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Maps, plates, charts, etc., may be filmed at different reduction ratios. Those too large to be entirely included in one exposure are filmed beginning in the upper left hand corner, left to right and top to bottom, as many frames as required. The following diagrams illustrate the method: Les cartes, planches, tableaux, etc., peuvent etre filmSs i des taux de reduction diff^rents. Lorsque le document est trop grand pour etre reproduit en un seul cliche, il est film6 A partir de Tangle sup^rieur gauche, de gauche it droite, et de haut en bas, en prenant le nombre d'images n^cessaire. Les diagrammes suivants illustrent la m^thode. 1 2 3 1 2 3 4 5 6 ! I ^'' [Ft'om the Quarxeuly Journal of the Geological SociEry for May 1881.] THE SUPEUFICIAL GEOLOGY OE BRITISH COLUMBIA AND ADJACENT REGIONS. ' (f f- Sb I bZll 272 G. M. DAWSON ON THE StTPERFICIAI, flEOLOOT OP Additional Observations on the Scperficial Geology of British Columbia and adjacent Regions. By George M. Dawson, D.Sc, F.G.S., Assoc. R.S.M., Assistant Director of the Geological Survey of Canada. Contents. Observations on the Southern part of the Interior of British Columbia. Observations north of the 54th parallel in British Columbia. Peace and Athabasca Basins. Additional Notes on the Coast. Glaciation of the Queen-Charlotte Islands. General Remarks and Conclusions. In two papers previously communicated to the Geological Society, the results of observations on the glaciation of the northern portion of the American continent from Lake Superior to the Pacific have been given *. The geological work of which these observations formed a part was carried on first in connexion with the North- American Boundary-Commission Expedition, and subsquently on the Geological Survey of Canada. In continuing tho exploration of British Columbia on the Survey last named, during the seasons of 1877, 1878, and 1879, many additional facts of interest have been gathered, which it is proposed here briefly to summarize and discuss with special reference to the second of the two papers above men- tioned, in which a description of the salient physical features of the province of British Columbia has been given, and a map published ; to these, which it is unnecessary here to repeat, reference should be made in considering the points now brought forward. Observatiom on the Southern part of the Interior of British Columbia. In the more detailed examination of that part of the southern portion of the province extending from the Fraser eastward to the Gold ranges, and including the whole breadth of tho region formerly called the interior plateau, traces of a general north-to-south glaciation have been found in a number of additional localities at high levels ; and it would appear that the ice, whether that of a great glacier or water-borne, pressed forwa,rd to, or even beyond, the line of the 49th parallel, notwithstanding the generally mountainous character of that part of the country. With the facts previously recorded, these now extend the luiown area of north-to-south glaciation to a portion of the plateau over 400 miles in length. The most striking instance of this general glaciation, and that which carries it up to a height greater than elsewhere observed, is met with in the case of Iron Mountain at the junction of the Nicola and Coldwater rivers. This mountain is one of the more prominent points of that portion of the plateau, which, toward the eastern or inland borders of the coast-range, becomes rough and broken. It rises in a broad dome-like form to a height of 3500 * Quart. Journ. Geol. Soc. vol. xxxi. p. 603, and vol. xxxiv. p. 89. BRITISH COLUMBIA AND ADJACENT REGIONS. 273 feet above the neigh])ouring river-valleys, or 5280 feet above the level of the sea. Its summit has been heavily glaciated, the projecting rocky masses being worn into ridges parallel to the direction of ice- movement, the indicated direction of which is nearly parallel to a bearing N. 2!)° W . to S. 2!)