IRTG-StRATEGy - Short Term

163-G 2.1

Anonymous — Fri, 25 Sep 2015 10:11:09 +0000

10|2018 – 09|2021

Quaternary landscape evolution Paleoseismology and active tectonics of the NW-Argentineian broken foreland under the influence of tectonic processes.

M.Sc. Gregor Lauer-DünkelbergPotsdam University Prof. Manfred Strecker, Ph.D.Potsdam University Prof. Dr. Fernando HongnSalta University (ARG)Dr. Carolina Montero LopezIBIGEO Conicet

Fault systems in the broken foreland of NW Argentina are associated with isolated seismicity, deformation, and uplift, and they pose a major problem in understanding the spatiotemporal characteristics of individual earthquakes and long-term deformation patterns. Range uplift in these environments is highly disparate in time and space, without a clear deformation front as in the foreland fold-and-thrust belt to the north. Some ranges constitute large anticlines that have formed over blind thrusts, such as the growing anticlines west of the town of Salta.

On geological time scales, the erratic tectonic behavior of fault-bounded intermontane basins has caused a disturbance of the fluvial systems and resulted in multiple episodes of basin filling and sediment removal to the foreland. Importantly, there appears to be a relationship between sediment removal and ensuing changes in crustal stresses in these environments. For example, fault reactivation within and along basin margins is observed to follow the removal of the sedimentary load on time scales of several 105 years.

To elucidate the mechanisms by which such fault arrays in broken forelands organize, activate, and deactivate over time, we will compare geomorphic and geologic records that integrate the activity of faults over multithousand-year timescales (i.e., by dating deformed geomorphic features such as fans and terraces using U/Pb dating) to million-year timescales (i.e., by applying geochronologic and thermochronologic methods). These types of observations will enable the determination of the spatiotemporal faulting history and help to assess how deformation may be transferred between fault fault systems over long timescales (PhD1). We will furthermore use the Gale geodynamic model 87 to study how topographic construction and changing constitutive properties of fault zones may moderate the transfer of deformation between such arrays (PhD2).

As deformation accrues and mountain ranges are built, body forces in the crust may cause one set of structures to become less susceptible to failure relative to surrounding structures. Deformation may then systematically migrate from areas of higher to lower elevations. However, coeval erosional processes export mass from the basins and ranges, and so may buffer the accumulation of body forces in the crust. Gale allows application of surface-processes rules, enabling us to couple erosion at the surface to changes in the deformation field within the upper crust. Combining field observations, geochronology and modeling is expected to help us ascertain plausible causal mechanisms of spatiotemporal patterns of deformation.

10|2015 – 09|2018

Spatiotemporal characteristics of paleo-, historic and recent earthquakes in the broken foreland of the south-central Andes

In this project we will investigate large and medium-magnitude earthquakes using waveform analysis of historical and modern seismograms for event location, magnitude, and depth as well as focal mechanisms and source-time function. Historical earthquakes recorded at analog stations worldwide (primarily recorded on paper or film) since the beginning of the last century can be digitized and analyzed with advanced methods to better constrain their characteristics. For example, using waveform inversion, we are able to derive depth, lateral extent, and the true fault plane as well as zones of increased slip along rupture planes. With such a data set, we aim to identify and quantify the related earthquake surface-rupture trace or remnants of earlier surface ruptures in the epicentral regions. High-resolution satellite imagery, aerial photography, cosmogenic nuclide exposure dating of offset geomorphic markers, fault scarp measurements, and fault trenching will complement this analysis and provide an unprecedented data set to assess earthquake characteristics. We will focus on the large magnitude, shallow crustal seismic events in the region in the Andean foreland, e.g., the 1894 (M8), 1908 (M6.8), 1929 (M6.5), 1944 (M7.8), 1952 (M7.0) and 1977 (M7.4) events. Depending on the quality of historic records and local conditions, we will select two sites (preferably the 1894 and 1952/1977 San Juan events). For these sites, we will relocate medium-size earthquakes, determine their seismic moment tensors (focal mechanisms) and depth from waveform inversion and thereby test possible relationships between recent seismic activity and surficial deformation characteristics. Deployment of temporary seismic stations in addition to existing permanent stations at one or two selected sites will help identify active structures from small magnitude events. We will reevaluate seismic-moment tensors for the foreland region for recent events, where the magnitude threshold depends on data availability. Taken together, the results will provide better insight into the relationships between aseismic and seismic deformation, the identification of active structures, and possible changes in the spatiotemporal deformation characteristics of important structures. Such knowledge will ultimately shed light on the dynamics of Quaternary tectonic activity compared to the overall tectonic and topographic evolution of ranges in the broken foreland and help elucidate the background sedimentation rates and patterns in light of tectonic forcing mechanisms.

