THE GEOLOGY OF THE BERGEN DISTRICT, NORWAY. 3 and often torrential; lakes of varied size, and often of great beauty, abound, but the great charm of the country arises from the fjords or inlets of the sea, which, running far inland, form a series of waterways throughout the district. The Hardanger Fjord has more than one opening to the North Sea a little to the south of Bergen, and penetrates into the country for a distance of over 90 miles. There is a network of fjords in the neighbourhood of Bergen itself, and one of them extends so far inland that the station of Bolstad, 48 miles from Bergen by rail, stands on an inlet of the sea. The Sogne Fjord lies to the north of Bergen, and its innermost port, Skjolden, is as much as J 30 miles from the open sea. Nordfjord is a district with a fjord about half the length of the Sogne Fjord, the different parts of which bear different names. All these fjords are deepest in the inner parts and have a shallow area dividing them more or less distinctly from the Norwegian Submarine Channel, and this is at least partly due to the deposit of moraine-material in the outer parts of the fjords at a time when the inner parts were filled with ice, and thus protected from deposition. No doubt some or all of them may be rock-basins to a certain extent, and there may be more than one rock-basin in the same fjord. Many of the lakes, too, may be rock-basins, but it is often difficult to say whether there may not be an old channel which is now hidden and filled with moraine-material; and in some cases the lakes are obviously formed by dams which are terminal moraines of retreated glaciers.

n.-THE ROCK-FORMATIONS OF THE DISTRICT. By H. W. MONCKTON. r. The Archcean Rocks.-A large part of the Bergen district is mapped" Grund/ie/d," or fundamental rock. It extends from Nordfjord to Sogne Fjord, including the whole area of the snowfield jostedalsbne ; it forms both sides of the Sogne Fjord from near Leikanger and Fejos to the sea; there are patches at Lserdal, Aurland, and other places in the eastern part of the district. It extends southward from the Sogne Fjord into the Voss district, forms several mountains near the city of Bergen and many of the islands off the coast. There are also large tracts of Gnmdjjeld around the head of the Hardanger Fjord and in other parts of South Bergenhus. The Grundjjeld, which is practically equivalent to the Archsean, consists of- r. Granite, more or less gneissic. 2. The Telemark Formation. 3. Gneiss, with which are associated various more or less gneissic igneous rocks, both acid and basic. 4 CARL FRED. KOLDERUP AND H. W. MONCKTON ON

Upper Telemark is an extensive district in southern Norway forming the northern part of the Bratsberg Amt, and a thick series of quartzites and conglomerates, associated with various igneous rocks, is developed there and is believed to be of pre-Cambrian age and to correspond to the Huronian of Canada. This series is known as the Telemark Formation. (Werenskiold, "Om pst Telemarken," Norges Geol. Unders., vol, liii, 1910, part 2.) Mr. Kaldhol, in 1903 (Norges Geol. Unders., vol, xxxvi, part 3), described the Telemark Formation in the Suldal-Roldal tract on the southern side of South Bergenhus, dividing the Archeean as follows:

I. The older granite (newest part of the Archrean). 2. The Telemark Formation. 3. The old Gneiss. Mr. Rekstad, in the same year, speaking of the mountain-tract which forms the eastern part of South Bergenhus, says (Norges Geol. Unders., vol. xxxvi, part 4): "Quartzite and gneiss-like rocks with the character of the Telemark Formation occur in several places below the Cambro-Silurian Series, and are traversed by numerous veins of the granite which occurs in the Archeean, thus showing that they are older than the granite which forms, as has been said, the newest part of the Archrean." Subsequently (No. 94) he has traced the Telemark Formation to the northern end of the peninsula, upon which lies the great snowfield Folgefond. The formation there contains a conglomerate of quartz pebbles varying in size from that of a hazel to that of the fist. The conglomerate is underlain by a thick bed of quartzite, the two together forming the Telemark Formation. The Archrean granite of this peninsula is described by Mr. Rekstad as being usually porphyritic, with large crystals of red or grey orthoclase, there being at times small flakes of albite and oligoclase, which form a microperthitic intergrowth with the orthoclase. Owing to pressure, the felspar crystals have often been broken up, and in places the rock has been converted into an eyed gneiss. Passing to the north of the Hardanger Fjord we find Archsean Gneiss associated with considerable areas of more or less gneissic igneous rock. There is, for instance, a rather extensive mass of diorite at Evanger, on the Bergen-Voss railway, and near Bergen itself there are several patches of granite, which in some places is very little altered, whilst in others it has been changed into an eyed gneiss. The islands off the Bergen coast consist mainly of gneiss and the associated older granite. (See the maps by Reusch and Kolderup, No. 72 and No. 79, and post, p. 18.) There are many beds of quartzite in the district north of the Hardanger Fjord, some of which may belong to the Telemark THE GEOLOGY OF THE BERGEN DISTRICT, NORWAY. 5

