Understanding modern and past sedimentary processes in selected lakes from the High Arctic and the Mediterranean realm

Lacustrine sediment sequences can provide valuable archives of past environmental and climatological variability in terrestrial realms. In order to unravel the history of a lake and of a lake’s catchment, a profound understanding of the sedimentary processes is required. This encompasses the supply of allochthonous organic matter, nutrients and clastic material to the lake, the subsequent redistribution within the lake as well as autochthonous organic matter and mineral deposition. These lake internal and external processes are closely linked to the environmental and climatological settings in the specific area and can be reconstructed by using geophysical and sedimentary data. Within the scope of this thesis, modern and past sedimentary processes of selected lakes from the High Artic (Lake El’gygytgyn, NE Siberia) and the Mediterranean Realm (lakes Dojran and Ohrid, Balkan Peninsula) were analyzed by using various datasets and analytical methods. The obtained information about variations in the lakes’ internal and external processes were subsequently used for paleoenvironmental and -climatological reconstructions in the respective area. At Lake El’gygytgyn, modern sedimentary processes were investigated by using geochemical, grain-size and mineralogical data from source rocks, inlet streams and surface sediments. The obtained informa- tion about modern sedimentary processes improved the understanding of hydro-acoustic and downhole logging data, as well as of variations in the granumoleric, geochemical and physical properties of core 5011-1 which covers the entire lacustrine succession of the 3.58 Ma year old Lake El’gygytgyn. Surface samples and downcore data were analyzed by using statistic methods such as Principal Component Analysis (PCA), Redundancy Analysis (RDA), Time Series Analysis and Cluster Analysis. At Lake Dojran, hydro-acoustic data and sediment properties (water content, OM, calcite (CaCO3) content, sulfur content, grain-size, XRF scanning, δ18Ocarb, δ13Ccarb, δ13Corg) of a 7m long sequence were used to untangle past sedimentary processes and environmental variations during the Late Glacial and Holocene period. Sediment (lithostratigraphic description, XRF scanning, water content, OM content, calcite content) and hydro-acoustic data were also used to characterize a 2 m thick Mass Wasting Deposit (MWD) in Lake Ohrid. As various analytical and statistical methods were used to investigate modern and past sedimentary processes in the selected lakes, an evaluation of these methods is conducted within the scope of this thesis. It could be shown that information about modern sedimentary processes derived from lacustrine surface samples and from catchment samples can help to better understand past sedimentary processes as it provides insights into spatial variations in the deposition processes. Spatial variations of past sedimentary processes and the overall sediment architecture of lacustrine deposits can be analyzed using hydro-acoustic data. However, the vertical resolution of hydro-acoustic data is limited and the data commonly lacks a robust chronology. Chronostratigraphic well constrained and high resoluted informa- tion about past sedimentary processes can be derived from sedimentary properties of a sediment core. These properties include lithologic information such as sediment structure, grain-size, and inorganic and organic geochemistry. These proxy data can be obtained by visual core descriptions and laboratory analyses. However, certain proxies can commonly only be used to reconstruct a specific part of sedimentary processes, for example grain-size data yields information about the transport energy during the deposition. Thus, a combination of multiple proxies is required to reconstruct the overall picture of sedi- mentary processes. If huge data sets are used for the reconstruction, statistic methods such as PCA, RDA, Time Series Analyses, and Cluster Analyses can help to simplify the data. However, it could be shown that mathematic methods can provide results that might lead to misinterpretations in a geological context. In order to interpret sediment sequences for paleoenvironmental and -climatological variations in a temporal context, an age model is commonly established by using for example radiocarbon ages and chronological tie points derived from tephrostratigraphic or paleomagnetic data. Cross correlation to well dated sediment sequences or wiggle matching to orbital parameters can improve a chronostrati- graphic modell. However, this involves the danger of misinterpretations or loss of information about the timing of geologic or climatic events

Mikroanalytik der Titanlegierungen 2020 -DGM

Vortrag Überblick über die Analyse der Mikroanalytik von Titan und Titanlegierungen. Überblick über verschiedene Analysemethoden und der dafür notwendigen metallographischen Probenpräpartion

Mikroanalytik der Titanlegierungen, DGM-Seminar2021

Ein Vortrag zur Titan- und Titanlegierungsanalyse und der dafür notwendigen Metallographie anhand von Beispiele

Mikroanalytik der Titanlegierungen

Abriss über die Mikrostrukturelle Analytik von Titan und die notwendige metallographische Probenvorbereitun

Complexity of diatom response to Lateglacial and Holocene climate and environmental change in ancient, deep and oligotrophic Lake Ohrid (Macedonia and Albania)

© Author(s) 2016. Lake Ohrid (Macedonia and Albania) is a rare example of a deep, ancient Mediterranean lake and is a key site for palaeoclimate research in the northeastern Mediterranean region. This study conducts the analysis of diatoms as a proxy for Lateglacial and Holocene climate and environmental change in Lake Ohrid at a higher resolution than in previous studies. While Lake Ohrid has the potential to be sensitive to water temperature change, the data demonstrate a highly complex diatom response, probably comprising a direct response to temperature-induced lake productivity in some phases and an indirect response to temperaturerelated lake stratification or mixing and epilimnetic nutrient availability in others. The data also demonstrate the possible influence of physical limnological (e.g. the influence of wind stress on stratification or mixing) and chemical processes (e.g. the influence of catchment dynamics on nutrient input) in mediating the complex response of diatoms. During the Lateglacial (ca. 12 300-11 800 cal yr BP), the low-diversity dominance of hypolimnetic Cyclotella fottii indicates low lake productivity, linked to low water temperature. Although the subsequent slight increase in small, epilimnetic C. minuscula during the earliest Holocene (ca. 11 800-10 600 cal yr BP) suggests climate warming and enhanced stratification, diatom concentration remains as low as during the Lateglacial, suggesting that water temperature increase was muted across this major transition. The early Holocene (ca. 10 600-8200 cal yr BP) is characterised by a sustained increase in epilimnetic taxa, with mesotrophic C. ocellata indicating high water-temperature-induced productivity between ca. 10 600-10 200 cal yr BP and between ca. 9500-8200 cal yr BP and with C. minuscula in response to low nutrient availability in the epilimnion between ca. 10 200-9500 cal yr BP. During the middle Holocene (ca. 8200-2600 cal yr BP), when sedimentological and geochemical proxies provide evidence for maximum Holocene water temperature, anomalously low C. ocellata abundance is probably a response to epilimnetic nutrient limitation, almost mimicking the Lateglacial flora apart from the occurrence of mesotrophic Stephanodiscus transylvanicus in the hypolimnion. During the late Holocene (ca. 2600 cal yr BP-present), high abundance and fluctuating composition of epilimnetic taxa are probably a response more to enhanced anthropogenic nutrient input, particularly nitrogen enrichment, than to climate. Overall, the data indicate that previous assumptions concerning the linearity of diatom response in this deep, ancient lake are invalid, and multi-proxy analysis is essential to improve understanding of palaeolimnological dynamics in future research on the long, Quaternary sequence

The Lake Ohrid Drilling Project: some initial interpretations of stable isotope data through the last 15 Marine Isotope Stages

The SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project is an international research initiative to study the influence of major geological/environmental events on the biologic evolution of taxa. The target site for this study is Lake Ohrid, which is considered to be the oldest lake with continuous existence in Europe and which has more than 200 endemic species

A high resolution Late Glacial to Holocene record of climatic and environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

Lake Ohrid (Macedonia/Albania) is one of the world’s oldest lakes and is renowned for its high degree of biological diversity. It is the target site for the ICDP SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project, an international research initiative to study the links between geology, environment and the evolution of endemic taxa. In 2011 a 10-meter core was recovered from the western shore of Lake Ohrid adjacent to the Lini Peninsula

Entrepreneurial development in South Africa through innovation: A model for poverty alleviation

Orientation: The development agency could be equipped with a model that will assist them in supporting mobile application development entrepreneurs towards enhanced competitiveness that could assist in alleviating poverty and reducing economic inequality. Research purpose: The purpose of this study is to explore the evolution of a model to support mobile application development entrepreneurs towards enhanced competitiveness. Motivation for the study: This study was motivated by the views on black economic empowerment where little has been done to impact the lives of black people on a larger scale. Broader participation of black people in the formal economy is required to achieve sustainable development and prosperity. Studies suggest that innovation through technology transfer is regarded as a contributor to economic growth. Research design, approach and method: This study adopted the Critical Realist Methodology Model via an inductive research approach. Focused interviews with academics, small and medium-sized enterprises in the innovation and technology industry and development agencies were conducted. Main findings: There is business potential in mobile applications, but entrepreneurs have difficulty in commercialising these. They could be assisted with a model that would transform their applications into real business opportunities. Practical/managerial implications: The antidote to disruptive innovation is a management response. What is required from management is that it needs to bring about a paradigm shift in the way that the whole notion of a business is remodelled. Contribution/value-add: This study reveals a multi-factorial strategy model in the form of the Disruptive Innovation State Response Model that could support mobile application development entrepreneurs towards enhanced competitiveness

Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial–interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before  ∼  320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial–interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial–interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes

Sedimentological imprints of environmental variability at the Balkan Peninsula on the sediment sequence of Lake Ohrid (Macedonia, Albania) between the Mid Pleistocene Transition and present days: the ICDP SCOPSCO project

The UNESCO World Heritage site of Lake Ohrid in the Balkans is thought to be the oldest, continuously existing lake in Europe. In order to unravel the geological and evolutionary history of the lake, a deep drilling campaign was conducted in spring 2013 under the umbrella of the ICDP SCOPSCO project. At the coring site “DEEP” in central parts of the lake, more than 1,500 m of sediments were recovered down to a penetration depth of 569 m blf. This sediment sequence is assumed to be more than 1.2 Ma old and likely covers the entire lacustrine deposits of the Lake Ohrid Basin