionis White, which by 

comparison with the occurrence of the type of this 

species in the Western Interior, suggests either the 

Benton or the lower Niobrara and therefore either the 

Eagle Ford or the lower Austin age of the beds. As 

high as 20 per cent of volcanic nlaterial was found in a 

greenish-gray sandstone lying only 10 feet below the top 

of theWoodbine formation and having an exposed thickness of 3 or 4 feet, in a low bluff on Red River, 1Y2 

miles north of the Ragtown settlement in the northwestern part of Lamar County. 

The mineral composition of materialfrom the locality 

is as follows: 

Composition of sandstone containing volcanic material 1Y2 miles 

north of Ragtown, Tex. 

Per cent 

Qunrtz_______________________________ 80 

Orthochtse_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ 6. 5 

Phonolite_____________________________ 12 

Magnetite __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 

Titanite, biotite, zircon, tourmaline, staurolite, and black spineL __________ Less than 1 

The tuffaceous sands of Texas are similar to the 

phonolite tuffs from the Owen place and Blue Bayou 

in Arkansas. (See fig. 17.) Most of thenl contain a 

larger proportion of detrital quartz and a little novaculite, but a few specimens are predominantly volcanic 

Dlaterial. The igneous material at Arthur City is 

largely in the form of rounded fragments of finegrained phonolite, but a few grains of the trachyte are 

present, and a very few grains of altered glassy pumice 

are to be found. The nlineral grains observed are 

orthoclase, a very little sodic plagioclase, biotite, 

augite, hornblende, titanite, magnetite, black spinel, 

find apatite. Magnetite, spinel, and titanite appear to 

be nearly as abundant as in the Arkansas localities, 

but hornblende and augite are extremely rare in most 

of the Texas deposits. A study of thin s,ections indicates that augite was originally abundant but has been 

almost completely replaced by calcium carbonate. 

The orthoclase, titanite, biotite, spinel, and magnetite 

show su bhedral to euhedral forms but are less commonly 

euhedral than in Arkansas. A few grains of brown 

tounnaline are present in all the samples. Orthoclase 

biotite, titanite, and black spinel are minerals that are 

lllore abundant in the pumice and trachytic tuffs than 

in the phonolite tuffs in the Arkansas areas, and this 

seems to indicate that trachyte and phonolite have' 

both contributed material to the Texas beds, although 

few trachyte grains and less glass are now recognizable 

in them. It seenlS probable that the greater distance 

of the Texas beds from the volcanic source has resulted 

in the destruction of the more delicate structures 

during transportation, and that in this way the pumice 

has largely disappeared, but at the same time the 

orthoclase and other minerals that represent the 

phenocrysts from the same source have escaped 

destruction. 

SILVER CITY FERRY, RED RIVER COUNTY 

Silver City Ferry, on Red River, is in Red River 

County, Tex., about 17.5 miles almost due north of 

Clarksville, the county seat. The bluff below the 

ferry reveals about 15 feet of tuffaceous sandstone of 

the Woodbine sand, overlain by about 10 feet of river 

alluvium consisting of loam, clay, and sand, with a 

band of gravel along the base. (See pI. 25, A.) 

The tuffaceous sandstone is a coarse green pebbly 

cross-bedded sand, irregularly cemented with calcite, 

which gives to the rock a silvery sheen. Thin veins of 

calcite also cut the sandstone in places. The sandstone dips perceptibly downstream and is underlain 

between the main exposure and the ferry by 10 feet of 

dark clay containing some vegetable particles and near 

the top a few poorly preserved leaves. Near the middle 

of the clay is a band of soft cross-bedded sandstone 

containing a few poorly preserved pelecypod casts and 

molds and SOlne nodules of lnarcasite. 

About 100 yards above the ferry and apparently at 

a lower stratigraphic level than the dark clay the bluff 

exposes 6 or 8 feet of greenish-gray clay with partly 

indurated sandy lenses near the base, and below this 

clay is 4 or 5 feet of mottled purplish sandyclayexp05ed 

just above water level. 

All the materials exposed in the vicinity of the ferry, 

except the overlying river alluvium, belong to the 

Woodbine sand. 

The specimens collected at Silver City Ferry are a 

dark gray-green calcite-cenlented tuffaceous sand, in 

which volcanic-rock lnaterials are more abundant than 

detrital grains. The following rock nlaterials and lninerals have been identified: Phonolite, quartz, novaculite, orthoclase, hornblende, lnagnetite, black spinel, 

titanite, zircon, apatite, garnet, and tourmaline. 

EAST OF KANAWHA, RED RIVER COUNTY 

Five or six feet of tuffaceous sand of the Woodbine 

fonnation is exposed in a ravine 2 miles east of ICanawha, about 0.2 lnile southeast of the intersection of 

the Manchester-KlOlnatia and ICanawha-Scrap roads. 

(See pI. 20.) The locality, which is about 20 miles 

northwest of Clarksville, is especially interesting on 

account of the occurrence of many individuals of 

Ostrea soleniscus Meek, a characteristic Woodbine species, in the tuffaceous sand. 

The sand is irregularly bedded and consists of quartz, 

fraglnents of volcanic rock and minerals, glauconite, 

and novaculite, named in the approximate order of 

their abundance. SOlne clay is interbedded with the 

sand. The sand is irregularly indurated to nodular 

masses. The oysters occur in great numbers, mainly in 
198 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

the lower 3 feet of the section, where in places the shells 

are attached to one another in clusters. The shells 

are not well preserved and are difficult to collect in 

good condition. This locality was reported to Stephenson by W. B. Sprague, a geologist of the Gulf 

Production Co., \vho visited it in 1924. 

The calcite-cemented tuffaceous sands examined 

from the Kanawha locality contained not more than 

25 per cent of volcanic mat~rials among the mineral 

grajns. The specimens are characterized by numerous fossil fragments, by a large proportion of cementing 

calcite between the mineral grains, and by abundant 

glauconite. Augite was originally present but has 

been completely altered to a calcite-glauconite aggregate. The following table gives the approxilnate 

mineral composition: 

Minerals and rock grains of tuffaceous sand east of Kanawha 

Quartz ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 47 

Novaculite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5 

GlauconUe______________________________ 25 

Orthoclase______________________________ 8 

Phonolite grains_ _ _ _ _ _ _ _ _ _ __ __ __ _ _ _ _ _ _ __ _ 15 

Minerals present in small quantities are biotite, 

hornblende., magnetite, black spinel, titanite, garnet, 

apatite, phosphatic grains, siderite, and pumice. 

PINE BLUFF FERRY, RED RiVER COUNTY 

The tuffaceous sand of the Woodbine is well exposed 

at Pine BJuff Ferry, Red River County, about 23 

miles northwest of Clarksville, Tex. (See pI. 20.) 

The river touches the edge of a high terrace plain at 

this locality, revealing the following section: 

Section at Pine Bluff Ferry, on Red River, Redl River County, Tex. 

Pleistocene terrace deposit: Alluvial loam, sand, and Feet 

gravel____________________________________________ 15 

Upper Cretareous (Woodbine sand): 

Massive sticky clay, poorly exposed________________ 15 

Coarse water-laid tuffaceous sand with only a small 

percentage of quartz and nova·culite; the sand is 

partly indurated, exhibiting many oval to irregular 

concretionary masses_ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 25 

Stratified tuffaceous sand with subordinate layers of 

quartz sand and some thin interbedded clay layers; 

contains some comminuted plant fragments__ _ _ _ _ _ 33 

Concealed by flood water; reported __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 6 

94 

The specimens collected at Pine Bluff are a dark 

gray-green calcite-cemented tuffaceous sand, in which 

volcanic materials are unusually abundant and fresh. 

The rocks and minerals present are listed below: 

Mineral and rock grains of tUffaceous sand at Pine Bluff 

Ferry, Tex. 

Phonolite_______________________________ 70 


Orthoclase _______________ ~______________ 10 


Quartz_________________________________ 5 

Novaculite___ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ 3 

Augite___ _ _ _ _ __ __ _ _ _ _ __ __ _ _ __ _ _ _ _ __ _ _ __ _ 4 

Small quantities of hornblende, magnetite, black 

spinel, titanite, garnet, apatite, and zircon are present. 

GOLDEN BLUFF, RED RIVER, LAMAR COUNTY 

Golden Bluff on Red River, 3 miles east of Arthur 

City, Lamar County, Tex. (see pI. 20), exhibits another 

section in the edge of a high Pleistocene terrace, the 

lower 35 feet of which is composed of tuffaceous sand. 

Section at Golden Bluff on Red River, Lamar Co'unty, Tex. 

Pleistocene terrace deposit: Alluvial sand, poorly ex- Feet 

posed___________________________________________ 35 

Upper Cretaceous (WOOdbine sand): 

Gray, more or less sandy, crumbly clay, with com- minuted plant fragments_ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 25 

Soft to hard, fine-grained, finely glauconitic sandstone, with . fossils abundant ~n places___________ O. 5-1 

Interbedded sandy shaly clay and impure fine sand, 

weathering somewhat mealy; a few imperfect fossil 

leaves noted ___ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 30 

Coarse, irregularly bedded mealy tuffaceous sand, 

indurated in part to irregular, more or less nodular 

masses. The sand is mainly quartz but contains 

a considerable percentage of volcanic material, a 

few pebbles, and a few fragments of fossil wood. 

Only 15 feet is exposed at the lower end of the 

bluff, but the sand rises upstream, reaching an exposed thickness at the upper end of the bluff of 35 

126 

The molluscan species found in the glauconitic 

sandstone are for ~he most part poorly preserved and 

with one questionable exception have been only generically identified. The bivalves include Nucula, Ostrea 

soleniscus Meek?, Exogyra, Pecten, Plicatula, Pholadomya, Isocardia?, Aphrodina, and Oyprimeria; the 

univalves are represented by Gyrodes?, Apporhais 

and several unidentified forms; and there are two 

chambered shells belonging to the amnlonite genera 

Metoicoceras, and Metengonoceras. Although in the 

light of present knowledge of the ranges of these fossils 

none of them' afford conclusive evidence of the age of 

the containing bed, comparison with other collections 

suggests that the bed belongs to the upper part of 

the Woodbine formation. 

The tuffaceous sands at Golden Bluff are predominantly quartz but contain about 25 per cent of volcanic materials. Phonolite rock fragments fonn about 

20 per cent, and small amounts of orthoclase, plagioclase, biotite, chlorite, apatite, and calcite-glauconite 

areas that represent altered augite are present. 

ARTHURS BLUFF, LAMAR COUNTY 

Arthurs Bluff, on the south bank of Red River just 

north of Arthur City, Lamar County, Tex" is one of 

the most accessible localities for studying volcanic 

material in the Woodbine sand, being reached both by 

rail and by highway. (See pIs. 20, 25, B, and 26.) 

The bluff serves as the south abutnlent of the Frisco 

Lines railroad bridge across Red River and as the south 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLAHOMA, AND TEXAS 199 

abutment of the bridge on the highway between 

Paris, Tex., and Hugo, Okla. 

Exposures of cross-bedded tuffaceous sand occur 

below the highway bridge and at and below the lower 

ferry and extend up the face of the bluff to a level 

about 10 feet above the river. (See pI. 25, B.) The 

sand is interbedded with and overlain by dark laminated more or less sandy clay, which rises at least 20 

feet above the river and which contains many wellpreserved fossil plants. A collection of plants obtained 

chiefly in clay above the nlain band of tuffac~ous sandstone at this locality, was deseribed byBerry,59 but fossil 

leaves were noted in the tuffaceous beds also. The sand 

is in large nleasure cemented by calcium carbonate, 

and the parts so cmnented crop out as ledges and as 

nodular and irregular Inasses a foot or more in dianleter. The sand is coarse to fine grained and is olivegreen when fresh but changes to yellowish green on 

weathering. Thin layers of clay ironstone (iron carbonate) are COlnnlon In the sand, but at the lower ferry 

there is a lens of this carbonate ranging in thickness 

frOlll a feather edge to 15 inches. Just below the hiO'h­ b 

~vay bridge a projecting ledge of tuffaceous sandstone, 

III places 5 feet thick, contains pebbles of novaculite 

and other rocks and in its lower part lanrinated Inasses 

of clay ironstone as nluch as 3 feet in dianleter tha,t 

have been tilted into all 'positions fr0111 horizontal to 

vertical. The sandstone of the projecting ledge is 

thus a conglonlerate. 

A t the upper ferry, above the railroad bridge, a 

section is' exposed which consists chiefly of irregularly 

bedded dark-gray to greenish-gray sandy shaly clay of 

the vVoodbine fornlation rising 20 to 25 feet above the 

river. At the upper end of the bluff several lenses of 

tuffaceous sand were noted in the clay. Leaf impressions occur in the clay in places. 

The Woodbine at Art,hurs Bluff is overlain by 2 to 

15 feet of Pleistocene alluvial terrace deposits. 

The volcanic tuffs are very well represented at the 

Arthur City Ferr~T, and their unusual purity at some 

horizons and the perfect preservation of materials 

Inake this the best locality in Texas for their study. 

The color ranges fronl yellowish green to dark graygreen where perfectly fresh. The color is due to glauconitic films around the individual luineral and rock 

grains. Secondary calcite has cemented the grains into 

rounded concretions, and commonly the concretions, 

several inches in dialueter in large areas, have uniform 

orientation and gin~ an ophitic appearance to the rock. 

The rock and mineral 'grains average about 0.5 millimeter in dianleter. 

A representative specimen of the rock is made up 

of mineral and rock grains in the following proportions, 

and Jhese are inclosed in calcite: 

69 Berry, E. W., 'rhe flora or the Woodbine sand at Arthurs Bluff, Tex.: U. S. 

Oeol. Survey Prot. Paper 129, pp. 153-181, 1922. 

Mineral and rock grains of tuff beds at Arthur City Ferry 

, Quartz _ _ _ _ _ ____________ _ _ _ _________ _ ___ 10 

ovaculite_ _________________________ _ ___ 6 

Phonolite___________________________ 70 

Orthoclase______________________________ 11 

With these are minor quantities of trachytic rock 

grains, pumice, augite, hornblende, biotite, magnetite, 

black spinel, apatite, zircon, tourmaline staurolite 

siderite, and phosphatic grains. ' , 

In all the specimens phonolite is the dominant 

igneous rock material, but traC?hytic volcanic rock 

fragments, orthoclase, and small quantities of dark 

minerals are always present. The phonolite grains 

have been largely al tered to a green " chlori tic" 

material that chemical tests seem to indicate are 

glauconite. 

GARRETS BLUFF, RED RIVER, LAMAR COUNTY 

The next locality west of Arthurs Bluff at which 

the main bed of tuffaceous sand of the Woodbine has 

been examined is at Garret:; Bluff on Red River about . . ' 18 miles northwest of Pans, Lamar County, Tex. (See 

pI. 20.) The section is in the edge of a Pleistoc.ene terrace that lies about 25 feet above low-water level, and 

the upper 15 feet of the section is composed of river 

alluvium. 

The tuffaceous sand is exposed beneath the alluviuIn 

for about 100 yards along the face of the upstream 

end of the bluff. The sand is coarse, greenish, and 

cross-bedded and is made up of quartz sand and volcanic materials in differing proportions in different 

parts of the bluff. One sample was obtained that was 

composed largely of volcanic materials. The sand is 

unevenly indurated, in places exhibiting round concretionary masses. One relatively small lens of hard, 

dense shattered iron carbonate was observed. A few 

pieces of silicified wood were noted in the sand. The 

tuffaceous sand dips perceptibly upstream and is 

underlain first by several feet of dark laminated clay 

an~ belo~ this by nlassive purplish-mottled clay,_ 

whICh chIefly makes up the bluff below the alluvial 

covering for the remainder of the distance downstream 

to the lower end of the bluff which has an estimated 

length of about half a mile. The section is very similar 

in its lithologic characters and in the succession of 

beds exposed to the bluff at Silver City Ferry in Red 

River County. The tuffaceous sand at Garr~ts Bluff 

has a characteristic nlineral and rock composition 

similar to that at Arthur City Ferry. 