Formation, but they are for the most part apparently of newer date. Two small patches of Telemark Formation are mapped near Hallingskarvet (see the map in No. 101). In the Lrerdal district the Archrean consists of gneiss with associated granite, and as the granite contains inclusions of gneiss it is clearly the newer of the two. The granite, which covers a large area, has been described by Mr. Rekstad (No. 86) as mostly porphyritic, the large felspar crystals consisting in part of orthoclase and in part of microcline. They include not in­ frequently smaller parts of a lamellar plagioclase (albite), and many examples contain also some oligoclase. The quartz usually shows undulating extinction under the microscope; the biotite occurs in bow-shaped crystals with often an unravelled appearance at the ends. Besides the biotite there is also some potash-mica, which seems as a rule to have followed on the decomposition of the felspar, This granite has also occasionally some hornblende. Accessory minerals are apatite, titanite, pyrites and magnetite. Zircon is not uncommon, and there is often epidote as a change­ product after plagioclase. The rock often shows fractured crystals of felspar and other signs of pressure. The Archrean between the Sognefjord and Nordfjord does not appear to have been much studied. It consists chiefly of grey and red gneisses, sometimes alternating with mica-schists. These gneisses are older than the gneiss-granites and porphyritic­ granites in this district. In the inner part of Nordfjord (Gloppen and Hyen) there is a formation of old quartzite. 2. The Cambro-Silurian Series.-The rocks which overlie the Archrean in Norway have been divided into a number of "etages," or stages, of which etages Ib to 9 represent the Cambrian and Silurian Series. These etages are not well developed in the Bergen district, and it is consequently only necessary to give a list of them here, and to refer for further details to Sir Archibald Geikie's "Text Book of Geology" (jrd Edition, 1903, vol. ii, pp. 924 and 969), and to the "Norwegian Geology" by Dr. Reusch (No. II2, p. 31).

CAMBRIAN SERIES. Etage lb.-The Dlene/lus-beds. Etage IC, td, and Etage 2.-Black shale known as the Alum-shale.

SILURIAN SERIES. Etage 3.-The Asaphus-beds, which include the Ceratof>yge- and Orthoceras-limestones and the Phyllograptus.shale. Etage 4.-The Chasmops-beds. Etage 5.-Consists of 5bthe Calcareous Sandstone-beds, and Sa the Gastero/Jod-limestone. Etage 6.-The Lower Llandovery with StricRlandia lens. Etage 7.-The Upper Llandovery with Pentamerus ob/ongus. Etage S.-The Wenlock Series with Spiriftrplicatlllus. Etage g.-The Ludlow Series, Spirifer e/evatus. 6 CARL FRED. KOLDERUP AND H. W. MONCKTON ON

