PhD Day Geosciences

Friday, 7th July 2017, 2 – 4 pm

Foyer House 29, Campus Golm

2

Participant - surname

Participant - first name

Institute Title

Al-Halbouni Djamil GFZ Distinct Element modeling of geophysical signatures during sinkhole collapse

Aranda Viana Germán UP Imaging and photogrammetry models of western scarp of the Candelaria range by Unmanned Aerial Vehicles

Arnous Ahmad UP Landscape evolution in response to reactivated faults in the broken foreland of southern Central Andes, NW Argentina

Borghini Alessia UP Variscan nanogranitoids in Bohemian Massif garnet clinopyroxenites: evidence for metasomatism and partial melting?

Brenner Johannes UFZ Towards reliable evapotranspiration in the semi-arid Júcar region

Coch Caroline AWI

Hydrological and sedimentary response of small watersheds in a Low Arctic setting – A case study on Herschel Island, Yukon Territory, Canada

Codeço Marta GFZ Chemical and 𝜹11B variations in tourmaline from the Panasqueira W-Sn-Cu deposit, Portugal

Escalante Leonardo UP

Allufial-fan terraces as strain markers for Quaternary contractile deformation in the interior of the southern Central Andes: Intermontane alluvial basin fills in the Calchaqui Valley of the Eastern Cordillera (Cachi-Payogasta area), NW Argentina (25°03'S, 66°07'W)

Figueroa Villegas

Sara UP

Holocene Tectonic Deformation Processes in the Transition between Sierras Pampeanas and Eastern Cordillera, Cafayate Valley (26°00’ – 25°50’LAT., 66°00’-65°50’LONG.),Salta

Friese André GFZ A simple and inexpensive technique for assessing contamination during drilling operations

Gholamrezaie Ershad UP 3D structure and conductive thermal field of the sea of Marmara

Ibarra Federico UP Lithosphere-scale 3D gravity and thermal modelling of the Central Andes

3

Participant - surname

Participant - first name

Institute Title

Korges Maximilian GFZ Quantification of ore-forming processes in magmatic hydrothermal Sn-W systems: a fluid inclusion study of the Zinnwald deposit

Liu Sibiao GFZ Influence of the orogenic lithospheric strength on the deformation of the foreland upper crust

Lorenz Melanie UP

REE variations in the pre-Andean crustal basement: Enrichment in a shear zone of Ordovician granitoids and mineralization in a fenitized Devonian monzogranite, Eastern Sierras Pampeanas

Maerz Sven UP

Pore Type Characterization and Detection of Effectice Pore Network with Digital Imge Analysis: A case study from Miocene Lacustrine Carbonates (Southern Germany)

Meijer Niels UP Astronomical forcing of Eocene monsoons

Müller Sebastian UP Extending Theis’ solution to incorporate heterogeneity into pumping test analysis

Nooshiri Nima GFZ Revision of earthquake hypocentre locations in global bulletin data sets using source-specific station terms

Ötztürk Ugur UP Identifying Typhoon Tracks based on Event Synchronization derived Spatially Embedded Climate Networks

Pascual Montanés

Joan GFZ High-resolution reconstruction of past climate and environment from lacustrine deposits in NW Argentina

Pommerencke Julia UP Rock Glacier Response in Changing Climate

Purinton Ben UP Digital topography for geomorphology and beyond: frontiers in meters to sub-meter resolution remote sensing

Ramage Justine AWI Terrain Controls on the Occurrence of Coastal Retrogressive Thaw Slumps along the Yukon Coast, Canada

4

Participant - surname

Participant - first name

Institute Title

Ramezani Ziarani

Maryam UP Determining hydroclimatic extreme events over the south-central Andes

Ruiz Ricardo GFZ Organofacies of the Yacoraite Formation, Salta Basin; Argentina

Schmidt Wera UP Testing long-term controls of sedimentary basin architecture, Tres Cruces Subbasin, Jujuy, Argentina

Siegmund Nicole ZALF Interaction between small scale landscape structure and erosive wind events in La Pampa, Argentina

Stolle Amelie UP Mountain rivers may need centuries to adjust to earthquake-triggered sediment pulses, Pokhara, Nepal

van der Veen Iris UP Defining moisture sources and organic matter transport processes in the NW Himalaya

Wetzel Maria GFZ Numerical homogenization approach for coupling of chemical and mechanical processes in the geological subsurface

5

Distinct Element modeling of geophysical signatures during

sinkhole collapse

Djamil Al-Halbouni, Eoghan P. Holohan, Abbas Taheri, Torsten Dahm

A sinkhole forms due to the collapse of rocks or soil near the Earth’s surface into an

underground cavity. Such large secondary pore spaces are derived by dissolution and

subrosion in the underground. By changing the stress field in the surrounding material, the

growth of cavities can lead to a positive feedback, in which expansion and mechanical

instability in the surrounding material increases or generates new secondary pore space. The

development of models for the mechanical interaction of a growing cavity and fracturing of its

surrounding material has been limited, however.

Here we report on the advances of a general, simplified approach to simulating cavity growth

and sinkhole formation by using 2D Distinct Element Modeling (DEM) PFC5.0 software and

thereby constraining pre-, syn- and post-collapse geophysical and geodetic signatures. This

physically realistic approach allows for spontaneous cavity development and dislocation of

rock mass to be simulated by bonded particle formulation of DEM.

The proposed model development and a possible archive of modeled scenarios may, in

combination with a geodetic and seismological sinkhole monitoring, contribute to an early-

warning tool for end-users and decision makers in areas affected by natural (e.g. Dead Sea)

or man-made sinkhole collapses (mines).

6

Imaging and photogrammetry models of western scarp of the

Candelaria range by Unmanned Aerial Vehicles

Rodolfo G. Aranda 1.2, Carlos Bianchi 1, Alejandro Aramayo 1, Luis Alvarado 1, Ahmad

Arnous 2,3, Fernando D. Hongn 1, Manfred R. Strecker 2

1Instituto de Bio y Geociencias del NOA (CONICET-UNSa), 4405, Salta, Argentina. E-

mail: german.aranda.gn20@gmail.com.

2Instituto de Ciencias de la Tierra y del Medio Ambiente, Universidad de Potsdam, 14476

Potsdam, Alemania, manfred.strecker@geo.uni-potsdam.de, 14476.

3Instituto Miguel Lillo, Universidad Nacional de Tucumán, 4000, Tucumán,

aarnous.aa@gmail.com, 4000.

