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Structural and rheological evolution of an accretionary wedge: The Makran

English title Structural and rheological evolution of an accretionary wedge: The Makran
Applicant Burg Jean-Pierre
Number 116579
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.09.2007 - 31.12.2009
Approved amount 337'022.00
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Keywords (2)

accretionary wedge; rheology

Lay Summary (English)

Lead
Lay summary
We investigate structures formed in saturated, overpressured and consolidated sediments of the Makran accretionary complex to constrain the rheological evolution of accretionary wedges and to study the interactions between near-surface deformation and erosion and deposition. Our research integrates analogue and numerical tests on field and laboratory measurements.The main objectives concern 3 points:(1) Geology: Field data, digital elevation models and analysis of multi-spectral satellite images. We aim at establishing a new and modern geological map of the study area and the construction of geological cross-sections (all GIS referenced). Ash layers being dated constrain the regional lithostratigraphy.(2) Low-temperature thermochronology: the technique provides a time framework to the studied structures and quantifies exhumation rates and erosion-denudation. Quantitative rates of uplift, exhumation, and denudation/erosion will be used to understand and interpret the geomorphological response to tectonic forces in the accretionary complex.(3) Analogue modelling focuses on the role of the overriding plate / backstop along the central part of the Makran. Experiments demonstrate that, in the presence of a ductile décollement level, this obliquity deflects the thrust in the wedge. In purely brittle systems, thrusts form against the backstop. Results explain many large-scale features we have been mapping. Further modelling will make use of a CT-topographer that will supply a 4D (3D + time) control on erosion-sedimentation in thrust wedge development. We will continue measuring strain throughout a broad region of the Makran accretionary complex. Systematic measurement of brittle features is yielding a stress field whose variations seem to explain the present-day seismicity of the area. More data are required to support this working hypothesis. Fieldwork will be further integrated with coupled mechanical-erosion-deposition physical and numerical modelling, the latter performed with programs written at the ETH by us to compare the observations with published regional dynamic models. Low-temperature geochronology will provide the time constraints. The origin and nature of the overpressured shales in the Makran will be studied through isotope, geochemical and microbiological analyses. Furthermore, we will constrain models of critical wedges through laboratory rheological measurements and numerical and analogue experiments. Those will focus on the effects of ductile layers at different levels on internal deformation patterns and final geometry of thrust wedges.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
126692 Towards understanding long-term accretionary wedge dynamics - an integrated modelling and field study of the Tertiary Makran and southern Sistan of Iran 01.01.2010 Project funding
107429 Structural and rheological evolution of an accretionary wedge: The Makran 01.09.2005 Project funding

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