° E, If not due to the general glaciation, those marldngs can have been caused only by ice from the coast- ranges ; and though ice has flowed from these as from the other mountain masses of the province during the later portion of the glacial epoch, I believe the situation of Iron ifountain to be such as to preclude altogether this mode of explanation. The mountains of the coast-raiigfs are neither high enough nor so near as to supply a body of ice capable of overridijig it. On the plateau south of Kamloops glaciated surfaces have been found in several places at an elevation of about 3200 feet above the sea. The locality is far removed from any mountain-ranges capable of giving rise to extensive glaciers, being situated in the very centre of the interior plateau. The rocks are broadly ice-shaped and not unfrequently polished, more rarely distinctly striated. The direction of movement varies from S. 6° E. to S. 27° E. On another part of the plateau, north of the course of the upper part of the JS'icola River between Stump and Dougliis Lakes, at an elevation of about 3622 feet, are glacial traces similar to the last, consisting of polishing and striation without fluting, having a general direction of S. 9° E. Still another instance of this general glaciation is found on the granite rocks near Chain Lake, between Lake Okanagan and the Similkameen River, in latitude 40" 40' N. Here, as in the cases before mentioned, the circumstances seem entirely to preclude any expla- nation by local glaciers, as the portion of the plateau on which it occurs is fully up to the general level, and surpassed only by a few insignificant hills at a considerable distance. The rock-surfaces are beautifully polished, and show striation varying in direction between S. 20° E. and S. 28° E., but no deep grooving. The ele- vation is 4075 feet. The Okanagan valley has been alluded to in the paper already referred to as the most important southern gateway of the interior plateau. The bottom of this valley, where it crosses the 40th parallel, is about 860 feet above the sea-level. It is wide, and must at one time have been much deeper, as its rocky floor is not now seen. It occupies the axis of a general depression of some magnitude, and appears to have carried the drainage of a great part of the interior of British Columbia at a former period. This valley has probably been subject to heavy ice-action during the time of general glaciation ; but to what extent the features now found may be due to this, and in how far to a subsequent period when, as a narrow arm of the sea or of a great lake, it carried southward ice produced by glaciers nearer the mountains, it is now difficult to ascertain. Glacial striation was observed descending obliquely from the sides toward the centre of the valley, and also in several places in the vaUey itself, but in both cases without distinct grooving. The rocks of the sides of the valley are often distinctly moutonnees ; and, as seen i'ZM)x5'l hrt-wat^w Ki wmtmm'mwn ^ ^w mKmfftim 274 U. 51. DAWSON ON ''nE SCPKRl'ICIAI, fiFOT.OGY OV from a distance, thosci on tlie lower ]nirt of the slopes hIiow flattened outlines, while those higher up uro more abruptly rounded and have not been so thorou{?ldy ground down. The general statements made in a former communication, in reference to the covering of ]5ouldor-clay or unmodified drift H])read over the entire area of the interior plateau, are borne out in the region now more jiarticularly in question. Erom the rearrangement of this material the great systems of terraces subsequently mentioned have been formed. Details need not be given of the evidence in striation and rock- polishing of the existence of glaciers radiating fron^ the various mountain-systems, tliough it may be mentioned that some of these seem to have had a very great extension down the lower valleys. In this southern portion of the interior plateau, terraces arc exhibited on a scale scarcely equalled elsewhere. They border the river-valleys, and at greater elevations are found expanding beyond tliese and attached to the higher parts of the plateau and mountains. None has yet been found here, however, equal in height to that previously described on ll-ga-chuz ^foimtain in the north at 5270 feet above the sea. Many of the terraces and " benches " of the valleys may be the "csult of the gradual cutting-down of the river- course in the hollow previously filled with glacial di'bris ; but for others, including more particularly those of the higher levels, no cxi)lanalion short of the complete flooding of the plateau-region will suffice. Knowing therefore that the water must have stood successively at every lower level, it is of comparatively little importance that in tho case of some of the lower terraces it becomes impossible to determine whether they belong to this period of tho retreating waters or to a sub- sequent river-erosion. In this region the terraces frequently surpass J-JOOO feet in eleva- tion above the sea-level. The more prominent of those seen on tho southward slope of Iron Mountain may bo taken as an example of the arrangement of these old water-marks. These terraces are as follows, the approximate heights being given in feet; — 238(), ',i0(')3, 3392, 3011, 3715. It is frequently observed, however, that tho occurrence of a terrace at any particular level is merely a matter of local circumstance, probably dependent on tho supply of material and other such causes ; and in different places not very remote the the scale of terraces often differs. Tliis is illustrated on Okanagan Mountain, situated east of the lake of the same name. On tho south side of this elevation the principal terraces were baro- metrically determined as follows— 18(52, 2042, 2141,2045,2800, 2839 feet ; on the northern slope six principal terraces were again observed, as follows— 1451, 1579, 1962, 2452, 2553, 2879 feet. The wide trough-like valleys which traverse the plateau are, over a considerable portion of its extent in the southern i)art of the province, partly filled with a deposit of white silt or loess-like material com- parable with that described under the same name in tho Nechacco basin to the north *. It is, however, unconnected with the latter, * Quart. Journ. Geol, Soc. vol. xxxiv. p. 105, imiTISU CuLCMltIA AND ADJACENT KKfllONS. Z,.> and at a considerably lower elevation, reaching a maximum height of about 1700 feet above the sea. In the vicinity of Kamloops Lake and in the Houtli Thompson and Okanagan valleys, it is well shown, generally forming the first terraces above the rivers. In origin it is j)robably, like that of tho Nechacco region, a deposit from the turljid waters flowing from glaciers at a time when these had a consideralde extension from the various mountain-ranges. At this time, either from general depression of the land, or the danmiing of tho valleys by ico or moraines, a system of winding water-ways, lakes or fiords, must have occupied the main valleys. 'J'lio heads of these valleys in tho (jlold ranges still hold long and deep lakes, on the banks of which, where they have been examined (more parti- cidarly in the Shuswaji region), drift deposits are comparatively un- important, and the white silts are not found. The fine silty material must have been deposited in somewhat tranquil waters ; but it appears difficult to explain its a1)scnce from the valleys on the flanks of the (Jold ranges. It may be suggested that tho currents in the upper jiarts of the valleys were so strong as to prevent the dejwsition oi' the silt ; but, a])art from the difficulty found in supposing such great bodies of water as the valleys must have held at this time to be in rapid motioii, there is no such sudden M^idening in the valleys at the points at which the silt commences as might account for the slackening of the current. It is perhaps on tho whole most probable that the 1)asins now occupied by the Shuswap lakes and others in a like jjosition were filled with glacier-ice, from which the water flowed down tho long valleys, while tho abrasion of the I'ocky beds of tho glacier,-; snpi)[ied in largo quantity the material of the silt deposiis. From tho height at which the silts occur, their greater coarseness in tlie lower part of the Okanagan valley, and the evidence of current-action in that valley near Osoyoos Lake, it is probable that this depression has served as the main outflow of the white-silt lake or sound. At the last it would appear that the glacieis retreated with considerable rapidity, becoming extinct or dwindling to nearly their present size, and leaving the upper portions of tho valleys whicli ])enetrato the (iold ranges almost free from debris and ready to form tho basins of the lakes which now generally occupy them. The explanation here adopted to account for the existence of these lakes Avill, I believe, be found applicable to many in otlier parts of Jiritish Columbia, and is again referred to on a subsequent page. It is the same advanced by A. llelland for Norwegian lakes *. Whether any of the lakes in the region now in question lie in rock basins of glacial formation has not been determined, as tho valleys below their outlets arc generally filled to an unknown depth with detrital materials. Observations north of the MtJi parallel in Britifih Columhia. An exploratory survey of the remote region lying between the 54th and 5(5th parallels in Thitish Columbia and of part of the * Qiiiirt. Jiuini. Gcol. hiof, xxxiii. p. lli;". 276 G. M. DAWSON ON THE SUPEKFICIAL GEOLOGY 01' I'cace and Athabasca river-basins to the east of the Rocky Moun- tains, enables the characters of glacial evidence to be defined further nortli, and has aided in the decision of some theoretical points referred to in tho se(juel. Most of the facts observed to the west of the Rocky Mountains reserable so closely those ])reviously dcflcribed for the regions south and east of this tluit they do nut require lengthened notice. The southward or south-eastward passage of gliicier-ice in the valley of Rabine Lake is indicated by glacial grooving, while the valley of the Skeena has formed a main channel of discharge of glacier-ice toward tho coast. In tho mountains between the valley of this river and Jiabine Lake a somewhat irre- gular, but still, I believe, distinct terrace-Hat was observed on tho watershed at an elevation of 43U0 feet. Its surface is strewn with water-rounded stones differing from those of the mountains of the vicinity. Tho region north-east of Stuart Lake, extending to M'^'Leod's Lake and the Parsnip River at the base of the foot hills of the Rocky Mountains, is deeply drift-covered, tho surface consisting either of Boulder-clay charged with erratics of varied origin, or terrace-flats formed by its rearrangement. This region lies to the north of and somewhat higher than the Neehaco basin, which is characterized by the white silts of a former paper *. The highest l)art of its surface crossed by the trail has an elevation of 2900 feet. In the valley of the Misinchinca, flowing westward from tho summit of the Pine pass of the Rocky Mountains, glaciation was observed in a few places parallel to th.^ direction of tho main de- pression. In tho Pine-River valley, draining eastward and joining tho Peace, no glaciated surfaces were seen — a circumstance which may arise from the comparatively soft character of tho rocks. Peace and Athabasca Basins. In the comparatively level country drained by the Peace and Athabasca rivers, to the north-east of the mountains, underlain by unaltered rocks of !Mesozoic and Tertiary age, the chief evidences of the glacial period arc found in the distribution of erratics, and !' e existence of extensive " drift " deposits. In travelling eastward from the mountains by the Pine-River valley, a remarkable absence of such deposits is noted in that ])art of the valley which traverses the eastern foot hills ; but at the Middle Forks the plateau, with an elevation of 1000 feet above the river, or 3000 feet above the sea, and at a distance of thirty miles from the indurated rocks of tho mountains, is strewn with rounded pebbles of (juartzite &g. from these rocks, though material of local origin preponderates. Eighteen miles further east, at the Lower Forks, the superficial deposits aro much more important, covering the surface of the i)lateau to a consideralde depth, and consisting of gravelly beds ])assing upwards into finer silty materials ; the elevation of the plateau is here 2l3o0 feet. In continuing eastward after passing over a summit of 3300 feet on the lino followed, Laurentian boulders which must have come * Q,uart. Jotu-n. Geol. See vol. xxxiv. p. 105. HU1XI8U COLUMBIA AND ADJACKNX Itr.OIONS. 277 from tho axia of thcHO rocks to the cast or iiorlh-caHt were firrtt ob- served, and appear in abundnuce, at a hciglit of from 'Svor> havo passed 8onu> distance soutliward to Pii;;et Sound, and wostward l)y llio Strait oi' Fuca. It hIIII remained, how- ever, to determine wlietlicr tlie ice supply of tliis pfhuier was wholly derived from the neifjchhouring mountainous country, or whether (as nii;,'ht he sup])Osed in accordance with some theories of glacial ion) ii great ice-sheet entered at (iucen-Cliarlolte Sound, and passed con- tinuously southward lietween it and the maiidand. It is now toiind tluit the last-mentioned idea must ho ahandoncd. In several ])lace8 ahout the northern end of Vancouver Ishiiid, l)ut more jiartiiuhirly on the little islands of the Mastorman group near Ilanly Jiay, and on those in Beaver Ilarhour, are marks of very heavy ghuiation from south-east to north-west, in hearings varying from N, 11)° W. to N. (ilJ° \y. This not only ])asses over the islands, hut has grooved, jiolished, and undercut vertical, or nc^arly vertical, faces on their south- eastern jiarts, while the north-western slopes are comparatively rough. These traces ])recisely resomhle those found in tli*' ^'•ack of tho Strait-of-(ieorgia glacier near Victoria*, and show .' t here, as there, the ice rode over tho low extremity of Vancouer Island. The seaward margin of the continental shore is hero also low, and tho width of the glacier of (iueen-Charlotte Sou" I jan sca.cely havu hcen less than twenty or twenty-five miles, and may have been aiuch greati . Some additional evidence of the movement of thr ippor p&i-ts of (he Strait-of-Goorgia glacier has hcen found at Naniimo, on tho inner coast of Vancouver Island, sixty miles north-west nf Victoria. Hard sandstone rocks which havo been bared on tho coUiery railway show heavy glacial grooving running parallel to the general trend of the cofust and Strait of Georgia in such a way as to prove that tho entire strait must here also havo been filled with ice. No local glaciation, which would radiate from tho mountains of the district, can account for the facts. In clays resting on thcfo gla- ciated rocks, shells like those formerly observed at ^'ictoria wore found, a small collection comprising Sd.vicava mr/osa, Mija truiicata, and Leila fossa. The height of the locality is about 7U feet above tho sea. Between Vancouver Island and the mainland, on both sides of tho central region from which the ice spread in two directions to form the Quccn-Charlotte-Sound and Strait-of-Georgia glaciers, well- stratified deposits of clays and sands occur, in some places forming clifi's 200 feet in height. In the course of tho Queen-Charlotte- Sound glacier, Cormorant Island may bo cited as an example of these deposits ; and in that of tho Strait of Georgia, Harwood, ^lary, Hernando, and Savary Islands, These deposits resemble those of Victoria, New Westminster, and the islands in the southern part of the Strait of Georgia previously described, but imply for tho period of their formation a decreased length in the glacier, from its point of maximum extension, of at least 100 e. iles. Harwood, Mary, Her- nando, and Savary Islands lie about the entrance of Bute and * Quart. Jouru. Oeol. Soc. vol. xxxiv. pp. 94, 9G, 99. 280 G. M. DAWSON ON IHE SUPERFICIAL GEO LOGY OF neighbouring inlets in such a position as to suggest that they may in part represent a moraine marking a stage in retreat of the ice. They form the projecting points of a comparatively shoal bank off these inlets, which, in their upper parts, are very deep, BouWors here occur in groat abundance on the beaches, and are probably derived from a Boulder-clay or morainic material underlying the well-bedded deposits. Glaciation of the Queen-Charlotte Islands. These islands were tho subject of geological examination in 1878. They form a compact arcaipelago widely separated from the southern extremity of Alaska to the north, and the western coast of British C!olumbia to the east, and may be regarded as a partly submerged nionntain system, the axis of which lies in a N.N.W.-S.S.E. bearing. In its central part summits surpassing 4U00 feet, and still bearing patches of perennial snow, are frequent, but it falls at both ends. On the north-east side of the mountain axis, at its north end, is a wide triangular attachment of flat land forming the greater part of Graham Island. In these islands we find everywhere evidence of the descent of glacier-ice from the mountains toward the sea, but (with one im- portant exception subsequently noticed) none of the passage across the group of any more ponderous ice-mass. The channels and fiords penetrating the southern portion of the islands show in general di- stinct and heavy glaciation which has evidently been local in cha- racter, the scoring and grooving being parallel to the main directions of the valleys, and changing with their course. In Houston- Stewart Channel, separating Prevost and Moresby Islands, the ico has evidently flowed from the axial mountains both eastward and toward the open Pacific to the west. Many of the boulders of the beaches are distinctly glaciated, and, as they lie in some places rudely packed together, seem to have been little disturbed since they were deposited by the ice. Sands, clays, and other detrital deposits re- ferable to the period of glaciation are here almost entirely wanting, and the water round the coast is deep. Further north, near Laskeek, where the width of the islaiids becomes greater, there is evidence, in the comparatively slight de- gree in which the rocks at the outer ends of the inlets are glaciated, that the glaciers did not long stretch much further out than the pre- sent coast-line. At Cumshewa Inlet (lat. 5;i°), and further north at Skidcgate Inlet, the character of the coast changes, becoming low ; but both these inlets still head in the higli axial mountains of the group. Traces of the glaciers of these inlets are found nearly to their mouths ; but while the upper parts are still deep and fiord- like, they are partly blocked at their seaward extremities by trans- verse bars, and shallow water extends far off shore. Further north a series of fiord-like valleys are still found pene- trating the eastern side of the mountainous axis of Graham Island, and the shoal-water