We present new high-resolution topographic data obtained with an Unmanned Aerial Vehicle

(UAV) and photogrammetric techniques to generate a digital cartographic base for future

earthquake-geology and tectonic geomorphology studies in the western edge of the

Candelaria range, Salta Province (Argentina). The surveyed region covered a rectangular area

of 1.82 km², which was chosen perpendicular to the inferred scarp and identified by terrestrial

control points using geodetic GPS. The set of images obtained were rectified in an

orthomosaic, then created a digital surface model (DSM) with a spatial resolution of 5.75 cm /

pixel. The digital elevation model (DEM) was derived from the original digital surface model,

filtering topographical anomalies related to the vegetation cover, following a combination of a

multi-stage automatic algorithm and manual filtering of noise. These results constitute one of

the first attempts to obtain high quality imagery in the area. Overall, the digital dataset produced

is intended to support neotectonics investigation in this region, and provide tools introduce new

workflows for the creation of Digital Elevation Models.

7

Quaternary Activity of the Canderlaria Fault, NW Argentina (26° LAT,

65° LON): New Insights from Geomorphic Mapping and Electrical-

Resistivity Prospecting

Ahmad Arnous 1.2, Angela Landgraf 2, Julien Guillemoteau 2, Antonio Gutierrez 1,

Rodolfo G. Aranda 1.2, Manfred R. Strecker 2

1Instituto Miguel Lillo, Universidad Nacional de Tucumán, 4000 Tucumán

2Institute of Earth and Environmental Science, University of Potsdam, 14476 Potsdam,

Germany

Quaternary deposits in the broken foreland of NW Argentina record the spatially and temporally

disparate character of tectonic activity. The Candelaria basement-cored range has

experienced seismicity on its western flanks, where the Candelaria Fault also offsets

Quaternary deposits and forms a pronounced topographic break. Vertical offsets of up to 15m

along the fault scarp affect Quaternary alluvial-fan deposits and point to potential earthquake

hazards along this fault.

our geomorphic mapping of the fault using satellite images and digital elevation models of 5m

reveals different generations of alluvial fans.

In an attempt to reveal the geometry and kinematics of the responsible faults, we acquired a

set of 2D electrical resistivity tomography (ERT) data perpendicular to the strike of the fault.

During an exploratory survey.

The resulting cross-sections of electrical resistivity show a significant contrast below the

inferred fault-scarp position at the surface.

The consistency between our geomorphic mapping and the electrical profiling led us to

interpret the prominent scarp as a reverse fault, where the western block is the hanging-wall

block that was thrust onto fan deposits along a westward-dipping fault.

8

Variscan nanogranitoids in Bohemian Massif garnet

clinopyroxenites: evidence for metasomatism and partial melting?

Alessia Borghini (1), Silvio Ferrero (1,2), Bernd Wunder (3), Laurent O. (4) , Patrick J O’Brien (1),

and Martin A. Ziemann (1)

(1) Universität Potsdam, 14476 Potsdam, Germany,

(2) Museum für Naturkunde (MfN), Leibniz-Institut für Evolutions-und Biodiversitätsforschung,

10115 Berlin, Germany

(3) Helmholtz-Zentrum Potsdam, GFZ, D-14473 Potsdam, Germany

(4) ETH Zürich, 9082 Zürich, Switzerland

Primary nanogranitoids have been identified in garnet from the garnet clinopyroxenites of the

Granulitgebirge, Bohemian Massif. Their distribution as clusters in garnet confirms they formed

during garnet growth. The inclusions can be polycrystalline or glassy and from 5-20 μm in

diameter. The phases were identified by Micro Raman Spectroscopy and the assemblage is

kumdykolite/albite, phlogopite, osumilite, kokchetavite and quartz and were identified. This

association of minerals and the presence of preserved glassy inclusions are consistent with

the origin of these inclusions as former droplets of melt.

Nanogranitoids have been re-homogenized at 1000°C, 22 kbar to a hydrous glass of quartz-

monzonitic composition in a piston cylinder apparatus. The chosen conditions correspond to

the formation of the garnet and thus of melt entrapment. The preliminary interpretation of

normalized trace element data show that the trapped melt is enriched in Cs, Rb and Pb. Such

patterns suggest the involvement of a white mica in the melt-producing reaction.

The studied garnet clinopyroxenites are enclosed in bodies of serpentinized garnet peridotites

hosted in turn in HP felsic granulites. They show a granoblastic texture dominated by garnet

and clinopyroxene with interstitial plagioclase, biotite, two generations of amphiboles and rutile

and ilmenite as accessories. The bulk rock composition is basic to ultrabasic.

These inclusions may be the result of two different possible processes: 1) localized melting of

metasomatized mafic rocks with simultaneous production of garnet, 2) or an interaction

between melted felsic granulites and metasomatized peridotites with consequent formation of

these garnet clinopyroxenites.

9

Towards reliable ET estimates in the semi-arid Júcar region in Spain

Brenner J.1, Zink M.1, Schrön M. 1, Thober S.1, Rakovec O.1, Samaniego L.1

1 Helmholtz Centre for Environmental Research–UFZ, Leipzig, Germany.

Current research indicated that the there is potential for improving evapotranspiration (ET)

estimates in state-of-the-art hydrologic models such as the mesoscale Hydrological Model

(www.ufz.de/mhm). Most models exhibit deficiencies to estimate the ET flux in semi-arid

regions. Possible reasons for poor performance may be related to the low resolution of the

forcings, the estimation of the PET, the joint estimation of the transpiration and evaporation,

poor process parameterizations, among others.

In this study, we aim at sequential hypothesis-based experiments to uncover the main reasons

of these deficiencies at the Júcar basin in Spain. We plan the following experiments: 1) Use

the high resolution meteorological forcing (P and T) to estimate its effects on ET and

streamflow. 2) Use local ET measurements eddy covariance stations to estimate evaporation

related parameters. 3) Test the influence of the PET formulations (Hargreaves-Samani,

Priestley-Taylor, Penman-Montheith).

We set-up mHM for two eddy-covariance sites at the local scale. In the second experiment, for

example, a parameter set is to be found as a compromised solution between ET measured at

local stations and the streamflow observations at eight sub-basins of the Júcar river.

Preliminary results indicate that higher model performance regarding streamflow can be

achieved using local high-resolution meteorology. ET performance is, however, still deficient.

On the contrary, using ET site calibrations alone increase performance in ET but yields in poor

performance in streamflow. Results suggest the need of multi-variable, simultaneous

calibration schemes to reliable estimate ET and streamflow in the Júcar basin.

10

Hydrological and sedimentary response of small watersheds in a

Low Arctic setting – A case study on Herschel Island, Yukon

Territory, Canada

Caroline Coch, Hugues Lantuit, Scott Lamoureux

Coastal ecosystems in the Arctic are being affected by climate change leading to permafrost

thaw, to a shifting streamflow regime and to changing fluxes of freshwater and sediment to the

Arctic Ocean. The hydrological and sedimentary response of large rivers to climate change

have been focus of numerous investigations as they cover 53% of the area draining into the

Arctic Ocean. Small catchments are yet widespread and could contribute large amounts of

sediment to the nearshore zone. Streamflow and sediment transport is being monitored

continuously only at a few sites, which constraints the understanding regarding water quality

and nutrient availability. This project is addressing this knowledge gap by investigating

streamflow regime and sediment dynamics of two adjacent catchments on Herschel Island in

the western Canadian Arctic. By comparing both watersheds, sediment sources and controls

of its mobilization are going to be investigated. This study will contribute to a baseline for pan-

Arctic assessments of sediment flux to the Arctic Ocean.

