UNITED STATES DIWARTMENT OF THE m&$f# ENT Or Harold L lckes. SecteEary

GROLOGICAL 9tFRVET RECEIVED

W. C. Msndmhmll. &ub+ FE; 2 2 1938

Bulletin 880-D NNEAU, ALASKA

-

THE ESKA CREEK COAL DEPOSITS + MATANUSKA VALLEY, -ALASKA '

BY

RALPH 'TUCK

CONTENTS

Abstracf---,--,---------------,,-,,.,*~,,*--*-,--,,,-,,-,,-,-, Inltrodud~n--,-,,-----------------.---,-,~.,,-,,,,,,--,--,--,,-,,

bffon,,-,,,,-------*---,*-,-,-,,--,,--,,,*,.,,,,,,-------- m n t invdgation md seknowIedgmenta ,,,,--111111111-11---11

Topoephy and drainage- - - - - - , - - - - - - - - - -- - - - - - * - - - - - - - - , - - - - - -- - General geologic featurea of the Mstanwka Valley ,,.,,,,,,-,,,-ureure--,. Btmtigraphy --,-,,----- ----iiii-iii--------.- -,-,,,-,,,,,,,,,,-,,,

Principal fmtnres ,,-, - - - - - -, , , , - - - - , , , , , , , , ,-.,- -, , , , ,, , ,, - -, , , Cbickaloon formation- - - - - - , , - , , - - - - - -- . , , , - - - - - - - - -, - -, , , , , , , , E d a ~on@omemh,,,,-------------------------,-----,---~----- Quaternary deposit~-- - - - - - , , , , , , , - - - - - - - - , - - , ,~-- - - -~-- - - - - - - - - -

Slide rock --,,- ---- ---------- ------------.---- --,---------

GlaoiaI and alluvial deposit~,-,.--.----.-,------.----------- medu~e-,---,----,,-*.,,,,,,--,,,"*----,----~---,---,,,-,-,,,-,,

h . i n d ~ f ~ t ~ r e a , , - - - - - - - - ~ - ~ ~ ~ . - - - - - - - - - ~ - - - - - - - - - - - - - - - - , , , , Faults ----,----,,--,-, ----------,-: ---,-----.----- ,.,-,,,,,,,, depsitB,- - -,-,,,- - ---,------- - ------------------ --*-,-------

General oocumce,-,,--,-,,,,,-,---,---,--,---------.-------- Character of the a o d ,-,, - -, - -,, -- - -, - - - -- -- - , -- - -- - -,- , --- -- - - Miningopemtlons-------------,-----------.---------------,----

E~kadne, ,+----- , - ----------------~- , - . - -------------- , . Evan Jonmmine-,-,-,--,---,----------------------------.

Coal exposures- ,, + - -, - -,-- -- - -- -- - - - - -- - - - - -- - - - - - - - - - ----- - - - CoaI beda in the fib mlne ,-,-- ----, ------- ----------- -,-- - Coal WE in the Evan Jon- mine ,--,-,-,,,,--,,-., --,--- - -- Coal be& locakd by W n g -,-- - -,----+-,.--------------- ,-

CoaI beds exposed by mrfaoe prospeeling- - -, - - - - - - - -, - , , , , , . Future rniningoperations -,,-,,-,- t t t t t - t t - + t t t ,,--,-,---,-,,,,,

Index,,,, ,,, ,- - - ,, ,* - - ,,- -------,------*--- - - - - -- -- - - - --------"-- --

ram 185 185 185 1

185 'I

187 Z

188 189 C

189 189 195 195 195 198 196 196 197 200 200 201 204 204 204 205 205 200 208 208 210 213

ILLUSTRATIONS r-

d P L A ~ 11. Topographic and geologic map of ther~aka Creek eod depoelta, S

Matanuska Valley, Alaska ---,-,--,--,-----,---,-,-- In pocket 13. Gealogio sections of the Eska Creek coal deposih, Matanusks

Valley, Alaakta ,,,,,,,-,-,----,--,------,-,---,- In p k e t 18, Beotions of principal cod Beds in vicinity of Ebka Creek,,, In pocket 14. Loga of churn-drill bolas in d o i d * of &ks Creek----,, In pocket

THE ESKA CREEK COAL DEPOSITS, MATANUSKA VALLEY,. ALASKA

m The o o d dapoaltn In the vicinity af Eake C w k , s d ttlbufarry from the

north C the Matanuska River, are a pad of the Matanuska cod field, One of the two oommercid coal-producing diafrfcts in Alneka, this field is in the south- oentrsl part of the Territory, at tho Imad of Cook hlet. It i~ 170 miles from &w&rd, the oman teminua of the Goverment-omed and -operated Almka %iltoad, and ia aerved by a brench line of t b t railroad.

A blgh-volatile bituminous aoal has been produced in the vicinity of Eaka Creek since 3917. The eod ocoura in the Chickdoon fomt ion (Eocene), which, in thh arae, Is composed of over 2,000 feet of nandstone, bale, and inter- bedded coal -. Tho Eaka conglomerate, mom t b n 1,100 feet thiok, ovwlies the Chickdoon formation. Both the coal bede and the intervening sandatone and ahaIe, comprisInp; the Chickaloon formation, vary in thfcknees and composi- tion within short diatanceu. Over 20 coal beds bring a thicknees of more than 3 feet am known to occur. Moat of the coal b d s are from 3 to 5 feet thick.

The underlying rock structure is exprsaaed by much of the topography. Wish- bone Bill, the dominant topogrphic feature, rcflecte the major structural feature, which ia a southweatward-plunging syncline. Strike and tmnsvem faulta me numeroue. The transverse favlta are usually normal and have the greater dlspleoemant, some of them more than 300 feet. The gtructure h e strongly ~Rected mining opaatIone: it hsa increased the c o d of development and mining and hae decread the quantity of recoverable coal and the production d lump coal.

Mast of the c a d reewes sre w e d of Eska W, on tha north Bide of WfShbone Biu. Ia epita of the detrimental effect of faulting, there are r e m e a of mamy million tooa of reaoverable coal above the preeent tunnel lev& and an equal if not grsaCr amount blow.

. - hc&m.-The Matsnuska Vdey, which separates the Chugach ?# Mountains on the south from the Talkmtna Mountains on the north, u

is in nouth+entral Alaska, at the head of Cook Inlet. Here is one of the two oammercial coal-producing fields of Alaska. a k a Creek is 6 ail- eb~E of Moose Creek; both am tributaries from the no& to the Matanuaka River, and their c o w are roughly pardel. All

. the coal now produced from the Mv~ataausb field comes from an m a in the mlleya of &me s treas . The parh of the cod field described in this report is about 3 square mileg in ares and extends westwmd from Bka Creek.

185

186 Y ~ R S L RESOURCES OF ALAS= EBB

Both the M o m Creak and Eska b k eoJ fields are a m d by branch.linea of the Oovernmmt-owmd and -opemted Alaska Railroad. Anchor*, the headquartem of the railroad, is 60 mites dietant, and Sewwd, its ocean terminus, about 170 miles.

- P ~ e m i n m d i g k and a&m&dgmn&.-The pment investiga- tion is a continuation of the cooper&tive work: of the Alaska Railroad and the 'United Statm Geological Sway, made possible thmugh an appropriation in 1931 for the investigation of minerd resources in the area, tributarg to the railroad. In the spring of 1934 the Ala~ktka Railroad wquestd tbe writer to xeprt- on the condition of its coat- leaaing unit 7, which is held for the emergency production af coal. It hm been the general policy of the Government, strictIy adhered, to by the Alaska Railroad, to ancourige the development ,of the coal fielda through private initimtive; but in 1933 one of the producing mines was accidentally flooded, and in 1934 mother p d u c e r ceased operations because of financial diEcdties. This created a situation in which the railnrttd waa dependent upon one mine, and in the event of a mine &aster its fuel mpply m d d have been jeopardized. To f o ~ t a I l such e situation nnit 7 was mapped geoIogkally and top+ graphically on a scale of 200 feet to the inch, with a.10-foot contour ht~rva l , and a program of putting the property into s stand-by condi- tion wm begun, In 1935 devehpment work on the railroad's cad lease was continued.

To determine the extent of the coal resew= and ta aid mine develop- ment, the Gdagieal Surrey recommended continuation of the map- piog of the me1 beds on s detailed scale. Upon the approval of this m~l~mends t ion by the railroad, the larger part of unit 6 was mappad ia tha summer md fd of 1935. Eventually the stmay will be extended to Mooee Creek ta embrace what is now the entire producing areaof the Matanuskacoal field. Amale of 400feet to the inch with a 20-foot contour i n t s d was used in mapping unit 6, and the topqpphy of unit 7 h~ been reduced ta that scale on plate 11.

The writar has been materially aided by the earlier published reporb of Martin and Chapin a and by unpublished reports of Caplt, W. P. T. Ha, of the United States .M&e Corps; B. W. Dyer, former Tersrtdial &e.hspecto~; Sumner S. Smith, iomer auperinhndent of the.Esk3ka mine; B. D. Stewart, now Commissioner of Mines for the Territory of Blaaka; and J* J. Corny* former Bureau of Mines and United States Geological Survey cod-mining engineer. Most of the

1 Martiu, 0.0, a d gS, F- J, -and u d @-el& d &o l o w M-mh V d h ~ U. 8, Otdol. 8 u n - e ~ Ed. bM, 1813. M d n , O. O., h l o g l e probhm at the Matramb cod mines: 0 . 8 . W!. B M Y a~n. rn gp. 288rw 1 1 0 .

I c b ~ ~ l n , T ~ B W I O ~ MMWJ d m w m b in tbr ~ r b n h OR^ w: U. B. M. a m ~ t l l l . ns, pp. 131-rm, I Q ~ V. a a d . B- Bun. nr, pp. 197-leg, leal.

toaI m a l ~ md some of the mewrements of the wd mtbm w e n f d h d by M. L. Sharp, of the Burmu of Mines, Anchoraga, Alaska. Through the cooperation of hwhderson , pmiden t and suparintend- -ant of the Evan Jones Coal Co., free actleas ta the company's mine workings wm readily granted. Considerable information was fur- niahed by Evm Jones, former mine foreman of the Eska mine, long identified with the development of most of the coal rninw in this region. T. N, Scott waisted in the topgrttpbic mapping. The fullest cooperation waa given by Col. 0. F. Oldson, general nanqer

4 of the Alaaka Railroad, and other officials. . -* TOPOQIUFEKY DRAlNdlaB

A The dominant topographic feature of the area is Wiabbne m1, whom name ia truly dwriptive (pl. 11). The hill lies midway between M w and Eaka Creeks and is elongate in a northemtrsouthwest dimtion. On the norkh, east, and southeast sides, it is encircled by clSs 50 to 300 feet high, scalable in only s few p l m , which make it an impfesaive landmark in. the lower Mtbtanuka Valley. Westward it slopes gently to Moose Creek. Most of the minor ridgm have t m d a padel to that of Wishbone EMI. There are many unusud topographic features, such as smooth, uniform slopes, terminated on one or more sides by cliffs; asymmetric ridges, many of them with irhep north dopea snd.gentle south slop~g; and G U P P ~ ~ I ~ ridges. All t h w land forms reflect the underlying rock structure.

