Description
This proposal is linked to the COSC scientific drilling project supported by ICDP. The COSC-1 drillhole was drilled down to 2.5 km depth in 2014. The hole was fully cored from 100 m down to total depth and an outstanding 100% recovery of core material of excellent quality was achieved. This project is a contribution from the COSC Geothermal Group, led by the applicant himself. Deep scientific boreholes allowing for fine determination of transient heat flow signals related to paleoclimatic changes back to the last Ice Age are very seldom. In addition, most of them are not or only partially cored. Detailed characterisations of the thermal properties of the penetrated formations, hence fine heat flow calculations, including the detection of subtle transient signals, are not possible. Normally, heat flow perturbations related to the sudden global warming at the end of the last Ice Age can be isolated in previous deep borehole data. Because of the above-mentioned limitations, less pronounced signals related to Holocene climate variations are more difficult to detect and to model. In this project we want to take advantage of the excellent quality of the COSC data and conduct a borehole paleoclimatology study of unpreceded resolution. The COSC-1 scientific borehole appears to be particularly promising and furnishes a unique opportunity to reach this aim.
- It is fully cored allowing for the construction of the highest resolution petrophysical profile ever attempted.
- It is completely covered with high resolution electrical logs including temperature logs.
- Fluid flow in the borehole is proven to be negligible, hence it does not produce any significant noise in the heat flow signal.
- Metamorphic foliation is mostly (sub)horizontal and thermal refraction effects are expected to be minor, reducing furthermore background noise levels. We propose to make a detailed log analysis in order to derive a precise lithological profile.
This lithological profile will guide the sampling of relevant lithologies in order to measure their respective thermal properties on 100 core samples and to construct a high-resolution petrophysical profile. Particular emphasis will be put on the first 500-700 m of the drillhole where recent paleoclimatic signals are expected. Temperature logs and measured thermal properties will be used to build a heat flow density profile and to isolate its transient components. Finally, we will use numerical methods to invert the geothermal data and to reconstruct the Ground Surface Temperature History from present-day back to the Last Glacial Maximum. The project is expected to furnish new insights on the recent paleoclimatic evolution of high latitude regions, on the deep geothermal regime of Fennoscandia but also on ice sheet dynamics.