11

Chemical and 𝜹11B variations in tourmaline from the Panasqueira W-

Sn-Cu deposit, Portugal

Marta S. Codeço1, Philipp Weis1, Robert B. Trumbull1, Filipe Pinto2, Pilar Lecumberri-Sanchez3

1GFZ German Research Centre for Geosciences, Potsdam, Germany

2Beralt Tin & Wolfram (Portugal), Barroca Grande, Portugal

3Dep. of Geosciences, University of Arizona, Tucson, USA

The Panasqueira W-Sn-Cu vein-type deposit in Portugal is Europe’s largest tungsten deposit.

The subhorizontal W-Sn-Cu-bearing quartz veins are hosted by metasedimentary units of the

Beira Schists and spatially related to a greisenized cupola of an S-type granite [1]. Tourmaline

is absent in the greisen but abundant in wallrock alteration zones which predate the main ore

stage. Tourmaline is also found in late-stage vugs.

We report results from high-resolution in-situ measurements (microprobe and SIMS) showing

the variations in chemical and boron isotopic compositions of tourmalines from the

Panasqueira deposit. All tourmalines have Li-free ferromagnesian compositions and display

optical and chemical zoning. The results show an increase in Fe, F and Na and decrease in

Mg, Al and Ca from core to rim. The total range in tourmaline B-isotope compositions is from

11B -13.3 to -3.7‰, including tourmaline from the wallrocks and vugs. These values are

compatible with either local metasedimentary or granitic sources. However, given the volume

of tourmaline and association with F, W, Sn, Ta, Nb, we consider a boron source from the

adjacent granite more likely.

The results suggest a dynamic hydrothermal system with multiple injections of magmatic-

dominated fluids [2]. The variations in tourmaline composition are interpreted to reflect a

combination of cooling and changes from wallrock- to fluid-dominated conditions.

[1] Kelly and Rye (1979) Econ. Geol. 74: 1721-1822.

[2] Foxford et al. (2000) J. Struct. Geol. 22:1065-1086.

12

Alluvial-fan terraces as strain markers for Quaternary contractile

deformation in the interior of the southern Central Andes:

Intermontane alluvial basin fills in the Calchaquí Valley of the Eastern

Cordillera (Cachi-Payogasta area), NW Argentina (25°03’S, 66°07’W)

Leonardo E. Escalante1, Manfred R. Strecker2, Fernando D. Hongn1.

1Instituto de Bio y Geociencias del Noroeste Argentino (IBIGEO), Consejo Nacional de

Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional de Salta (UNSA), 9

de Julio 14, 4405 Rosario de Lerma, Salta, Argentina.

2Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Karl-Liebknecht-Straße 24,

14476 Potsdam, Germany.

The E Cordillera of the southern Central Andes in NW Argentina is characterized by

intermontane basins flanked by reverse-fault bounded ranges. The basins are located in the

interior parts of the orogen and straddle the eastern boundary of the high-elevation intra-

orogenic Andean Plateau. One of the largest intermontane basins is the N-S oriented

Calchaqui Valley. In its northernmost sector the valley is bounded by E and W-dipping reverse

faults, respectively. The basin exposes deformed Tertiary strata that are unconformably

overlain by Quaternary conglomerates that are part of coalesced alluvial fans. This sector of

the valley narrows considerably and neotectonic activity in this area has been thought to be

associated with the range-bounding faults. In addition, it has been proposed that the main

Quaternary faults reflect the reactivation of Tertiary structures. The effects of Quaternary

deformation in this area are recorded by faults, folds, unconformities, and cataclasized and

tilted conglomerates. In addition, changes in paleocurrents and provenance, anomalies in the

drainage network, and convex longitudinal stream profiles unambiguously demonstrate the

impact of Quaternary tectonic activity in the Calchaqui Valley. Taken together, available

sedimentological, geomorphological, and structural information as well as historical and

instrumental seismicity data show that the northern sector of the Calchaquíes Valley has been

actively deforming during the Quaternary. This emphasizes the need to perform additional

systematic investigations of the characteristics of the Quaternary deposits and their tectonic

overprint at regional scale to help understand the spatiotemporal evolution of tectonic

processes in light of ongoing contraction and potential hazards.

13

Holocene Tectonic Deformation Processes in the Transition between

Sierras Pampeanas and Eastern Cordillera, Cafayate Valley (26°00’ –

25°50’LAT., 66°00’-65°50’LONG.),Salta

Sara Figueroa Villegas, Escalante Leonardo1, Hongn Fernando1, Strecker Manfred R. 2

1 Instituto de Bio y Geociencias del NOA (UNSa-CONICET). 9 de Julio 4, Rosario de Lerma.

2 Institut fürr Erd- und Umweltwissenschaften, Universität Potsdam, D-14476 Potsdam,

Alemania

The Quaternary deformation in Cafayate valley has been documented, near to Quebrada La

Yesera, mainly as sinsedymentary structures in Cafayate-Santa María paleolake. (13,830

years BP. until 4800 years BP). In this work it has been described the deformation that affect

the fluvio-aluvial Quaternary deposits as well as Cafayate-Santa María paleolake deposits in

the piedmont of Sierra de León Muerto. This range is bounded by the E-dipping Castillo Fault.

The structures that affect the Quaternary deposits are reverse faults that has been interpreted

as splay faults (footwall shortcut) of the Castillo Fault that generated thrust folds. Our new data

documents sustained Holocene shortening in this structurally complex region.

14

A simple and inexpensive technique for assessing contamination

during drilling operations

André Friese1, Jens Kallmeyer1, Jan Axel Kitte1, Edgar Kutschera1, Ivan Montaño Martínez2,

Satria Bijaksana3, Dirk Wagner1, the ICDP Lake Chalco Drilling Science Team and the ICDP

Towuti Drilling Science Team

1 GFZ German Research Centre For Geosciences, Section 5.3. Geomicrobiology, 14473

Potsdam, Germany

2 Laboratorio de Paleolimnologia, Instituto de Geofísica, UNAM, Mexico

3 Faculty of Mining and Petroleum Engineering, Institut Teknologi Bandung, Indonesia

Exploration of subsurface environments relies on drilling, which inevitably causes infiltration of

drilling fluids, containing non-indigenous microbes from the surface, into the core. It is of

paramount importance to assess the degree of contamination to identify uncontaminated

samples for geomicrobiological investigations. To do this, a tracer is mixed into the drilling fluid,

usually dissolved gasses like Perfluorocarbon or microbe-sized fluorescent particles

(microspheres). For microspheres the main problem was the high price, which limited their use

to spot checks or small drilling operations.