The drhage of the western part of the mapped area flows south- weatward into swamps and lakes, which have no surfaoe outlet. The s e v s d small em& in the NES sec. 18 flow narthwsrd into s e w a p that 63epmtes Wi~hbone Hill from the Tdkeetna Mounhhs scad ultimately d& into MQCM C w k . The eashm part of h e area, including Slipper Idre, is drained into &ka Creek. &ka Cmk bas its murce in a number of small tribukieg which

head wainst the muthern flank of the, Talkwtna Mounhhs, 8 e v d d e s to the north. The headwaters of the creek, al&ough md in

+ area, me often subject to torrential r d d l s , whose deBkructiva -- iduence is usually moat severe in the portion of Esks Creek shown

3 on plats 11. Here the flood plain of Eska Crmk is only a b u t 200 feet s wide, with steep w d s on bob11 side^. During early mining operations

aome of the camp and mine build@ were constructxd on this flood plain, but high wabr ha8 destroyed m o ~ t of those so situated. The greatar part of the high water comes from the west fork of Eska Creek, which d m h a part of the area on the north side of Wishbone Hill but has its eou~.ce in a large epring high on the south aide of the Tdkeetna M o u n h s . GenemlJy, August is the parid of high water, although the deetruetive f l d s usually occur only every a or 4 para.

G f E N m UEOLOGXC FEATURES OF TlTE MATbEfUBgd VALLEY

The formations of the Matanuska Valley are predominantly Upper Cretaceous shale and sandstone ; Tertiary arkoee, conglomerate, smd- stone, and shale, with interbedded coal setuns; and Quaternarg glacial rand alluvial. deposits of gravel, sand, clay, and boulders. Older find more complex igneous and sedimentary rocks am exposed in the valley walls, which are from 4 to 6 miles apart. In the eastern part of the valley numerow dioritic sills and dikes intrude the Cmtaceoua and Tertiary wdimentsry rocks, bnt to the west they nre progre~ivdy less P abundant until in the vicinity of Kska and M m e Creeks they are 2 entirely absent.

The valley is in part structural as well as erosional, having been .r

ttn ares of faulting and folding since the Cretaceous period. Most of the folda and a part of the faults trend east, paralleling the trend of the valley. A major f~dt bound8 the north ~ i d e of the vdep and brings the younger formations into contact with an older granodiotih batholith, which forms the main maw of the Talkeetna Mountsins. It is pmbable that a major fault bounds also the south side of the valley, because there the vdey formations lie against the older and more highly deformed slate, graywacke, greenstone, and diorite that comprise the bdk of the Chu~acb Mounths. Thua, lying between these two major faulta, the valley is assentially a graben of folded and faulted Upper Cretaceous and Tertiary sedimentary rocks. Both strike and tramvem faulta are numeraus, and they have caurmd most of the difficulties of mining.

Moat of the Tertiltry cod-bearing rocks occur in ~ ~ a r & & p a d areas, many of which are e n t i d y surrounded by Crst~eous rocks, The ctod-bearing formation is much less mistant to weathering and erosion than the Crotmeoua rocks, and ita p m m f i o n is commonly due to downfaulting into the more mistant m c b or to the pmence of a capping rock. The major part of the Moose Creek-Eska Creek coal field ia of the latter type, Wishbone Hill being composed of a welI4emented mng1omsmte that overlies and promts the coal- -i

bearing rocks. The coal mines of this area are located mound the - eroded margins of this conglomerate. .+

The coal of the Matanuska Valley increases pmgroesively in rank from the wetern to the eastern part of the valley. In the lowland of the Susitna Valley, beyond the western limits of the Matmwka Valley, only lignite is found; 10 miles to the osst of that locrtlity, in the vicinity of Wishbone Hill, the coale m e bit.uminous; in the eastern part of the valley, on Antbrarite Ridge, there are beds that approach anthracite in composition. lacreased folding and dike intrusion have contributed to t l k p w s s i v e devo la~a t ion , which h# wcurred w i t h w disbnce of 40 miles in the same formation.

ESKA CREEK COAL DEPOSITS 189

The stratigwphy-detemin~tion of the character, sequence, a d thichesa of tho individual beds Chat make up the rock formations- is of great practical vJue in the development of the coal mines in this field. If it were fully known, any outcrop would give inlomation, w i t h limitations, regarding the location of the cod beds that may lie ahva or below any recognized bed. The practical limitations are numerous faults ; the similarity of many of the rocks, which proven ts

b C a them from being easily distinguished; and the lenticdar nature, or 1: rapid change in thicknw, of the individual beds. Field work, how- - evor, will often show the prmence or absence of faults; surface strjp-

ping wiU increase the visible seatien so that it can be recognized; and, in spite of the Iemticulnr nature of the formations, approxhationer aa to the position of individual beds can be estimated. Underground work and surface stripping and trenching are constantly adding to the completeness of howledge of the strn tigmphy.

The formations in the vicinity of Eska Creek have been mpped as three separate UniMhickaloon forma tion ( c o a l - b e ) , Eaka congIomerste, md Quaternav slide rock. (Set, pl. 11.) hTatml exposures of the coal-bearing m k s are not numerous, aa they are easily eroded into smooth slopes, which rsre mually covered with vqet~tion, glacial snd allvial boulders, gavel, and sand. The Eska conglomerate, because of its resistance to erosion, is well exposed, usudly as cliffs. T h e distribution of the glacial and alluvial deposits has not been shown on plate 11, ras to do so would almost entirely obscure the underlying cod-baring rocks. The neareat occurrence

- of Cretsceous m k is in the extreme southeast corner of sec. 16, on the bank of Ealia h e k .

The cod-bearing Chickaloon formation is the oldest m h unit shown on pJab 11, and the nature of tha flora it contains indicates

+ that it i8 Eocene. These rocks underlie the entire area, but only those in tha eastern part are &own on plate 11, as in the wesbm part they

s5 t

are overIein by the Eska conglomerate. The tots1 thickness of the cod-bearing formation in this area, is over 2,000 feet.

Sandstone, shale, and interbedded cod seam make up tbe major part of the formation; shale has t.he greatest aggregate thickness. The shale and sandstone, of varying texture, are gray, drab, and craameolored. Whan fresh, these rocks are cobemt, but only s few of the aandshnea offer much resistance to weathering, Concretions cemented with iron c~rhnate ~bre common in the shde but usually are noticeable only in the werathored rock. The lower part of the forma- tion contains more ssndstone than the upper part. The following

190 MINERAL RESOURCES OF ALASKA, 1 W

~action wae mmtaured from the b r w t t o 4 the p o d in the n m crowcut tunnel that is ~ h o m on the map near the muth-central piwt of the NEX rm. 16. In this tunnei the beds dip northwest, so that the emtion as given starts with the uppermost members and the last-mentioned unih rn ttha lowest. The lowemmt beds are among t bme that are stratigmphieally the Iommt exposad in this area.

Bone- ,- - , - , , , - , - - - - ,,,, - - - - - - , - + , , , - , -a , , , , -, , , , , , , , Myehale------,------,-----,,-------,-,-,,,----,- Hsrdbri~htooal--,---+,-,----------h-,-*,-- ,,,,,,, Coslyshale-+,-----------l----,----.-,,,---,,,,,-,,, Shale-, , , ,- - - ,, -- - - - - - -- - - - - -- - - -- - - - , -- , , - - , - - , - -- &anddam, - , - - - - - - - - - - - - - - - - - - - * - , -, - - , - , , - a . , . . , , a 8hde -, -, ,,-- +-- - - - -- - - - - - - - - - +- , -- - - --- , , - - ,. - , , - - Upper ghaw-&bed -,,,-------,-,,,, ,,-, ,,,,,,.,,,, C o a 1 y a W e , - - , - - - - - - - - - - - - - - - - , - - - - - Y Y Y Y - ~ Y ~ ~ - - ~ . ~ ~ LouFer Shaw ma1 bed-, ,,------,,-----,,-,.-,,----. ,,

Coaly ahale,------------------,-----,,,.---,-----+,, Fine-gminedsandstone, -,-----,,-----.,-,---------,- Cody shale-- --- ---,--- --,---,- - *--,---- --, ---,,, --- - Ma* cod bd:

Coar,,------,------------,-*------*-----+---,-- Coaly awe- - -, - , , , , , - - , , -, . - , , , - - . - , - - , , . , - , - , , Gal,, - - - - - - , , , -, - - , * * -a , - * * - " - - - * * - - - - - - , - --

Bone -------,---,.,-,,,-,- -,,-,--,*-.----,- ----,-------

awl -----, ---- - -, ," -----I - - ,- - - - - - - .- - * - - - - - * , - - + * - , --- Cody &ale ,,-,,-: ,-,,,,, ---,---*-----,- ---,,-------

Pinegrsined aand~tane with ooal veinleta ,-,,, ,--,,, ,--- Cod land bone- -, , , , , , , , , , , , . , , , . -, - -, , , , , -, - -, , - - - . Cody ahale -,,,,,-,-,.,,, -- --------- --,- ,----+--- - - -

Gray nhle -,,,,,,.,-,,,,, --- - - . - - - - - - - - - - - - - - - - - - - --- CoalyahaIe,-- , . - , . - . --- ,--------------------------- Concretionary grey shale -,--------.-,-----+----------

Nodular and banded 8h&,,,,,.-,,,,,.---------k----- Bhale with tMn coal sestna ,,-,,,,,, - ,---------,, shale,,,,,---,---,----.,-*--*--d---------+----*---- Sandetone,,,,,.,,,,,,,,,,,,--,.,-,---------,-,---,, Bhale,,,,,,,,-,,,,,--,,--,,----,,------,*--- Coaly mhrde d t h 1- to a-inch -ram,, - - - - - . - -- -- - mB - -- mB mB

