Cooling and denudation history of Spitsbergen, and inferences for tectonics, climate and long-term landscape evolution

Ph.D. Project Nina Dörr

This project is a research cooperation between the University of Bremen, the Federal Institute for Geosciences and Natural Resources (BGR), and other partners. The project applies apatite fission track (FT) and (U-Th-Sm)/He thermochronology, clay mineral and vitrinite reflectance analysis for reconstructing the thermal history of basement rocks and sedimentary cover. The principle aim of this research is to investigate the Phanerozoic crustal dynamics of northern and central Spitsbergen, its implications on the opening of the Atlantic and consequences on regional long-term climate evolution. Four specific objectives are:
1) Passive margin evolution of Svalbard
2) Late Mesozoic and Cenozoic regional tectonic history
3) Thermal evolution of the Central Tertiary Basin
4) Coupling of Neogene climate change and tectonics, and long-term landscape evolution.


Sources and Sinks of Pliocene erosion: Investigating the latest-stage exhumation history of the Alps

Ph.D. Projects of Simon Elfert & Wolfgang Reiter

The Alps as well as many other Cenozoic orogens experienced an approximately threefold increase of sediment deposition rates during the last ~5 Ma. The reasons for this increase are controversially discussed in the literature since more than a decade. The goal of this project is to improve our understanding of timing, rates, and changes of denudation during the late-stage evolution of the Central and Western Alps. Tracking regional differences in the timing of denudation events may answer the question whether Pliocene enhanced erosion was dominantly climatically or tectonically controlled. We try to achieve our foals by a combination of detrital thermochronology on Alpine-derived debris deposited in circum-Alpine basins (Rhine, Rhone, and Bresse-Graben) and high-resolution thermochronology on key areas of the Alpine source regions (Lepontine Dome and Aar Massif).

This project is part of the EUROCORE Program Topo Europe, Collaborative Research Project Thermo Europe: Coupled climatic / tectonic forcing of European topography revealed through thermochronometry.

Cooperation partners are Maria Laura Balestrieri, University of Florence, Onno Oncken & Charlotte Cederbom, GFZ Potsdam, Peter van der Beek, University of Grenoble, Sean Willett, ETH Zurich, Paul Andriessen, University of Amsterdam, Piotr Krzywiec, University of Warsaw.


Low-temperature thermochronology: applications and inter-laboratory calibration

Quantification of geological processes is a demanding task of primary importance for different Earth science topics. A valuable tool is given by low-temperature thermochronology (mainly fission-track and U-Th/He analyses) which finds many applications in oil industry, in the exploration and sustainable management of water and mineral resources and in the analysis of the relationships between tectonics and climate change. In fact, because these methodologies are sensitive to the thermal regime in the shallow crust, they allow to give some constraints to the analysis of magmatic, sedimentary, tectonic and geomorphic processes. Main applications of thermochronology are: (i) quantification of exhumation processes and relationships between tectonics, uplift, erosion and climate;(2) thermal history of sedimentary basins; (3) provenance of sediments.

This project has two primary aims: (1) The transfer of knowledge to developing countries. Low-temperature methodologies are relatively low-cost techniques (this is especially true for fission-track analysis) which can find many applications in different fields. For this reason, many developing and emerging countries were trying to set up new laboratories in the last years but a considerable gap of knowledge is still existing. (2) The testing of the methodologies for applications. Although fission-track analysis is used since some years in hydrocarbon and mining industry as well as in tectonic studies, the potentialities of integration of different methodologies are partially unexplored. Moreover, the development of modelling techniques can improve the significance to the obtained results.

This project is funded by IGCP / UNESCO and in cooperation with Max Zattin (P.I., University of Bologna), John Garver (Union College, USA), Vitaliy Privalov (Donetsk University, Ukraine), Alexei Soloviev (Russian Academy of Science, Moscow), Maarten de Wit (University of Cape Town, South Africa), Dewen Zheng (China Earthquake Administration, Beijing).