We developed a modified microsphere tracer approach using an aqueous fluorescent pigment

dispersion, that costs four orders of magnitude less, allowing for a liberal use even in large

drilling operations. Its suitability was successfully tested at two ICDP Drilling campaigns at

Lake Towuti, Indonesia and at Lake Chalco, Mexico.

Contamination can be detected by fluorescence microscopy or by flow cytometry at a

sensitivity that is in the range of established techniques. By using a small portable cytometer,

high-resolution data can be obtained directly on-site with minimal effort. Also, the tracer is

stable and can be detected long after core retrieval. Therefore this approach offers an

inexpensive but powerful alternative technique for contamination assessment for future drilling

campaigns.

15

3D structure and conductive thermal field of the sea of Marmara

Ershad Gholamrezaie (1,2), Magdalena Scheck-Wenderoth (2,3), and Oliver Heidbach (2)

(1) University of Potsdam, Potsdam, Germany

(2) Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Potsdam,

Germany

(3) RWTH Aachen University, Aachen, Germany

The Sea of Marmara and its basins mainly evolved due to the activities of the Thrace-Eskisehir

Fault Zone (TEFZ) in Neogene and the North Anatolian Fault Zone (NAFZ) in Quaternary. At

present-day, the Sea of Marmara is still evolving due to the NAFZ and the Marmara region is

an earthquake danger zone while hosting around 20 million of inhabitants. For a better

understanding of the tectonic processes and geodynamics evolution, it is important to model

the geological structure and the thermal field of this region. The aim of this study is to build a

3D lithospheric-scale structural model and a 3D conductive thermal model for the Sea of

Marmara and including its adjacent onshore areas. Therefore, we integrate different geological

and geophysical data such as existing structural models, well data, seismic observations and

gravity to build a new 3D lithospheric-scale structural model which is additionally constrained

by 3D gravity modelling. The final 3D structural model differentiates various sedimentary,

crustal and mantle units and is the base for the 3D thermal field calculation. The 3D conductive

thermal model is a numerical solution to the Fourier’s law equation in steady-state condition

and considering the thermal properties of the corresponding structural model. Our 3D

lithospheric-scale models of the geological structure and the conductive thermal field are the

key points for further general research and useful particularly for mechanical modelling,

considering variations in rheology and strength of the lithosphere in the Marmara region. In

addition, our results have application in geo-resources exploration and would be helpful in risk

management and hazard mitigation.

16

Lithosphere-scale 3D gravity and thermal modeling of the Central

Andes

Federico Ibarra

We developed a lithosphere-scale 3D thermal model of the Central Andes between 20-30ºS

and 76-61ºW. The aim of this work is to investigate the thermal state of the region and

characterize its anomalies. The thermal calculations are based on the assumption that the heat

is transported mainly by conduction in the lithosphere using the finite element method. The

lithospheric structure on which the calculations were made is taken from a previous 3D density

model, simplified and updated with new published data and constrained by forward modelling

of the Bouguer anomaly. Six thermal fields were calculated using different boundary

conditions, keeping one of them as the final model. The resulting thermal field shows

anomalies consistent with the location of low velocity zones, and the temperature is also high

enough to produce partial melt in the crust. This is the first 3D thermal model developed for

the region and it will contribute to understand and quantify geological and geodynamical

processes.

17

Quantification of ore-forming processes in magmatic hydrothermal

Sn-W systems: a fluid inclusion study of the Zinnwald deposit

Maximilian Korges1, Philipp Weis1, Volker Lüders1, Oscar Laurent2

1GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany

2Institute of Geochemistry and Petrology ETH Zürich, Clausiusstrasse 25, Zürich, Switzerland

The Sn-W-Li deposit in the roof zone of the Zinnwald granite is associated with Sn-bearing

greisen and sub-horizontal veins containing economical contents of cassiterite and wolframite.

The relation between the contrasting mineralizations remains elusive. We analysed fluid

inclusions from samples of the German part of the deposit using conventional, infrared-

microthermometry and LA-ICP-MS.

The most common primary FI in the quartz veins show homogenization temperatures (Th)

between 360°C and 380°C and high variability in salinity (1–8 eq.w(NaCl)). IR

microthermometry of FI in ore from the vein reveal lower Th but higher salinities (12

eq.w(NaCl)). In contrast FIA in greisen have similar Th (360–380°C) to the vein quartz and

salinities between 5 and 8 eq. w(NaCl). Few quartz vein samples contain boiling assemblages

of brine (up to 35 eq.w(NaCl)) and vapor-rich inclusions (Th = 300-340°C)

LA-ICP-MS data show that all elements required for forming a Sn-W deposit are included in

the hydrothermal fluid. The results suggest that ore formation is controlled by two processes:

1) fluid rock interaction during greisen formation and 2) boiling and the loss of HCl leading to

ore precipitation in the veins, which are interpreted as former fluid pathways in the peripheral

parts of the granite.

18

Influence of the orogenic lithospheric strength on the deformation of

the foreland upper crust

Sibiao Liu1,2, Stephan V. Sobolev 1,2, Andrey Y. Babeyko 1, Frank Krüger 2, Javier Quinteros 1

and Anton Popov 3

1 German Research Center for Geosciences GFZ, Potsdam, Germany

2 Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany

3 Institute of Geosciences, Johannes Gutenberg University Mainz, Mainz, Germany

In the Central Andes, the Altiplano-Puna Plateau was formed with a pronounced N-S oriented

deformation diversity including a broad thin-skinned Sub-Andean thrust belt in Altiplano and

the thick-skinned deformation in the Santa Barbara system in south Puna foreland. The

mechanism of different deformation patterns in the orogenic foreland remain controversial.

Previous studies suggested that they might be controlled by strength variations of the

lithosphere in which the lithospherical and crustal thickness, the thermal regime, as well as

sedimentary loads and their strength play an important role. Here we use high-resolution

numerical models to investigate these factors controlling mechanical and thermal strength of

the lithosphere. Our model results demonstrate that the first prerequisite for thin-skinned

deformation in the foreland sediment cover is internal weak sedimentary rocks due to high pore

fluid pressure. With the friction drop of foreland sediments, the simple shear shortening

accompanied by thin-skinned thrusting at the uppermost crust of foreland is formed by the

weakening of the orogenic lithosphere by either thickening the crust or thinning the entire

lithosphere. The deformation shifts from thin-skinned to thick-skinned structure in the foreland

uppermost crust when the orogenic lithosphere is getting stronger due to the cold and thick

lithosphere or the weak sediment cover above the foreland is absent. In addition, the transition

from compression to extension on top of the orogen is controlled by the intensity of sediments

weakening.