Coal--,---.,,-,,--*,**,-+--,,,-----,------ Well-oameuted ssnddw,, . - , - - , - - - - - - - - - - - - - - - , - - - - - - Gouge; amaU strike fault ,,,,,,---,,,----,,-,---,----- Gray ~hale -,,, , - - , , - , , , , ,,-, - - - - - - - - - - - - - - - - - - - - - - - - - , - Goa1,--,-h,-----,------,-,---------t----+---------- Gray # M e ,,,,,,, --,,,,, --------__- -----------+-------

Cody ~hale ,,,,,,-,-,,,,-------,,------------,,-+---,-

Gray ma&- ~hate -,--,,,------------,-------------- , C o a l ~ ohale ,,,,,,, ,--,-,,,--- -----------------,----,

Shale snd a d y ~hale ,,-,,, --------------- --,,-, --------

n. In. 8

Brommhale----------,----------------r------------ . C d y ahale ------,-,,.-...-----------,------------,--

M&ahde,, ,-------------:---------------------- Fin~gsained mndstone------.---------..--------------, Gray ~haEe-,,,,, ,----------------------------------- Brown shal~, , , , ----------- , ------------------------ Coaly ~hde--- , - , ----------- , ----------------------- Brown ahale--,,------------------------------------ Cody~haIe--,--,,,,,,--------~----~---------------- Brown ~hsle----,,,,,-.------------~*--------~-+--- My~hale-- - - - - - , , , , - - - - - -~-- - - - - . - - - - - , , - , - - - - - - - - Fineb laminated aandnbme- - -, - - - - - - - ,,- - - - -- - -- - - - - - - - Coaly shah and r few carbonized log - - - -, ,- - - - - ,, M d r e gmy sW-,,,--,-----------,--.------------- F i n w e d aanddone and i g m e n b of oarbbnbed wood, Laminsted gray shale----------------------------+--- Coal and ahale,,,------------------------,---------. &nrlstone-----------------------------,----, ,------ Gouge; strike fault-- - -- - - ,-- ----- --- -- --,-- --- Cody ~hale with a taw thin coal aenms ,,,,,---.,.------ Gray u i v e ~hale,,,,,---------------------..--.--~ m y shale and a few aarbonixed loge ,,-- ------- -,, ,-,, Laminated mndy 8- with leaf Impmwions Coaly shale,,,--,-,,---------------------,-----,---- Coal- - - - - - - - - - - - - - - - - - - - - -. - - - - - - - - - - - - - + - - - -- - - - - - CoalyebaLe,,,,,,,--,--r---I-r------------I------------ 8andefone,----,,-----------,-----------.-,----r--- Cod sndehale, , , , , , ------- , , , - , , ------------------- Canlandbona-,,,,-----------,---------,,---------- Coaly shale,--------,,------*--,-----------*--------- Shale, - - - ,, , , , , - -, , , - - - - - - - - - - - - - - - - - - - - - - - -. , .. - - - - C o d y me-----,--,--,-----------,,-,------------,--- Bandysme,,,-,------.-,-----------,------+-------- Cd,---,-,,.,-+-,,---------------------------,---- Shale-- , , ------ ,----- .--- , , , ------ . . -------------- . Coal and B M ~ ,,,------ --.-- -.-----.-----,-- -------- 8hele,, , ,-----, ,-,---------rr--------+--------------- Gray hale-------.----------,-----------.--.----+--- C~alyahare,---,,,.,,----------~--+-----*--~.-,---,, h d & a n e and soma carbnized wood,, - - - - - - - - ,, . ,--,- Gmy mmeive mndy shale -----. -, . , ------------ ,,---- Sheared ~hale and gouge; small fault-. , , - - - - -- - , . - .,, - - CarhnmeousaWe--, . , , . . ------------------------- , M d v e mediurn-gmined shale- - - - - - , . . , . ,-- ------ -. -- F i n ~ g f a i o d aandatone with carbonized wood an8 smsll

c a a l l e n ~ - ~ . , - - - - - ~ - , , _ _ - - - - - - - - - - - - - - ~ ~ ~ ~ , ~ - - - + - , - Medium- b atwrse-grained uandutone ----,------------- Laminsfed aandy able with leaf I m p d o n a ,,,,,-----,,

The beds of hale and sandstone are not persistent but vary in th ich~s& within short distances. Some of the sandstones, B U C ~

the one over the porhl of the Eska West tunnsl, are embedded. The mpid change in thickness is well illustrated by the interval be- tween the Esh and Emery ma1 beds. On Eska Creek 226 feet, of mdimentary rocks intervene between these coal beds, but t h i ~ m- quence thins so quickly that about half a mile wmt, in the northeast corner of the NE%NW$ sec.. 16, the internal between the two beds is only 125 feet. The sandstone overlying the Maitland bed shown a similar variation. On the west side of the creek it is 47 feet thick; on the east side, only 25 feet, These apparent changes in thickness are not all the result of depositional thickening and chimimg; strike faults causing elimination or repetition of the stratma are dm present in themfieTd. Howe~er, in general, there appears to be a thinning of the coal-bearing zones toward tho southwsst.

Coal beds are nurnm~~a; over 20 haeng a thiekngss of 3 feet or more are known. These beds are nU in the upper 1,500 feet of the QhickaIoon formation, and t,hep extefld within a few hundred feet of the barn of the overlying Eska ronglomcrate. Like the sandstone and ahale, the coal beds vary in thickness, so that correlation is d3E- cuIt. Some of the coaI beds have persistent shale markers, but these markers cannot always be relied upon to identify the bed. The pmi- Eion of the markers and the changm in thickness of coal are graphically ilIustrated by the eections of the coal beds on plate 13.

Two well-known p u p s of coal beds crop out on Eska Cmk: !lie lowor, known as the &kt~ ma1 p u p , consist8 of the Eska, Shaw, and Martin beds; the upper, known aa the Maitland coal group, consists of the Maitland, David, and Emery bede. These are stratigmphically the lowest beda that have been mined; dl other minable beda lie between them and the baee of the Eska conglomersh.

Umudis td A qf the coat msasurss on i%h &4uk

shale -,,,,---,-, ...................................

CbapIn ,bed-- -, - - - -, - - - , , , , - -, - - - - , , , , . - - .. - - - - . . , , , , Sanddona, -, - , ,, , ,- - - - , , , , , - - - - - - , , , , , - - - - - - - , . , , ,, Maitland bed,,---,,,,,,-------------,,-------------+- Shale with a little mndstone, - -- - -. , - - - - - - - - - * - - - - - - - - David bed, - -- - -- - - - - - -, , ,, - - - - - - - -,,,, - - - , - Shale, largely nodular -,,---------,-,----- --,-,,,,- - Eme~kd,------,------,,,,,,,--,,,,,------,,-,-,, 5% Sandstone and ahale-, ,,-------- -,,,, .-- --, -,,- -- ,-, -,, 126-286 Eaka bed -------------,,,---,-,,--,------------ * --,-- 3 Shale------,,,------------------,,,,,,,,-,,,,,,-,,., 29 ShawM--,----------,-------,-,,,,,-,,,,,,,--,,.,, 10 Shale snd bmhne-, --,-,,-, ---- -- ,,,,,,- ----- ,,,,,, 4-11 Martla bed- - - - - -- - -- - , + , ,,- - - - - - - - , , -. - - - - - - - - , - , - - 4% Shale with thin wal emma.

Beae l o d y known BS beds 5,6,7,7A, 7B, and 8 were intemeckd on - the north limb of the syncline by the crosscut tunnel of the Evan

Jones mine. This section of coal beds overfies the Eska ma1 group and probably also the Maitland, as it has not been inkmated by the new Eska crosscut tunnel and is not exposed on the baaks of Eska Creek. Furthermore, struc t u r d mnsiderations and the tenhative correlation of the; two coal beds on the eastern edge of the NEJiNEji nec. 17 as the Eska and Shaw beds suggest that the beds on the north limb of the syncline at the Evan Jonas mine are stratigraphically above the Eska m d Maitland groups.

8adian ia wassaJ tutand on nwfh limb s y d i w , Evan Jma minu

Joneervme fault. Fed 8 U e and Bne-grdned mndstone--, ,,, ---, , , , - - , - ----- , - --- 30 Bed 6 ,,,,,,,,,,,-,,,,,, ,- - - - - - - - - - - - - - - - - 5 Bhde and ahdy mdatone ,,,,-,,-,,,,---,,-,--,,--h-------- 86 R d B , , , , , ,,,,, ,-,,,,,, ,- - - - - - - , - - - - - - - - - 4 8hde and fine-grelned randatone- - - - -, ,,-----,,-,---,,,-,--, 50 G a l , bone, m'd conly shale,, ,-, ,--, ,,--,,,,,----,,---- -- 5 B h a l e , , , , , , , , , , , , - , , ~ , , , - , - , - - - - - , - , 14 Bed 7 , , , , , , , - - , - - , , , - - - - - - - - - - - - - - - - - - - - - - -I - 36 Shale md finegrained ssndstone ,--,,,,,,,,,----,----, 24 Bed 7A ,,,,,,,,,,,,,,,-,-,,- - ------- - - - - , - - - - - 6 Gray ahde ,,,,,,,,,,,,,.-,-,----,,,--,--,---- 18 Bed 7B ,.,,,,,,,,,,,,,,,-,,,----,---,--------- 4 Bhale nnd dne-grained d e t o n e , ,,,,,,,,----,,,--,--,--, 30 Bed 9 --,- *--,* ----,, *,-,*,-- -,--,--,-------- -- - - - 6 shale and f i n w i n e d sandstone d t h a few thin emma of d, 75

The d b d e on the muth limb of the syncline in the Evan Jones &s are stratigraphically the highest known in this area, with the possible exception of the little-known e x p o r n in the NEK mc. 18. Both of these p u p s of beds are within a few hundred feet of the base of the F ~ k a conglomerate, and they may be at the =me horizon. In the face of the olfff above the Evan Jonea t w e 1 no ma1 beds are expod between bad 4 and the base of the conglomerate; therefore, the I d a that crop out in tho western part of the SE5NW)S sw. 16 must be lower in the sequence. These beds are graphicdy r e p sented by mtion 48, plata 13, and lie between the north and south limb sections of the Evan Jonea mine, but they are not visible, ae they are cut. out by the JonegvilIe fault. The following ia an approximte section of the coal M a on the wuth limb of the syncline in the Evan Jones mine. A part of the cromut tunnel ia timbered, and exact memmmenta oduld not be obtained at dl pointa.

