Fully funded 3-year Ph.D. thesis project (2009-2012) available:
Multidisciplinary approach to reconstruct the Oligocene-Miocene morphologic
and exhumational evolution of the western Alps, France
Matthias Bernet and Pierre Tricart
LGCA, Université Joseph Fourier,
Grenoble - France
The aim of this Ph.D. project is to use a multidisciplinary approach
combining petrologic, geochemical and thermochronologic source-area
indicators, in order to reconstruct the evolution of erosion and sediment
routing in the western Alps during Oligocene and Miocene times. The record
of this evolution is preserved in the pro- and retro-side basins of the
western Alps in France and Italy. Several studies on heavy minerals and
index minerals have been done in these basins to discriminate sediment
source areas, but still confusion exists concerning the provenance of
certain heavy minerals. For example, on the basis of new studies on
metamorphic rocks in the western Alps it is now possible to discriminate
between sillimanite, staurolite, kyanite, andalousite, glaucophane and
Na-clinopyroxene derived from the internal and external western Alps.
However, serpentine group minerals can be derived from two main sources. The
first is an ophiolitic source such as the Chenaillet ophiolite that escaped
Alpine metamorphism. This potential source is characterized by chrysotile
and lizardite serpentine minerals. The second potential serpentine source in
the western Alps are metamorphic rocks in the Piedmont, Schistes Lustrés,
and Monviso units, which are dominated by antigorite minerals. By using
combined XRD and Raman spectrometry the mineralogy of detrital serpentine
group minerals will be determined precisely, in order to discriminate
metamorphic and non-metamorphic sources. This is done to test the hypothesis
that the metamorphic rocks of the internal western Alps were exhumed
successively, which means that younger molasse sediments contain detritus
from more deeply exhumed rocks of the internal Alps than older molasses
sediments.
In addition, fission-track analysis of bedrock and detrital apatite and
zircon, and 40Ar/39Ar thermochronology of white mica are excellent tools for
studying the cooling history of orogenic sediment source areas. Because the
three systems have different closure temperatures, they are sensitive to
upper crustal exhumation processes, such as erosion and normal faulting, on
different time scales. Because of volcanic activity in the Alps at around 30
Ma it will be crucial to supplement fission-track dating of detrital zircon
with U-Pb analysis on the same individual grains (double-dating) to clearly
identify zircon of volcanic origin which may bias the erosional exhumation
signal. Therefore, source area characterization using a multidisciplinary
petrologic, geochemical and thermochronologic approach on detrital and
bedrock samples is the overall theme of this three-year Ph.D. project.
This project will be supported by Master student projects which will be
focused on certain minor aspects of the Ph.D. project. This project is
financially supported through an ANR research fund, including a Ph.D.
student salary of 1.757, 00 € (gross monthly income). Starting date is
September 1st 2009.
For further information or to apply please send a letter of motivation, CV
and name and addresses of two references to Matthias Bernet:
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