19

REE variations in the pre-Andean crustal basement: Enrichment in a shear zone

of Ordovician granitoids and mineralization in a fenitized Devonian

monzogranite, Eastern Sierras Pampeanas

Melanie Lorenz1 , Uwe Altenberger1, Robert Trumbull2 ,Raúl Lira3 , Monica López de Luchi 4,

Nicolas Viñas5, José Pablo Lopez6

1 University of Potsdam

2 GFZ Potsdam

3 University of Córdoba

4 University of Buenos Aires

5 Michelotti e hijos Córdoba

6 University of Tucuman

In the light of an increasing demand for high-tech elements like rare earth elements

for the globa markets, this study focuses on obtaining knowledge about the genesis

of their primary deposit and secondary enrichment processes.

An unusual REE-bearing assemblage was identified in a hydrothermally altered

(fenitized) biotite-monzogranite at Rodeo de Los Molles, which is part of the

Devonian Las Chacras-Piedras Coloradas Batholith in San Luis province, Eastern

Sierras Pampeanas. The fenitization occurs in an elliptical, NNE-SSW trending zone

that may be fault-related. Fenitization is characterized by metasomatic gain of Na

and K as well as loss of Ca and Sr. The fenitized zone is locally enriched in light

rare earth elements (LREE) and has been subject to a mineral exploration

campaign (Lira et al., 1999). Drill-core samples from that campaign and new surface

samples are the basis for the present investigation, which aims to decipher the fluid

evolution and REE-mineralization.

In the Sierras de Paiman, an Ordovician mountain range in the north-west of the

Eastern Sierras Pampeanas, a one kilometer long strain profile along a mylonitic

shear zone was sampled. Fluid-rock interaction during shear zone evolution is

commonly associated with strongly channelized fluids as well as changes in element

chemistry. The mobility of fluid mobile elements like LREE is controlled by the

stability of minerals in which they are incorporated in as well as by the nature of

infiltrating fluids, which forms another focus of this study.

20

Pore Type Characterization and Detection of Effective Pore Network

with Digital Image Analysis: A case study from Miocene Lacustrine

Carbonates (Southern Germany)

Sven Maerz

University of Potsdam, Institute of Earth and Environmental Science, Potsdam, Germany

In addition to routine porosity and permeability measurements, the application of Digital Image

Analysis (DIA) results in quantitative data of pore geometry, which is the main factor controlling

petrophysical properties in a sedimentary rock. In this study, these DIA-derived data are

utilized to characterize each occurring pore type and to detect the most effective pore types

which form an interconnected pore network and therefore determine permeability. We provide

a step by step workflow of a new approach based on DIA, performed on 76 samples of marginal

lacustrine carbonates from the northern lake margin of the Miocene Nördlinger Ries crater lake

in Southern Germany. This method comprises four main steps, each providing multi-scale

information to characterize each individual pore, each pore type and the entire pore system.

Since each pore type is confined by the sedimentary fabric and linked to a distinct genetic

process, results can be transferred to recent and ancient analogues settings, and complement

to diagenetic studies of the paragenetic history of the pore-hosting sedimentary rock. As a

result, the extraction of the interconnected (or effective) pore network leads to an improved

correlation between porosity and permeability which eases the often difficult prediction of both

petrophysical parameters in carbonates.

21

Astronomical forcing of Eocene monsoons

Niels Meijer1,2, Hemmo Abels3, Mustafa Kaya1,2, Pierrick Roperch2, Alexis Licht4, Rik Tjallingii5,

Yang Zhang6, Zhaojie Guo6, Zhongping Lai7, Guillaume Dupont-Nivet1,2,6

1) Institute of Earth and Environmental Sciences, Universität Potsdam, Germany.

2) Géosciences Rennes, UMR CNRS 6118, Université de Rennes, France.

3) Department of Geosciences and Engineering, Delft University of Technology, The

Netherlands.

4) Department of Earth and Space Sciences, University of Washington, USA.

5) Section 5.2: Climate Dynamics and Landscape Evolution, GFZ German Research Centre for

Geosciences, Germany.

6) Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, Beijing,

China.

7) School of Earth Sciences, China University of Geosciences, Wuhan, China.

Monsoons are the major source of moisture for central Asia but their dynamics remain poorly

understood. To provide insight in their driving forces we focus on early monsoonal records

during the transition from a greenhouse to an icehouse world, as a part of the ERC “MAGIC”

project.

The continental mudrocks of the Xining Basin in central China provide a unique opportunity to

study early monsoons because of their relatively continuous deposits from 40 to 15 Ma yielding

reliable records of Earth’s magnetic reversals and observed astronomically-forced alternations

of monsoonal moisture. This study specifically aims to extend the stratigraphy further back in

time to examine cyclicity in the Early to Middle Eocene.

Magnetostratigraphic analysis of three parallel sections near Xining shows three chrons that

are correlated to C20, C21 and C22. The lithostratigraphy shows dry mudrocks alternating with

wetter fluvio-lacustrine intervals in regular 10-12 meter cycles. These cycles are paced by the

405 kyr eccentricity cycles according to the age model, with lacustrine facies occurring in

eccentricity maxima. This indicates astronomically-forced monsoons at this time. Towards the

Late Eocene the lacustrine intervals become increasingly gypsiferous and the cyclicity

disappears. This has been linked to the 4th Paratethys sea incursion supplying moisture via

the westerlies.

22

Extending Theis’ solution to incorporate heterogeneity into pumping

test analysis

Sebastian Müller (1,2), Alraune Zech (1), Carsten Leven (3), Falk Heße (1), Peter Dietrich (1,3),

Sabine Attinger (1,2)

(1) Helmholtz Centre for Environmental Research - UFZ

(2) Institute of Earth and Environmental Sciences, University of Potsdam

(3) Center for Applied Geoscience, University of Tübingen

A framework for interpreting transient pumping tests in heterogeneous transmissivity fields is

developed to infer the overall geostatistical parameters of the medium without reconstructing

the specific heterogeneous structure point wise. This method is applied to the field sites

“Horkheimer Insel” and “Lauswiesen” (South- West Germany) to estimate the respective

parameters of heterogeneity from pumping test data of each site. The methodology is based

on the upscaling approach Radial Coarse Graining which is applied to deduce an effective

radial description of multi-Gaussian transmissivity. It was used to derive an Effective Well Flow

Solution for transient flow conditions including not only the storativity, but also the geometric

mean, the variance, and the correlation length of log-transmissivity. This solution is shown to

be appropriate to characterize the pumping test drawdown behavior in heterogeneous

transmissivity fields making use of ensembles of simulated pumping tests with multiple

combinations of statistical parameters. The whole procedure is described in detail in Zech et

al. 2016 (doi: 10.1002/2015WR018509).

