a b s t r a c tTectonics and erosion are the driving forces in the evolution of mountain belts, but the identification of their relative contributions remains a fundamental scientific problem in relation to the understanding of both geodynamic processes and surface processes. The issue is further complicated through the roles of climate and climatic change. For more than a century it has been thought that the present high topography of western Scandinavia was created by some form of active tectonic uplift during the Cenozoic. This has been based mainly on the occurrence of surface remnants and accordant summits at high elevation believed to have been graded to sea level, the inference of increasing erosion rates toward the present-day based on the age of offshore erosion products and the erosion histories inferred from apatite fission track data, and on over-burial and seaward tilting of coast-proximal sediments.In contrast to this received wisdom, we demonstrate here that the evidence can be substantially explained by a model of protracted exhumation of topography since the Caledonide Orogeny. Exhumation occurred by gravitational collapse, continental rifting and erosion. Initially, tectonic exhumation dominated, although erosion rates were high. The subsequent demise of onshore tectonic activity allowed slow erosion to become the dominating exhumation agent. The elevation limiting and landscape shaping activities of wet-based alpine glaciers, cirques and periglacial processes gained importance with the greenhouse-icehouse climatic deterioration at the Eocene-Oligocene boundary and erosion rates increased. The flattish surfaces that these processes can produce suggest an alternative to the traditional tectonic interpretation of these landscape elements in western Scandinavia. The longevity of western Scandinavian topography is due to the failure of rifting processes in destroying the topography entirely, and to the buoyant upward feeding of replacement crustal material commensurate with exhumation unloading.We emphasize the importance of differentiating the morphological, sedimentological and structural signatures of recent active tectonics from the effects of long-term exhumation and isostatic rebound in understanding the evolution of similar elevated regions.

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The pre-drift Wegenerian model of Pangea is almost universally accepted, but debate exists on its pre-Jurassic configuration since Ted Irving introduced Pangea 'B' by placing Gondwana farther to the east by V3000 km with respect to Laurasia on the basis of paleomagnetic data. New paleomagnetic data from radiometrically dated Early Permian volcanic rocks from parts of Adria that are tectonically coherent with Africa (Gondwana), integrated with published coeval data from Gondwana and Laurasia, again only from igneous rocks, fully support a Pangea 'B' configuration in the Early Permian. The use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for Pangea 'B'. The ultimate option to reject Pangea 'B' is to abandon the geocentric axial dipole hypothesis by introducing a significant non-dipole (zonal octupole) component in the Late Paleozoic time-averaged geomagnetic field. We demonstrate, however, by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from Gondwana as well as Laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for Pangea 'B' in the Early Permian. We therefore regard the paleomagnetic evidence for an Early Permian Pangea 'B' as robust. The transformation from Pangea 'B' to Pangea 'A' took place during the Permian because Late Permian paleomagnetic data allow a Pangea 'A' configuration. We therefore review geological evidence from the literature in support of an intra-Pangea dextral megashear system. The transformation occurred after the cooling of the Variscan mega-suture and lasted V20 Myr. In this interval, the Neotethys Ocean opened between India/Arabia and the Cimmerian microcontinents in the east, while widespread lithospheric wrenching and magmatism took place in the west around the Adriatic promontory. The general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right-lateral shear couple between Gondwana and Laurasia during the Permian. Transcurrent plate boundaries associated with the Pangea transformation reactivated Variscan shear zones and were subsequently exploited by the opening of western Neotethyan seaways in the Jurassic.0012-821X / 03 / $^see front matter ß

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In light of recent additions to the Palaeozoic palaeo-magnetlc database , particularly for the Ordovlclan era, a revised apparent polar wander (APW) path for Baltica has been constructed following a rigorous synthesis of all Late Precambrlan-Permlan data The APW path is characterized by two prominent loops Firstly, a Late Precambrlan-Cambrlan loop probably relating to a rifting event and secondly, a younger loop relating to a Mid-Silurian (Scandlan) colhsion event These features Imply major change In plate-tectonic reconfiguratlon Baltlca probably represented an individual continental unit m Early Palaeozoic times and was positioned m high southerly latitudes in an "'inverted" geographic orientation In such a reconstruction Baltlca was separated from the northern margin of Gondwana by the Tornqulst Sea and from Laurentla by the Iapetus Ocean The Tornqulst Zone is thus interpreted as a passive or dextral transform margin during the early Palaeozoic While undergoing counterclockwise rotations (up to 1 6°/Ma), Baltica drifted northward through most ol the Palaeozoic, except for a short period of southerly movement in Late Silurian-Early Devonian times after colhslon with Laurentla. Rapid movements in latitude (up to 9 cm/yr) are noted m Late Precambrlan/early Palaeozoic times and slgmficant decrease in velocities throughout Palaeozoic time probably reflect the progressive amalgamation of a larger continent by Early-Devonian (Euramerlca) and Permian (Pangea) times The Tornqulst Sea had a principal component of palaeo-east-west orientation. Hence it is difficult to be precise in the timing of when micro-continents such as Eastern Avalonla and the European Masslfs ultimately collided along the southwestern margin of Baltica These micro-continents are considered to have been peripheral to Gondwana (m high southerly latitudes) during the Early Ordovlclan. Eastern Avalonla clearly had rifted off Gondwana by Llanvlrn-Llandedo times and may have collided with Baltlca during Late Ordovlclan times, although the present available Sdunan palaeomagnetlc data from Eastern Avalonia may suggest colhslon in Late Silurian times Across the lapetus facing margin of Baltica, Laurentla was s~tuated in equatorml to southerly latitudes during most of the Lower Palaeozoic These continents collided in Mid-Silurian times, l e a first collision between southwestern Norway and Greenland/Scotland which gave rise to the early Scandlan Orogeny (425 Ma) in southwestern Norway possible followed by a later, but less dramatic, Scandlan event in northern Norway at around 410 Ma Since Baltlca was geographically reverted m early Palaeozoic times, the colhsional margin could not have been a margin that once rifted off Laurentm as assumed in a number of plate-tectonic models