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Section IV., 188;).

[ 143 ]

Trans, liov. Sue. Canada.

V. — Ndic on fhr Tridssir of tin liochji Moinidilns (tiid British Cnhnti/iia.
Ih/ GEoi!(iK M. Daw.^on. ]),S., F.G.S.

(ncnil Miiy 2.'., issii.)

The Triiissic rock.K (il'tlic W^nI |>rcsfiil tliciiisi'lvcN iiiidcr two very <lis.siiiii];ir a.'^pccts,
llii'ir cii.'-'cni iMi' (■(iiisisliiiu- ol' i( d hcil.'*. cliiflly .^^iiiKlstdiit's. \\ liili- on tlic INuilic .slope (lie
rliMractcr of their iiiiiti'iiiil is imuli iiioic vuiied ; tliey iiirlu<le mr.iierous fossils, iiiid sire
e\i(leiitly truly iiiiiriiie in oriiiiii. The most (•()iiii)lele (diiipurisoii o| these two < hisses of
(h'P<isits hiis heeii luiide l)v Cliireiiee KiiiL!' iiitlie I'Hh piinillel reiiioii. Thi' red heds iire
there louiid participiitinu' in the IJoeky Moimtniii iiplilt. hut hiive oriiiiiiidly passed eoiii-
l)letely across the position ol'lhis ranac and extend westward to the Wahsatch Mouniain.s
(loniritndc 11:2 ) whieli here eoiistituted the -western slion- of the sea in whieh they wero
dejHisited, The rocks ai'e descrihed by Kinii' as consistinn' ueneraiiv of sandstones, tlie
ui)per hair heiiii;- always of liuliter cuhiurs than the lowci', and intercidated more or less
with heds of dolomite and livpsum. The lower part of t lie series is usually from hrick
to vermilion red, the upper jiart pale red and hull'. Tlie (h)ltiniitic and liypsum heds arc
local in chaiacter, hut Die latter soiueiinn's reach fortv ^vv\ in thickness of pure calcic
suljdiate.

in the Kocky ^Mountains, in tiiis latitiuh', the Triassic is from :!iio to lood feet in
thickness hut. on ai)proachinu' the Wahsalch shore, thickens to 'JOOO or :,'.Vmi feet, and holds
some conii'iomerates. I'ossils are almost com|ih'tcly wantimr.

In many other districts of the western States and Territories, the Triassic heds aro
developed with similar characters. As far east as the liiack Hills of Dakota, thev are
descrihed hy Professor N. II. AVinchell as mainiaininu- a thickniss (,f overwind feet, and hold-
ing great quantities of white iiypsum. They h;ive been observed by Dr. Ifayden in tiie
mountains at the head waters of the ^lissouri, and in addition lo the dejxisits of gyjisum
are in i)laces impresrnated with salt.

lieturning to the 40th parallel reuion.and passim;' westward fioni theWahsatch range,
no Triassic bi'ds are met w itii till loiuiitude 117^' 'SH' is reached, at a distance <if nearly
;iilil miles. The rocks of this period aie there found to be represented by the Star Peak
and Koissats ufoups of Kinn', the former and ui)per stibdivisioii consisting of fossiliferous
limestones, with (piartzites ami slates, the latter of (puirtzites, argilliles and j)ori)hyr.»ids,
the whole with all auuieiiale thickness of ovir HI.tMXi f( • Marine fossils ar ■ very

aliundant in some parts ol' tin' Stai' I'eak subdiv isioii. and are almost precisely similar in
forms with those of the St. C'assiaii ami Ilailstadt beds of the Alps. Tin- term Alpine
Trias has coiise<pieiitly often l»een used in spe.ikiiig of those rocks.

The red be" .>f the Roi'ky ^rouiitain rcLiioii cle.uly point to the conditions of deposi-
tion found in a shallow body of water, more or less comph'iely shut oil' from the oicaii
or only in occasional and brief connect ion with it. while, for the most part, the sediments
of the Nevada Triassic are, as unmistakably, such as miuht be produced under ordinary
marine conditions in greater or less proximity lo a c(.ast line.

144

(iROlWK M. DAWSON ON T!Ii; THIASStr OV TUK

The (listiiKlioii (luis iiiMikcil is di'Mily cin oinili'icd iiiui li rurtlicr sotitli llimi llio 40th
]>!irallrl ii'iiion. ;iii<l il is wiili tin- purpose ol' tracini;- it to tlic iiorlli ol'llic tilth parnllcl
that tilt' ]>n'si'iit iinic is pi-cscntt'd.

Ininndiiilrly to thi- north ol' llir J'.Mli dcii'n'i' ol' lat it >;<!('. in tin- Ivocky Mountains. ahout
tlic Soiilii Koolanif I'ass. liic rrd hcds an- (liararlcristiiMily di'\ flopcd, witlia thickness of
alunU :!(in led. Tlie ujipcv portion ol' the section in tiiis part ol the mountains, is as
ToUows. ill <h'seeiidinL;' order: —

Srn'is If. l''a\vn-coiourc(l llauuy heds.seen oiijyat a distance. 1)ut from their ajipearaUHe
an<l anaioiiy with Series F, iimhahly lliiiid)e(hh'd doloinitic sandstones and limestones.
Thnxiuhout Ion icrl.

Srrirs a I'eds c liai.:' Ieri/<il liy a predominant red colour, hut including' some thin.
Q'reyish layers ;iiid doiomil ic sandstones. Tlu' whole lieiicrallv lliin-hcdded. lkip|)le mark.s
hiin-cracks. im|>ressioiis of salt ci'ystals. -UU) jcct. Passes uiadually down into

Srn'is F. I'aw n-ciiluiircd llau'jy heds ol'dolomiiic sandstone ;ind limestone, with more
red sandstone layers, whiih are especially ahundani toward the top. •Jilil feet.

Sirirs E. AniyLidalojd.d trap, ."id lo 1(1(1 feet.

The last iiieiii ioiicd immediately o\-erlies the compact hluish limestone ol' Carhouirerous
aiz'e. and. \\ ilh the exception ol' the inteiruptioii causeil hy this contemi>orane()us sheet ol'
volcanic matier. the whole of the series are coiironnahle and pass u'radually each into the
next.

The conditions indicated iire. in ("arlioiiil'erous times, a somewhat deep sea gradually
shoaliiu;-. Tile o<( urreiice of ;iu important volciinic outl)n>ak. and shortly then'al'ter tho
more or less complete closure of the cominuni<atioii ol' this area with the ocean and the
format ion of theTriassic inland sea.

W'esi ward from this reuioii similar heds may ln' traced hy information supi)lied hy
^Ir. ir. l?auermaii. foi' ahout fort v miles, hut heyond this point they have nowhere heeii
ohserved in ihiiish Columliia, Noithward, alonu' the imiiii raiiiie of the lloeky Mountains,
I have ohserved them for ;d)out fourteen miles only, heyoiid the 4!Mh ]iarallel. They
were not seen hy me in the Crow Nest I'ass. in latitude 41'^ ."id', nor anywhere aloim;
the eastern hase of the mountains Ironi this point to the lUnv Pa.ss (latitude h\ ) or in that
pass. Neithei- have they hec^n noted hy Dr. Hector in any part of tlie Uocky Mountains to
the north of the Dow which he traversed, or hy Dr. Selwyn in the Yellow Head Pass.
While, therefore, the evidence sc far adduced is purely neiiative. it would appear that the
Triassic inland se.i in this lonuilude found its northern shove not far heyoiid th(> 4!'th
])arallel. and prohahly never extended west of tin' Selkirk and (rold Ivaiiii'es of Central
Ihitish Columhia.