23

Revision of earthquake hypocentre locations in global bulletin data

sets using source-specific station terms

Nima Nooshiri

Global earthquake locations are often associated with very large systematic travel-time

residuals even for clear arrivals, especially for regional and near-regional stations in

subduction zones because of their strongly heterogeneous velocity structure. Travel-time

corrections can drastically reduce travel-time residuals at regional stations and, in

consequence, improve the relative location accuracy. We have extended the shrinking-box

source-specific station terms technique to regional and teleseismic distances and adopted the

algorithm for probabilistic, nonlinear, global-search location. We evaluated the potential of the

method to compute precise relative hypocentre locations on a global scale. The method has

been applied to two specific test regions using existing P- and pP-phase picks. The first data

set consists of 3103 events along the Chilean margin and the second one comprises 1680

earthquakes in the Tonga-Fiji subduction zone. Pick data were obtained from the GEOFON

earthquake bulletin, produced using data from all available, global station networks. A set of

timing corrections varying as a function of source position was calculated for each seismic

station. In this way, we could correct the systematic errors introduced into the locations by the

inaccuracies in the assumed velocity structure without explicitly solving for a velocity model.

Residual statistics show that the median absolute deviation of the travel-time residuals is

reduced by 40–60 per cent at regional distances, where the velocity anomalies are strong.

Moreover, the spread of the travel-time residuals decreased by ∼20 per cent at teleseismic

distances (>28◦). Furthermore, strong variations in initial residuals as a function of recording

distance are smoothed out in the final residuals. The relocated catalogs exhibit less scattered

locations in depth and sharper images of the seismicity associated with the subducting slabs.

Comparison with a high-resolution local catalog reveals that our relocation process

significantly improves the hypocentre locations compared to standard locations.

24

Identifying Typhoon Tracks based on Event Synchronization derived

Spatially Embedded Climate Networks

Ugur Ozturk1,2, Norbert Marwan1, Jürgen Kurths1,3

1Potsdam Institute for Climate Impact Research, Potsdam, Germany

2Institute of Earth and Environmental Science, University of Potsdam, Potsdam, Germany

3Department of Physics, Humboldt University, Berlin, Germany

Complex networks are commonly used for investigating spatiotemporal dynamics of complex

systems, e.g. extreme rainfall. Especially directed networks are very effective tools in

identifying climatic patterns on spatially embedded networks. They can capture the network

flux, so as the principal dynamics of spreading significant phenomena. Network measures,

such as network divergence, bare the source-receptor relation of the directed networks.

However, it is still a challenge how to catch fast evolving atmospheric events, i.e. typhoons.

In this study, we propose a new technique, namely Radial Ranks, to detect the general pattern

of typhoons forward direction based on the strength parameter of the event synchronization

over Japan. We suggest to subset a circular zone of high correlation around the selected grid

based on the strength parameter. Radial sums of the strength parameter along vectors within

this zone, radial ranks are measured for potential directions, which allows us to trace the

network flux over long distances. We employed also the delay parameter of event

synchronization to identify and separate the frontal storms' and typhoons' individual behaviors.

25

High-resolution reconstruction of past climate and environment from

lacustrine deposits in NW Argentina

Joan Pascual-Montañés

The lake-complex Lagunas de Yala (24°06’S, 65° 29’W, NW Argentina) is located along the

slope of the Eastern Cordillera (EC) in the Central Andes. The high topography blocks moisture

from equatorial latitudes and defines an abrupt precipitation gradient from the humid EC foothill

and Chaco foreland basin to the arid Puna Plateau. For this work, an 82cm long surface core

from Comedero Lake (24°06’50”S, 65°29’03”W, 2026m above sea level) was analyzed.

According to geochemical data and microfacies analysis, five different facies have been

identified along the core, and the lithology for every facies has been established. Among them,

extreme events layers have been identified along the complete record. Wood and leaf remains

have dated the lowermost sediments to 600yr cal. BP. Micro-XRF data, organic matter analysis

and microfacies observation show the potential of the Yala Lakes sedimentary sequence as a

high-resolution archive of environmental and climate change in the tropical Andes and will

provide crucial information of the evolution of the South America Monsoon System (SAMS)

during the mid-late Holocene. Identifying and understanding extreme events and climate

variability recorded in Comedero Lake sediments provide essential knowledge for predicting

future climate change and managing resources in this region.

26

Rock Glacier Response to Climate Change

Julia Pommerencke (1), Oliver Korup (1), Stella Moreiras (2)

(1) University of Potsdam, Institute of Earth and Environmental Science, Potsdam, Germany

(2) Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, Mendoza, Argentina

Rock glaciers are bodies of frozen debris and ice that move under the influence of gravity in

permafrost areas. They play an important role as potential prime mover of the Central Andean

sediment cascade. Using temperature and precipitation data from the global climate model

(CCSM 4) from the WorldClim dataset, rock glacier response under different climate scenarios

were analysed for upper Atuel River catchment, south of Mendoza Province (Argentina). Rock

glaciers are traditionally viewed as diagnostic of sporadic alpine permafrost. Their tongues are

often near the annual mean 0°C isotherm located.

Rock glaciers in Atuel River are sensitive to changes in temperature, and may change in

activity and abundance. Where active rock glaciers become inactive their coarse material,

which was bounded by ice, will be released into the sediment cascade.

27

Digital topography for geomorphology and beyond: frontiers in

meters to sub-meter resolution remote sensing

Ben Purinton

Since the flight of the Shuttle Radar Topography Mission (SRTM) in February 2000 the

geoscience community has benefited from rapid improvements in the coverage and quality of

digital elevation models (DEMs). Most recently the 12 m resolution TanDEM-X DEM was

released by DLR for research purposes, with many submitting successful proposals to attain

this cutting edge dataset. Additionally, there now exists a plethora of open-access, commercial,

and research agreement DEMs, both as edited products and raw data for manual processing,

at resolutions of 1-10 m. Many of these datasets are derived from satellite sensors, which

provide wide-coverage in remote regions of geologic interest. Importantly, many geologists

utilizing DEMs to quantify changes in topography do so without rigorous accuracy

assessments that include not only vertical and horizontal elevation errors, but also the effect

of various sensor types (e.g., radar versus optical) and platforms (e.g., SRTM versus TanDEM-

X) on key derivatives of elevation, such as slope and curvature. In this PhD work we seek to

test the quality of satellite derived (and drone/lidar) DEMs across a range of scales, from

individual catchments to entire mountain ranges, in order to provide a fuller assessment of

DEM applicability for the calculation of geomorphic metrics. This work has already begun with

a comparison of DEMs from the SRTM, ASTER, TanDEM, and ALOS missions in northwestern

Argentina on the Puna Plateau. Here we assessed vertical accuracy by comparing standard

deviations of DEM elevation versus 307,509 differential GPS measurements, followed by

channel profile analysis of m/n values, a comparison of slope and curvature distributions, and

a 2D Fourier analysis of high-frequency noise in the DEMs. Ongoing work involves the

comparison of the SRTM and TanDEM-X DEMs for elevation differencing, accounting for

systematic biases between the datasets. This work is applicable not only to geomorphologists,

but also to glaciologists interested in using these DEMs for glacier mass-balances. Future PhD

work will include the use of lidar and drones to create dense 3D point clouds. In combination

with satellite data, these point clouds will be used to bridge the gap between individual plots

and catchment-scale geomorphology and to answer questions related to fine-scale variability

in hillslope and channel morphology related to climatic, tectonic, lithologic, and biologic

forcings.

