H. Wittmann

• PhD
• Permanent staff at GFZ Helmholtz Centre for Geosciences

Silicate weathering reactions generate alkalinity that drives carbonate burial in the ocean, ultimately considered to balance solid‐earth CO2 degassing. Because silicate weathering occurs at a climate dependent rate, it provides a negative feedback on long‐term climate evolution that regulates Earth's temperature within a habitable window. Quantify...

Alluvial fans are hypothesised to record signals of past hydroclimate changes in their depositional chronologies and slopes. However, direct tests of this hypothesis have been limited due to challenges in precisely dating the responses of alluvial fans to past climate forcing. Here, we present a new chronology of alluvial‐fan deposition at the Sier...

Theory suggests that the response time of alluvial channel long profiles to perturbations in climate is related to the magnitude of the forcing and the length of the system. Shorter systems may record a higher frequency of forcing compared to longer systems. Empirical field evidence that system length plays a role in the climate periodicity preserv...

Drainage density is a fundamental landscape feature that determines the length scale for hillslope sediment transport and results from the competition of diffusive hillslope and advective stream incision processes, whose efficiencies are known to vary with rock type but are notoriously difficult to quantify. Here, we present a comprehensive analysi...

Knowledge of the rates of carbonate rock denudation, the relative apportionment of chemical weathering versus physical erosion, and their sensitivity to climate, vegetation, and tectonics is essential for disclosing feedbacks within the carbon cycle and the functioning of karst landscapes that supply important services to humans. Currently, however...

The hyperarid Atacama Desert is one of the driest and oldest deserts on Earth, rendering it a valuable climate archive. However, unraveling its past climate is particularly challenging and the few studied paleoclimate records of the region reveal strong temporal and spatial variabilities. To enhance our understanding of these dynamics we investigat...

Plain Language Summary To identify how geologic and climatic conditions control how fast soil is removed from the Earth's surface (denudation), we need to measure these rates over long periods, like thousands of years. A common method makes use of a rare radioactive nuclide, cosmogenic ¹⁰Be, formed by cosmic rays in quartz. However, if rocks do not...

Quantitative analysis of fluvial topography and sediment yield changes are often independently used to detect major river capture events and episodes of drainage reorganization. Here we use a unique set of geological and in situ 10Be cosmogenic data from Corsica, Western Mediterranean, to provide evidence of major river capture events affecting the...

Theory suggests that the response time of alluvial channel long-profiles to perturbations in climate is related to the magnitude of the forcing and the length of the system. Shorter systems may record a higher frequency of forcing compared to longer systems. Empirical field evidence that system length plays a role in the climate periodicity preserv...

Examining the links and potential feedbacks between tectonics and climate requires understanding the processes and variables controlling erosion. At the orogen scale, tectonics and climate are thought to be linked through the influence of mountain elevation on orographic precipitation and glaciation; the only documented erosional processes capable...

Beryllium isotopes have emerged as a quantitative tracer of continental weathering, but accurate and precise determination of the cosmogenic ¹⁰ Be and stable ⁹ Be in seawater is challenging, because seawater contains high concentrations of matrix elements but extremely low concentrations of ⁹ Be and ¹⁰ Be. In this study, we develop a new, time‐effi...

The hydrogen isotope composition of leaf wax biomarkers (δ2Hwax) is a valuable tool for reconstructing continental paleohydrology, since it serves as a proxy for the hydrogen isotope composition of precipitation (δ2Hpre). To yield robust palaeohydrological reconstructions using δ2Hwax in marine archives, it is necessary to examine the impacts of re...

Major strike-slip fault systems on Earth, like the North Anatolian Fault (NAF), play an important role in accommodating plate motion, but surprisingly little is known about how such structures evolve through space and time. Along the central sector of the NAF in the Central Pontides, transpression and crustal thickening along the northward restrain...

