From the Early Paleozoic Platforms of Baltica and Laurentia to the Caledonide Orogen of Scandinavia and Greenland

Abstract

The Caledonide Orogen in the Nordic countries is exposed in Norway, western Sweden, westernmost Finland, on Svalbard and in northeast Greenland. In the mountains of western Scandinavia, the structure is dominated by E-vergent thrusts with allochthons derived from the Baltoscandian platform and margin, from outboard oceanic (Iapetus) terranes and with the highest thrust sheets having Laurentian affinities. The other side of this bivergent orogen is well exposed in northeastern Greenland, where W-vergent thrust sheets emplace Laurentian continental margin assemblages onto the platform. Svalbard's Caledonides are disrupted by late Caledonian faults, but have close affinity with the Laurentian margin in Northeast Greenland. Only Svalbard's Southwestern terrane is foreign to this margin, showing affinity to the Pearya terrane of northern Ellesmere Island in arctic Canada. Between the margins of western Scandinavia and eastern Greenland, the wide continental shelves, now covered by late Paleozoic and younger successions, are inferred to be underlain by the Caledonide hinterland, probably incorporating substantial Grenville-age basement. In northernmost Norway, the NE-trending Caledonian thrust front truncates the NW-trending Neoproterozoic Timanide orogen of northwest Russia. Much of the central and eastern parts of the Barents Shelf are thought to be underlain by Caledonian-deformed Timanide basement. Caledonian orogeny in Norden resulted from the closure of the Iapetus Ocean and Scandian collision of continent Baltica with Laurentia. Partial subduction of the Baltoscandian margin beneath Laurentia in the midlate Silurian was followed by rapid exhumation of the highly metamorphosed hinterland in the early Devonian, and deposition of Old Red Sandstones in intramontane basins. Late Scandian collapse of the orogen occurred on major extensional detachments, with deformation persisting into the late Devonian.

Orogenic paleofluid flow recorded by discordant detrital zircons in the Caledonian foreland basin of northern Greenland

“…2 Pb/ 206 Pb ages are preferred for analyses older than 1000 Ma, and the 238 U/ 206 Pb ages are preferred for those younger than 1000 Ma. Concor- The fluid front is recognized in the study area between samples 255628 and 303569; this is ~120-190 km west of the known limit for Caledonian thrusting (e.g., Gee et al, 2008). The location of the fluid front is drawn using the more conservative, minimum distance of ~130 km.…”

“…Thrust sheets comprise far-traveled allochthons of clastic Cambrian-Silurian and Neoproterozoic sediments are overthrust onto shallow-water, predominantly carbonate, Cambrian-Silurian sediments ( Fig. 1; Gee et al, 2008). Higgins et al (2004) estimated displacement of 35-100 km along low-angle thrust faults that were subsequently reactivated in a normal sense during orogenic collapse.…”

Origin and significance of intra-basement seismic reflections offshore western Norway

“…1a) during Devonian, Permian-Triassic, Jurassic and cretaceous rifting (bartholomew et al 1993;Faerseth et al 1995;Doré et al 1997). convergence of Laurentia and baltica during the caledonian orogeny resulted in the formation of a range of predominantly contractional structures, such as low-angle thrusts and folds (Gee et al 2008). The structures associated with this major tectonic event are particularly well developed in onshore Norway (e.g.…”

Seismological evidence for a fossil subduction zone in the East Greenland Caledonides

“…Magmatic arcs in the uppermost thrust sheets in Scandinavia showing Laurentian affi nity and ages predating the Scandian phase have been interpreted as evidence for an early eastward subduction (e.g., Yoshinobu et al, 2002) along the eastern margin of Laurentia (Roberts, 2003;Gee et al, 2008).…”