28

Terrain Controls on the Occurrence of Coastal Retrogressive Thaw

Slumps along the Yukon Coast, Canada

Justine Ramage

Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic; their

number has increased significantly over the past decades. While processes initiating discrete

RTSs are well defined, the major terrain controls on the development of coastal RTSs at a

regional scale remain unrevealed. Our research brings new insights into the dynamics

of coastal RTSs. We reveal the main geomorphic factors that determine the development of

RTSs along a 238 km coastal segment of the Yukon Coastal Plain, Canada. We 1) show the

current extent of RTSs, 2) ascertain the factors controlling their activity and initiation, and 3)

explain the differences in the density and areal coverage of RTSs. We mapped and classified

287 RTSs using high-resolution satellite images acquired in 2011. We highlighted the main

terrain controls over their development using univariate regression trees. Both activity and

initiation of RTSs were influenced by coastal geomorphology: active RTSs and RTSs initiated

after 1972 occurred primarily on terrains with slope angles greater than 3.9° and 5.9°,

respectively. The density and coverage of RTSs were constrained by the volume and thickness

of massive ice bodies. Differences in coastal erosion rates along the coast did not affect the

model. We infer that coastal erosion rates averaged over a 39-year period are unable to reflect

the complex relationship between RTSs and coastline dynamics. We emphasize the need for

large-scale studies of RTSs – to evaluate their impact on the ecosystem and to measure their

contribution to the global carbon budget.

29

Determining hydroclimatic extreme events over the south-central

Andes

Maryam Ramezani Ziarani (1,2), Bodo Bookhagen (1), Torsten Schmidt (2), Jens Wickert (2,3),

Alejandro de laTorre (4), and Jan Volkholz (5)

(1) University of Potsdam, Potsdam, Germany

(2) GFZ German Research Centre for Geosciences, Potsdam, Germany

(3) Technische Universität Berlin, Berlin, Germany

(4) Austral University, Buenos Aires, Argentina

(5) Potsdam Institute for Climate Impact Research (PIK), Potsdam,Germany

The south-central Andes in NW Argentina are characterized by a strong rainfall asymmetry. In

the east-west direction exists one of the steepest rainfall gradients on Earth, resulting from the

large topographic differences in this region. In addition, in the north-south direction the rainfall

intensity varies as the climatic regime shifts from the tropical central Andes to the subtropical

south-central Andes. In this study, we investigate hydroclimatic extreme events over the south-

central Andes using ERA-Interim reanalysis data of the ECMWF (European Centre for

Medium-Range Weather Forecasts), the high resolution regional climate model (COSMO-

CLM) data and TRMM (Tropical Rainfall Measuring Mission) data. We divide the area in three

different study regions based on elevation: The high-elevation Altiplano-Puna plateau, an

intermediate area characterized by intramontane basins, and the foreland area. We analyze

the correlations between climatic variables, such as specific humidity, zonal wind

component, meridional wind component and extreme rainfall events in all three domains. The

results show that there is a high positive temporal correlation between extreme rainfall events

(90th and 99th percentile rainfall) and extreme specific humidity events (90th and 99th

percentile specific humidity). In addition, the temporal variations analysis represents a trend of

increasing specific humidity with time during time period (1994-2013) over the Altiplano-Puna

plateau which is in agreement with rainfall trend. Regarding zonal winds, our results indicate

that 99th percentile rainfall events over the Altiplano-Puna plateau coincide temporally with

strong easterly winds from intermountain and foreland regions in the east. In addition, the

results regarding the meridional wind component represent strong northerly winds in the

foreland region coincide temporally with 99th percentile rainfall over the Altiplano-Puna

plateau.

30

Organofacies of the Yacoraite Formation, Salta Basin; Argentina

Ricardo Ruiz

The Yacoraite Formation (Maastrichtian-Danian), of the middle Balbuena Subgroup, has been

identified as the main oil-source rock in NW Argentina in the Salta Rift Basin. It was deposited

immediately following Lower Cretaceous rifting, and represents the last Cretaceous marine

ingression (Marquillas et al, 2007) although some evidences have also been found for a

lacustrine setting in some areas (Terra et al., 2012; Schmidt et al, 2017). Depending on its

depositional environment, this formation exhibits wide ranges of organic content from poor up

to rich (up to 6% TOC) and I - II kerogen types (Stinco and Barredo, 2014). The biggest oil

field is Caimancito where light oil (42º API) is produced. In this work rock-eval pyrolysis results

are shown to preliminary assess oil potential and it´s depositional environment of Metán-

Alemanía (M-A) and Tres Cruces (TC) sub-basins.

31

Testing long-term controls of sedimentary basin architecture. Tres

Cruces Subbasin, Jujuy, Argentina

Wera Schmidt (1), Claudia Galli (2,3), Maria Mutti (1)

1 University of Potsdam, Potsdam, Germany

2 Universidad Nacional de Jujuy, Argentina

3 Universidad Nacional de Salta, Argentina

Concepts of reciprocal sedimentation link the vertical alternation of clastics and carbonates

and their lateral continuity in shallow-marine environments with relative sea-level changes.

Mixed, clastic-carbonate strata of the Maastrichtian to Danian Yacoraite Formation (Salta

Group) provide an ideal setting to test how the concept of reciprocal sedimentation can be

applied in a syn- and post-rift basin with significant lateral and vertical facies heterogeneity.

Focus of this study is the Tres Cruces subbasin. The Tres Cruces subbasin is the northern

extent of the triradiate Salta basin (NW Argentina). A total of 14 stratigraphic sections have

been measured along two regional transects. The physical correlation of the facies packages,

integrated with petrographic, geochemical and biosedimentary analyses, provide a tool to

visualize how facies and sedimentary architecture change throughout the Tres Cruces

subbasin.

The spatial superposition of lithofacies at basin-scale indicate a longer-term control by relative

sea-level changes. However, observations at the outcrop scale suggest that a locally

heterogeneous facies distribution is governed by environmental changes. Hence, concepts of

reciprocal sedimentation must be applied with care in spatially complex rift basins, because

environmental conditions may locally overrun regional stratigraphic patterns.

