In the Arctic Seas Part 30

4. The Lias Rocks.

5. The Superficial Deposits.

I shall describe these successive formations briefly, and add a few remarks of a theoretical character, to indicate the important inferences which may be drawn from the facts respecting them made known to us by M'Clintock's discoveries.

I.--_The Granitic and Granitoid Rocks._

These rocks form a considerable part of North Greenland, on the east side of Baffin's Bay, and constitute the rock of the country at the east side of the island of North Devon, which forms a portion of the coast-line of the west of Baffin's Bay, and the north side of the entrance into Lancaster Sound.

1. _Whale Fish Islands_, lat. 69 N., are composed of a very fine-grained, flaggy, black mica schist, composed of black mica in very small plates, occasionally putting on a hornblendic lustre, and minute grains of quartz interstratified with the mica. The softer varieties are cut by the natives into grissets and cooking utensils of various shapes, some of which resemble the cambstones found in Ireland, which are made from a kind of potstone, abundant in parts of the County Donegal.

2. _Upernivik_, lat. 72 N., Greenland.--This district is famous for the occurrence of large quantities of plumbago, which is found in a metamorphic rock of the following character. Fine-grained, amorphous, granitoid rock, composed of minute particles of grey quartz; a honey-colored felspar of waxy lustre, of unknown composition; minute particles of red semitransparent garnet, of conchoidal fracture; and small particles, with occasional large nests, of plumbago. The plumbago occurs both amorphous, and in long acicular crystals. Sometimes the rock becomes of coarser texture and more crystalline, and the yellow color of the felspar gives place to a greenish tinge; and it sometimes also becomes a felspar of perfect cleavage, semitransparent, and white. The dodecahedral crystals of garnet reach the diameter of one inch.

The general character of the rocks near Upernivik is different from that of the rock in which the plumbago is found; they consist of a fine-grained black mica schist, with very little felspar or quartz, and intersected by thin veins of elvan composed of quartz and white felspar.

The cooking utensils of the natives are made from this fine schist, in preference to any other description of rock.

3. _Woman's Islands._--These islands, off the west coast of Greenland, are composed of a garnetiferous mica slate, formed of black mica in layers, with alternating plates, composed of white felspar and quartz, and filled with fine garnets, rose-colored, vitreous in fracture, and transparent.

4. _Cape York_, lat. 76 N., Greenland.--This cape is composed of a fine-grained granite, consisting of quartz, white felspar, with minute specks of a black mineral, of pitchy lustre, composition not yet determined.

5. _Wolstenholme and Whale Sounds_, lat. 77 N., Greenland.--At Wolstenholme Sound the granitoid rocks of Greenland become converted into mica slate and actinolite slate of a remarkable character. The mica slate is composed of large plates of an intimate mixture of black and white mica, the chemical examination of which will doubtless prove of interest. These plates of mica are separated by bands of pure white felspar. The actinolite slate is dark green, and formed by an almost insensible gradation from the mica slate. In the low ground between Wolstenholme and Whale Sounds, the granitic rocks cease, and are covered by deposits of fine red gritty sandstone, of a banded structure, and a remarkable coarse white conglomerate. The boundary between these formations is also marked by the development of masses of dolerite and clayey basalt.

6. _Carey's Islands_, 76 40' N., Greenland, lie to the westward of Wolstenholme Sound, and are composed of a remarkable gneissose mica schist, formed of successive thin layers of quartz granules, containing scarcely any felspar, and layers of jet black mica, with occasional facets of white mica. This mica schist passes into a white gneiss, composed of quartz, white felspar, and black mica, penetrated by veins, coarsely crystallised, of the same minerals. Yellow and white sandstones are also found in small quantity on the islands, reposing upon the granitoid rocks.

7. _Capes Osborn and Warrender_, lat. 74 30' N., North Devon.--The granitoid rocks between these two capes are composed of graphic granite, consisting of quartz (grey) and white felspar; this graphic granite passes into a laminated gneiss, consisting of layers of black mica and white translucent felspar, sparingly mixed with quartz: with the gneiss are interstratified beds of garnetiferous mica slate, consisting of quartz, pale greenish white felspar, black and white mica in minute spangles, and crystals of garnet, rose-colored, disseminated regularly through the mass. Quartziferous bands of epidotic hornstone occur with the foregoing beds; and the whole series is overlaid by red sandstones, of banded structure, which bear a striking resemblance to those that overlie the granitoid beds of Wolstenholme Sound.

8. _North Somerset._--The granitoid rocks are found again on the west side of the island of North Somerset, where they form the eastern boundary of Peel Sound. Boulders of granite are found at a considerable distance (100 miles) to the north-eastward of the rock _in situ_, as at Port Leopold, Cape Rennell, etc. The general character of the granitic rocks in the north and west of North Somerset are thus described by Captain M'Clintock:--

"Near Cape Rennell we passed a very remarkable rounded boulder of gneiss or granite; it was 6 yards in circumference, and stood near the beach, and some 15 or 20 yards above it; one or two masses of rounded gneiss, although very much smaller, had arrested our attention at Port Leopold, as then we knew of no such formation nearer than Cape Warrender, 130 miles to the north-east; subsequently we found it to commence _in situ_ at Cape Granite, nearly 100 miles to the south-west of Port Leopold.

"The granite of Cape Warrender differs considerably from that of North Somerset; the former being a graphic granite, composed of grey quartz and white felspar, the quartz predominating; while the latter, or North Somerset granite, is composed of grey quartz, red felspar, and green chloritic mica, the latter in large flakes; both the granite and gneiss of North Somerset are remarkable for their soapy feel."[30]

[Illustration: Cape Bunny, Peel Sound.]

To the east of Cape Bunny, where the Silurian limestone ceases, and south of which the granite commences, is a remarkable valley called Transition Valley, from the junction of sandstone and limestone that takes place there. The sandstone is red, and of the same general character as that which rests upon the granitoid rocks at Cape Warrender and at Wolstenholme Sound. Owing to the mode of travelling, by sledge on the ice, round the coast, no information was obtained of the geology of the interior of the country, but it appears highly probable that the granite of North Somerset, as well as that of the other localities mentioned, is overlaid by a group of sandstones and conglomerates, on which the Upper Silurian limestones repose directly. A low, sandy beach marks the termination of the valley northwards, and on this beach were found numerous pebbles, washed from the hills of the interior, composed of quartzose sandstone, carnelian, and Silurian limestone. The accompanying sketch was made by Captain M'Clintock, on the spot, in 1849, and afterwards finished by Lieutenant Browne. It represents the island called Cape Bunny, which forms the eastern headland of the entrance of the now famous Peel Sound, down which the 'Erebus' and 'Terror' sailed, three years before it was visited by Sir James C. Ross and Lieutenant M'Clintock, in their first sledge journey on the ice.

Cape Granite is the northern boundary of the granite, which retains the same character as far as Howe Harbor. It is composed of quartz, red felspar, and dark green chlorite; and is accompanied with gneiss of the same composition. I have in my possession a specimen of this granite, found as a pebble at Graham Moore Bay, Bathurst Island, S.W., a locality 135 knots distant from Cape Granite, to the N.W.

9. _Bellot Strait_, lat. 72 N., separate North Somerset from Boothia Felix. The 'Fox' Expedition wintered here in 1858, and had abundant means of ascertaining the geological structure of the neighborhood. The junction of the granitoid and Silurian rocks occurs in these straits, the low ground to the east being horizontal beds of Silurian limestone, while on the west the granite hills of West Somerset rise to a height of 1600 feet above the narrow straits. The granite here is of three varieties.

a. Blackish grey, fine grained, gneissose granite, composed of quartz, white felspar, and large quantities of fine grains and flakes of hornblende, passing into black mica. The gneissose beds of this granite dip 13 S.E.

. A red granite, graphic texture, composed of quartz and red felspar, coarse grained.

?. Syenite, composed of honey-yellow felspar and hornblende, in very large crystals, the felspar passing into red and pink, and the whole rock mass penetrated by veins of the same material, but fine grained.

This variety of igneous rock was met with principally at Pemmican Rock, western inlet of Bellot Strait. Large quantities of hornblende are also met with at Levesque Harbor, Bellot Strait, composed of facetted crystals agglutinated together into large masses, forming a crystalline hornblendic gneiss.

10. _Pond's Bay_, _Baffin's Bay_, lat. 72 40' N.--In this locality a quartziferous black mica schist underlies the Silurian limestone, and is interstratified with gneiss and garnetiferous quartz rock, all in beds, inclined 38 W.S.W. (true).

11. _Montreal Island_, mouth of the Fish River, lat. 67 45' N.--The granitoid rocks, which everywhere, in the Arctic Archipelago, underlie the Silurian limestone, appear at Montreal Island as a gneiss, composed of bands of felspar (pink) and quartz (1/4 inch thick), separated by thin plates composed altogether of black mica; the whole rock exhibiting the phenomena of foliation in a marked degree.

The east side of King William's Island, though composed of Silurian limestone like the rest of the island, is strewed with boulders of black and red micaceous gneiss, like that of Montreal Island, and black metamorphic clay slate, in which the crystals of mica (qu. Ottrelite) are just commencing to be developed. It is probable that the granitoid rocks appear at the surface somewhat to the eastward of this locality.

12. _Prince of Wales' Island_, west of Peel Sound.--The granitoid rocks extend across Peel Sound into Prince of Wales' Island, in the form of a dark syenite composed of quartz, greenish white felspar passing into yellow, and hornblende. This rock is massive and eruptive at Cape M'Clure, lat. 72 52' N., and occasionally gneissose, as at lat. 72 13'

N. Between these two points, at lat. 72 37' N., a limestone bluff occurs containing the characteristic Silurian fossils, and is succeeded at 72 40' by a ferruginous limestone, bright red, and a few beds of fine red sandstone, like those observed by M'Clintock at Transition Valley, North Somerset. The entire western portion of Prince of Wales'

Land is composed of Silurian limestone, which in the extreme west, at Cape Acworth, becomes chalky in character and non-fossiliferous, resembling the peculiar Silurian limestone found on the west side of Boothia Felix.