The hydrogen isotope composition of leaf wax biomarkers (δ2Hwax) is a valuable tool for reconstructing continental paleohydrology, as it serves as a proxy for the hydrogen isotope composition of precipitation (δ2Hpre). To yield robust palaeohydrological reconstructions using δ2Hwax in marine archives, it is necessary to examine the impacts of regio...

While landscapes are broadly sculpted by tectonics and climate, on a catchment scale, sediment size can regulate hillslope denudation rates and thereby influence the location of topographic highs and valleys. In this work, we used in situ 10Be cosmogenic radionuclide analysis to measure the denudation rates of bedrock, boulders, and soil in three g...

In a semi-arid and a mediterranean study site in the granitoid Chilean Coastal Cordillera, we investigated drilled weathering profiles of 100 m depth and found significant differences in the depth of the weathering zone. Where rainfall is limited, fractures may be transport pathways for water to depth, inducing deep weathering. With more rainfall p...

While landscapes are broadly sculpted by tectonics and climate, on a catchment scale, the density of bedrock fractures can influence hillslope denudation rates and dictate the location of topographic highs and valleys. In this work, we used 10Be cosmogenic radionuclide analysis to measure the denudation rates of bedrock, boulders, and soil, in thre...

The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters...

Climate change affects the stability and erosion of high‐alpine rock walls above glaciers (headwalls) that deliver debris to glacier surfaces. Since supraglacial debris in the ablation zone alters the melt behaviour of the underlying ice, the responses of debris‐covered glaciers and of headwalls to climate change may be coupled. In this study, we a...

Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Ac...

It has been proposed that at short timescales of 102–105 yr, climatic variability can explain variations in sediment flux, but in orogens with pronounced climatic gradients rate changes caused by the oscillating efficiency in rainfall, runoff, and/or sediment transport and deposition are still not well-constrained. To explore landscape responses un...

The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters...

Rivers transfer terrestrial organic carbon (OC) from mountains to ocean basins, playing a key role in the global carbon cycle. During fluvial transit, OC may be oxidized and emitted to the atmosphere as CO2 or preserved and transported to downstream depositional sinks. The balance between oxidation and preservation determines the amount of particul...

The tectonically active Taiwan orogen features numerous rivers that yield a high amount of sediment with fluxes exceeding 10⁴ t/km²/yr. Amongst these, the landslide‐dominated Liwu River is well studied regarding its dynamic surface processes. However, the quantification of denudation in the Liwu Basin is still an ongoing task as rates obtained to d...

The evolution of Earth's climate over geological timescales is linked to surface erosion via weathering of silicate minerals and burial of organic carbon. However, methodological difficulties in reconstructing erosion rates through time and feedbacks among tectonics, climate, and erosion spurred an ongoing debate on mountain erosion sensitivity to...

The cosmogenic meteoric 10 Be that is produced in the atmosphere and mainly scavenged by rainfall is a valuable tool for determining dates and rates of Earth surface processes. A key prerequisite for its applications is the knowledge of the long-term 10 Be depositional flux to Earth's surface. Previous efforts on obtaining 10 Be depositional fluxes...

The Labrador Sector of the Laurentide Ice Sheet is characterized by a complex network of ice divides and an extensive landform record outlining two broad and opposing ice flows that are separated by a narrow Horseshoe Intersection Zone (HIZ). This geomorphic system gave rise to contrasting reconstructions, which reflect uncertainties on the tempora...

Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium-10 (10Bem) in...

Meteoric cosmogenic ¹⁰Be is a powerful tracer to quantify dates and rates of Earth surface processes over timescales of 10³-10⁵ yrs. A prerequisite for its applications is knowledge of the flux at which ¹⁰Be, produced in the atmosphere, is delivered to the Earth surface. Four entirely independent approaches are available to quantify this flux: 1) G...

We compile detrital 10 Be concentrations of Alpine rivers, representing the denudation rates pattern for 375 catchments across the entire European Alps. Using a homogeneized framework, we employ state-of-the-art techniques for inverting in-situ 10 Be concentrations into denudation rates. From our compilation, we find that (i) while lithologic prope...