32

Interaction between small scale landscape structure and erosive

wind events in La Pampa, Argentina

Nicole Siegmund

The landscape of the semiarid Pampa in central Argentina is characterized by glacial aeolian

depositions (loess) leaving large planes with sporadic dune structures. Since the land use

change from pasture to arable land, the upper soil is exposed to frequent and strong wind

events. How far the old structures influence the recent erosion processes by wind was

investigated on a sandy measuring field in the province La Pampa. This study is focused on

the inter-relationships between small topographic characteristics and wind erosion of different

directions at the plot scale. To investigate the spatial variability of mass-transport by saltation

18 Modified Wilson and Cook (MWAC) were installed on a 1.44 ha large field in a 20 x 40 m

grid. Seven storms from three different wind directions were analyzed. Physical and chemical

soil properties from the upper soil as well as a digital elevation model were recorded in a 20 x

20 m grid. The spatial high resolute analysis of the soil properties and the aeolian transport

processes allows conclusions about the individual pattern of erosion and deposition for each

storm.

It can be shown that erosion occurs on exposed and luv and deposition on sink and lee terrain

positions. Furthermore, a multiple regression model is build, explaining up to 90% of the

variance of erosion by just using four predictors: topsoil thickness, relative elevation, carbon

content and slope direction. Our findings suggest a structure-process-structure complex where

the ancient dune structure determines the recent wind erosion and the ongoing erosion

process can lead to an increase of the soil heterogenity.

33

Mountain rivers may need centuries to adjust to earthquake-

triggered sediment pulses, Pokhara, Nepal

Amelie Stolle (1), Oliver Korup (1), Wolfgang Schwanghart (1), Anne Bernhardt (2), Basanta Raj

Adhikari (3), Christoff Andermann (4), Hella Wittmann (4), Silke Merchel (5)

1Institute of Earth and Environmental Sciences, University of Potsdam, Germany

2Institute of Geological Sciences, Freie Universität Berlin, Malteserstr. 74-100, 12249 Berlin,

Germany

3Institute of Engineering, Tribhuvan University, Kathmandu, Nepal

4Helmholtz-Zentrum Potsdam, German Centre for Geosciences GFZ, Germany

5Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource

Technology, Dresden, Germany

Mountain rivers respond to strong earthquakes by rapidly aggrading to accommodate excess

sediment delivered by co- and post-seismic landslides. Detailed sediment budgets suggest

that it takes rivers several years to decades to recover from such seismic disturbances,

depending on how recovery is defined. We test this notion and study how rivers adjusted to

catastrophic sedimentation triggered by at least three medieval earthquakes in the central

Nepal Himalaya. Rapid aggradation formed a large fan in the Pokhara Valley covering 148 km2

of mountainous terrain. A robust radiocarbon chronology provides an ideal framework for

gauging average rates of fluvial incision and adjustment. We use high-resolution digital

elevation data, geodetic field surveys, and historic aerial photos documenting channel

changes. We estimated removed volumes, use long-term denudation rates, clasts counts and

several re-exhumed tree trunks in growth position as proxies to define whether the river system

is adjusted since medieval times. We find sediment yields of up to 4200 t km–2 yr–1 that greatly

exceed the density-adjusted background rates of 10Be catchment-wide denudation. The

lithological composition of active river banks differs from local bedrock and confirms that rivers

are still excavating medieval deposits. Pronounced knickpoints at tributary junctions add to the

picture of a drawn-out fluvial response, while the re-exhumed tree trunks indicate that terraces

at tributary margins have been incised to near their base. Our results challenge the notion that

mountain rivers recover within years or decades. The Pokhara Valley document that even

highly erosive Himalayan rivers may need centuries to millennia to adjust. Our results may

motivate some rethinking of post-seismic hazard appraisals and infrastructural planning during

the rehabilitation phase in earthquake-struck regions.

34

Defining moisture sources and organic matter transport processes

in the NW Himalaya

Iris van der Veen

δ2H and d18O values of surface waters provide information on snowmelt time and magnitude,

moisture sources and evapotranspiration processes. Increased rates of glacial/snow melt not

only increase river discharge and flood potential, but also the temporal heterogeneity in river

discharge. This study focuses on the western Himalaya where moisture originates

predominantly from the Indian summer monsoon, while higher elevation catchments receive

precipitation from the Westerly Disturbances. δ2H in both the Sutlej and Alaknanda transects

show a significant negative correlation with mean catchment elevation, which is mainly caused

by Rayleigh fractionation in progressive rainout during orographic uplift, and cooling of moist

air masses. Second, a 6-25% increase in d-excess during peak snowmelt season, and a

decrease in snow cover from >90% in winter to <30% in summer indicates substantial input of

snow/ice melt into surface waters of high-elevation catchments. The time series shows a

relationship between spring snowmelt and surface water d-excess values. These results

suggest that snowmelt in high elevation catchments can alter surface water isotopic content,

and can be used as a tracer for snow/ice meltwater. Additionally, we use compound specific

stable isotopes (δ2H) and GDGTs along four altitudinal gradients, to investigate the impact of

environmental factors on δ2H and brGDGTs. These transects have varying precipitation

regimes, relative influences of moisture sources and vegetation. Combining this multi proxy

study with satellite derived root-zone soil moisture content and TRMM-derived precipitation,

we strive to identify the controlling secondary factors that complicate the relationship between

source water δ2H and soil alkane δ2H.

35

Numerical homogenization approach for coupling of chemical and

mechanical processes in the geological subsurface

Wetzel, Maria; Kempka, Thomas; Kühn, Michael

Reactive transport and related processes as dissolution and precipitation of minerals may

substantially change rock composition, and consequently its geomechanical properties.

However, this chemo-mechanical interaction is rarely considered in assessments of

subsurface processes. An approach to determine the macroscopic stress-strain-relationship of

a composite material, based on the mechanical characteristics of its constituents is provided

by analytical homogenization models. This method is widely used within the field of materials

sciences and highly promising for geoscientific applications. However, none of the analytical

models can accurately determinate elastic parameters of the composite for the entire range of

the inclusions mechanical properties, their specific volume fractions and aspect ratios.

Numerical 3D models allow for a more precise quantification and help to overcome the

limitations of analytical solutions, especially regarding the spatial distribution of inclusions and

their interaction. For a representative rock volume element, effective elastic properties are

determined in our approach by taking into account the characteristic geomechanical

parameters of all relevant mineral inclusions. We successfully validated our model against

available analytical solutions and published experimental data. Sensitivity analyses indicate

that the calculated elastic rock properties vary up to 28 % due to the spatial distribution of the

inclusions within the rock matrix. Additionally, the developed numerical homogenization

method enables an improved quantification of rock parameters: particularly for high inclusion-

to-matrix-volume fractions and high mechanical property contrasts, the analytical solution

deviates up to 58 % from the numerical results. In conclusion, the introduced homogenization

approach provides an essential basis for coupling chemical and mechanical processes in

numerical simulations related to the geological subsurface.