Working Package:

WP2 - Tectonics

Temporal Process:

Short Term

Dr. Martin ZeckraPotsdam University apl. Prof. Dr. Frank KrügerPotsdam University Prof. Dr. Fernando HongnSalta University (ARG)Dr. Patricia AlvaradoSan Juan University (ARG)

163-G 1.2

Anonymous — Fri, 25 Sep 2015 10:08:52 +0000

10|2018 – 09|2021

The role of mass wasting in glacial forelands of the Andes

M.Sc. Elisabeth SchönfeldtPotsdam University Prof. Oliver Korup, PhD.Potsdam University Dr. Diego WinocurBuenos Aires University (ARG)

Large segments of the Andean foreland have been repeatedly shaped by Quaternary glaciations. The many diagnostic landforms include large glacial lakes, staircases of moraine ridges, and extensive outwash plains, and have inspired generations of Quaternary geologists to reconstruct the processes, magnitude, and timing of ice build-up and decay along the mountain front, adding to a reference chronology of Southern hemisphere glaciations. What only a few of these studies have noticed are several hundreds of very large (>>10⁶m³) mass-wasting deposits that fringe the Andean foreland. Many of these debris mounds intersect with many well-dated moraine ridges or former meltwater-lake shorelines and offer exciting opportunities of exploring the hitherto largely unknown role of mass wasting in the glacial forelands of the Andes.

Studying the timing of these large landslides provides a stringent test for models of paraglacial landscape evolution. Preliminary work on large landslides glacial moraines indicates that moraines can fail catastrophically several thousand years after they formed. Several landslide bodies entered former glacial lakes shown by distinct horizontal breaks in landslide deposit morphology, thus raising the possibility of past and future landslide tsunamis.

The project aims to understand what we can learn from and what can we generalize about the mass-wasting activity of low-gradient glacial forelands. The Andean foreland may well host the largest cluster of (relatively) dated large, low-gradient landslides on Earth, which so far has been elusive in studies of the Andean sediment cascade. How does this estimate compare to sediment transport data, and what do we learn about sediment transfer from glaciated mountain belts to their proximal forelands?

10|2015 – 09|2018

Rock slides vs. rock glaciers: feeding the central Andean sediment cascade

This project explores the role of both large (>10⁶ m³) catastrophic rock slides and rock glaciers as prime movers of the central Andean sediment cascade. Recent hypotheses concerning the triggers of large non-volcanic bedrock landslides in the central Andes favor earthquakes, judging from the distribution of tell-tale landslide deposits with respect to active faults and shallow seismicity. Rock glaciers share a very similar topographic niche, but are traditionally viewed as diagnostic of sporadic alpine permafrost, though they may have also originated from earthquake-triggered supraglacial rock slides. Rock slides and rock glaciers are not only voluminous point sources of coarse debris, but also decisive barriers to incoming sediment flux. The aim of this project is to quantify to first order the regional net balance between such sediment release and sequestration by large rock slides and rock glaciers in central Andean headwaters using a multi-scale methodology: First, we will expand an existing regional inventory of large landslides and rock glaciers in the region to quantify the spatial pattern, topographic characteristics, and volumetric distribution of large Andean debris deposits from digital topography and remote sensing data. We will compare classic operator-based mapping with state-of-the-art automated object-oriented mapping techniques. Second, fieldwork will involve local ground truthing of landslide and rock-glacier geometries and provide vital input data for gauging regional volumetric budgets of denudation rates and intermittent sediment storage. We will estimate the fraction of valley fills causally linked to catastrophic slope failure and rock-glacier dynamics to gauge the overall relevance of catastrophic hillslope input to the central Andean sediment cascade. Samples collected in the field will further provide age constraints of strategically selected rockslide and rock-glacier surfaces or correlate backwater sediments with ¹⁴C, ¹⁰Be, lichenometry or dendrochronology, depending on available samples. Third, we will quantify metrics of geomorphic impact of these deposits on the fluvial network (changes in fluvial transport capacity, formation of knickpoints, epigenetic bedrock meanders, etc.), and the sediment cascade (barrier lakes, floodplain aggradation, etc.). We will expand existing numerical models of channel adjustment to landslide and rock glacier impacts to estimate fluvial response and recovery times. Similar work that we conducted in other regions revealed decisive controls of large landslide deposits on bedrock channel geometry, and the size and age distribution of valley fills that are potential sinks of alluvial georesources. Moreover, large river-blocking rock slides and rock glaciers may form important temporary buffers to incoming, and potentially adverse, sediment pulses from local disturbances.