Recent developments in terrestrial cosmogenic nuclide (TCN) exposure dating and the reinterpretation of TCN boulder ages from moraines have improved our understanding of the glacial chronology in the Central Andes. According to these records, glacial advances throughout the region correlate with insolation-driven changes in the intensity of the Sou...

Terrestrial cosmogenic nuclide concentrations in fluvial deposits allow estimation of paleo-erosion rates and reconstruction of the response of landscapes to climatic perturbations. In partly ice-covered landscapes, however, incorporation of subglacially-derived sediments that were shielded by ice from cosmic can lead to erroneous erosion rate calc...

Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium‐10 (¹⁰Bem) in...

Cosmogenic nuclide analysis in sediment from the Earth's largest rivers yields mean denudation rates of the sediment-producing areas that average out the local variations commonly found in small rivers. Using this approach, we measured in situ cosmogenic ²⁶Al and ¹⁰Be in sand of >50 large rivers over a range of climatic and tectonic regimes coverin...

The novel ¹⁰Be (meteoric)/⁹Be system, where ¹⁰Be is delivered by precipitation and stable ⁹Be is released by weathering, provides denudation rates over weathering‐erosion timescales. The new tool is applicable to quartz‐poor lithologies, for example, mafic rock and claystone, which are not readily accessible by the commonly used in situ‐produced ¹⁰...

Plain Language Summary Clay minerals can form on land by the chemical breakdown of rock‐forming minerals, but clays can also form in the ocean. When clay formation takes place in the ocean, CO2 is released. To date, there is no method that can easily measure the amount of clay minerals formed in the ocean. We used two isotopes of the same element,...

The cover image is based on the Original Article* Effects of long soil surface residence times on apparent cosmogenic nuclide denudation rates and burial ages in the Cradle of Humankind, South Africa by Tebogo Vincent Makhubela** et al., https://doi.org/10.1002/esp.4723.***

In situ cosmogenic nuclides are an important tool for quantifying landscape evolution and dating fossil‐bearing deposits in the Cradle of Humankind (CoH), South Africa. This technique mainly employs cosmogenic 10‐Beryllium (10Be) in river sediments to estimate denudation rates and the ratio of 26‐Aluminium (26Al) to 10Be (26Al/10Be), to constrain a...

Concentrations of in-situ-produced cosmogenic 10Be in river sediment are widely used to estimate catchment-average denudation rates. Typically, the 10Be concentrations are measured in the sand fraction of river sediment. However, the grain size of bedload sediment in most bedrock rivers covers a much wider range. Where 10Be concentrations depend on...

There is growing interest in geochronological applications of terrestrial in situ-produced cosmogenic nuclides, with the most commonly measured being ¹⁰ Be and ²⁶ Al in quartz. To extract and then separate these radionuclides from quartz and prepare them in the oxide form suitable for accelerator mass spectrometry (AMS) requires extensive and caref...

The intermontane Humahuaca Basin in the Eastern Cordillera of the northwest Argen-tine Andes lies leeward of an orographic barrier to easterly derived moisture. An average of >2000 mm/yr of rainfall along the eastern flanks of the barrier contrasts with <200 mm/yr in the orogen interior. Paleoenvironmental reconstructions suggest that the basin bec...

Advances in cosmogenic nuclide exposure dating have made moraines valuable terrestrial recorders of palaeoclimate. A growing number of moraine chronologies reported from the Central Andes show that tropical glaciers responded sensitively to past changes in precipitation and temperature over timescales ranging from 10^3 to 10^5 years. However, the c...

Advances in cosmogenic nuclide exposure dating have made moraines valuable terrestrial recorders of palaeoclimate. A growing number of moraine chronologies reported from the Central Andes show that tropical glaciers responded sensitively to past changes in precipitation and temperature over timescales ranging from 10^3 to 10^5 years. However, the c...

Concentrations of in situ-produced cosmogenic ¹⁰Be in river sediment are widely used to estimate catchment-average denudation rates. Typically, the ¹⁰Be concentrations are measured in the sand fraction of river sediment. However, the grain size of bedload sediment in most bedrock rivers cover a much wider range. Where ¹⁰Be concentrations depend on...