Coupling of lithosphere dynamics, surface processes and ice sheet evolution – constraints from Marie Byrd Land, West Antarctica

Ph.D. Project Julia Lindow

West Antarctica combines one of the largest active rift systems with one of the largest ice sheets on earth. Complete melting of the West Antarctic ice sheet would result in a global sea level rise of ~5 m. Understanding ice sheet dynamics is of major importance for predicting future deglaciation processes in Antarctica. Generally, it is assumed that the geodynamic activity of Western Antarctica as the “cradle” of the West Antarctic ice sheet exerts a strong influence on ice sheet dynamics, but coupling and feedback mechanisms are poorly understood. Also, information on both, the geodynamic evolution of West Antarctica and on long-term changes of its ice sheet is scarce.
Our project aims to apply geophysical and thermochronological methods for unravelling the geodynamic evolution of Marie Byrd Land (West Antarctica) in terms of crustal structure, exhumation and erosion rates, fault activities, and (paleo-) geothermal gradient. Furthermore, we will use cosmogenic nuclide analysis for reconstructing thinning rates and glacial retreat in Marie Byrd Land. The combination of both data sets will provide information on spatial and temporal correlations of geodynamic activity and ice sheet evolution. This will contribute to our understanding of interrelations between lithospheric processes, surface processes, and ice sheet dynamics, thus providing benchmarks for future deglaciation models.

Project in cooperation with Karsten Gohl (Alfred-Wegener Institute, Bremerhaven) and Joanne Johnson (British Antarctic Survey)


The influence on climate and tectonics on uplift and denudation of the Terra Nova Bay region (Transantarctic Mountains)

Ph.D. Project Jannis Prenzel

The Terra Nova Bay region forms a segment of the Transantarctic Mountains (TAM) in the western Ross Sea that is characterized by extreme landscape contrasts. There, a high Alpine coastal morphology developed in immediate vicinity to high-elevated inland plateaus and deep, structurally defined glacial troughs. Structural geology, geomorphological observations and sampling of basement and cover rocks in this region during the expedition BGR GANOVEX X (2009/10) will provide the ground truth for the subsequent application of thermochronological techniques (fission track and (U-Th-Sm)/He analyses). Based on these data and thermal history modelling, the regional uplift and denudation history of the Terra Nova Bay region will be constrained with the four main topics: (1) the evolution of t a Cretaceous “Victoria Basin” on the continental crust of SE Australia and the western Ross Sea, (2) the diachronous rifting processes across the two escarpments of Pacific passive margin and West Antarctic rift shoulder /TAM, (3) timing and amount of the final denudation of the TAM since the Eocene / Oligocene, and (4) quantification and explanation of development of landscape contrasts within the Terra Nova Bay region resulting from the interplay between climate, tectonics and lithology. This aspect also comprises implications for the long-term climate evolution on the margin of the East Antarctic Craton.

Project in cooperation with Andreas Läufer (Federal Institute for Geosciences and Natural Resources (BGR)


Thermotectonic Evolution of Ellesmere Island and the Nares Strait area:
Relations between plate movements, landscape evolution, exhumation and glaciation processes

Proposal submitted to the German Science Foundation

In recent years the Arctic regions have been in the focus of public and scientific interest because of their key position for understanding past and present climatic change. Structural and climate evolution of the Arctic, however, is still poorly understood. Our project studies tectonic history and landscape evolution of Ellesmere Island and northwest Greenland, and potential couplings with the glaciation history. Our main interests are (i) understanding controlling mechanisms (i.e., climate vs. tectonic) on formation of the fiord systems of the Arctic archipelago, (ii) testing potential links between tectonically induced relief formation and early glaciation of the northern hemisphere, and (iii) reconstructing plate tectonic movements along the North American continental margins (Nares Strait and Canada Basin). In terms of methodology, our study will mainly be based on thermochronological analysis (fission track and (U-Th-Sm)/He dating), in conjunction with geophysical, structural, sedimentological, and paleo-botanic data. Our project will provide key new data on the regional evolution of the Arctic realm, and on interrelations between tectonics, landscape evolution, and climatic processes.