II.--_The Silurian Rocks._

The Silurian rocks of the Arctic Archipelago rest everywhere directly on the granitoid rocks, with a remarkable red sandstone, passing into coarse grit, for their base. This sandstone is succeeded by ferruginous limestone, containing rounded particles of quartz, which rapidly pass into a fine greyish green earthy limestone, abounding in fossils, and occasionally into a chalky limestone, of a cream color, for the most part devoid of fossils. The average dip of the Silurian limestone varies from 0 to 5 N.N.W., and it forms occasionally high cliffs, and occasionally low flat plains, terraced by the action of the ice as the ground rose from beneath the sea. The general appearance of the rocks is similar to the Dudley limestone, and would strike even an observer who was not a geologist. This resemblance to the Upper Silurian beds extends to the structure of the rocks on the large scale. Alternations of hard limestone and soft shale, so characteristic of the Upper Silurian beds of England and America, arranged in horizontal layers, give to the cliffs around Port Leopold the peculiar appearance which has been described by different Polar navigators as "buttress-like,"

"castellated;" this appearance is produced by the unequal weathering of the cliff, which causes the hard limestone to stand out in bands.

Excellent sketches of this remarkable appearance, drawn by Lieutenant Beechey, are figured at page 35 of Parry's First Voyage, 'Hecla' and 'Griper,' 1819-20. The Western side of King William's Island (now, alas! invested with so sad an interest) is a good example of the low terraced form which the limestone rocks assume at times.

The following lists contain the names of the principal fossils brought home by Captain M'Clintock:--

No. I. GARNIER BAY (Lat. 74 N.; Long. 92 W.)

1. _Cyathophyllum helianthoides_, several specimens.

2. _Heliolites porosa_. Garnier Bay. Another specimen from near Cape Bunny.

3. Specimens of carnelian, gneiss, chalcedony, etc., etc., from the shingle near Cape Bunny.

4. _Cromus Arcticus_, several specimens.

5. _Atrypa phoca_ (Salter).

6. _Atrypa reticularis._ 7. Brachiopoda on slab (various).

8. Cyathophyllum.

9. _Columnaria Sutherlandi_ (Salter). Several specimens.

No. II. PORT LEOPOLD (Lat. 73 50' N.; Long. 90 15' W.).

1. Limestone containing numerous fossils of the Upper Silurian type: _Calamopora Gothlandica_, Goldf. _Rhynchonella cuneata_? Dalm.

_Cyathophyllum_, sp.

2. Dark earthy limestone, containing multitudes of the _Loxonema M'Clintocki_, as casts--1100 feet above sea-level on North-east Cape.

3. Fine specimens of selenite from shaly beds in cliff.

4. Fibrous gypsum from same.

No. III. GRIFFITH'S ISLAND (Lat. 74 35' N.; Long. 95 30' W.).

1. Beautiful specimens of the _Cromus Arcticus_. Pl. VI. Fig. 5, Journ. R. D. S., Vol. I.

2. _Orthoceras Griffithi._ Pl. V. Fig. 1, Journ. R. D. S., Vol. I.

3. An Orthoceras with lateral siphuncle, and simple circular outline of septa.

4. _Loxonema Rossi._ Pl. V. Figs. 6, 8, 9, 10, 11, Journ. R. D. S., Vol. I.

5. Numerous specimens of crinoidal limestone.

6. _Strophomena Donnetti_ (Salter). Sutherland's Voyage; Pl. V.

Figs. 11, 12.

7. _Atrypa phoca_ (Salter). Pl. V. Figs. 3, 4, 7, Journ. R. D. S., Vol. I.; and a ribbed Atrypa, not identified with European species, and undescribed.

8. An undescribed bryozoan Zoophyte. Pl. VII. Fig. 6, Journ.

R. D. S.,Vol. I.

Chapter end

Courier New
Comic Sans MS
Oh o, this user has not set a donation button.
lingua italiana
Русский язык
Novel Cool
Read thousands of novels online
Success Warn New Timeout NO YES Summary More details Please rate this book Please write down your comment Reply Follow Followed This is the last chapter. Are you sure to delete? Account We've sent email to you successfully. You can check your email and reset password. You've reset your password successfully. We're going to the login page. Read Your cover's min size should be 160*160px Your cover's type should be .jpg/.jpeg/.png This book hasn't have any chapter yet. This is the first chapter This is the last chapter We're going to home page. * Book name can't be empty. * Book name has existed. At least one picture Book cover is required Please enter chapter name Create Successfully Modify successfully Fail to modify Fail Error Code Edit Delete Just Are you sure to delete? This volume still has chapters Create Chapter Fold Delete successfully Please enter the chapter name~ Then click 'choose pictures' button Are you sure to cancel publishing it? Picture can't be smaller than 300*300 Failed Name can't be empty Email's format is wrong Password can't be empty Must be 6 to 14 characters