HYATTS BLUFF, FANNIN COUNTY 

Hyatts Bluff, on the south bank of Red River, 7 miles 

northwest of Ravenna, Fannin County, Tex., reveals 

the westernmost observed exposure of tuffaceous sand 

in the Woodbine formation. (See pIs. 20 and 27.) 
200 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

The exposure, about half a mile long and 25 feet high, 

is in a steep slope and cliff that rise from the water's 

edge. The upper half of the exposure show~ dark 

laminated clay interbedded with thin layers of greenish 

tuffaceous sand. Both the clay and the sand contain 

nlany nodules and lenses of dark-gray clay ironstone 

(iron carbonate), some of them 2 inches thick, and 

in one layer of clay marine invertebrate fossils were 

found. The lower half of the exposure consists of 

greenish fine to coarse-grained cross-bedded sandstone 

in which there are a few invertebrate fossils and some 

clay ironstone both as pebbles and nodules. Some 

of the sandstone on weathering takes the form of 

spherical masses, the largest a few feet in diameter. 

The rocks in the exposure at this locality were described 

by Stephenson 60 in 1918, but the tuffaceous character 

of some of the beds was not then recognized. " 

The tuffaceous sands from Hyatts Bluff are predominantly volcanic material, but with this is an unusually large proportion of siderite in rounded grains 

with a radial habit. There are many rock grains 

made up of quartz and feldspar in" a greenish clay 

matrix, and these evidently represent fragments of an 

older sedimentary rock that have been transported to 

their present location without disintegration. The 

presence of volcanic material in the grains indicates 

that redeposition has taken place since the first 

volcanic activity. The phonolite fragments are unusually well preserved, but associated with these are 

trachyte and pumice fragments. Therefore both 

phonolite and trachyte have contributed material to 

form the beds at IIyatts Bluff. 

PHONOLITE TUFFS OF LOUISIANA 

Volcanic tuffs of the phonolite type crop out on the 

Prothro salt dome, in T. 14 N., R. 6 W., Bienville 

Parish, La.,61 where they form beds 75 feet thick that 

sta~d almost vertical. Volcanic material of the same 

kind has been found in the"Rayburn salt dome, in 

T. 15 N., R. 5 W., Bienville Parish. It has also been 

found at a depth of 2,945 feet in sec. 28, T. 14 N., R. 

6 W., Bienville Parish, about 3 miles south of the 

Prothro salt dome, and at a depth of 2,456 feet in a 

well in sec. 16, T. 22 N., R. 3 W., Claibourne Parish. 

Specinlens from the Prothro dome were collected by 

Spooner, and the minerals and lithology were studied 

by Ross and the fossils by Stephenson. The fossils 

indicate, according to Stephenson, that this rock is 

younger than the Eagle Ford clay and is probably 

of the age of the typical Austin chalk and of the 

Tokio formation. 

The tuffaceous sand that crops out in the Prothro 

dome, although younger than the phonolitic tuff beds 

60 Stephenson, L. W., A contribution to the geology of northeastern Texas and 

southern O!dahoma: U. S. Geol. Survey Prof. Paper 120, pp.145T146, pI. 25 A,1918. 

61 Spooner, W. C., Am. Assoc. Petroleum Geologists Bull., vol. 10, pp. 245-256, 

1926. 

in Arkansas, Oklahoma, and"Texas, differs from them in 

no essential characteristic. The approximate proportions of its rock and mineral components are listed on 

page 194. Small, well-round edgranules of phonolite 

low in dark minerals are, next to quartz, the most 

abundant material in the rock. Orthoclase is present 

in considerable proportions, and augite, plagioclase, 

hornblende, titanite, biotite, magnetite, black spinel, 

apatite, and zircon are igneous-rock minerals that 

occur in small proportions. Minerals that have developed since deposition are glauconite, siderite, 

calcite, and pyrite. Metamorphic-rock minerals are 

garnet, tourmaline, and staurolite. The beds are completely cemented with calcite like some of those in 

the Texas areas. Two types of glauconite are present; 

one, consisting of small -rounded blue-green granules 

composed of overlapping crystal plates, is the normal 

glauconite that is believed to form on the sea bottom 

during sedimentation, and the other is the yellow-green 

material that formed after sedimentation ceased and 

replaced mineral grains and rock fragments. The 

beds at the Prothro dome differ slightly from the tuffs 

of Arkansas in containing marine fossils, a larger proportion of the marine type of glauconite, and a little 

plagioclase. Volcanic material of the saIne type occurs 

in the Rayburn salt dome, about 5 miles northeast of 

the Prothro dome.62 

RILEY PLACE AND TWIN KNOBS, PIKE COUNTY, ARK. 