M s d sgnaltne; mdmbm and shale broken by many mi- faulte. ~d

Rhnle, d d m q md he-gmined oonglmerate- - -- ,- --- - -, - 190 &d 4 ---- *,.,*,,,- -,,,,------ *---- --------- - ,--+- *--- 3% &ale and wried 6andubne ,-,,-,- -------- -----,----- 35 Bed 3 - - - , - , , , , ~ , , , - , , , , - - - - - - - - - - - - + - - - + 8 Cody&da ,,,,,-------,.- - - , - - - ~ - - ~ - - - - - - - - - - + - - - - 8 Btd2-------,,-,-----,,4---*-------*,--------- 3 Fault with amrll dirpbment. Saud&one and shale-, , ,,,-, .,. ,,,--*, - -+ w 4 -- - -+ ------- 12 Bed 1, d y shale -,-,.,,,--,,,,.,--.,,.-,.----,------- 7 h4andane and W e with a few mm1l faulfa -,,- ,--,-----, - 105 d 0 6 Coaly shale and s mall fault ,-,,, , , . , -, , , - -, , , . , - - - - - --, 6 Bed O O - , - - : l - - - - - - - - - - , ~ - ~ h ~ , - , , - - - ~ 5 Crud14 hale; fanlt ,,-,,,- ,-. ,, . -- - * - - - - - *- - - - - - - - 1 &haleand gand-e -,,,,,,------,,,.-,-.,,-----,.--,,,- 8Q

A stratigraphic column of the total sssembloge af r;oaEbea&g mcb in thia m a can d y be peralizad, becauss of rapid change in thick- ness of iedid~d membem and the doubtfulness of eome of the cumelations that have bmn mde . Thu following eeqnence of mka and their thioka- is sug&ad, although revisions wjll undoubtedly be made as more information iagsined from development wmk.

lhka c o & o ~ able, mindstone, and m e d &omer*fa ,,,,,,,

C d beds 4,& 2,1,4 00, and btemalag mndstoae and

Unknown interval, - - - - - , - - - - - - -- , - -- - - - - - - - - - -, - - - Coal bed (SESNWg ~ec . 16) -------,-,,,,,,,-,--,,-- 8 a n W n e (SEsNWg m. 16) -,,,----,---,,- - -----, - Coal hd ($E%NW)$ see. 16) -,,---, ------ - --- - ,- ---- Unknown interval ,,,,,-,-,------------------------ Wale and Bne-grained madatone-, , , - -,, ,--,--- ---,,

Coal beda.6, 6, ?, ?A, 7B, 8, and intervening sandstone and Ue,,,--2--------------- ,+-I--------------

8hala snd firegrained mndstone ,,--,- - , - - - - - - - - - - - - - Unknownink~al-,,---,-,------------------~,--,,

Chapin coal bed -------,--. -,----,, - ----,--- ---,--- 1 B n d s t h e ,,,,,-------- ,- - - - - - ---------lr.,-,,,,, 25-47 MsitFand group of cad W-, , ------------ --- -- -- - - 110 Bandatone and sha le - - - - - - , - - - - , - - , - , -+ - - - - - - - - - - 1-286 E~kagmupafeod W,,,--.----------,--------- 52 Bhale end ssndstone withi few thm eoal beds,, ----,-,, 650

IBKA WEEK COAL WEPOEIITS . I95

The Erika mngIomenate overlies the coal-bearing formations and is exposed in the wmtern hdf of the arearea. It, crops out on the ridge imediatelg north of Jonesdle and forms the main mags of Wish- bone Rill. Because of its Te8istsnce to weathering, it forms extansive cliffs on the north, east, and southeast aid- of Wishbone Hill. The congEomerate is indurated and is composed of well-rounded pebble8 and boulders as much as 6 inchea in diameter in s matrix of sand. It is n~ually massive, and the bedding is visible only in large exposure,

> I - although in the more m d y portions cros&edding ie common. Lenses

of shale and sandstone are interbedded with the conglomerate, and, a although t$ey form only a amall part st the htal thickness, some of

them attain an individual thichess of 40 feet, ns in the south-central part of the SW%NE% aec. 17. Here the small but pronounced aouth- ward-facing dip dope, just east of the top of Wishbone Hill and at nn elevation of 2,080 feet, owes its origin to a soft bed of sandy shale that lies in tho conglomerate formation. The btal thickness of conglom- e ~ a t s ,is ovgr 1,100 feet, as illustrated by section A-A" plate 12. It i s p s t a s t jn bhe wastern part of this am, becauae of the westerly plunge of the syncline. .

- The conglomerate is conformable in stmctura with the underlying Cbickdoon formation, but the ridge n o d of Jonesville b the only locality whore the contact between the two formtttions is exposed. This outcrop ehowa the coal-bearing rocks grading into the conglom- errata.

OUATERHUP 13EpoSXT8

Side rock.-The slide rock, because of its thickness and sml ox tent, has been mapped aa e separata unit; it is present st the base of dl the conglomerate cliffs and ia very extensive on the southeast and south aidea of Wisbbone Hill, around Jonesville.

The formation is cornposod predomhsntly of a c h t i c mass of irregular-shaped blocks of Eska conglomerate, some of which are 4 0

f ..'c. feet in, diameter. In places, such a.9 the portal of t h ~ Evan Jones

mine, the dide rock is over 150 feet thick @1. 12); it commonly lies directly on tha coal-barhg rocks nnd on their contact with ths Eska

4 conglomerate. Its origin is due to tho relative difference in resistance to weathering of the Eska conglomerate and the Cbickaloon foma- tion. The mng1omerat.e is resistant, weethering to &em cliffs, whereas the underlying coal formation is easily eroded, so that the oanglom- emte is continually being undermined.

A part of the slide rock is so recent that it is not covered with vegetation, m d the nature and migin of the material ars apparent; other parh ere covered with a mantle of soil nnd a heavy grow+ of v~getation, so that their origin is not e d e n t , except by the presence

of numerous depressions, aharacteristi~ of formations of slide rock. Some of the depmsiong -southwest of J m d e and immediately south of the &ma mapped ars 100 feet deep and 4.00 feet long. Although most of the slide rock is of recent origin, some may be doubtfully regarded as preglacid.

@acid a l E d &po&ds.--Glacial boulders, gravel, sand, and silt mantle all but the teep pest slopes. The gkeakst thickness of glacial material is east of Eska Creek, ivhere 50 feet i91 indicated by the driU l o p (pl. 14). West of Eska Creek tho covering is thinner, 20 feet being the greatest thicknsas encountered in drill holes and teet pits; the average is 3 to 5 feet. Glacial boulders are found on the top of Wishbone E l l , indicating that it was overridden by the Mamuska Valley glacier. R a n t alluvid deposits are m&ed almost antirely to Eska Creek, where they form a narrow flood plain.

The dominant s t r u o t d feature is an open ~ y n c h e , strildng S. 66O hi 80" W. and plmging muthwwt, In a few placeg along the Irxis of the syncine the plunge is as much as 2S0, but. the average is about la0. (See eection &E', pl. 12.) Bmwe of this southwest plunge, formations higher in the cbal series crop out progmsivelg to the west, until-the 0perIyirig Eska mglornerate caps the hill, so that the maJ. beds occur only at eonsiderebla depth or around the rn- of the syncline,

Ea~t of Esks Creek the ayncline is asymmetric: the north lirnb,d+pa lo0 to 20°, and tbe south limb, 4s0. In the W D E 5 aec. '18 the aver* dip is 28O on the north limb asd 45' on the south limb (mw tion D-D', pl, 12), Farther west the syncline is sheper on the north side than on the aouth, which ia largely eroded.

On the north aide of Wishbone m, on the line between secs. 17 and 18, there is a gentle depression in the otherwbe steep northward- facing. dfTs @L 11). The conglomerate ahom no ePidence of faulting, and the change in dimtion of dip suggeeta a minor flmm on the. north limb of the fold at this locality. The u p p r ~ x h a t e position of the synclinal d is in&cakd on plate 11; it is faulted more than shown. on the map, however, and many of the aharp e m may be offaeta due to faulting.

Both transverse and strike fsulta are mmmon in the spcline. Many of the minor faults and fle~trrea in the coal-bearing rocks do not appear in the Eskg congIomerate, beoaw of its grwter compe- tmcs, or resistmcn to deformation.

Many of the structural details ttra reflected by the topography, and Wishbone Hill derivw i& name from the topogmphio expression of the southwestward-p'Iunghg ~puline. In the Wg em. I6 t h i d

~ynclinal plunge ie mflectd in the curving ridgea of b t a n t sand- stone. Minor data&, each aa the southwest trend of ridges and depressions, reflect tha strike of the beds. Some of the slopes, like the hilI on the line between sem. 16 and 17 and the top of Wishbone Hill, am dip slopes further indicative of the stmcture.

The dip of the formations ranges from a few degrees at the axis of the aynclina to nearly 90" in some of the faulted blocks. West of Eska Creek the averago dip of the spclhe and minable be& of md is drom 18' #a SO0.

4: FAWLTI

Very few of the cod b d s in this field, when followed more than 1,000 feet dong the strike, are not found to be faulted. The Eargmt - known virtually unfaultad coal Beam is that being mined by the Evan Jones Coal Co. On bed 8 of that company i~ a block of coal over 2,200 feet Jong and 1,300 feet on the dip, which ia broken only by ra few minor faults that have not seriously interfered with mining operatione. The practical importance of the study of faulting in this field cannot be overemphasized. The a t of prospecting, develop rnent, and -g bas been increased and the mount of recoverabls coal and the percentage of lump coal that can be produced have been decrewd by the faulting of the beds. Surface prospecting, with a preliminary study of the faulting, would eliminate many weag that

i,muId not be mined economically, and development casts would be matdally lowered.

The faults htrve displseements ranging from a few inches to several hundred feet, The transversa faultg &ow the greater mount of movement and have predominant19 southeast dips. Most of the faults: are of the normal type, so that tha southeast block bas moved down relative to the northwest block. Plate 11 shows some of the more prominent faults.

One of the h t h o w n faults on a e &ka leasing unit is the Eska fault, which is well exposed on the south side of EBka Creek in the

I southern part of the SWKSEg see. 9. Thia fault cuts the fikn,

\C S h w , and Martin beds in the old Eska Wwt workhga. Surftlce tj~rmpmting had disclosed the Eska group of coal beds west of the downthrown block, and they were picked up again after the tunnel had been driven 600 feet through the massive sandstone that overlisa the Eska coal beds. The continuation of this fault on the north side of the creek is indicated by a mawive sandstone lying against soft coaly &ales. How far it continues to the muthwest is not known, but coal outcrops in the eastern part of the NEKNW% sea. 16 are faulbd; it is probable that the axh of the syncline is o u t by tbe same fault. Near the p&al of the old Eska West workings are two transverse faults; one b h g g the Shaw and Eska coal M s together, and the other the Shaw and Martin beds. Both of these faults are

198 MINERAL, ?E;SOUIZGES OF AWSKA, 1@%

mposq l at ~0 eurfme on the steep south w d of Etika Crsek. Them am, &to geverd faulta of minor displacement in the E h West workin@.

