TERRA NOVA

Refining the Tor Exhumation Approach (TEA)

This project aims to do a comparative study, between former glaciated and never glaciated tor-areas (Tors are large residual rocks which are still attached to the bedrock) in the UNESCO world heritage Geopark Estrela (Portugal). The objective is to compare the isotope signature of tors at two end-member sites (one previously glaciated, and the second never glaciated) with the signature of soils in close proximity to tors. Using in-situ ¹⁴C and combines ²⁶Al/¹⁰Be, the complex exhumation process of such tors can be unravelled and erosion as well es surface denudation rates be reconstructed from single to few hundreds of millennia. Pu-isotopes, furthermore, will help to relate the long-term evolution off erosion rates to modern ones (over the last few decades). To establish a time trend-model with surface responses, the obtained results will be linked to climate change and other controlling factors.

The TEA (Tor Exhumation Approach) was developed at the University of Zurich by Raab et al., (2018), Raab et al., (2019) and Raab (2019). The TEA enables the capturing of past surface denudation and soil erosion variations over multi-millennia (Holocene–Pleistocene) in contrast to catchment-wide derived rates which only provide average rates in distant areas to the actual denudation zone. At the current state of research (see above), the TEA contributes to fill the research gap of missing in-situ surface denudation and soil erosion rates within the denudation zone for time-scales of a few thousand to >100,000 years.

Here are some 3-D drone models of the investigated tors at the wonderful Estrela UNESCO Global Geopark. The sampling campaign was delayed by the COVID-19 pandemic by several month. Yet luckily we could use a short period between the lock-downs in early summer 2020 which enabled us to collect the intended sampling series along rock tors and local soils. Our team, Gerald Raab, Markus Egli, Wasja Dollenmeier, Gonçalo Vieira and Piotr Migoń, collected samples for cosmogenic isotope and fallout radionuclide measurements as well as luminescence dating. Samples are now being processed.