RECENTLY FINISHED PROJECTS

Perturbation of isotherms below topography: constraints from tunnel transects through the Alps

Ph.D. Project of Christoph Glotzbach (now University of Genoble, France); Post Doc Project of John Reinecker (University of Tübingen)

In recent years, a number of studies was dealing with the effect of topography on temperature distribution in the shallow crust. These studies predict that the position of isotherms may be influenced by overlying topography in that isotherms are wider spaced below ridges and compressed below valleys. The extent of this perturbation effect largely depends on geologic and geomorphic parameters such as denudation rate, relief amplitude, topographic wavelength and geothermal gradient. The perturbation effect has large bearing on thermochronologic studies in mountainous regions, since it may, on one hand, lead to substantial overestimations of exhumation- and cooling rates, on the other hand it can be used as a base for paleotopographic reconstructions. Most previous studies had in common that they were based on (semi-) analytical solutions and numerical modelling. Modelling has the advantage, that the influence of a variety of parameters can be tested in different model runs. This study, in contrast, aims to directly measure the position of isotherms below topographic relief under a given framework of denudation rate, topographic wavelengths, relief amplitude, and geothermal gradient. Our study areas are three tunnel transects through the Central and Western Alps; the Gotthard, Lötschberg, and Mont Blanc tunnels. All three profiles are situated in rapidly exhuming areas with relief between 1500 and 2800 m and topographic wavelengths of about 10 km, thus representing typical geomorphic features of active orogens. Samples from the tunnel profiles and their corresponding surface profiles will be dated by zircon fission track, apatite fission track, and apatite (U-Th)/He analysis. Distributions of these ages will (i) yield two-dimensional profiles showing the positions of isotherms below topography. The two-dimensional profiles may at least partly be correlated to three-dimensional images, (ii) show the sensitivity of the different thermochronologic dating techniques to the perturbation effect, and (iii) give a measure of the perturbation-induced overestimation of exhumation rates inherent to the different dating techniques. The results will be used to test existing models and to provide benchmarks for future model concepts.


Thermal evolution of an intracratonic rift: The Donbas Foldbelt (Ukraine)

Post Doc Project of Martin Danisik (now University of Perth, Australia)

The Ukrainian-Russian Pripyat-Dniepr-Donets basin is a large intracratonic rift structure formed during the Late Devonian. It is situated at the southern margin of the Precambrian East European Craton, adjacent to the Hercynian Tethyan belt in the Black Sea area and the Alpine Caucasus orogen. Its structural evolution is characterized by frequent changes between extensional and compressional settings, and periodically rejuvenated magmatism. The eastern part of the Pripyat-Dniepr-Donets basin – called Donbas foldbelt – is strongly folded and inverted. The exact timing of inversion is still under debate, but may have taken place during a major erosion period in the Permian, or in response to Alpine tectonics during the Late Cretaceous to Early Tertiary. The structure of the Donbas foldbelt was recently investigated by seismic reflectance and refraction in the frame of the international collaborative DOBRE project.

In this study, the Donbas foldbelt is used as an example to investigate the evolution and inversion of an intracratonic rift basin. Zircon and apatite fission track analysis, as well as apatite (U-Th)/He analysis will be applied along two profiles; one follows the DOBRE seismic section across strike, transecting the major structural units of the Donbas foldbelt as well as the adjacent Ukrainian shield, the other section follows the former rift axis along strike. The thermochronologic data will be used to (i) relate the thermal evolution of the basin to the structural evolution, as revealed by the seismic profile, and (ii) to reconstruct the thermotectonic evolution with special emphasis to the Permian and Late Cretaceous/Early Tertiary tectonic activity that led to basin inversion.


Natural long-term annealing and diffusion studies in thermally well-controlled settings: calibrations for low-temperature thermochronology

Low-temperature geochronometers (zircon and apatite fission track, (U-Th)/He on apatite) cover a temperature range from ca. 240 to 40°C and are applied in a wide field of geosciences. Especially the apatite fission track and the (U-Th)/He method were subject of rapid development and increasing interest in the past years. The main obstacle for both methods is the insufficient knowledge of annealing/diffusion behaviour over geological time scales. The annealing behaviour is the base for computer algorithms used for modelling the time-temperature path of the investigated rock. Most of the existing studies dealing with this problem were carried out in geological settings with only limited independent control of the thermal history. For rocks involved into tectonic activity it is extremely difficult to reconstruct the thermal evolution with the desired precision. This study aims (1) to create a large data set from natural long-term annealing/diffusion experiments in thermally well-controlled settings, and (2) to use this data set to test existing models and to use it as a base for new models. The long-term annealing/diffusion experiments will be carried out on ash layers of drill cores from oceanic boreholes. The oceanic environment gives a much better control of the long-term thermal evolution than a continental setting.

Project in cooperation with Andrew Gleadow and Barry Kohn (University of Melbourne, Australia)