The best exposures of the peridotite tuff "(?) are on 

the Riley place, in the W.Y2 SW.U sec. 22, T. 8 S., 

R. 25 W., half a mile northeast of the Ozark diamond 

mine near Murfreesboro, Pike County, Ark. (See pI. 

20.) The ~aterial, which was studied by Miser in 

1912, was revealed at the time of examination in a 

well, a pit, and two trenches. Marion Riley, who 

dug the well, says it was originally 41 Y2 feet deep and 

that the tuff (?) extends to the bottom and the well 

did not go through it. The well at the time of examination was only 18 feet deep. The pit south of the Riley 

house is 12 feet deep. The bed here consists of a 

greenish-yellow coarse-grained earth and shows lamination and cross-bedding. It consists principally of 

well-rounded grains of quartz sand intimately :mixed 

with possibly an equal or larger quantity of altered 

serpentine grains and a little mica in small flakes. 

Some quartz pebbles and fragments of gray sandstone, 

semivitrified clay, black shale, and weathered peridotite are also present. A horizontal layer of clay and 

several lenses of clay lying along bedding planes were 

observed. Some diamond prospectors have thought 

that the tuff (?) bed is weathered peridotite and that 

i.t forms a part of an eastward extension of the peridotite body that is exposed half a mile to the southwest, 

near the mouth of Prairie Creek. The mineral com· 

62 Spooner, W. C., op. cit., pp. 260-265. 
WATER-LAID VOLCANIC ROCKS IN ARKANSAS, OKLA~OMA, AND TEXAS 201 

position of the bed and the arrangelnent' of its material, 

however, show without doubt that the bed was waterlaid. The bed apparently lies at the base of the Tokio 

formation (Upper Cretaceous) in this locality. 

Another exposure of the peridoti te tuff (?) was 

o bserved in 1912 by Miser in two slnall pits on the 

north side of Twin Iillobs, near the center of sec. 22, 

T. 8 S., R. 25 W., a nlileeast-northeast of the Ozark 

dial110nd lnine. The following section was measured 

on the north slope from the base to the top of the 

north knob. 

Section oj Tokio formation at Twin Knobs 

Feet 

Gravel on top of hill and on slope; in places there are exposures of clay _ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 60 

Gravcl___________________________________________ 20 

Clay; the earth shown in the two pits is near the middJe 

of this bed; altered serpentine grains and mica are present in the materiaL ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 40 

Gravel (base of Tokio formation) ____________________ 10± 

Clay (Trinity formation) ___________________________ 10± 

DIAMONDS IN VOLCANIC DEPOSITS OF WOODBINE 

AND TOKIO FORMATIONS 

Diamonds have been prospected for in the peridotite 

tuff of the Tokio formation on the Riley place, half a 

mile northeast of the Ozark diamond mine, near 

Murfreesboro, Ark. Search has also been made for 

them in volcanic tuff in the Woodbine formation on 

and near Mine Creek, from 3 to 4 Iniles north of N ashville, Ark. (See fig. 17.) No dia~onds have thus far 

been reported fronl the Riley place, but the discovery 

of five slnall stones has been reported from the Will 

Sanger place, 4 Iniles north of Nashville, and three 

small stones have been reported from the George Power 

place, 3 miles north of Nashville. (See fig. 17.) 

Some stones nlay occur in the peridotite tuff' (?) 

on the Riley place and at other loealities of such tuff, 

but it does not seCIn likely that the diamond content 

would equal that of the dialllond-bearing peridotite at 

the mines near Murfreesboro, Ark. This conclusion 

apparently follows fro In the fact that much sand and 

sedilnentary clay are component parts of the tuff. 

The discovery of additional stones may be reported 

fr0111 the volcanic tuff of the Woodbine near Nashville, 

but the fact that only a very small quantity of peridotite fraglnents-if any actually are present~ccurs 

in t.he tuff leads to the conclusion that not more than 

a few stones \vill ever be found in the tuff. 

The peridot.ite tuff (?) on the Riley place, contains 

pebbles of peridotite and grains of altered serpentine 

that were washed from an exposure of peridotite or 

were ejected as fragluental In a terial from voleanic 

vents. This lnaterial apparently lies at the base of 

the Tokio formation in this locality. To determine 

whet.her or not the lnaterial contains diamonds the 

Ozark ~1ines Corporation washed 1,000 loads (16 

cubic feet each) of it. No diamonds were found. 

The prospecting for diamonds on Mine Creek 4 miles 

north of Nashville has been done at times by various 

persons. The work, which has been done on land belonging to "\"Vill Sanger, consisted of digging volcanic 

tuff from the bed and bank of the creck and sinking a 

pit 20 feet deep on the west side of the creek. During 

the work a small sluice trough was used to separate 

grains of transparent feldspar from the claylike material inclosing the feldspar grains. The strata exposed in the bed and banks of the creek at this locality 

consist of greenish volcanic tuff containing lenses of 

gravel, the pebblcs of which include both igneous and 

sedimentary rocks. The tuff is a part of the main tuff 

bed in the upper part of the Woodbine formation. 

Some persons have thought that a part of the material 

in the tuff at this locality was derived from peridotite 

and that consequently the tuff might be diamondbear-ing. That a very little of it was so derived is 

likely, but the microscopic study of the tuff by Ross 

failed to disclose any fragnlents of peridot.ite. Prospecting that was done here in 1920 by Captain Dixon 

is reported by him to have led to the discovery of five 

small diamonds, which have been present~d to the 

American ~tfuseum of Natural I-listory. 

Three small diamonds shown to Ross and Miser in 

1923 are said by George Power to have been found in 

that year on his place in sec. 11, T. 9 S., R. 27 W., about 

3 miles north of Nashville. (See fig. 17.) Mr. Power 

says that two of the stones, one a light-yellow stone 

weighing about a third of a carat and the ot.her a white 

stone weighing about one-fifth of a carat, were found on 

the pile of material obtained from digging his well in 

1919. The well passed through 14 feet of gravel and 

then penetrated 36 feet of greenish and gray material 

without passing through it. This material, although 

Illuch weathered from four years' exposure on the surface, is apparently volcanic tuff. It was in tIllS apparent volcanic tuff that Mr. Power says he found the two 

diamonds. A third stone, white with a flattened ricelike shape, was, according to Mr. Power, found by him 

100 yards southeast of h1s house and thus some distance away from the material reIlloved from the well. 

DEPOSITS OF KAOLIN (ALTERED VOLCANIC 


MATERIAL) 


Beds of kaolin occur in the Tokio formation in the 

hilly, wooded region between Murfreesboro and 

Delight, Ark. (See pI. 20.) The kaolin, as explained 

on pages 186 and 187, is probably altered and reworked 

feldspathic material derived from volcanic ash. It 

occurs as horizontal layers near the tops of hills at 

several localities. The greatest thickness observed 

by the writers is 5 feet, but the greatest reported 

thickness is 9 feet. The deposits have been prospected, and the kaolin is reported to be a satisfactory 

fuller's earth for refining edible oils and petroleum. 
202 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1928 

One of the best-known occurrences is at the Adams 

kaolin pits, on land of the Ozan Lumber 00., in the 

NE. SE. sec. 24, T. 8 S., R. 24 W., 5 miles eastsoutheast of Murfreesboro. Here a 5-foot bed has been 

opened by three or four cuts on the hill slopes. The 

kaolin is underlain by a bed of sand fully 32 feet 

thick and is overlain directly by sand and this sand in 

turn by gravel. The sand and gravel overburden on 

one hill is 13 feet thick and on a near-by hill, southwest 

and west of the first pit, 20 to 25 feet thick. The bed 

lies horizontal. Apparently not enough prospecting 

has been done to determine the extent or continuity 

in thickness of the bed, though the thiclmess in the two 

cuts examined by the writers is 5 feet. 