In the Bergen district these divisions can very rarely be recognised, and the whole Cambro-Silurian is included in one great formation which is mapped Fyllit or Ltrglimmtrskijtr, and is of Cambrian and Silurian age. A rather narrow band runs across the district in a north-easterly and south-westerly direction, forming much of the shore of the Lyster Fjord, crossing the Sogne Fjord at Fejes, and running into the Voss district, where it has a considerable extension. To the east of the two Amts or Provinces of Bergenhus there is a large area of this formation around the lake Vangsmjosen, It crosses our boundary near Maristuen, and is seen in the valley of the River Lsera and at many places between that valley and the Aurlands Fjord. It occurs as patches on the high ground over which the Christiania­ Bergen railway runs, and is found on Hardangervidden. It forms much of the shore of the Hardanger Fjord and is also developed around Bergen, where it has been known under the name Bergeus Skifernt (see p. :22). In 1865, Dr. Tellef Dahll found Dictyonema in the dark phyllite of this formation at Hulberget, on Hardangervidden, and some years later Dr. Reusch found fossils near the village of Os, some 1 S miles south of Bergen, at two places in Sondhordland, on Froyen in the Sondfjord district, and in Samnanger. Dr. Kolderup has also found fossils in this formation at other places, and he has subsequently examined the strata near Os and in Sondhordland and found new fossils, which have been studied by Prof. Kiser in Christiania. The result of Prof. Kiser's deter­ minations shows that the phyllite on the island :of Stord, in Sondhordland, belongs to the Stages sa and 6 of the Silurian, and that the fossiliferous marble of Os belongs to Stage sa, and the phyllites at DIven to 6c. Some further details as to these fossiliferous beds will be found in the Paper by Dr. Kolderup, post, p. 19, and in the Report of our Excursion, p. 42. In the south-eastern part of the district the series consists of the following beds in descending order: SILURIAN.-I. Phyllite, grey to green, greatly crumpled and full of twisted quartz layers, Sometimes it contains felspar and passes into a phyllite-gneiss. It is of considerable thickness. Occasionally there is a bed of limestone at the bottom. 2. A blue-grey rock, probably equivalent to the blue quartzite of eastern Norway, is found beneath the phyllite over most of Hardangervidden, though it is wanting in the west and north of that mountain district. It is usually thick-bedded and contains generally a little felspar. It varies in thickness from a few yards up to some 200 feet. CAMBRIAN.-Dark phyllite, not unlike the Alum schist of the Christiania district. Dictyonema jlabelliforme has been found at THE GEOLOGY OF THE BERGEN DISTRICT, NORWAY. 7

Hulberget, or Holberget, on the eastern side of Hardangervidden (see Rekstad, 81, p. 21). This series in the Voss district has been described by Dr. Reusch (No. 89, p. 32) as consisting of dark grey to blackish phyllite, passing from soft rock to a hard rock tolerably rich in quartz. Lens-shaped patches of white quartz are usually present; the whole is often much crumpled and Dr. Reusch gives some diagrams showing the crumpled quartz-eyes. The tract between the Voss district and the Sogne Fjord has been described by Mr. Rekstad (No. 107, p. 12 and map). He says that the phyllite is, for the most part, grey-black to greenish-grey with, as at Voss, numerous quartz-layers, the whole much crumpled. In places, more especially near the junction with the overlying igneous rocks, it has a gneissic appearance. Mr. Rekstad (No. 86, pp. 10-18) has also described the Lserdal-Aurland district. The Cambro-Silurian Series occurs as rather thin bands between the Archrean gneiss and granite below and the newer eruptive rocks above, and in some places it forms patches on the high ground. It has been greatly altered, often contains a great deal of quartz, and then resembles a gneiss. It may be studied on the Valders route between Husum and Borgund, In the district to the west of the Lyster Fjord the phyllite is well seen in the beautiful ravine which runs in a south­ westerly direction from Marifjreren. At the western end of the ravine there was in 1907 a good exposure, by the road-side, showing a conglomerate with large pebbles of gneiss, some of which had been flattened by pressure. The Silurian rocks of the neighbourhood of Bergen are dealt with on page 19. 3. The Younger Sparagmite and S!lndstone.-This group includes a variety of rocks which rest upon the series of strata which is assigned to the Cambro-Silurian, and are probably newer, unless, of course, they are overthrust masses of older rock. A reddish, felspathic sandstone belonging to this series is found in the mountains named Mellene, which lie some fifty miles east of the Lserdalsoren, As this formation approaches the igneous masses of the Jotunheim it becomes more like a quartzite or gneiss. A considerable area by the Tyen Lake is mapped as Younger Sparagmite, and is well exposed on the road from Nystuen to the lake. Other patches are mapped on both sides of the Lyster Fjord. They are gneissic rocks and quartzites which overlie the Cambro-Silurian, but Dr. Reusch considers their age to be doubtful (No. 10 I, p. IS). In the Voss district there are thick beds of light-coloured and dark quartzite associated with fine-grained gneiss-like rock, and these appear to overlie the Cambro-Silurian phyllite. Dr. Reusch (N o. 89, p. 73) remarks that at several places just over the phyllite the quartzite is beautifullyschistose, and is then used asroofing slate. 8 CARL FRED. KOLDERUP AND H. W. MONCKTON ON

. The Voss slate-industry is of considerable importance. The slates are not very thin, light green, and stand the Norwegian climate well. The report of our visit to the quarries will be found on page 44. 4. The Devonian Conglomerates andSandstones»-:Dr. Kolderup contributes the following note on the Devonian Series in the district: "In the western part of the North Bergenhus Amt we have four great areas of conglomerate and sandstone. The southernmost of these is that of the Sulen Islands at the mouth of the Sognefjord. Then we have the district of Kvamshesten, between Dalsfjord and Fordefjord, and the district of Haastenen in Hogdalsfjord, both in Sondfjord ; and last, but not least, the district of Hornelen, the famous mountain at the mouth of Nordfjord." "These conglomerates and sandstones have not been folded and altered like 'the underlying Silurian rocks. They contain fragments of a white granite which cuts the Silurian, and must consequently be younger than that formation. In the excursion from the Bergen Museum of 1910, Messrs. Aasebo, Omvik, and Dr. Kolderup found a great quantity of plant remains in the sand­ stone in the districts of Hornelen and Kvamshesten, and although they are badly preserved Prof. Nathorst has determined them to be of Devonian age." (See also Kolderup, No. 82.) 5. :Ihe Igneous ROCRS.-The igneous rocks of the great tract between Nordfjord and Sognefjord are very varied in character. They include coarse pegmatites, granites, and other rocks, both acid and basic, all more or less altered, and most of them belonging to the Archrean. Dr. Kolderup, however, informs me that the white granite of Bremangerland and Sogneskollcn, and probably also the syenites between Dalsfjord and Fordefjord, are younger than the altered Silurian rocks of the western part of this tract. (See Kolderup, No. 1I4.) Around the head of the Sognefjord we find also a post-Silurian Series of igneous rocks, largely basic, and extending for a distance of some 120 miles from the mountains of Jotunheim in the north-east to the Voss and Hardanger districts in the south-west. In addition to the basic rocks there is a good deal of granite, and all these rocks have in places a schistose or gneissic appearance. Mr. Rekstad has studied the igneous rocks in the inner Sognefjord area, and divides them as follows: r. Hornblende granite with a red felspar is the oldest of the series,' and has been largely altered into gneiss­ granite. 2. Gabbro, which contains a good deal of iron ore and a little quartz. The pyroxene has often been changed to hornblende. 3. Labradorite-rock. The well-known white felspar-rock THE GEOLOGY OF THE BERGEN DISTRICT, NORWAY. 9

of the Nserodal. In places it cuts the gabbro, but the two are very closely associated. 4. White granite, with veins which penetrate all the. above rocks, showing it to be the newest of the series. It is to be seen in Lserdal, Aardal, Sogndal, etc. Mr. Rekstad thinks it possible that 2, 3, and 4 may all be differential products from the same magma. He remarks that on the northern side of the Aardals Fjord the Labradorite-rock is penetrated by such a network of veins of the white granite that in places it is hard to determine which colour to place on the map (No. 86, p. 20.) The Labradorite-rock of the district and its associates are very fully dealt with by Dr. Kolderup in a paper written in German (No. 79), and some further details are given by him at page 23. Mr. Kaldhol (Norges Geol. Unders., vol. xxxvi, NO,3, 1903), dealing with the district of Suldal in Stavanger Amt, describes a younger granite which is intruded in, and consequently is newer than, the Cambro-Silurian schists. It is of medium grain and with very little sign of gneissic structure. 6. The High-Moull1ain Formation and Overthrusts.-The experience of British geologists in the North-western Highlands of Scotland has led us to be on the look-out for examples of overthrust in a country so similar to Scotland as Western Scandinavia, and at the International Geological Congress at Stockholm in 1910 we heard a great deal about overthrusts on a. large scale in the northern part of the Scandinavian peninsula. The possibility of overthrusts in the Bergen district has not been lost sight of by the Norwegian geologists, and they have long suspected that certain cake-like masses of granitic and gneissic rock, which rest upon the Cambro-Silurian series and have been termed the High-mountain Formation, may be over­ thrust portions of the Archrean. The question is discussed by Messrs. Reusch; Rekstad, and Bjorlykke in their paper on Hardangervidden, 1902 (No. 78); by the last of these writers in his work on Central Norway, 1905 (No. 85); by Dr. Reusch in his explanation of the map of the district between the Jostedals snowfield and Ringerike (Norges Geol. Unders., vol. xlvii, 1908) ; and in his recently-published "Geology of Norway " (No. 112). He explains (No. IJ2, p. 84) that the name Hoifjeldsformationer has been applied to a group of metamorphic rocks of which the mountain-tract of Western Scandinavia is largely composed and which are distinct from the Archsean Series. The group consists (p. 86) of granite, crystalline schists, gneiss, hornblende-schist, etc., and forms masses which overlie the Cambro-Silurian phyllite. He adds that some geologists consider the formation to be newer than the Cambro-Silurian, whilst others hold that the division is, jn the main, rock of Archsean age which has been pushed over 10 CARL FRED. KOLDERUP AND H. W. MONCKTON ON the Cambro-Silurian along horizontal thrust-planes. Dr. Reusch himself thinks that the most satisfactory explanation is that the rock is overthrust Archrean, and that during the overthrusting the phyllite series, being soft, acted as a lubricant between the under­ lying and the overlying hard masses. He remarks that this will account for the very complicated bedding which we often see in the Cambro-Silurian phyllites. The High-mountain Formation can be studied in the neighbourhood of Finse. Patches of the rock are found around the snowfield Hardanger J oklen, and the long ridge named Hallingskarvet is formed of a cap of gneiss and granite, which rest upon rocks of Cambro-Silurian age. (See Rekstad, 81, Reusch 112, and also post, page 45).

IlL-THE PRESENT SURFACE-FEATURES OF THE DISTRICT.

By H. W. MONCKTON.

I. Mountazns.-It has been pointed out by Dr. Reusch (No. 73) that the present surface of the district belongs to two perfectly distinct periods. The older or Palseic surface, character­ ised by rounded hills and wide, shallow valleys, dating from pre­ Quaternary, and perhaps from pre-Tertiary time, whilst the newer, with deep and narrow valleys, has been cut out in the older surface and belongs to a more recent geological date. The deep, narrow valleys frequently have a steep, rounded end over which the rivers run as waterfalls, and it is in these valleys that the fjords lie. The mountains of the J otunheimare mostly situated in the Christians Amt, but the mountain district extends on its western side into North Bergenhus. One of the many peaks, Galdhopig, 8,402 feet, is the highest mountain in Norway; another peak. Glittertind,attains a height of 8,380 feet; and several others rise more than 6,000 feet above the sea. These mountains have an alpine appearance and character, but the greater part of the high ground in the Bergen district consists of more or less extensive plateaux, the highest of which are above the snow-line and are covered with perpetual snow. The level of the snow­ line varies in different parts of the district, and is higher inland than near the sea, but it is usually not much above or below the level of 5,000 feet. 2. Snowjields.-The sheets of perpetual snow or snowfields in the district are very numerous and of the most varied shape and size, but one of them, Jostedalsbrre, is far larger than any of the others, having a length of about 40 miles and a breadth in places of over 8 miles. The snow rests upon a plateau which stretches in a north-eastern and south-western direction between