In the old undargmund workings, an the esst aide of E t a Creek, are two tramvee faults. The northeast fault brings the Ernerg and Msrtin beds together; and the other, which is farther to the southeast, bringa the David and Maitland beda together. The northea~t fault ~trikea across the west bank of Eska Creek near the d a of the ayn-

. cline; farther to the southwest it ofiaetts the E B ~ . E>ed on the south limb of the qnl ine , having topogr&phio e x p d o n in the amall gully b in the western part of the SE)iNE% sec. 16. On bhe east side of Eska Creek it dips 72' SE., and probably it hm a &nilar inclination on the wmt side. I€ is a n o d fault, the southeast block having been w

downthrown fmm'300 to 400 feet. The fadt that bas moved the Maitland East bed into continuity

with the David Elret bed is normal, with small displacement. Becauss of the low dip of the cad beds, only a small verticd displacement (30 to 50 feet) is nec- to w u n t for the lappment 300 feet hori- - zon tal 'displacement shbwn on plate 11. This hul t has not been found on the west side d the creek, dtbough it may be p m n t undek the Emery bed on the muth limb of the spcline.

In the undergrodnd workin@ on the west bank of Eske Cseek the Maitland, David,, and Emery beds on the south Iimb of the ayncline have been cut off by fgulta that may be continuations of thme in the Eska Wea t tunnel. The Eska bed on the south limb, in the central part of the SE)4NE% sec. 16, is dm offset by what may be one of the same faults. On the west bank of Eska Creek, 'just north of the axh of'the qm-

cline, the steep dip and cru&ed mnditibn of the David and Maitland beds, as weU aa the absence of the Emev bed, indicate that they lie in a f d t block.

A mall amount of surface prospecthg has faded & disi!10se the westward cantinuation of the E s h coal bed in the northem-part of the SWflES mc. 16: perha* a'fault mcurs at this locdity. Major P * fadting batween the Eska bed of the muth limb of the syncline and bed 4 of the Evan Jon- mine is evident, as the east~ard prolongation of bed 4 and the westward exhn~ion of the Eska coal group would bring the str1ktigraphica11y highest and lowest known coal beds almost into canmtinuity. The curve of the a x i ~ of the sgnclin~, as shown on plate 11, in the SSNWJi set. 16, may be a fault. Perhaps the Eska fault ia continnous to the southwest ahd causes a part of tbis apparent displacement. T h e tabrup t termination of the ridgas at the east bound- ary of the NWgN Wg m. 16 is Jso suggestive of faulting.

The faults shown on the south-limb working of the Evan Jon= mine @I. 11) have bsen compiIed from the old mine map, as theee w o r m are now inaccessible. The magnitude of the fault that

ESRA CREEK COAL D E P O P ~ ~ 199

hrminah W e 3 md 4 on the east is not horn, but the dlepllulernenl may be e x p d at the a t u - f w by the lower elevation of the wt and of the ridge of Eska coagIomarate,

Tbe Jonmde fault 61 another northeastward-strikhg tra,nsverae fault and is well exposed in the c m u t tunnel of the Evan Jones mine about 150 feet aouth of bed 5. Here it d ip 80' S. 60' E. m d has about 3 feet of gouge and crushed rock between the wdh. The drag of the Geda indicate8 that at thia location the fadt is normal. Old mine maps show that beds 6 and 8, e a ~ t of the cromut tunnel,

L and be& 3 and 4, on the weat, were cut off by the same fault; a11 thee workings, bowaver, are now abandoned and c a d .

At the surface the Jonesville fault i~ e x p f e d by a welldefined I valley En t he SE)iNE% sec. 17. Aa a m ~ d t of the dispEacement, the

base of t h ~ mnglomerate on the aouthwardeIoping hill, eaat of the fault and on the h e between mx. I6 and 17, is 300 feet lower than

' the b a ~ of the eong1omerata west of tbe famlt and on the east end of Wishbone HiU, BO that them is that much vertical displacement at this hdity. On account of the slide m k , which obseures a11 expo- a&@, the fault has no further d a c e expression to the southwest. The ridge ta the northeast, in the muithem part of the NE)iNEK-wc. 17, d m wt show any topgraphic expression of the fault except on the north side, where the c o m e of a small, creek may be determined by it. Pmof of the fault hem is dependent on the catrelation of the cad beds uneoverod on the west edge of the N W m W 5 aec. 16. In g e n d , they agrea with M s 7, ?A, 7B, and 8 of the Erm Jonee mine, and the appsrent horizontal displacement js about 300 feat. The Evan Jones cmsscut tunnel has been driven 150 feet north of bed 8 without intelgecting any coal; if the fadt were not present, the most mutherly of the four cod be& in the we&m part of the NWjiNWJi sec. 16 should b s ~ e been enmuqtered.

The con1 M s on the east side of the NEWEX sec. 17 appear to be the Shaw and Eska beds, rn inference which would furth~r s u b stan tiate thie interpretation. If the comlations m correct, however,

w ,P the thickness between bed T and the base of the conglomerate east of

the fnul t is inadequate as compared with the thickness betweon the same beds wgst of the fault, (Compare sections B-33' and C-C', pl. - 12.) Therefam a fault is ~nspechd on the north side of the con- glomerate hill an the line between secs, 16 and 17 (section GC', pl. 12). A small &mount of surface work in the m. 17 would rtslrdiry determine the situation and would give informetion of vahls for future clevelopment at the Evan Jones mine. So far as can be learned, no records have been kept & forma-

tiom ancountered at the fault in the axtrme west end of the gangways of bed8 3 and 4. Reports that mngiomerata mnrs west of the fault would seem b be true, to judge from the projected position of

142121-47-2

the babee of tha congIom81t~b at ..the BUrfm in the northam qart of mc. 20 @I. 11). If this is true, the sotlthwt aide of the Jonesville f ~ u l t must have moved northeastward relative to the block on the northwest Bide, so that the horizontal mmponent was much greater than the vertical. The Evans Jones c m ~ u t t w d bWta rn m a of broken

ground south of the Jonesville fad t, at the axis of the epncEine. Nu- merous small fanits are known, but as this part of the tunnel is timbmed, it is impossible ta detect the presence of any major dislmatione.

Bed 8, west of the cmscut tunnel, has been cut by several amd faults, of which ody the largest, about 1,400 feet weat of the c m m ~ ~ t , is indicated on plate 11, and in ~ection SB', plate 12. It is a low- angle normal fault amkg a,2Drfmt displamamt oT-,&e bede exposad in the gangway. The present face of the gangway ia in a small b~ul t , whiah hae not yet been driven through. The topography of the coal-bearing formation. above the face of the g w a y , in the southern part of the NW$mX sec. 17, is imgdar.

The geologic time at which the deformation tmk place cannot be clowly d e t e h e d . The Eocene formations were h t folded, rrnd it may be that the strike faults, which preceded the tmnsvem iaulte, were formed at this t h e . The transverse faulte, most of which stand at a high angle, lare Inter than the folding. The period of faulting predad the glacial epoch and mny have boen late Tertiary.

COAL DEF0611TB

GEIU~BAXI o u m a 9 w a E

The aggregate thiclmess of coal in the known 2,000 feet of sedi- m e n t ~ rocks mking up the Cbickdoon formation is over 80 feet, which is a ratio of ma1 to noncombustible m k between 1 to 20 and I to 26, similar to that in many other coal fields. The cod beda uerually ODC:IV in p u p or zones, separated from each ather by 100 feet or more of mck. Part of a ma1 Zion@ is composed of bone (coal with over 60 percent ash) and cosly and carbonamoua. ~halm. The baning wall of the coal beds has more Femmonry a aharper contact than the footwall. The footwall is cummonly campomd of bone, which, like the coal, change8 rapidly in composition as well EM thick- ness and in placea within a short distance changes, to coal.

Pregent information hdicate~ that there nre at least five coal- bearing zones or group of beds. The lowest, the Eska coal p t l p , ia mrnposd of t h e beds within a thicknew of 55 feat of strata; this whole sone, however, with the underlying thin coal seams, i~ about 100 fwt thick. The Maitland group consiets of three con1 bede in a stratigraphic thickness of f 10 feet. The beda on the north l i b of

ESKA UHREE COAL DEPOSITB 201

the syncline in the Evan 3ones mine f o m another auch group: here there -&e seven beds in 212 feet of strata. The complete section of tho formation in the wwtern paxt of the SEMNWji sec. 16 not h o r n , but there am at least two large cod bed8 within 55 feet. On the south limb of the syncline in the Evan Jones mine there are four beds w i t h 85 feet. Beds 0 and 00 may be a part of the coal-bearing zone in the weskm part of the SEYfiWg sec. 16 or a sleparate mne. Most of thesa zoma are separated by smdstone, m g a definite change in sedimentation during tha deposition of tho Chickdoon

2 foma tion. OHARACTER OR OOAL

The coal in thie part of the Mafandm Vdey ia a high-volatile r

bituminous coal. When fd it bas s brjght luster, which it loses upn,.expo~m -to weather, although it does not check quickly, The coal hm wddeveloped prhmstic cleavaga and is friable, rn that it is di&icult to obtain a lwga p e m t of lump. Calcite is common on cleavage surfaces in the vicinity of f a u k . Some beds, such as the Eska and Chapin, contain pet i f id logs.

Mmt of the cad beds in this part of the field have rn asb content rangbg fmm 10 to 25 percent, and even the few bed^ of low ash content are difE~ult to keep clean because of the condition of the hangbg wall. The s p d ~ a c i o n s of the Alaska Railroad, the chief oonsumsr of the coal. p r d u d in this field, call for s penalty on coal containing 14 percent or more ash on a mois~ur~frde qasis,.m that washing planta are almost essential.