The kaolin at the Adams pits is chalky white to 

creamy, but the lowest layer, a foot thick, has a lavender color. The kaolin is very fine grained, breaks 

with a conchoidal fracture, and readily absorbs water, 

sticking tightly to a person's tongue, but it does not 

become plastic even with fine grinding. It shows laminations along which it ·splits with some difficulty, and 

it contains a few fossil leaves, a collection of which 

was obtained from the, two principal openings. The 

collection has been studied by E. W. Berry and found 

by him to represent an Upper Oretaceous flora. 

A second locality, which is about 1,000 feet eastnortheast of the Adams pits, is in the SE. ~ NE. }~ 

sec. 24, T. 8 S., R. 25 W., on land of the Grayson-~fcLeod Lumber 00. The locality has been prospected 

by several pits, but the results are not known except 

that a 5-foot bed of kaolin similar to that at the Adams 

pits was found. 

The kaolin on the land of the Ozan Lumber 00. and 

the Grayson-McLeod Lumber 00. has been tested by 

comnlercial firms to determine its value both as a 

china clay and as a fuller's earth. Test pieces of china 

made from the clay are said to have been of excellent 

quality except that the color of the fired china was 

cream to yellow. Tests are said to show that the kaolin 

as fuller's earth has proved satisfactory in the refining 

of both edible oils and petroleum. That the kaolin 

has the properties of fuller's earth was verified in the 

chewical laboratory of the United States Geological 

Survey by testing a sample collected by Miser from the 

Adams pits. 

Thinner deposits of kaolin were examined by the 

Arkansas Geological Survey some 35 years ago. One 

of these, containing 2 feet of kaolin t.he upper foot of 

which is pink and the lower foot white, occurs in the 

NW. ~ SW.~ sec. 19, T. 8 S., R. 24 W.63 Analyses 

are given below. 

Analyses of kaolins from Vaughn Creek, Pike County, Ark. 

[Dr. T. C. Van Nuys, analyst] 

Upper bed Lower bed 

Silica (Si0 ) ____________________________ 48.87 47.39 2

Alumina (AbOa)________________________ 36.51 34.67 

Ferric oxide (Fe20a)_____________________ .98 2.31 

Lime (CaOL___________________________ .19 .32 

Magnesia (MgO)________________________ .25 Trace. 

Potash (K20)___________________________ ________ .20 

Soda (Na20)___________________________ ________ .39 

Watec ___ _ _ __ _ _ _ _ ____ ______ __ _ _ _ _ _ _ _ __ 13. 29 13. 89 

1----1---­

100. 11 97. 17 

Water ~t 110° to 115° C_________________ ________ 1. 00 

Other reported deposits in the same vicinity as the 

three localities described above are briefly described by 

Branner. Some of the thicknesses reported to lllembers 

of the Arkansas Geological Survey were as great as 

9 feet. 

A 5-foot bed of kaolin like that at the Adams pits 

was reported by O. W. Adams to lie in a small hill in 

the sW. ~ SE. ~ sec. 24, T. 8 S., R. 25 W. The 

overburden of sand and gravel is said by Mr. Adams 

to be 15 to 20 feet thick. 

A bed of kaolin 23 inches thick was observed' by 

Miser in 1909 in a cut and pit in the NE. Ji sec.' 29, 

T. 8 S., R. 24 W. It is pearly white, is free from sand, 

and does not appear to be plastic. It is closely laminated, and thin films al'e stained red and yellow along 

the laminae. 

Two pits revealing hard nonplastic kaolin were 

examined by Miser in 1909 in the southeastern part of 

sec. 9, T. 8 S., R. 24 W. One of the pits showed 24 

inches and the other 28 inches of white kaolin stained 

with iron oxide along many joints and laminae. The 

kaolin is underlain by sand and is overlain by sand 

and gravel that probably attain a thickness of 15 to 

20 feet on the top of the hm. 

63 Branner, J. C., The clays of Arkansas: U. S. Oeol. Survey Bull. 351, pp.148-153, 1908.