How stable is the Fennoscandian Shield? Insights from low-temperature thermochronology and numerical models

Cratons are ancient parts of the lithosphere, often characterised by long-term stability. Geological observations indicate that the Fennoscandian Shield in the East European craton has likely experienced some of the slowest erosion rates on Earth over the past approximately 1.5 billion years¹. However, a contrasting perspective has emerged based on apatite fission-track thermochronology, suggesting multiple episodes of kilometre-scale burial and exhumation during the past 1.1 Ga². This raises the question: How stable has the Fennoscandian Shield been since the Mesoproterozoic?

Since a Phanerozoic sedimentary record is not preserved in Finnish Fennoscandia, we investigate this question using new data from (U-Th)/He thermochronology and integrated modelling of multiple thermochronometer systems.

We have collected 20 samples from Finnish Fennoscandia, from which we obtained 64 single-grain zircon (U-Th)/He dates (1553 to 1.8 Ma) and 55 single-grain apatite (U-Th)/He dates (1178 to 99 Ma). In addition, we analysed 25 zircons from the Kola peninsula in Russia and obtained (U-Th)/He dates ranging from 1929 to 215 Ma. Samples from southern Finland and the Kola peninsula show a strong decrease in zircon (U-Th)/He dates with increasing U-Th concentrations, due to the effects of radiation damage. We leverage this date dispersion to determine plausible thermal histories using different inverse modelling software (QTQt³, Thermochron.jl⁴ and T_c1D⁵) and explore the complex (U-Th)/He date patterns through separate and joint inversion of the zircon and apatite data.

Preliminary inverse modelling results using QTQt and Thermochron.jl suggest that regions in southern Finland and the Kola peninsula may have experienced protracted residence at shallow upper crustal levels for at least 1 Ga. In contrast, areas in northern Finland, near the Caledonian front, show evidence of heating and cooling likely linked to burial and exhumation following Caledonian orogenesis.

Ongoing work focuses on refining the preliminary thermal history models by integrating published apatite fission track and ⁴⁰Ar/³⁹Ar data with our (U-Th)/He dataset to more effectively constrain the magnitude, timing and rates of burial and exhumation in Fennoscandia and its possible drivers (e.g. extreme glaciation, orogenies). This will not only provide insight into the exhumation history of Fennoscandia, but also the resolving power of low-temperature thermochronology for reconstructing thermal histories in cratonic areas where timescales are immense and the geological record is limited.

 

¹ Hall, A.M., Putkinen, N., Hietala, S., Lindsberg, E. and Holma, M., 2021. Ultra-slow cratonic denudation in Finland since 1.5 Ga indicated by tiered unconformities and impact structures. Precambrian Research, 352, p.106000. 

² Green, P.F., Japsen, P., Bonow, J.M., Chalmers, J.A., Duddy, I.R. and Kukkonen, I.T., 2022. The post-Caledonian thermo-tectonic evolution of Fennoscandia. Gondwana Research, 107, pp.201-234. 

³ Gallagher, K. (2012), Transdimensional inverse thermal history modeling for quantitative thermochronology, J. Geophys. Res., 117, B02408, doi:10.1029/2011JB008825.

⁴ Keller, C.B., McDannell, K.T., Guenthner, W.R., and Shuster, D.L. (2022). Thermochron.jl: Open-source time-Temperature inversion of thermochronometric data. 10.17605/osf.io/wq2U5

⁵ Whipp et al. (2025). HUGG/Tc1D: v0.3.2 (v0.3.2). Zenodo.  https://doi.org/10.5281/zenodo.17590819