Phanerozoic denudation across the Kola Peninsula, Northwest Russia: implications for long-term stability of Precambrian shield margins

Abstract

Contrasting views exist on the stability of the Earth's shield regions over the last 1 Ga that have major implications for reconstructing erosion patterns on shields and the supply of sediment to intra-cratonic and marginal basins. This paper explores Phanerozoic denudation rates and patterns on the northern part of the Fennoscandian Shield in the Kola Peninsula, Northwest Russia. This shield region was intruded by magmatic rocks of the Kola Alkaline Province (KAP) in the Devonian and Early Carboniferous. The KAP comprises a varied suite of alkali-ultramafic plutonic and hypabyssal intrusions, diatremes and dykes that was emplaced at various depths in the crust and allows assessment of depths and rates of erosion during and since the KAP magmatic episode. Further evidence of long-term denudation is provided by Mesoproterozoic and Neoproterozoic cover rocks found around the margins of the Kola Peninsula and in the White Sea. The burial and exhumation history is compared to available Apatite Fission Track (AFT) data for the Kola Peninsula and adjacent areas. Post-Devonian denudation rates on the shield rocks of the Kola Peninsula have varied in space and time. Around the periphery of the Kola Peninsula, low long-term denudation of shield rocks is indicated by the survival of Riphean cover rocks and Late Devonian lavas, kimberlite crater facies and near-surface emplacement of dykes. In contrast, in the main belts of KAP intrusions, 4-6 km of rock was removed in response to doming between 460 and 360 Ma. Deep denudation is indicated by the emplacement depths of alkaline intrusions and Phoscorite-Carbonatite pipes (PCPs). Erosion on the Kola Peninsula since 360 Ma has been far more limited. Extensive, shallow, late-stage magmatism associated with PCPs, dykes and the large alkaline intrusions in the KAP indicates that erosion depths nowhere exceeded 2 km. PostDevonian denudation has removed <1 km of rock from the margins of the Kola Peninsula and from the backslope of the Saariselkä-Karelia scarp in northern Finland. AFT data point to an important phase of erosion in the early Mesozoic but depths of unroofing of 3-5 km based on AFT cooling ages for this later phase are in conflict with the evidence of lesser erosion provided by the late-stage KAP intrusions and also require unrealistic depths of former Devonian to Triassic cover rocks. Mean denudation rates were greatest (up to 40 m/Myr) during the KAP magmatic phase. Post-Devonian rates across the Kola Peninsula and adjacent shield areas were much lower (<3-6 m/Myr) and are compatible with low long-term denudation rates for other cratons. Further resolution of long-term denudation patterns and rates on the Kola Peninsula requires the application of low-temperature thermochronometry, detailed examination of the regional geomorphology and firmer dating of ancient weathering episodes.

Thermochronology and Exhumation History of the Northeastern Fennoscandian Shield Since 1.9 Ga: Evidence From 40Ar/39Ar and Apatite Fission Track Data From the Kola Peninsula

“…Available estimates of the Phanerozoic denudation from the Kola part of the Fennoscandian Shield and the corresponding amplitudes of its vertical movements are largely ambiguous. Semiquantitative estimates of the Phanerozoic erosion of sedimentary cover and Devonian intrusive bodies and diatremes show significant differences in the amplitude of the denudation of the area—from 0 km on the periphery of the Kola Peninsula up to 6 km in its central part (Hall, ). Reliable models of the Precambrian thermal history and quantitative estimates of the denudation volume of the Kola Peninsula are absent.…”

Linking an Early Triassic delta to antecedent topography: Source-to-sink study of the southwestern Barents Sea margin

“…3C; Puchkov, 2009;Glørstad-Clark et al, 2010;Norina et al, 2014). At the same time, around the Permian-Triassic transition (Vigran et al, 2014), smaller sedimentary systems started to prograde from the Fennoscandian Shield into the Barents Sea Basin (Glørstad-Clark et al, 2010;Henriksen et al, 2011a;Hall, 2015), and from Greenland into the Barents Sea Basin in Svalbard ( Fig. 3C; Mørk et al, 1982;Wignall et al, 1998).…”

“…1) since the late Proterozoic, and it represents a long-lasting hinge line separating areas of net uplift on the shield from areas of net subsidence in the basin (Hall, 2015). The Troms-Finnmark fault zone is the main boundary between the basin and the mainland on the western Finnmark Platform, and the Austhavet fault zone is the main boundary on the eastern Finnmark Platform ( Fig.…”

“…The present-day Fennoscandian Barents Sea coast ( Fig. 1) is likely a close approximation to the long-term boundary between the successive sedimentary basins located in the Barents Sea and the eroding uplands of the Fennoscandian Shield (e.g., Worsley, 2008;Hall, 2015). The area has also largely escaped extensive modification by Quaternary glaciations (Riis, 1996;Ebert et al, 2015;Hall et al, 2015) and is therefore an ideal location in which to test and develop models for linking ancient sedimentary systems to catchments.…”

“…However, in the Early Triassic of the Barents Sea, several of these hampering issues are alleviated: Biostratigraphic dating has a relatively high resolution (~1 m.y.) due to rapid evolutionary diversification after the Permian-Triassic extinction event (e.g., Chen and Benton, 2012); the climate during this period has been the subject of several studies, as it was a time of major climatic shifts (Péron et al, 2005;Sellwood and Valdes, 2006;Svensen et al, 2009;Hochuli and Vigran, 2010;Sun et al, 2012); and minor tectonic change has occurred in this area since the Carboniferous (Bugge et al, 1995;Riis, 1996;Gudlaugsson et al, 1998;Hall, 2015). The present-day Fennoscandian Barents Sea coast ( Fig.…”