found off Cumshewa and Skidogate is repro- BBlXISa COLTTMBfA AND ADJACENT REGIONS 281 sentcd by the wide stretch of flat land before alluded to. Several of the fiords here open together into a large sheet of water forming the upper part of Masset Iiilet, which communicates with the sea to tlie north by the long narrow passage known as the Masset Sound. The fiords are heavily glaciated, bordered in most ])lace8 by steep rocky shores, deep and free from drift deposits, and contrast in these respects markedly with the low-shoal eastern shores of the Masset expansion into which they open. The composition of the low land to the east and north-east is best shown in the cliffs forming its eastward-facing margin. A few miles north of Skidegate a low cliff or bank shows deposits which are evidently of glacial age, cut. off above by a gently undulating surface of denudation, above which is 10 or 15 feet of material which shows no sign of blending with that below. The upper de- ])osit consists of sand and well-rounded gravel in regular and often nearly horizontal layers. It has here become in many places quite liard, being apparently cemented by ferruginous matter. Its lower layers hold small boulders, a few of which are from 18 inches to 2 feet in diameter. The lower deposit in one place is a typical Boulder- day, with many half-rounded or subangular stones and occasional boulders of some size. The matrix is bluish grey, hard, and some- what arenaceous, the whole being irregularly mingled, and having no distinct bedding. At a short distance this Boulder-clay begins to show bedding, and to become interleaved with hard clayey gravels composed of well-rounded pebbles. The stratification of these is undulating and rather irregular, and there is some local unconformity by erosion between the different layers. A few paces still further on these become interbcdded with, and are eventually replaced by, hard, bluish-grey, arenaceous clays, which hold some pebbly layers and an abundance of broken specimens of moUusks, among which Lcda fossa is the most common. A small Cardium-like shell and fragments of a Balanus were also observed. Further north on this coast the clays, with the overlying sandy deposit in greater or less thickness, form long ranges of cliffs ; and tliough locally irregular, their general character continues the same. The clays are, in some places, very hard, and were observed to hold fragments of trees quite brown in colour, but not mineralized. These deposits, as a whole, very closely resemble those previously described as occurring at Victoria, on the south-eastern extremity of Vancouver Island. Lying like Masset Inlet near the junction of the hilly and low countries is Naden Harbour, and between this and Masset Inlet are two largo freshwater lakes, which doubtless occupy an analogous position, but have so far not been visited by any but Indians. Southward there is reason to believe that there are one or more basins in a similar relation between Masset Inlet and Skidegate. Boulders are very numerous on the coast of some parts of the noithorn portion of Graham Island ; and these and the beach- gravel are in many cases formed of rocks which must have been transported from the mainland to the north or cast, and quite luilike i:iia0.5 282 G. M. DAWSON ON THE SUrBRI'ICIAL OEOLOUY OK those of the Qucen-Charlotto Islands. Similar erratics appear to churacterizo in greater or less abundance the whole of the low count rj' above described, but are not found about the heads of the south-western extremities of Masset Inlet. It has previously been shown that at the time when the Strait-of- Georgia glacier began to diminish the sea must have stood consider- ably higher in relation to the land than at present, and the glaciated rock surfaces about Victoria and Nanaimo no sooner appeared from beneath the glaciers than they were covered by de])osits holding marine shells. Such must have been the state of affairs also in the (iueen-C'harlotte Islands ; and to this time are doubtless to be rcforrod the clay and sand deposits of the low north-eastern part of Graliam Island above described. The material of these must have been sup- jjlied from the glaciers of the islands themselves, but added to also (as the nature of the boulders proves) by the debris borne on tloating ice from the larger glaciers of the mainland, the sea levelling and s])reading abroad the material, and i)reventing the formation of any well-marked terminal moraines by the island glaciers. The rocky beds of the fiords and ilassct-lnlet expansions must have been shaped to some extent ])y the ice ; but the absence of drift material from their areas, and especially of the erratics derived from the mainland, are, w-ith their situation, good reasons for supposing that they mark the regions last covered by glacier-ice, and from wliich it eventually re- treated with some rapidity, leaving the hollows formerly occuj)ied by it to become first inlets, and then, with iucreaiiing elevation, in some instances lakes. The exceptional case which seems to show the impingement on the Queen-Charlotte Islands of ice not produced on them was found on the north coast on the little islands lying outside the entrance to Masset Inlet ; but it is probable that similar traces might be found by search in additional localities in this vicinity. AVider exposures of basalt a few feet above high-water mark here show very heavy though somewhat worn glaciation in a direction S. 10° E., or N. 10° W., but probably the former. The depth and parallelism of the grooving would appear to show that it is glacier work. The moun- tainous axis of tlie islands in this their northern ])art does not ex- ceed in height about KWO feet, and wliere nearest is about lo milts from the locality, while the direction of the marking is not that which would be followed by ice descending from the mountains under any circumstances, being more ncarlj' parallel to than radiant from them. It is, however, just that which ice-masses fionling up or duwn the strait separating t'.ie islands from the raainlnnd must have taken, or gliicier-ice pushing southward from the long fiords of tlio I'rince of Wales group in Southern Alaska, sixty mih's distant. It may, I believe, be attri])Utcd with greatest ])robability to the last-named agent ; and in view of the great extension whicli the glaciers of other parts of the coast must at one time have had, that required for the Prince of Wales group and adjacent channels docs not appear excessive. -»- BRITISH COLUMBIA AND ADJACENT BEGIONS. 283 General Remarhs and Conclusions. It is somewhat difficult to connect tho various observed facts of the glaciation of British Columbia in a general theory of glaciation, owing to the complexity of its physical features and their marked character. Several conjectural schemes were advanced in a former communication ; but, abandoning the seemingly untenable theory of a great polar ice-cap, two probable hypotheses appear to remain. A general north-to-south movement of ice is indicated by striation in a number of places in the central-plateau zone, extending now for a length of over 400 miles. This region, from elevations ex- ceeding 5000 feet downward, is also covered thickly with drift-de- posits requiring, by their character and mode of arrangement, tho action of water. To account for these facts it was thought that cither the flow of strong arctic currents bearing hcavj' ice during a period of great submergence might be supposed, or that the whole region may have been buried under a massive confluent glacier, tho drift-deposits being laid down as it retreated in the water of the sea during a period of subsidence, or in that of a great lake held in by glacier-dams in the valleys of the several mountain-ranges. It was presumed that the gaps of tho Peace and Pine rivers in the Ilocky-:Mountain range might have sufficed for the entrance from the north-east of such currents and masses of ice as would bo required by the first theorj' ; but the examination of the region, with this supposition in view, has convinced me that, notwithstanding the general decrease in elevation and width of the Ilocky Mountains, tho valleys of tho rivers are too narrow and indirect, and the sur- rounding mountains too high, to allow tho inflow of sufficient cur- rents with t'le degree of subsidence which would be required by most of the localities of glaciation and by the superficial deposits. Neither is there any evidence of tho passage of drift-material in this region across the mountains either from east to west or in the oppo- site direction. It therefore appears to remain as the most probable hypothesis that a great glacier mass resembling the inland ice of Greenland has filled the region which may be called the Interior Plateau, be- tween the Coast Mountains and the Gold and Ilocky Mountain ranges, moving (though perhaps very slowly) southward and south- eastward from the region of great precipitation and high mountains of tho northern part of tho province*, and discharging by tho Okanagan depression and through the transverse valleys of the coast range. It still appears to me most probable, however, that this stage of the glacial period was closed by a general submergence, during which the deposit referred to as Boulder-clay was laid down in the inteiior plateau, and that as the land again rose it assumed its present terraced character. Conditions may bo suggested to account for tho temporary existence of a great lake in the interior » Explorations in the northern part of :.io province in 1879 have shown that the mountains here are even higher ana more extensive than had been supposed, several ranges exceeding 8U00 feet in great portions of their extent. 