摘要:

Within the central part of the Scandinavian Caledonides, autochthonous Proterozoic crystalline basement rocks, with a thin veneer of Lower Palaeozoic sediments, are exposed in the thrust front in Sweden. Similar basement and cover units reappear further west in windows where they are treated as parautochthonous; they can be followed a distance of ca. 200 km westwards into the interior of the orogen. Upper Cambrian radioactive black shales, well-known on the stable Baltoscandian Platform for their high contents of trace elements such as U, V and Mo, retain their geochemical signature within the orogen in this sedimentary veneer despite the increase in metamorphic grade from sub-greenschist facies in the east to amphibolite facies in the west. The Baltoscandian Platform in the Late Cambrian extended at least as far west as the present Norwegian coast. In the front of the orogen, a décollement style dominates the structure, the cover-shortening occurring over a passive basement. Further west, towards the border between Norway and Sweden, the sole thrust passes beneath an allochthon composed of basement rocks, penetratively foliated but otherwise closely comparable with those in the underlying parautochthon. Basement-shortening of at least 70 km is implied by these relationships and may be substantially greater if the basement cores in the Swedish windows (treated here as parautochthonous) prove to be allochthonous. The major allochthonous units of the Swedish Caledonides, the Offerdal and Särv Nappes and Seve-Köli Nappe Complex, overlying the tectonic units referred to above, thin westwards, but reoccur in Norway beneath the Trondheim Nappe. This tectono-stratigraphy is treated here with particular reference to the Grong-Olden, Tømmerås and Trollheimen areas.

ISSN:0016-786X    

DOI:10.1080/11035898009454500

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The bedrock of the Kjølhaugan area is subdivided into the Seve-Köli Nappe Complex overlain by the Trondheim Nappe. The former comprises mica schists and amphibolites (Seve) overlain by garbenschiefer (Köli). The upper (western) unit is a segment of the Trondheim Nappe Complex. It overlies the Seve-Köli Nappe Complex in the western limb of the Sylarna-Riksgränsen Antiform and is composed of metamorphosed volcanic and sedimentary rocks. The upper units of the succession have been investigated in detail in the vicinity of Mount Kjølhaugan and a new stratigraphy has been established based on re-interpretation of the structure. Graptolite-bearing black phyllites (Llandoverian age) of the Slågån Group occur in the vertical to overturned (60°W) limb of the Liafjellet Syncline, and are overlain to the east by the turbidites of the Liafjellet Group. The Slågån Group passes westwards, downwards into the inverted stratigraphy of the Kjølhaugan Group, which in turn passes down into the Sulåmo Group with the basal volcanogenic Lille Fundsjø conglomerate.

ISSN:0016-786X    

DOI:10.1080/11035898009454501

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A newly-discovered fossil locality in the Köli of west-central Västerbotten County, Swedish Lapland, contains gastropods in a thin intercalation of dolomitic limestone near the top of a serpentinite conglomerate belonging to the Tjopasi Group. The specimens are poorly preserved but are of great stratigraphic interest since fossils are seldom found in this metamorphic terrain. The gastropods probably belong to the superfamily Macluritacea and are inferred to be of Ordovician age. A highly speculative correlation suggests a position near the Lower-Middle Ordovician boundary. The Tjopasi Group is overlain by quartzites and fossiliferous limestones of Ashgillian age.

ISSN:0016-786X    

DOI:10.1080/11035898009454502

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A study of major element geochemistry and petrography of metabasites in the Proterozoic basement in the Olden and Tømmerås Windows indicates an alkaline magmatism. A clear alkaline character with respect to content of trace elements is not developed. Two groups of metabasites with small geochemical differences and characteristically low Nb contents occur. A comparison between the metabasites in the basement and the Ottfjället dolerites of the Särv Nappe suggests that no relationship exists. Thus the root-zone of the Ottfjället dolerites is not to be found either in the Olden Window or in the Tømmerås Window. Metabasites of Olden type also occur in a basement nappe, thrust from the west over the parauthochton of the Tømmerås Window. One of the Olden groups is correlated with dolerites of ∼ 1200 Ma (Central Scandinavian Dolcrite Group) intruding the basement east of the Caledonian Front.

ISSN:0016-786X    

DOI:10.1080/11035898009454503

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The Olden granite is a highly differentiated Proterozoic granite occurring in a basement window within the Caledonian orogenic belt. The granite is extensively affected by the Caledonian orogeny. A minimum age of 1500 Ma and an initial87Sr/86Sr ratio of 0.7134 ± 0.0012 have been established by a Rb-Sr whole-rock age determination. Rb-Sr mineral determinations and K-Ar determinations reflect a considerable Caledonian influence.

ISSN:0016-786X    

DOI:10.1080/11035898009454504

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In the Oppdal area, a sequence of Caledonian thrust nappes was metamorphosed, recumbently folded, and refolded during the Caledonian orogeny. The well known Oppdal augen gneisses are Proterozoic rocks belonging to a single nappe unit in the tectonostratigraphy. Another distinctive nappe unit was formed from feldspathic sandstone, intruded in late Proterozoic time by pre-tectonic dolerite dikes. Despite the new thrust interpretations, the early concept of ductile infrastructurel deformation below a more rigid superstructure may still be accurate here in one of Wegmann's type localities of theStockwerktectonic model.

ISSN:0016-786X    

DOI:10.1080/11035898009454505

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A thick upper Proterozoic sedimentary sequence (4.5–6 km) has been identified in the Särv Nappe of the southern Swedish Caledonides. The sequence, defined as the Tossåsfjället Group, is divisible into five formations named in ascending order as the Lunndörrsfjällen Formation (alluvial), Kråkhammaren Formation (alluvial-littoral), Storån Formation (littoral), Lillfjället Formation (glacial-periglacial-aquatic), and Lövan Formation (alluvial). Palaeocurrents throughout the whole of the group suggest a general sediment transport from the Fennoscandian Shield towards the northwest. The group is cut at high angles by a tholeiitic dyke swarm. During the Caledonian Orogeny the Särv Nappe was displaced east-southeastwards over a distance exceeding 250 km. In its main outcrop area in Jämtland the nappe occurs as a major recumbent fold; its lower limb is highly attenuated, mylonitized and largely cut out by the basal thrust plane.

ISSN:0016-786X    

DOI:10.1080/11035898009454506

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The Kvitvola Nappe in southeastern Norway and adjacent districts of Sweden consists of the Upper Proterozoic sedimentary Engerdalen Group and crystalline basement rocks. The Hylleråsen Formation occurs at the base of the nappe and is a carbonate unit. Diagenetically formed dolomite, magnesite, chert and dolomite pseudomorphs after gypsum indicate a warm palaeoclimate. The Koppang Formation (diamictite) lies with erosional unconformity on the Hylleråsen Formation and is interpreted to be a tillite from the Varanger Ice Age. It is succeeded conformably by the Høyberget Sandstone which includes the Lekjenna Member (calcareous sandstone) and represents fluvial and shallow-marine facies. The Engeren quartzite may be a tectonic remnant of a unit beneath the Hylleråsen Formation. The Engerdalen Group is compared with other Upper Proterozoic sequences in the Scandinavian Caledonides, and the location of the palaeoenvironment is discussed.

ISSN:0016-786X    

DOI:10.1080/11035898009454507

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A 54 km long seismic refraction profile has been measured just south of the river Indalsälven and lake Storsjön in west-central Jämtland. The profile cuts across the Caledonian front in an area where the Precambrian crystalline basement is covered by folded Lower Paleozoic sedimentary rocks belonging to the Jämtland Supergroup. The time-delay method was used in the interpretation of the travel-time data. In the final model a linear increase with depth was assumed in both the basement and its cover. The model shows that the thickness of the sedimentary cover increases from about 300 m along Storsjön in the east to a maximum of some 1800 m south of the lake Ockesjön to the west. Further westwards the thickness of the sedimentary cover again decreases to less than 300 m and the possibility exists that the basement may be allochthonous. The velocity of the uppermost basement proved to be 5.93 km/s+0.11 km/s-km.

ISSN:0016-786X    

DOI:10.1080/11035898009454508

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The Nasafjället Window in the Seve-Köli Nappe Complex is composite consisting of three minor windows. Each of these is composed of Proterozoic granites overlain by quartzites and phyllites of the Mierkenis Group. The minor windows have been overthrust by the Gargatis Nappe, a tectonic unit composed mainly of Proterozoic acid and intermediate volcanites, granites and basic dykes; the uppermost part of the nappe consists of sediments of the Mierkenis Group. The Mierkenis Group is presumed to be of Late Proterozoic-Ordovician age and is correlated with the ‘Hyolithus-zone’ along the eastern margin of the Swedish Caledonides. The thrust at the base of the Gargatis Nappe is discussed in relation to the décollement-style tectonics of the eastern Caledonian thrust front.

ISSN:0016-786X    

DOI:10.1080/11035898009454509

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor