Fakultät für Geowissenschaften - Digitale Hochschulschriften der LMU

Biological carbonate hard tissues, such as the shell of the bivalve Mytilus edulis, are composites of biopolymers and minerals. M. edulis has two distinct layers, the outer layer consists of fibrous calcite and the inner layer is composed of nacreous aragonite. Close to the interface between nacreous aragonite and fibrous calcite, a 1-2 micrometer wide zone exists that consists of granular aragonite. Aragonite granules and tablets as well as calcite fibrous are embedded into matrix biopolymers.

In order to understand the composite nature of these hard tissues, biomimetic experiments using hydrogels were carried out. Hydrogels are able to model biogenic matrix environments due to their ability to confine space and to determine diffusion rates, local concentrations and supersaturation of the solutes. Hydrogels have local crystallization microenvironment that is distinguished from that in solution by confinement of solutes in the hydrogel pores. However, hydorgels only mimic biological extracellular matrices to some extent as the hydrogel fiber organization lacks any order, unlike it is in the case of the cholesteric liquid phase, e. g. chitin. The hydrogel strength is adjustable by changing its solid content. It further increases local hydrogel fiber co-aligments that to some extent will mimic organic matrices in biological hard tissues. Different kinds of hydrogels were used to study calcite crystallization (silica, agarose, gelatin). As each hydrogel has different characteristics, hydrogels can act differently in promoting or inhibiting crystallization. Hydrogels have an ability to mechanically impede the growth of a crystal depending on the strength of the hydrogel. Gelatin hydrogel is a poly-peptide material derived from natural collagen through hydrolytic degradation. The hyrolitic degradation breaks the triple-helix structure of collagen into single-strand molecules. Gelatin contains both acidic and basic amino acids with isoelectric point values near ∼5 and with predominance of acidic moieties. Agarose hydrogel is a linear polysaccharide extracted from marine red algae. It consists of beta-1,3 linked D-galactose and alpha-1,4 linked 3,6-anhydro-alpha-L-galactose residues. Gelatin and agarose hydrogels are composed of a fibrous structure that have varying mesh void dimensions depending on the hydrogel solid content. Hydrogel with 2.5 wt % gelatin solid content exerts less pressure against the growing calcite crystal aggregate than a hydrogel with 10 wt % gelatin solid content. Silica hydrogel does not exert strong pressure against the growing calcite crystal aggregate due to its nature as it is composed of minute (less than 20 nm) sized spherical particles that do not appear to form a network. The hydrogel strength together with the growth rate of the crystal defines the amount of incorporated hydrogel into the growing calcite crystal aggregate such that a strong hydrogel will incorporate more gel into the calcite crystal than a weak hydrogel.

Calcite grown in Mg-free silica hydrogels has a rhombohedral shape and is elongated on the c-axis. It grows as dumbbell-shaped aggregates in the presence of Mg. Silica hydrogel either Mg-free or Mg-bearing does not give a major influence on the co-orientation of the obtained crystal aggregate. Calcite grown in Mg-free agarose has two morphologies: rhombohedron-shaped calcite crystals and calcite radial aggregates. Calcite grown in Mg-bearing agarose has sheaf-like and peanut like morphologies. The presence of Mg in agarose influences the co-orientation of calcite crystals within calcite Mg-bearing agarose composites. The calcite/Mg-free agarose composite has several large crystal subunits while the calcite/Mg-bearing agarose composite shows a spherulitic microstructure. In the case of gelatin hydrogel, the precipitate consists of calcite aggregates that have a variety of features i.e. the formation of mosaic crystals and mesocrystal-like subunits in one aggregate, the formation o

Problem. More than ever, some of the biggest challenges to society involve governance of natural resources. From large-scale resource systems such as the rain forest and oceans to small-scale systems such as lakes or alpine pastures, cooperative efforts are required to ensure sustainable and yet productive use of natural resources. In Switzerland, the management of alpine pastures has for centuries been predominantly organized by local governance institutions, avoiding an overuse of the scarce resources. During the past decade, the use and maintenance of common property pastures (CPP) is declining, leading to land abandonment and forest regrowth. However, CPP provide significant services to the mountain regions, such as additional grazing grounds, assets for the tourism industry, protection from soil erosion, water run-off and landslides, and high biodiversity. These services are currently threatened by reduced use and maintenance of the CPP.

Research Aims. The research presented herein aims for a better understanding of social-ecological interactions driving the use of CPP to provide policy recommendations for the sustainable governance of CPP.

Methods. To generate a holistic understanding of the variables driving CPP use, this research used multiple methods to investigate CPP use in Grindelwald, Switzerland as a social-ecological system (SES). The research was structured in 4 modules. First, qualitative methods were applied to analyze institutional change in the governance of CPP. Second, regression models were built from survey data to better understand farmers’ land-use decision. Third, an analysis of the ecological system was conducted bases on land-cover statistics. Forth, a systems dynamics model of the local SES was built and combined with formative scenario analysis to investigate potential future developments of CPP use.

Results. The outcomes of the different modules suggest that: First, local governance systems originally designed to prevent overuse of CPP are able to adapt to problems of declining use and maintenance of CPP by altering a set of rules. Second, farmers’ use of CPP depend on personal attributes, including farm size, norms, and dependence on the resource. Furthermore, the analysis suggests that high local demand and prices for alpine cheese are a central factor in the sustainable use of CPP. Third, the land-cover analysis showed that afforestation occurs in Grindelwald at a relatively moderate pace and defines the area most prone to afforestation and bush encroachment. Fourth, the simulation model allows for the display of complex social-ecological interactions, showing that afforestation tendencies are likely to continue, although at different pace depending on the scenario setting.

Conclusion. This research provides a better understanding of CPP use through the analysis of the subsystem characterizing the SES. It showed how the general framework for analyzing social-ecological systems can be operationalized using a broad set of methods. It thereby contributed and advanced central themes within the study of the commons such as institutional analysis, users’ behavior in cooperative dilemmas, and modeling of SES. The integration of the findings from different modules into a simulation provided insights about the effects of different policies on the sustainability of the SES, and thereby demonstrated why particular policy blueprints will rather accelerate than counteract the problem of CPP abandonment.

The Central Asian Orogenic Belt (CAOB) is one of the world's largest accretionary orogens, which was active during most of the Paleozoic. In recent years it has again moved into focus of the geological community debating how the acrreted lithospheric elements were geographical arranged and interacting prior and/or during the final amalgamation of Kazakhstania. In principal two families of competing models exist. One possible geodynmaic setting is based on geological evidence that a more or less continuous giant arc connecting Baltica and Siberia in the early Paleozoic was subsequently dissected and buckled. Alternatively an archipelago setting, similar to the present day south west Pacific was proposed.

This thesis collates three studies on the paleogeography of the south western part of the CAOB from the early Paleozoic until the latest Paleozoic to earliest Mesozoic. It is shown how fragments of Precambrian to early Paleozoic age are likely to have originated from Gondwana at high southerly paleolatitudes (~500 Ma), which got then accreted during the Ordovician (~460 Ma), before this newly created terrane agglomerate (Kazakhstania) migrated northwards crossing the paleo-equator. During the Devonian and the latest Early Carboniferous (~330 Ma) Kazakhstania occupied a stable position at about ~30°N. At least since this time the area underwent

several stages of counterclockwise rotational movements accompanying the final amalgamation of Eurasia (~320 - ~270 Myr). This overall pattern of

roughly up to 90° counterclockwise bending was replaced by internal relative rotational movements in the latest Paleozoic, which continued probably until the early Mesozoic or even the Cenozoic.

In Chapter 2 a comparison of declination data acquired by a remagnetization process during folding in the Carboniferous and coeval data from

Baltica and Siberia lead to a documentation and quantification of rotational movements within the Karatau Mountain Range. Based on this results it

is very likely that the rotational reorganization started in the Carboniferous and was active until at least the early Mesozoic. Additionally, the data shows that maximal declination deviation increases going from the Karatau towards the Tianshan Mountains (i.e. from North to South). This observation supports models claiming that Ural mountains, Karatau and Tianshan once formed a straight orogen subsequently bent into a orocline. The hinge of this orocline is probably hidden under the sediments of the Caspian basin.

In chapter 3 we show that inclination shallowing has affected the red terrigenous sediments of Carboniferous age from the North Tianshan. The

corrected inclination values put this part of the Tianshan in a paleolatitude of around 30°N during Carboniferous times. These results contradict previously published paleopositions of the area and suggest a stable latitudinal position between the Devonian and the Carboniferous.

Chapter 4 presents paleomagnetic data from early Paleozoic rocks from within the North Tianshan. They imply a second collisional accretion event

of individual terranes in the Ordovician.

To further constrain the dimensions of these early Paleozoic terranes, chapter 5 presents a compilation of all available paleomagnetic data from the extended study region of southern Kazakhstan and Kyrgyzstan. Apart from a broad coherence of paleolatitudes of all studies at least since the Ordovician and the exclusive occurrence of counterclockwise declination deviations, no areas with the same rotational history can be detected. Also a clear trend caused by oroclinal bending can not be observed. We conclude that first order counterclockwise oroclinal bending, shown in chapter 2, resulted in brittle deformation within the mountain belt and local block rotations.

In order to improve our understanding of intra-continental deformation a study combining the monitoring of recent deformation (Global Positioning System, GPS) with a paleomagnetic study of Ce

The scientific investigation of the solid Earth's complex processes, including their interactions with the oceans and the atmosphere, is an interdisciplinary field in which seismology has one key role. Major contributions of modern seismology are (1) the development of high-resolution tomographic images of the Earth's structure and (2) the investigation of earthquake

source processes. In both disciplines the challenge lies in solving a seismic inverse

problem, i.e. in obtaining information about physical parameters that are not directly observable.

Seismic inverse studies usually aim to find realistic models through the minimization of the

misfit between observed and theoretically computed (synthetic) ground motions. In general, this approach depends on the numerical simulation of seismic waves propagating in a specified Earth model (forward problem) and the acquisition of illuminating data. While the former is routinely solved using spectral-element methods, many seismic inverse problems still suffer from the lack of information typically leading to ill-posed inverse problems with multiple solutions and trade-offs between the model parameters. Non-linearity in forward modeling and the non-convexity of misfit functions aggravate

the inversion for structure and source.

This situation requires an efficient exploitation of the available data. However, a careful analysis of whether individual models can be considered a reasonable approximation of the true solution (deterministic approach) or if single models should be replaced with statistical distributions of model parameters (probabilistic or Bayesian approach) is inevitable.

Deterministic inversion attempts to find the model that provides the best explanation of the data, typically using iterative optimization techniques. To prevent the inversion process from being trapped in a meaningless local minimum an accurate initial low frequency model is indispensable. Regularization, e.g. in terms of smoothing or damping, is necessary to avoid artifacts from the mapping of high frequency information. However, regularization increases parameter trade-offs and is subjective to some degree, which means that resolution estimates tend to be biased.

Probabilistic (or Bayesian) inversions overcome the drawbacks of the deterministic approach by using a global model search that provides unbiased measures of resolution and trade-offs. Critical aspects are computational costs, the appropriate incorporation of prior knowledge and the difficulties in interpreting and processing

the results.

This work studies both the deterministic and the probabilistic approach. Recent observations of rotational ground motions, that complement translational ground motion measurements from conventional seismometers, motivated the research.

It is investigated if alternative seismic observables, including rotations and dynamic strain, have the potential to reduce non-uniqueness and parameter trade-offs in seismic inverse problems.

In the framework of deterministic full waveform inversion a novel approach to seismic tomography

is applied for the first time to (synthetic) collocated measurements of translations, rotations and strain. The concept is based on the definition of new observables combining translation and rotation, and translation and strain measurements, respectively. Studying the corresponding sensitivity kernels assesses the capability of the new observables to constrain various aspects of a three-dimensional Earth structure. These observables are generally sensitive only to small-scale near-receiver structures. It follows, for example, that knowledge of deeper Earth structure are not required in tomographic inversions for local structure based on the new observables.

Also in the context of deterministic full waveform inversion a new method for the design of seismic observables with focused sensitivity to a target model parameter class, e.g. density structure, is develo