Working Package:

WP1 - Climate

Temporal Process:

Short Term

M.Sc. M.Sc. Julia DrewesPotsdam University Prof. Oliver Korup, PhD.Potsdam University Prof. Dr. Stella MoreirasCuyo National University (ARG)

163-G 1.1

Anonymous — Fri, 25 Sep 2015 10:08:11 +0000

10|2018 – 09|2021

GNSS-based remote sensing: Innovative observation of key hydrological parameters in the central Andes

M.Sc. Nikolaos AntonoglouGFZ Potsdam Prof. Dr. Jens WickertGFZ Potsdam Prof. Dr. Bodo BookhagenPotsdam University Prof. Dr. Alejandro De la TorreAUSTRAL University (ARG)Prof. Dr. Andreas GüntnerGFZ Potsdam Dr. Torsten SchmidtGFZ Potsdam

The central Andes are characterized by a steep climatic gradient where key hydrologic variables change across short distances. One of the largest unknown component in this environment is the storage of water in the atmosphere, soil (soil moisture) and the snow height (or snow water equivalent). Both are parameters that can be quantified with modern remote sensing technology and we seek to enhance our understanding of the complete water fluxes in this environment – especially the highly dynamic fluxes that are often associated with hydrometerological extreme events.

In the past two decades, innovative GNSS (Global Navigational Satellite Systems) based remote sensing techniques were successfully tested and established and the resulting observations evolved into an important data source for numerous meteorological applications. The most prominent example for this development is the operational use of GNSS-based temperature and water vapor data to improve day-by-day regional and global weather forecasts since 2006. The exploitation of Earth reflected signals (GNSS Reflectometry, GNSS-R), however is not yet operationally applied and still focus of international research to reach operational application level as well. GNSS data provide an excellent opportunity to study the dynamics of hydrometeorological extreme events, because of the very high sampling interval.

This project relies on close collaboration with Argentinean researchers that maintain a regional GNSS ground network. In the framework of this project, new stations at specific, key locations will be installed and the data used to decipher hydrologic process. This project requires strong quantitative skills and thorough environmental knowledge.

10|2015 – 09|2018

Characterization of atmospheric processes related to hydro-meteorological extreme events over the south-central Andes

Extreme rainfall events fundamentally impact erosion and deposition. The combination of the South American Monsoon System (SAMS) and high topography of the Central Andes constitutes the most important drivers for the highly asymmetric distribution of rainfall. In light of these conditions and climate variability involving the SAMS, the South American Convergence Zone, the El Niño Southern Oscillation, and the Southern Hemisphere Westerlies, meteorological observations and detailed analysis of the atmospheric circulation over South America at various spatiotemporal scales are required to create models and derive predictions of the response of surface-process systems to climate change. For more than a decade, the GPS radio occultation (RO) method has offered a promising tool for the global characterization of atmospheric temperature and tropospheric humidity. Here, we will use ground (weather stations, radiosonde stations, and S band radar stations) and space-based (RO and other satellites) observations and meteorological re-analyses (ERA interim, ERA40) to obtain a detailed view of the dynamics of the SAMS, the related humidity fields, and precipitation patterns. In addition, this approach will help to decipher the characteristics of annual and seasonal variability, and the linkage to extreme precipitation events. The considered time scale will range from the time since RO observations are available (since 2001) and extend to the beginning of the ERA40 dataset covering the 1950s. Finally, we will associate the combined observational and re-analysis data with their spatiotemporal variation to QBO and ENSO events for a better understanding of the interplay between natural atmospheric variability and the observed humidity/rainfall amount and distribution. Due to a recent southward shift of the SAMS and an amplification of the jet stream, coupled with increased southward moisture transport from Amazonia and annual precipitation, it can be expected that variations in atmosphere dynamics, tropopause structure, and gravity-wave activity will occur, an issue that will also be addressed in this study. Combined, the results of this project will be essential to understanding regional erosional and sedimentological processes on short timescales, and will help clarify the couplings between climate and surface-process reflected in geological archives of intermontane and foreland basin fills.

