Regional Caledonian structure within an oblique convergence zone, Dronning Louise Land, NE Greenland

Abstract

Dronning Louise Land includes a well-exposed part of the marginal thrust zone that defines the western limit of the NE Greenland Caledonides. The autochthonous Laurentian craton west of the thrust zone comprises an orthogneissic basement which is overlain unconformably by sedimentary rocks of the Mid-Proterozoic Trekant Series and the Skolithos- bearing Zebra Series of probable latest Precambrian-early Cambrian age. This cover-basement sequence becomes strongly folded towards the thrust zone. The zone is characterized by numerous east-dipping thrust slices of mylonitized basement and metamorphosed equivalents of the Trekant and Zebra Series. Allochthonous rocks above the thrust zone are mainly heterogeneously reworked basement gneisses which in areas of low strain are similar in character and pre-Caledonian history to those of the foreland. Synclinal inliers of metasedimentary cover rocks include sequences correlated with the Zebra Series. The Caledonian thrust zone in NE Greenland does not therefore separate markedly different geological terrains. The orogen-parallel, sinistral Storstrømmen shear zone lies east of Dronning Louise Land, and it appears that the Caledonian deformation pattern in this part of the orogen is the product of sinistral transpression. The sequence of structures can be interpreted in terms of early low-angle sinistral strike-slip, followed by partitioned sinistral strike-slip and oblique thrusting, and later more or less orthogonal thrusting and folding. This sequence may indicate a significant component of oblique collision between Lauren tia and Baltica during closure of the Iapetus Ocean.