Polyorogenic imbrication and metamorphism of northwest portions of the Baltoscandian miogeocline

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6594810

Hames, W E; Dallmeyer, R D

Within central portions of the Scandinavian Caledonides the record of sedimentation, fossil occurrences, and geochronology require a polyorogenic evolution. This record also appears to characterize portions of the arctic Norwegian Caledonides where a composite Precambrian basement terrane (BT) is structurally overlain by a variety of Caledonian allochthons. Highest structural units are represented by the Tromso Nappe Complex which may reflect portions of the Laurentian miogeocline. Amphibole from both the BT and lower Caledonian allochthons record /sup 40/Ar//sup 39/Ar plateau ages of c. 475-500 Ma. Porphyroblastic muscovite from the same units yield /sup 40/Ar//sup 39/Ar plateau dates of 375-385 Ma. A sample of metagranodiorite from the BT yields a whole-rock mineral isochron age of 388 +/- 4 Ma. The available field and geochronologic data suggest a polyorogenic evolution consisting of late Cambrian-Early Ordovician structural imbrication and associated amphibolite grade metamorphism and a Middle Silurian-Early Devonian tectonothermal overprint. The later event is consistent with the overlying eastward transport of the LNC. These results are consistent with the model of Dallmeyer and Gee (1985) in which initial imbrication of the Baltic miogeocline occurred within an accretionary prism developed within a west-dipping subduction complex outboard of the Baltic platform. This was followed by Late Silurian-Early Devonian collision of Baltica and Laurentia which resulted in translation of composite allochthons over the previously metamorphosed Caledonian basement.

• Research Organization: Univ. of Georgia, Athens (USA)
• OSTI ID: 6594810
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
580201 -- Geophysics-- Seismology & Tectonics-- (1980-1989)
AGE ESTIMATION
BASEMENT ROCK
EUROPE
FOSSILS
GEOLOGIC HISTORY
GEOLOGIC MODELS
METAMORPHIC ROCKS
METAMORPHISM
OROGENESIS
PALEONTOLOGY
PETROGENESIS
PLATE TECTONICS
ROCKS
SCANDINAVIA
SEDIMENTARY ROCKS
SUBDUCTION ZONES
TECTONICS
WESTERN EUROPE