284 G. M. DAWSON ON THE SUPERFICIAL GEOLOGY OF plateau of British Columbia ; but this will not explain the great height to which water-action has extended on the east side of the Rocky Mountains*, which was probably synchronous. The last stage of the glacial period in the northern part of British Columbia appears to have given rise to the silts of the Lower Nechacco basin, while on the opposite side of the liocky Mountains similar deposits were laid down over the Peaco-lliver country, the elevation of the two districts being nearly alike. The general question of the origin of the drift-doposits of the Great Plains having been fully diwcussed elsewhere t, it will be unnecessary here to enter into it at length. The most remarkable feature of the glacial deposits of the plains is the Missouri Coteau, which it was supposed ran northward from the region near tlie 49th parallel, where it was more particularly studied, nearly following the margin of the third prairie steppe. This supposition has since been in great measure confirmed ; .and on the journey from Edmonton to Winnipeg, in the autumn of 1879, I was able to examine cur- sorily the character of this feature where it touches the north Saskatchewan near the " Elbow," and to observe the great accumu- lation of heav; boulders of eastern and northern origin in that vicinity. Further north, the facts now^ advanced show that with the general lowering of the surface of the country the well-defined zone of drift-doposits known as the Coteau is more or less completely lost, the material being scattered broadcast over the upper parts of the basins of the Peace and Athaba'^ra rivers, and approaching in considerable mass the highlands near the base of the Rocky Moun- tains. Over the whole western portion of the plains, from the 49th to the 56th parallels, there is a mingling of the eastern and northern Laurentian debris with that from the Rocky Mountains to the west, the latter consisting largely of certain hard quartzite rocks, and the overlap seeming to imply the existence of a sea in which ice derived from both sources floated freely. Discussion. The President spoke of the care with which Dr. Dawson con- ducted his researches, and the value of his observations. Mr. Bauerman stated that he was not acquainted with the distinct described by Dr. Dawson ; but he thought, from what he had seen in Oregon and the Columbia valley, that many of the conclusions of Dr. Dawson could be established. He, however, doubted whether the ice had been quite so widely spread as Dr. Dawson supposed. He dtiscribed some of the great terraces on the Barrier River ; there were sixteen, one over the other, on a stupendous scale. He had traced them on the Columbia River to 2300 feet above sea-level ; * Quart. Journ. Geol. Soc. vol. xxxi. p. 018. t Quart. Journ. Geol. Soc. vol.xxii. p. 6();i. 49th Parallel,' p. 0. ' Geology and Resources of the iS^^ BRITISH COLUMBIA AND ADJACENT RKGIONS. 285 and they could bo found still higher but for the degrading actiou of the climate. The rapid melting of the snow, followed by freezing, and slipping of the ice then formed, produced well-defined ice- scratches in a very short time. Prof. Boyd Daavkins said that he had studied the glacial phe- nomena in America, though he had not been so far north ; and, 80 far as he could form an opinion, that northern area appeared to have been a great area of dispersal of ice. In the Western and Pacific States, however, there was no evidence of a great ice-sheet, only a rather larger extension of local glaciers. On the eastern side the southern boundary of the confused glacial deposits, or the drift, passed from the latitude of New Brunswick in a N.W. direc- tion towards the area of the Mississippi, forming a low range of well- marked hills. To the south of this are the "Champlain terraces" and traces of local glaciers on the higher hills. So that in North America there are two great systems of glaciation — one in the N.W., such as Dr. Dawson had described ; and another in the N.E. region, apparently pointing towards Greenland and Labrador.