GFZ German research centre for geo sciences

Section 3.3: Earth Surface Geochemistry

Current Projects

PALAVAS will track weathering and erosion rates of basalt rocks through time based on isotope-geochemical and cosmogenic nuclide-analyses of soils, rivers, and detrital sedimentary archives, and thus will deliver updated view of how weathering and erosion evolve on volcanic tropical islands, and how this evolution impacts global CO₂ consumption.

The aim of the Devendra project is to develop the meteoric ¹⁰Be/⁹Be proxy to quantify the weathering of basalt and carbonate rocks and to decipher their impact on the Earth's vegetation and climate system:

The project investigates whether the silicate weathering feedback was weakened during the Middle Eocene Climate Optimum (MECO) 40 million years ago by analyzing silicon and lithium isotope records from microfossils to understand the dynamics of silicate weathering and carbon cycling.

Using numerical modelling, we simulate the ice cover during the last glacial cycle and the resulting isostatic adjustment of the Alpine lithosphere.

The ratio of the boron isotopes ¹¹B and ¹⁰B in seawater is a critical value for determining the CO₂ concentration in the past. We are developing a new model, based on new knowledge about the boron cycle, to reconstruct the 11B/10B value of seawater over the last 100 million years.

We combine cosmogenic nuclides with a variety of field and lab based approaches to investigate the effects of climate, biota, fracturing, and lithology on hillslope denudation rates, fluvial incision and landscape evolution in the Coastal Cordillera of Chile.

We combine field observations, cosmogenic nuclides, remote sensing and numerical modelling to quantify erosion rates of steep rock walls in glacial landscapes and assess the sensitivity of these landscapes to climatic changes.

Meteoric ¹⁰Be, produced in the atmosphere, can be used to quantify denudation rates (the sum of weathering and erosion) when normalized with the stable trace element ⁹Be. We measure this ¹⁰Be/⁹Be ratio in river sediments, soils, but also in water or even plants.

Past Projects

Within the framework of "DeepEarthShape", projects from the fields of geochemistry, microbiology, geophysics, geology, and biogeochemistry are involved in investigating the weathering zone in the subsurface of the Earth.

We study land-to-ocean pathways of ⁹Be and the distribution of ¹⁰Be/⁹Be ratio at the land-ocean interface with the aim to better understand the marine geobiochemical cycle of beryllium and to investigate the potential applications of Beryllium isotopes in different oceanic environments.

In the Eastern Southern Alps-Dinarides region, we investigate the geometry of major active faults, their sense of motion, and how they drive erosion. Erosion rates are mainly provided by the new meteoric cosmogenic ¹⁰Be/⁹Be proxy as the study area features limestone rocks, but we also obtained erosion rates from classic in situ ¹⁰Be data from quartz minerals.

We use geochemical proxies (biomarkers, stable isotopes and cosmogenic nuclides) to investigate the feedback of vegetation, weathering, erosion and sediment export on climatic changes after the LGM. For this purpose, we use marine sediment cores offshore Chile and compare them with recent samples from Chilean rivers.

Meteoric ¹⁰Be, produced in the atmosphere, can be used to quantify denudation rates (the sum of weathering and erosion) when normalized with the stable trace element ⁹Be. We measure this ¹⁰Be/⁹Be ratio in river sediments, soils, but also in water or even plants.

We quantify denudation rates in the Himalaya over the Plio-Pleistocene period by measuring cosmogenic ¹⁰Be in foreland basin sediments.

We use experimental approaches to determine the isotope fractionation during the uptake and translocation of silicon, iron and magnesium. For this purpose, the organisms are cultivated in controlled laboratory experiments and the stable isotope ratios in the growth solutions as well as in the plant parts and fungi are determined.

We measure cosmogenic nuclide concentrations in fill terraces of the Yamuna River, India, to determine the temporal variability of hillslope erosion rates and to unravel how a rapidly eroding landscape in the Himalaya has responded to climatic changes in the past.

We use field observations, cosmogenic nuclides, topographic analysis, and stream power modelling to assess the influence of biota on discharge variability and river incision across a pronounced north-south climate and vegetation gradient in the Chilean coastal Cordillera.

In EarthShape BioSoils we will explore the links between denudation - the removal of mass due to chemical and physical weathering and erosion - and soil production - supply of regolith mass from rock or dust - via biogenic weathering.

Dr. Richard Ott is quantifying changes in erosion rates on different time-scales from river sediments by measuring cosmogenic radionuclides.

In montane temperate forest ecosystems, the long-term nutrition of forest ecosystems is maintained by balancing nutrient loss from the shallow forest floor (fast "organic nutrient cycle") with deep rock weathering (slow "geogenic nutrient cycle").

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