The available andysee of the principal coal bcida are gved in the foUowing table; whem~er pmpible, a n a l y ~ with cross sectiowq of the bess have been selected. The sections are referred to in the table and are given on plate 13. The analyses m placed in the order of stratigraphic sequence of the beds from which the mmples were taken; a stratigraphic range of over 2,000 feet is ~epresented, but the fuel ratim (ratios of volatile matter to fixed carbon) do not increase in the

" beds at lower horizons, as ia the case in some fields. For cumparimn w four andysea of bed 8 are given-two from the gangway, 1,380 feet

apart; one o o m p h andpi8 of 8,270 tons of washed coal prodwed

3 in 2935 ; and a mmposite analysis of a shipment of 200 tow of picked nut-lump cod produced in 1935. A composite analysis of 12,800 tons of run-of-mine cod produced in 1923 from the Eska and Shaw h d s of the Eska mine is dm included. The Maitland and Chapin beds are highly regarded for domestic mnsumption, although the approxi- mate rtnelyse~ do not indicate any exmptiod qualities. Tbe David bed ia the best blacksmithing coal in this part of the field and has tho highest Beating value, as is shown by analysis 15.

ssmpre tataD h m W r t l d 41, plate 18. ?VlthouS I4 inches of cod md shale Bt hp. ,

I 8mpb bkm 6 40, phta IS.

Compdta omph or m tnas ot pI&d ant-lamp shipped in 1%

.# 7 . 1 1 l2.m I I Tmm 0.8. O d c q I d 8m-

.55.7,821) 16, 17fl veq Bull. 711, P. 137. - 5 7 7,527 13, MQ .R1,8, 119114,Q14

molsmrs and ash itea

ESKA CREEK COAL DEPORXTS - 203

Anofyam of urn1 from tha G m I y of Eska Chek-Continued

I B . d 4 , E . a n l m m m i a a ~ p k t b ~ C a p t . W P T.HllPannlgrsdbyM.L.Bbarp. B B& ?, E- J- mhs! Barnpled and may& bk M. L '8barp. 3. B d Z Evm loam mine: -pled by C R I I ~ . W. P. T. Bill; ~nalyged bf M. L. Bbup C Red 0, ~ v n n lwes m e f Earnpled by M L. Gbarp. amlyre4 b y 8. M. Cwm. 6. Bed 00, KVRD Jmm minb, m p k d try M. L. ~ h n & analyzed by U. M. Cmm. 8. Red 6. E v m Jon= mmt: sampled by M. L, Sharp; nnnl!.rcrl hy FI. M. Cmpsr. 7. Bed 5, Evan Jnons mine: -pled b y M. 1,. Khnrp; anelpzed by U. M. Cmw. ... A. Bed & Rvm Jonm mme. sampld by Ralph Tuck; ~ n ~ l s r r t l hy M. I,. 8hary) 9. Bed 8, Evan Jon- mha; m m p l e d by H I Bm~tb m d I1 U. Slew&. m s l y z 4 by H. M. C-. 10.11. Bed 8, Evan Jon- mlne, s~mplsd m d nnaly MI h y M . L Shnrp. 12. Chaplo bed R*ta mlne' sampl& by Hal h Tuck, andjesd by M L. Bbstp. 13. Upper ~ ~ i i l a o d Id, ukt vide n! Eska &ek. 14. Inwor Mlutland bsd, wmt side of E s k ~ C w k . 15. David k d 15. Em- M. 17. EskB bed. la. Mmtun! of %ka md 8 h . r M s . 39. Vppet Shuw b d D9W R b rroaa?al t - l - e a d by m p b Tuck d Y S d bY M. L. g b ~ . !XI. Lover fihar & mw ah aos~cnt tannelf sam lad bp Ralph ~ a c k f anal by M. L. & h w . 21 Mwtm bed. n w Esb -r tunnel- ssm Icd Ralph Tu&. a a a i y d p H . t. B h w .

. & C ~ I M ~s asn E S ~ cnnscot t u n s < MU Peot from pnna~; s a i p ~ ~ by R& T U ~ ; md~ted by M. L Sharp 23. Coal bed b mw ErLa m t tunnel. SXl lest Imm portal; moplad by Rnlph Tuck a n d g A b7

M. I. Ghmv. %. Cml bed In wr E s h h n d . 343 Mt &om -1, amplad by h l p b Tmk; malytmd bY U. L. Bharp.

m a OPnRArnOrn

Bka miw-The original application for cod-l&g & 7, known as the Eska mine, was made in 1916 by William Martin and associafes. Mining operations began in J m u q 1917, and during the followhg spring a rdmad spur was constructed. In the early underground work several faults were encountered; the opormtors. did not have sufficient capital for the necessq exploration, and in June 1917 the Alaska Rdmad, w i a l m g to be assured of a reliable fuel supply, purchased their equities in the lewe. A modem osmp was constmc ted and coal was mined. Operations stopped in October 1921, aa private opsr~tom were then able to produce ma1 in sufficient quantity for

- dl railroad and local purposes. Late in 1922 the Eska mine was reopened, the &ad's fuel supply being endangered by a fire st one of the producing mines, but it was shut down again in June 1923. No shipments of coal from this mine have been made since 1923, but some maintenance work was done h the old openings west of ma Creek. Accoding to the fles of the Alaska Railroad, the total amount of coal produced from the Eska mine to dste ia 215,000 tons, of which 6,OCKi tans was mined prior to its purchase by the railroad. In 1932 a flood an Eslra Creek did much damwe- to the old plant.

This rtisa~ter and the cavd conditions of tho old underground workings made advisable a now opening to maintain the property in a condition for emergency pdaction. This development was undertaken during the s m o r of 1934; a new spur from the Jonesville branch of the Alaska Railroad was constructed; and a new omascut tunnel was started in the ~outheast comer of the SWSNEX sec. 16, ta open up coal beds on the south limb of the syncline and ltfter, in the event of continuous production, to extend the wor- to the north limb.

Emn Jonm mine.-Coal-leasing unit 6 is held by the Evan Jonea Goal Ca. Undqmwd opemtions wem &t s t a r t 4 in October 1920, and cod wae sledded to the Eska spur during that winter. In 1921 a qur wns c ~ r n b ~ u ~ t e d I;O the mine from the Eska branch of the Alaska Rdmad. The early mining operations, through m upper tunnel on beds 2, 3, and 4, were on the south limb of the syncfine. Ln 1925 a new tunnel wss driven at a Iower elevation tm mosscut to t h ~ north limb of the ayacline, and ME 5,6,7,7A, 7B, snd 8 were found. (Sea pla. 1 l and 12.) The upper tunnel md the southern worErq have been abandoned, d all the coal now mined comes from bed 8 in the lower tunnel. Because of a h, the mine was shut dawn for several months in 1922 and 1923, but since then operations Iritv~ been practically continuous. In 1928 the equity of W. A. Vinal in I e h g e t 5, which adjoins

the original Evan Jones lesse on the west, was p m h d , and in 1933 thla lease waa included with unit 6.

ESKA CREEK COAL D E P ~ I T S 205

me property, the largest coal producer kt the Matanuska field, - is fully equipped, hcludmg a mmening and washing plant. The msxiaum daily capacity is over 200 tons.

COAL EXPOSWgIl

The following descriptions of mal beds that are exposad or have Geen located by pqect ing suppl@ment the cod ssctions ~hown on plats 13. In order to make this information as wmplete as powible, description~ and gections are included from publisbd reports of

> - Martin "d Chapin,' and fmm unpublished reports by Sumner Smith,B. D. Sbwnrt, W. P. T, Hill, B. W. Dyer, J. J. Corey, and M. L. Sharp. Most of these sections am now conceded became of

t

the abuhnment of old workings. As far as possible, %he coal see tions of individual beda on plate 13 have been so placed that they am in sequence from muthwest to northeast, and the intmvmhg dis- tances are given; the changes in thickness of coal and the position of h a l e markers can be e ~ ~ i l y seen.

The following dewription includes all the coal b d a enmmtered in both the old and new underground warking at Eska. The maI beda that have been mined are stratigmphically the lowest in this district. The Martin, Shw, Eska, Emery, David, and MaitIand beds were mind from 1917 to 1923; the grater part of tbs production came from the Eska and upper Shaw beds. Tbs Chapin bed, the l$g;hest of this p u p , bas been mined only during the Iast 2 pars to supply coal for camp use. The beds are dewxibed in stratigraphic sequence, the lowest fmt. In the new Esh crasacut tunnel, 350 feet from its portd, are two

small coal beds that are stratigraphically the lowest known in this m e . The lower bed is 21 inches thick, md the upper one 36 inches. %tharegraphicallyshownbysectionM,plate13. Analyaes23and ., 24 were made from samples taken across theso sections.

? 9 Sample 22 was taken from s cod bed 20 inches thick, occurring

840 feet from the portd of the new tunnel. About 20 feet farther north is s 28-inch bed of dirty coal, which was not analyzed. - The Martin bed is the lowest that has been mined. In the old Eska workings it consists of about 3 feet 5 incl~ee of coal, which occurs in two benches aepsxated by a 13-inch parting of ehde (mation 2, pl. 13) ; in the new Eska tunnel it is somewhltt thicker (mction 1, pl. 13). A s m d coal bed that closely underlies the Martin bed wga not analyzed. The Martin bed was mined on both the east and west sides of Eeka Creek, on the north limb of the ~yncline.

8 MwMn, 0. U., o& dk (Bonn. WIO md 693. Chapjn, Tbodm op dt, ma. PlZsnd ?I@, - . ,

The Bhaw bed h two benches of md sepnmted by 3 to 8 fwt of shale. . The lower Shaw bed, which ia high in ash becautm of aumemui shale partings, wm mined on the east alde of Eska Creak up to the northeast f ~ u l t ; on the wmt side it wes mined for a distance of about 600 faet from the portal. h t i o a s 3 to 9, plate 13, indicate that it thina to the south and west. The c o d a t i o n of the bed on the east edge of the NESNEX see. 17 as the lower Shsw is b d lsrgely on ih &ation with two other beds that would be the equivalent of the E s h md uppr Shaw.

The upper S h w bed is present in tha workhga on the east aide of the c m k 88 B maly shale, which changes rapidy Eo the week and m t h (98~Cions 10 to 14, PI. 13) and W&B mined in the S ~ B W West workings. This bed is thickmt and cEemmt nn the south limb of tbe syncline in the new Eska tunnel (section 14, pi. 13).

The EBb bed ia 2% to 3% feet thick and hse been &ad on both the east and weat ddm of &ka Creek. Above the me1 there is about 6 hchee of cody s u e with a chamkristic d persistent shale marker. The bed bas not yet been cut by the new Eska mosscut tunnel, but aurfabe exposures h o w that it is pkent on the muth limb of the syncline (section5 18 and 19, pl. 13).

At pmmt the Emery bed is not exposed in the new tunnel, but it is rep-ted by sections 23 and 24, plate 13. Them is a @- bility that the nortbernmmt exposure of coal in the N W)iNW% m. 16 is the Emery bed, which is mentioned in the dimmion of bed 8 of the Evan Janee mine.