Still further north, however, we meet with e\idenceof a more decided character. 1<

or.

m the ui)per line ami Jcaci

I V

h'ivers. on the eastern Hank of tiie mouiitaiiiH, a series of

lilackish shales and aruilliti's. sometinn's calcareous, occur, and hold characteristic Alpine
Trias fossils, lieds containiiiL;' similar forms are found in a iiumher of places to the west
of the Crold ltaiiu;e ill llrilish Columhia. and it is prohahle that the Triassic ocean, in the
latitude of the I'eaee Uiver, extended completely across tho Cordillera lielf eastward. No
mountain hoiindary occurs hetweeii this reLfioii and that first (h'scrihod ) the sou.li. hut
a tract of prohahly low land must ha\e sejiarated these two areas in the Triassic period.
In till' 'iui'eii Charlotte Islands Triassic rocks, holding fo.ssils of the same strictly

ROCKY MOUNTAINS AND lilMTISIl COLUMlilA.

145

lUiiviin' chiivactcr, nic l:iiu<'ly (Icvdopcd. and tlicy also occur witli almiidaiit iiioUuscous
iviiiains in llic nortlifin pari of Vaiifonvcr Island. In the soutlii'vn part ofth(> interior of
Hrilihh Columbia, not far west of the Selkirk and Gold IJanuvs, rocks also oc. ur nncon-
i'ornial)ly ovcrlyinu' the t'arhoniii'rous series, i'roui which a few fossils, wilh little dou!)t,
l)eloM!4-in!i' to the same Alpine Trias fauna have been ohtained ; and it is I'urther prohahle
,l,j,| — jiis iii Oalifoniia — the u-reater part of the auriferous shales are attrihutahle to this or
the succeediiin' Jurassic si'rii's.

Ill the Queen (^iiarlt.tte Islands. Van«ouver Island, and on the mainland of t lie province,
however, the Triasic .series is larii'ely compo.sed of rocks of volcanic orii;in. some of whii li
have been lavas while others are a!j;'ulomerateor ash beds, made up of fraunienis of iuiieous
material. iU(ire or less perfecllv stratilied. Tlu-se are mini>-led with. schistos.' and slaty rocks.
:ind in. some places witii massive l)hiish lime-stone. de|)ositeddurini^- periods of triin(piillity ;
and it will reipiire the most careful and systenuiticexaminalion tocompleti'ly .separate tiiis
from the underlying strata. I have little doubt that the so-called ' porphyroids ' of Kinu-'s
Koipato groitp indicate an extension of similar volcanic activity over the t'lth parallel
reiiion to the south.

A word may be added with relereuce to the climatic .ontlitioiis implied by the Red
Ueds of the interior. The basin in which they were formed has not only been i)relty o<>ni-
pletely cut oil' from the ocean, but the rati' of evaporation, of its waters must iiave been
normally in excess of that at whi. h they were re-supplied by precipitation or drainage
from neiuhboring lands. It is probable that at that time, as at the present day. westerly
winds prevail. -d in this part of the northern heuiisphere, and. if the North Tacilii' Ocean
I lien exist ed, t hesc would carry, as t hey do now, an abundance of moisture and atlbrd a copious
rainfall on the west coast. As the laml barrier of the inland .sea to the west cannot have
been of very great width, it must liave been of such lieiuht as to cau.se the almost c<niiplete
desiccation of these oceanic winds by precipitation before they readietl the area o<cupied !)y
liie Triassie Mediterranean ; and this old mountain range, must, in IJrilish Columbia, have
o/cupied nearly the ix.sition of the Selkirk and Gold Ranges of to-day, at a time when ihi-
ijoiky Mountain region proiier was still a Hat expanse of Palirozoic rocks.

'["() the north, at the present time, between the .'>4tliand alith parallels, the Gold l\anue
almost completely disappears, and it is through this gap that the Triassie ocean must have
Ihnved eastward to the upper Tea.e River c(mntry and. perhaps, nuuh farther east— though
the Cretaceous, and Larai.iie beds, oc<upying the Hut country, render it impossible to
trace its deposits in that direction.

Sec. IV., 1883. 19