Deposition of fluvial sediments within actively eroding mountain ranges typically documents a change in the climatic or tectonic forcing. However, reconstructions of changes from valley fills are often ambiguous and based on correlating chronologies with regional climatic changes. In this study, we present in situ-produced cosmogenic 10Be derived p...

Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess sediment delivered by co‐seismic landslides. Detailed sediment budgets indicate that rivers need several years to decades to recover from seismic disturbances, depending on how recovery is defined. We examine three principal proxies of river recovery after eart...

The lower Amazon basin contains vast floodplains that exchange sediment with the main river. The exchange of sediment between the floodplain and the channel follows a seasonal cycle that is anticorrelated with the hydrological cycle. At low water stages, sediment that has been stored in the floodplain for potentially several thousands of years is e...

Terrestrial cosmogenic nuclide (TCN) concentrations in fluvial sediment, from which denudation rates are commonly inferred, can be affected by hillslope processes. TCN concentrations in gravel and sand may differ if localized, deep‐excavation processes (e.g. landslides, debris flows) affect the contributing catchment, whereas the TCN concentrations...

Field geologists and geomorphologists are increasingly looking to numerical modelling to understand landscape change over time, particularly in river catchments. The application of Landscape Evolution Models (LEMs) started with abstract research questions in synthetic landscapes. Now, however, studies using LEMs on real‐world catchments are becomin...

Field geologists and geomorphologists are increasingly looking to numerical modelling to understand landscape change over time, particularly in river catchments. The application of Landscape Evolution Models (LEMs) started with abstract research questions in synthetic landscapes. Now, however, studies using LEMs on real-world catchments are becomin...

The study of fluvial fill terraces provides information about the tectonic and climatic history and is fundamental for understanding landscape evolution. Deposition of fluvial sediments within actively eroding mountain ranges could result from changes in tectonic uplift rates, climatic conditions and/or surface processes. However, reconstructions o...

The uplift of the Shillong Plateau, in northeast India between the Bengal floodplain and the Himalaya Mountains, has had a significant impact on regional precipitation patterns, strain partitioning, and the path of the Brahmaputra River. Today, the plateau receives the highest measured yearly rainfall in the world and is tectonically active, having...

Erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation, relief development, and crustal weakening. In many orogenic systems, it can be difficult to distinguish whether true feedbacks exist, or whether observed features are a consequence of tectonic forcing. To help elucidate these interacti...

Understanding past changes in the Antarctic ice sheets provides insight into how they might respond to future climate warming. During the Pliocene and Pleistocene, geological data show that the East Antarctic Ice Sheet responded to glacial and interglacial cycles by remaining relatively stable in its interior, but oscillating at its marine-based ma...

Quantifying rates of weathering and erosion of mafic rocks is essential for estimating changes to the oceans alkalinity budget that plays a significant role in regulating atmospheric CO2 levels. In this study, we present catchment-wide rates of weathering, erosion, and denudation measured with cosmogenic nuclides in mafic and ultramafic rock. We us...

Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal li...

Detrital thermochronology is often employed to assess the evolutionary stage of an entire orogenic belt using the lag-time approach, i.e., the difference between the cooling and depositional ages of detrital mineral grains preserved in a stratigraphic succession. The impact of different eroding sources to the final sediment sink is controlled by se...

At an ocean margin site 37°S offshore Chile, we use the meteoric cosmogenic 10Be/9Be ratio to trace changes in terrestrial particulate composition due to exchange with seawater. We analyzed the marine authigenic phase in surface sediments along a coast-perpendicular transect, and compared to samples from their riverine source. We find evidence for...

When using cosmogenic nuclides to determine exposure ages or denudation rates in rapidly evolving landscapes, challenges arise related to the small number of nuclides that have accumulated in surface materials. Improvements in accelerator mass spectrometry have enabled analysis of samples with low ¹⁰Be content (5 atoms), such that it is timely to d...