The David bed b 2% to 3 feet thick ma, wbem mined w Ehe west sida of Eske, Creek, hm a pereiatent parting of yellow ~ h d a ( w d m 25, pl. 13). It hm s higher heating value than m y other ma1 in the field and w m &mined on both sides of Eska Creek until cut off by faults.,

The Maitland bed has two benches of cod, separated 67 4 to 7 feet of maly shde (~ection 27, pl. 13), and is one of the ht-burning coals in the field, It was mined in the old workings on both sidea of Ehka Creek until cut oE by faults.

The exposure of the Chapin bed at the of the spncline on the west bmk of Eska Creek is now concealed, but the same bed has been opened up on the east aide of the c d by a short tunnel. On the east side of the creek there are two benchea of coal anparated by 3 feet of shale (section 28, pl. 13), but only one an the wmt side is mentioned by Chapin.&

~ B E D B m T B g l W I W ~ ~

Underground work st the mine of the Evan Jones Coal Co. hna disclod several coal beds, and the numerical ddgnationa here u d are those in common ussge at the mine, Bade 1, 2, 3, sll$ 4 were

~ v e r e c f by the upper tunnel in the SE%W& see. 17. The lower funnel, the portal of which is in the SW S/iW K aec. 16, intemechd the same beds and, in addition, the underlying beds 0 and 00, which are & on the same side af the syndine. Upon the extension of the tunnel a c m the qncline, beds 5,6,7,7A, 73, and 8 were discovered. Beds O,OO, 1,2,3, and 4 are not exposed in the cmsscuh tunnel on the north limb of the syncline, as they have been cut out by the Jonesville fault. h the folIowing description the coal beds are described In their stratigraphic sequence, the oldest h t . The numbered sections are &own on plats 13, and the ansly- are given in the table on pages 202-203.

A greater tonnage has been exhmcbd from bed 8, which is now being mined, than fmm other in this area. Measuremenb of sections 40 and 41 and samples for anaEysia were taken from the gangway. Andy& 8 d m not include the 8 inchm of coal and 6 inches of shde shown at the top of mction 4 1. Tentatively comlated ag bad 8 ia the northernmost coal bed in the NWjiNW %, see. 16, w k c h ig m p m t e d by sections 42 and 43. The correlation i~ b m d on the s a a r i t y of sections 40 and 41 to sections 42 and 43 md on the sequence of overling beds. The northernmost coal bed in the NW JiNWW aec. 16 is ofFset from bed 8 (see pl. f 1 ), and tbe amount end direction of ckp1acament as ~hown ate approximately correct if the Jonesville fad t strikes between them. If this correlation is incorrect sections 42 and 43 may be the Emery bed, as the sequence of overlying beds ie somewhat the m e .

Bed 7B is graphically shown by section 38; a correlation with the cual bed illashrated by section 39 is sugg'mted.

Bed 7A (section 36) may be correlated with the cod bed ilustmhd by seotion 37. This bed has two benches of cod; if sections 42 and 43 should prove to be the Emery bed, section 37 would then represent the Mnitlmd bed.

Bed 7 has 3% feet of coal md is r e p m u by the lower part of mtion 34. T h e aection overlying the bed is partly obscured by timbering, and only the part that could be meam& is ahown. The muthemmost coal exposure ia the N W m W g m. 16, represented by section 35, mby be bed 7. Sactions 34 and 35 do wt hava much similarity, and the suggmted correlation is made on the basia of the sequence of the underlying beds at both 1maPitim.

Bed 6, sometimes h o r n as the Guidone bed, is 35 feet thick; gndysia 7 represents a sample that was wt from s section of the bed ~ h o m by mtion 33.

Bed 5 ia %onetimes known as the hussac bed; d y s b 6 repwamb a sample of the cod that was cut from =tion 32. This section does not repment the entire bed, as there is coal md bone both above and below it.

Bed 00 i~ the .lowet 6ed on the eouthern limb of the synche. It ovsrlim bad 5, but the exact thicheas of jntervmhg sediments is not h o r n . Xt is graphically represented by section 29, a d andysia 5 wss made on a sample cut from this srrction.

Bed 0 ia repmenbd by section 30 and analysis 4. Bed f has never b o a mined and is properly not a cod bedd. This

dmiepation, on the old mine maps, was given to a 7-foot zone of mdy shale.

Red 2 has an averayfe thicknms of 32 inches, and and* 3 was msde from such a eection.

Bed 3 is r e p m t e d gtfphically by section 31 and chemically by andy& 2. Because of the shale, parting, this b d was mined in two benches.

Bed 4 is stratigraphicrally the highat hown coal bed in this area. Analpi 1 represents a thichesa of 40 inchee of coal, including a 1% inch shale parting. The average th iches~ of thie b d la 3% feet.

COAL BY I I R D i m

In 1917 the A l m h Engineering Commission, whoae functions were later taken over by the Ala~ka Railroad, driIled 47 holes in pmpecting the coal bede immediately adjacent ta Eska Creek. The l m d a of them drill holes is shown by pIste 11. Holm 1 to 35 were . drilled on the wt side of Eska Creek, and holes 36 ta 47 on the west side; records of their logs, obtained from the fles of the Alaska Rail- road, am shown graphically on plate 14.

D d holes 40 and 47 cut a coal bed at s depth of 60 feet. Tbis bed has also been m c a v e d on the surfws, where it is believed to be the Eska. The Shaw md Mrvtin beds, which should underlie it, were not encountered by the d14l holes, although hole 46 was drilled to a sufficient depth to intemt them if the usual interval of sedimentary beds had been present. The c o d bed cut by hole 42 may be the '

Emery. Holes 36 ~AI 41 probably am in faultgd and broken ground. . A part of the area that was d d e d on the east side of the creok has since been mined; in the remthinder, BO far as is h o r n , them is little coal above the level of &ka Creelr.

C U b t ~ ~ B Y E I V R F A C E ~ Q

A c o d bed ws9 found in the extreme northweat comer of the SW jQiZ% sec. 16, but it has not been dEdently uncovered to expose the entire section. The dip of the bed indicates that it ia near the axis of tha syncline. It may be on'e of the upper Maitland group of beds or one of the coal beds found on the north limb of the syncline in the Evan Jones mine. In the central part of the N ' W j 4 4 N sec. 16 a coal bed has been

exposed. The complete section is not h e w n , but this outcrop may be one of the Maitland p u p of be&, as the stratigm~hio internal

between it and the Eska md bed in the old Fda Wwt tunnel is about the asme as the usual distance Getwsen these bds. (See mctiou D-D', pl. 12.)

In the eastern part of the N E v % sm. 16 a w e d c o d outmops have been uncovered on the bank of a small creek. One of theso is regular in strike and dip, but the remainder have varied inclinations, showing evidence of f~ulting. They may lie within the Eska fault block encountered in tho old E ~ k n West tunnel. The northernmost coal bed, exposed on both aidas of tho small creek, is the only one that appears unfaulted. Section 46, plate 13, was determined from thew exposures. On bath sides of tha creek, 90 feet to the south, is 30 inches of cod with mma crushed shale and gouge, aIl in a vertical position. About 50 feat farther e a t , on the ewt side of the creek, there is 3 feet of coal; the top and bottom of tho saction are conceded. At 80 feet fmther wuth, on the west side of the creek, is 3 faet of coal; tihis bed strikes N. 8' W. and thus is not in mcord with the regional strike.

Several thin coal beds have been found on the north bank of a creek in tho gouthwest corner of the SWmEjrC get. 16. Section 45, plate 13, was nleasured at that locality, These beda have been traced sou th- west for 600 feet. The strike is practically continuous with that of the smell coal beds that were cut in the new Eska crosscut t u m d 350 feet from the portal; the swtions are somewhat similar, but s fault may occur between these two sxposum. The presence of coal blossom indicates the probability of seveml coal beds on the bank of the creek in the muthem part of the SEBNW% sec. 16.

Two large coal beds are e-qmed on the sides of a deep gully in the WfhSEKN?T% m. 16. These beds are on or near the m i s of the sgn- c h e , which hem pPunp steeply to the west. Section 48, plate 13, W R ~ metwud on the west side of the gully. In the northeast corner of the SWXNWg s*. 16 is the oaal bed

represented by section 47, pleta 33. It is not known whether this bed is sbove, below, or s part of the beds represented by section 48. The coal beds uncovered in the NW%NW% sec. 16 have been tenta-

tively comlated with the beds on the north h b of the syncline in the Evan Jon= mine, and those in the NE%NE}i sec. 17 with the Shaw tbnd Eska beds. In 1931 the Evan Jonas Coal Co, prospected the two gullies on the

north ~ i d e of Wishbone Hill, in the northern part of ssc. 18 (pl. 11). The itrenches and tunnels have cwed so that accurate aections of the beds axposed in them cannot be measured. A ~hort report by the 8vm Jones Coal Co. states that the pro~pmting exposed a 700-foot tbicknsas of coal-bearing rocks, extending from the base of the Esks conalomerata to the swamp on the north side of Wmhbone Hill. In. this tbiches~l nina coal beds ware exposed, seved of which were within

s ehort & h c e of the base of the conglomerate. Similar -tiom were q o m d in both gullies.

The totnI coal m r v e s of tbis area are not known, a9 the strati- graphio column .b not complete. An estimate of the amount of cod would give but little murate infomattion of the tonnage that could be rewvmed, becaum numerons faults, particularly in unit 7, w d d prohibit the mining of m a y blocka of coal. Many of the; ma1 beds am close together, and beds freer of ash or of bettar quality closely underlie Iesrs deab1e beds, so that the overlying coal may be lost by the exhation of the underlying one h t .

Because of the topography, the amount of cod above the natural &&age level on the east i d e of Eska Creek is mill. Soma cod could be extracted from the Chrspin bed; the present opening: would man strike the m e fault that bring8 the Maitland and David beds together, but in dl probability the continuation of the Chapin bed could easily be f m d an the southeast side pf the fault, as the appmxi- maw mount of displwement is known. On the south limb of the syncline the M @ h d and Eska p u p a of coal beds may be p-t. T h w beds would elso have to be developed from slope workings, becaw of the topog~aphy. Little is h a m of this &ma, however, as the overburden is thick, and the few holes that have been d d h d were E+haUow. On tha west side of E'lra Creek the new c m t tunnel hae made

available coal sficimt for emergency purposaa for the railrod. When tb area is mined out, which wodd take mveral yeam at the present rste of milroad mnaumption, -the new tunnel can be adaided into the NW% mc. 16. Hem the Eska, Maitland, and JonesailIe groups on the north limb af the syncline and possibly several over- lying cod bsda mill be hterseFted. Tbis constituteg the hqpt mmve on unit 7; in some place there will be 1,400 feet of cod on the dip of the bed, above the tunnel level. The l q p t h o r n r e m e in the Matmuska coal Ssld, consisting

of several million tom, lies in unit 6 and ite w ~ t e r n addition, formerly unit 5. So far M abt4 known, tha coal beds on the north side of Wish- bone ElEiU me prwticauy continuous for 2 miles. Bed 8, where first mined, had 1,500 fmt.of coal on the dip of the bed above the level of Eh@. g w 8 y ; where bed at plW€& it hm 1,300 feet, md b@~a?.lE€l of the ~opopaphy the thiaheaa will continue to d e c ~ ia &a west. Other coal bads occur stratigraphically rsbve and M o w bed 8; those above dl have a gmaW distance above the tunnel level than bed 8, whereas t b below will have l a . Thgoreticd conrd.dera.tions indicate %hiit the %a and probably the Maitland group of coal beds wiU be intemted by the extension of the Jonesville crosscut

E S U CREEK COAL DEPOSITS 211

tunnel; and that the Jonesde fault bas eliminated from the aromut tunnel d the beds overlying bed 6 on the north limb of the syncline. Tt~ese beds, however, muld be intersected northwest of the fault at the p m n t tunnel level, as to fhe west the overlying coal beds rare carried d o m by the muthwest plunge of the syncline. (See sections B-B' and E-E', pl. 12). Valuable prospecting work that should be done on unit 6 would be to obtain, by surface trenching and stripping, a cross section of the formations downward fmm tho base of the Eska conglomerate, on the north side of Wishbone Rill, which would yield information regarding the location, tckness, and qurrlity of cod.

Besides the m m m on the north side of Wishbone Hill, there are equal if not gmmter reserves bdow the present bumel level, along the mia of the syncline and on the uneroded remnant of the south limb. Some of the c o d along the axis map be crushed and faulted, but undoubtedly there are large minable blocks.

INDEX

Page pm A M ------- - ----- * ---------- -- JM C d b 3 s + ~ d , b y ~ ~ - hkw- f ~ # rid, .--,---,......d,d,d,d,d, 188 lug-: ,_-_.-----..------ :- 20&PI[E, $. 18 ~ ~ ~ k m ~ n g ~ m d a g ~ q m e m t m g M 01, by mns~ *-+.-.---- ,. m, ~ I O . 11, t r

by 208, pk. 11,14 D a ~ d m a l b e d , d p ~ o l m a l h m ...--.-.-- ma ~ o o , d ~ a l c ~ a l f m m ------..---.---.- m bolts cutting ...._..._,,.---------- *- 1w

g~laalbmol------.-----.-.- m , p l . l a general 18~tareu of. ......,.,.,,-., sDB, pl. 13 t W & m of .---++---+--.*----------++ lP4 tMc- of ..---.---.,-...,.....--- 1Q2, pl. 13

B s d O . ~ ~ o f d f m m .,,.--,.. + ,-.- aCra R m l n ~ ----------------------------+- 187, pi. 11 t h i c h m 01- +-- 194 EmerymaEbsd,ndywd~lfmm .--....... aa3 section OF pl. 13 mlatim oL ...--..---...--..-- a?, ma, pl. 11

Bd I, chwa~w Me,, ,.....,.-,.--.---.-.. zOB Wtr: wtting .---..---.------------------ 1% t- of ..,---------.-----..-..---..-- 104 g m e d i ea tm of .......----.--.. ,. % pl. 13

Bed5 a c l a l ~ o f d ~ .,..,_ , ,_.---... !a2 t h i c b 01 .....--..---..-..-.------ 102, pl. la thictncm d ----.-----.---.------------ - W2as E u k a ~ s l h e d , ~ s n d a a a l ~ d m s l

~ 3 . a n a l y . w d m a l h m .,,.......-...-- .. i~ from ----- 2(15a08 bulb cottiug .-..---..----------------- --. IS9 &stron of+* ,...,.....--_..--*--+-. aOg zOg - g e d laatoaw d .--...---.-.-.-... m, pl. 13 tanlta mttlu~ 197-188 t h i c k m o l ..-.-.-.-..,...---------- -+. 194 g e m 1 ~~ of +......-. .---. ..... SMi, pl. l a

Bd4, a d m w o l d hmm .-..---.,-,....-- Bo2 t b i c m a1 .--..--...--..----------- lg2, pl. 13 ra~~lta cuttsng --,.........----.-------- - 1 W W F&n mmpiomte, Pbmak and thlcbm g e n ~ reatures of ..,..,....,..-... a08, 81. 13 or ...--..-...-.-...---------- 195. pt. la thi* ol .,-,..--...----.,..,.....--. W E k h ~ a a a l y s e e o l ~ f m m v l d n i t y 01. 205203

Bed5,mal~-sasddIrom ----.---..---..-- aOz floods on .--.,-.,-.-..--------------- a7, 87,. 11 I ~ u l t ~ cutting -..-.+.....-+ -.----.----.- 199 g e o a r s l l e a d s a ~ t i u n d d m m m m o n + ~ ~ ~ ~ 182 general fmtumot -.-....._.-__..-_- XW, gl. l a Eskn er-t tonna1, &Ion In. .. ..-,...-,, 1BP-101 thfckasss d .----.-.--..-.-.---.- 188,lW, pl- 13 Eaka fault, ml beds cut by .-.-.--....-..--. fw-188

Bsd 8, anslusm of md bml..--..---.----..-- a02 E ~ g r o u p , d b e d s o 1 , -.---_..,_..,-,_.,... 182 mrwral feat- o ~ . . .----.----.---.-- 2 ~ 7 , pi. 13 cml aeasol. t u r n rnlrhg d ....-...-.-... 210 thiclrn89.q of ---..---,.-......-... Is& IW, p?. 13 ar-m ot ..........-...--.. - 200

Bed 7, -lation of -.----.----..-------- ZM. pl. 19 thlcktws of ..-...-__...-....---------- 18s thZeknass ol. ----.---.--.------.. lW 194, PI- 13 Eska minq andysm of a from ..--.-...-... 208

Bed 7A, mrrdatlon d -,-. - ..-.---..--- p37, PI. 13 ma1 beas h.. .--.-.....---._---.4--- "-- #lbm ihlcknws d.. --...---...---.---- 183,104, pl. 13 production Irom .-....--...-....+--------- 2(M

Bsd 7 0 . oorrdath a t -----.--,..,_.-- 2[17. pl, 13 work at ..-...---.--.....--.------++---++.- 204 thlckam of.- -.--...,.....--.--- lW, 1W, pl. 18 E ~ ~ n n w m i n e . ~ ~ o l c a a l h m m m m m m m m m 2nZ

Bed 8, u d y s e s of d from-- ----,....-.-.-- SlDa Ewrl beds in ..---. . ---.. --. . . -+-. - --- - - +- %#ma oosl minert Rom ......,..-..--.--------- - #rr CMtl bada 01, omelatton of --.-.---...-.--- m hdta outring -.--.----...---.--,... ,. 1-rn occunvlnee of ---..-.....-__.--+-.- ++ a00-Ml mzura mfnlng of --........--------------- 210 balk7 cuttlw -.---.---..------ maw, pls. 11-la general l e a t m 0L ------...........+---- ZW m i b i e enpowre of d h d of-. W t h i ~ k m ~ of.- --.......-----..-- X@, 1M, PL 13 relntive &anw ofiaults in ...,...---..... 11)7

Chapin w d b A d . ~ s a d n n a l ~ o f c a a l m U w s in ._..--_.---_----.-----.------ - 1 ~ ~ 8 4 h.0- ..----.------.- -.---.-- Blk-Dn work nt. ............................... Xbi-mI fsataras oL.- BM, Dl. 13 h l t s , nge or -----.--...----......--_.---..... a00

tuture mining d .----.----..-.-..---.----- ZIO general rcmme of ,..__--.-_ i sam, g~n. 11-12 t h l c k m 01 .--- -- 1% IW, PI- 13 Cteo1~ty .-. .__. .-_. . .-. . .---, ,-+ --- - --+-* b g ~ , p.11

CbIcknloo~ l~-mUon, -and th icba Cddona bed. E a Bed 8. Of. .-...-.,.-__..-------- 1-194, PI. 11 JonasviUa fault, mal beds wt by .---. I-, pi. 11

d wrap aeotiona of -,-..---......--- -194 JomviHn group, d bed9 of, fntureminh~g ol. ad, mud+ OL - ax?-"203 h t i o n of a m .-..-.. ..---.-..,...-,.. .... 1 ~ 6 ~ 8 ~

C h m 01 ..--- ---- --..--..----------- mi-203 Lcussac bed. &rBadS. depoi1t.v d, isatmw d .-.----...,...-_-- ~ W X I ~ Maitimd cod bed. nndm o l d bum .----- a 2 a*posur~ of -.-.,----,..----------- 2 a M l O m I s t i o n o r --.....---....,..--.- m, pl. 13 htm mining of 210-211 kults ratting 1BB mInlog opemllm d -... - 206-205 pnersl fmtum of. -. .--,,--_,.. 'bW. pl. 13 l~mrcse ot .--.--..---.----,-,..,...., ZIC-211 thickriees of 193, pl, 18

213

P W IYIdWmlgon~,cusl~d -....,...-..---. 192

ml Ids 06. ruture mtdng of .-.---------+ aW amnmenm ot ......---.---..-------.- ~ X I pmsIbb%xpmm of -dm.---..-+.... 9XI&m BtrntigrapbIo Of .---...-...._. 192 t h i m or 1~

Martin ma1 bnd, sndm of wal horn .-,-..-- a03 Iaults nrl'tIn& 1W-1-188 g m e d latnras d ....,..--..--...--. 205, pl. 13

- thl&wm of ....-....-.,----.--------- 192, pl. 18 mvions work 186-1W

. . .

Page -aiths-vn .-..-------------- 1%8 Q a s m s-, daposita of-. S I M , g h 14 '-

Bbaw cml bed. aaalyses OK oDal b m ....---.-- rorrelatron of ---.---....--.--.-----.-----+ aOg

. IeDfta mt'kbg 181-IllR ,-'

WWBI rmtum ol....---..----.---.- BOB, ISI. la .- thickness of 1Ba. pL I 3

Btraaigrsghp, g m t d #&tum 01 .,-..--..--- fR&lQ6 Bmctuw, ganetal fen- of +.,_. IWIW, pls. Il-la Toponn~hy 187, pl. tl WLuhbone Dm, festurw dL:-.-;.: .--.. 187, pl. 11