Working Package:

WP1 - Climate

Temporal Process:

Short Term

Dr. Maryam Ramezani ZiaraniGFZ Potsdam Prof. Dr. Bodo BookhagenPotsdam University Dr. Torsten SchmidtGFZ Potsdam Prof. Dr. Jens WickertGFZ Potsdam Prof. Dr. Alejandro De la TorreAUSTRAL University (ARG)

WP(1): Climate-tectonic impacts on surface processes

Anonymous — Fri, 25 Sep 2015 09:51:52 +0000

Over the last two decades, numerous theoretical and modeling studies of erosion and depositional processes in tectonically active mountain belts have been used to better understand the principal allogenic processes that are responsible for the characteristics of sedimentary records^1,2,3. Most of these models are based on short-lived perturbations of steady-state conditions, either through variations in subsidence rates or in the amount of precipitation, until new steady-state conditions are reached after a response time of about 10⁵ to 10⁶ years⁴. These models demonstrate that similar stratigraphic architecture may result from different forcing conditions, rendering many field-based interpretations of the causal mechanisms unclear⁵. This ambiguity is especially prevalent in settings where outcrops are not continuous, where little or no information is available on the tectonic and erosional history of the sediment, and where significant time lags exist between the timing of stress-field and kinematic changes, resulting fault activity, and sedimentary responses.

A further problem in realistically portraying the complex relationships between different forcing mechanisms of depositional processes has been that precipitation regimes and tectonics have been treated as individual, rather than co-varying parameters, often ignoring possible feedback mechanisms between deep-seated and surface processes⁶. Many state-of-the-art numerical landscape evolution models simulate erosion but neglect deposition, resulting in less knowledge of intermittent sediment storage within mountain belts. Such sediment storage is crucial in decoupling hillslope from channel processes; attenuating water, sediment, and biogeochemical constituent fluxes; hosting archives of environmental change between source and sink; and ultimately producing flat terrain in an otherwise steep, dissected landscape⁷. Furthermore, as the construction of mountain ranges fundamentally influences atmospheric circulation systems over time, the long-term interaction between topographic growth, rainfall, and erosion may in some cases alter the structural evolution of wedge-shaped fold-and-thrust belts and the locus of tectonic activity, potentially leading to out-of-sequence deformation^8,9.

The convergence between the Nazca and South American plates¹⁰, the geometry of the downgoing oceanic slab, and its interaction with the upper plate¹¹ create the forces that generate retroarc topography, deform rocks, and mobilize the fluids and sediments that ultimately are involved in the creation of metallic and energy resources in the southern central Andes. Between 15 and 27°S, the Altiplano-Puna plateau, Earth’s second largest orogenic plateau, spans Bolivia and NW Argentina with an average elevation of 3.7 km. This internally-drained region comprises contractional basin-and-range topography characterized by isolated and sometimes coalesced sedimentary basins^12,13. The interference of the N-S distribution of Andean topography with global atmospheric circulation patterns has resulted in highly asymmetric rainfall, erosion, and sedimentation patterns. In the Central Andes, the principal moisture sources affecting the E flanks of the orogen are the SAMS and the SACZ. In contrast, the orogen interior and its western flanks are arid to hyperarid, but they appear to have repeatedly received higher precipitation on millenial timescales¹⁴. Today, most of the extreme hydro-meteorological events observed in the Central Andes are intimately associated with ENSO or the tropical quasi-biennial oscillation¹⁵.

Temporal Process:

Short Term

Long Term

Work Package:

WP1 - Climate

Bibliography:

¹ Babeyko and Sobolev, 2005; ² Babeyko et al., 2006; ³ Armitage et al., 2011; ⁴ Whipple and Meade, 2006; ⁵ Burbank et al., 1988; ⁶ Molnar, 2009; ⁷ Straumann and Korup, 2009; ⁸ e.g. Willet, 1999; ⁹ Whipple and Meade, 2006; ¹⁰ Allmendinger et al., 1983; ¹¹ Sobolev and Babeyko, 2005; ¹² Jordan and Alonso, 1987; ¹³ Alonso et al., 1991; ¹⁴ Strecker et al., 2007; ¹⁵ Mo and Berbery, 2011