The ratio of the meteoric cosmogenic nuclide ¹⁰Be, precipitated from the atmosphere, to the stable nuclide ⁹Be, released by silicate weathering, was measured in suspended sediment of the Ganga River basin to determine denudation rates, degrees of weathering, and sediment storage in the floodplain. The ¹⁰Be precipitated and the ⁹Be released are carr...

Large rivers are known to buffer pulses in sediment production driven by changes in climate as sediment is transported through lowlands. Our new dataset of in situ cosmogenic nuclide concentration and chemical composition of 62 sandy bedload samples from the world largest rivers integrates over ∼25% of Earth's terrestrial surface, distributed over...

Fluvial fill terraces in intermontane basins are valuable sedimentary and geomorphic archives that record tectonic and/or climate-driven changes of river networks and their adjacent hillslopes. However, the rarely complete preservation of such geomorphic features, often combined with large distances from sediment source areas, complicates the ident...

As an integral part of the Eastern Cordillera, the intermontane Humahuaca Basin in the NW Argentine Andes is located in transition between the arid and internally drained Puna Plateau to the west and the humid broken foreland to the east. In combination with moisture-bearing air masses sourced in the Atlantic Ocean and the Amazon Basin, the present...

Variations in the mass distribution within an orogen may lead to transient sediment storage, which in turn might affect the state of stress and the fault activity. Distinguishing between different forcing mechanisms causing variations of sediment flux and tectonic activity, is therefore one of the most challenging tasks in understanding the spatiot...

We analyze the source-to-sink variations of in situ 10Be, 26Al and 21Ne concentrations in modern sediment of the Po river catchment, from Alpine, Apennine, floodplain, and delta samples, in order to investigate how the cosmogenic record of orogenic erosion is transmitted across a fast-subsiding foreland basin. The in situ 10Be concentrations in the...

The southernmost thrust of the Himalayan orogenic wedge that separates the foreland from the orogen, the Main Frontal Thrust (MFT), is thought to accommodate most of the ongoing crustal shortening in the Sub-Himalaya. Steepened longitudinal river-profile segments, terrace offsets, and back-tilted fluvial terraces within the Kangra re-entrant of the...

In the Central Andes, several studies on alluvial terraces and valley fills have linked sediment aggradation to periods of enhanced sediment supply. However, debate continues over whether tectonic or climatic factors are most important in triggering the enhanced supply. The Del Medio catchment in the Humahuaca Basin (Eastern Cordillera, NW Argentin...

Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity...

New developments in Geochemistry during the last two decades have revolutionized our understanding of the processes that shape Earth's surface. Here, complex interactions occur between the tectonic forces acting from within the Earth and the exogenic forces like climate that are strongly modulated by biota and, increasingly today, by human activity...

Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution and depositional systems. In the Sub-Himalaya, late Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on times...

The Song Gianh is a small-sized (~3500 km2), monsoon-dominated river in northern central Vietnam that can be used to understand how topography and climate control continental erosion. We present major element concentrations, together with Sr and Nd isotopic compositions, of siliciclastic bulk sediments to define sediment provenance and chemical wea...

The temporal evolution of erosion over million-year timescales is key to understanding the evolution of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge evolution predict an instantaneous response of erosion to pulses of rock uplift, stream-power based landscape evolution models predict catchment-wide erosion maxim...

We present an extensive investigation of a new erosion and weathering proxy derived from the 10Be(meteoric)/9Be(stable) ratio in the Amazon River basin. This new proxy combines a radioactive atmospheric flux tracer, meteoric cosmogenic 10Be, with 9Be, a trace metal released by weathering. Results show that meteoric 10Be concentrations ([10Be]) and...

Quantification of river dissolved and particulate fluxes is essential for understanding the role of weathering and erosion in geochemical cycles. The Amazon River is a natural laboratory where novel methods to quantify riverine fluxes can be verified, because of the density of published data on present-day sediment and dissolved loads (e.g. [1-3])...

The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating...