Institute: University of Calcutta
Title: Ph.D. Student
Country/Region: India
Period: 2023/07/01 - 2024/06/30
Theme: Holistic understanding of fold-thrust belts combining observational and experimental insights with an application to the Zagros fold-thrust belt
Host: Junichi Fukuda
Introduction: I am an experimental structural geologist specialising in laboratory scale analogue
experiments simulating both crustal and lithospheric scale models. I received the Ph.D degree
in Geology form the University of Calcutta in 2023 where my work was primarily focussed
on understanding the genesis and evolution of large scale deformation structures in fold-andthrust belts, emphasising on the pertinence of ductile deformation mechanisms. I used
laboratory scale viscous wedge models to understand the mechanism of development of
spatially varying ductile structures within deforming fold-and-thrust belts. Strain analyses
from models deformed over a weak decollement could be correlated with the development of
L-tectonites (reported from the hanging wall rocks of Lingtse granite in the Main Central
Thrust/MCT) in the extreme hinterland of the Darjeeling-Sikkim Himalayan wedge (eastern
India) during the intermediate stage of wedge growth in response to Indo-Asia tectonic
collision. Coupling experimental analyses with field observations revealed that the Main
Himalayan Thrust (basal decollement) beneath the Darjeeling-Sikkim Himalayan wedge was
rheologically weak, leading to the development of cross folds, L-tectonites and dome-basin
structures. My experiments also dealt with the spatial variations in fold geometry within the
deforming FTBs where interference of closely spaced cylindrical upright folds with
bifurcated axial planes, resulting in pervading non-cylindricity of fold axes as reported from
natural fold-and-thrust belts like the South western Iberian belt in Portugal and the TripuraMizoram belt in north eastern India. The mechanics of the development of a convex upward
topographic profile of accretionary wedges like the Ryuku and Kuril wedges of Japan were
also analysed from my experimental models. Additionally my experiments provided a strong
basis for understanding the cause of along-strike variations of topography and seismic
activities in active fold-and-thrust belts like the Himalayan wedge.
Here at ERI, I will be hosted by Prof. Junichi Fukuda and co-hosted by Prof. Yosuke
Aoki as well to develop an integrated and robust model for gaining insights on the
deformation metrics involved in the Zagros fold-and-thrust belt and to extrapolate these
insights to other compressional orogens. We will attempt to integrate accurate geodetic
estimates of ground surface velocity and strain rates alongside focal mechanism data to
understand the present day strain partitioning in the Zagros FTB by comparing the
deformation in NW Zagros (from previous literature) and the Fars arc on the east. We will
additionally aim to analyse if the rate of change of curvature of the Fars arc can be estimated
or predicted from the integrated data in long time scale and also to understand whether the
remaining part of the Zagros deformation front continues to evolve as a linear belt or not.
Folds and faults with associated seismicity are ubiquitous in the Zagros FTB. Therefore we
will also aim at developing high resolution estimates of the spatio-temporal variations in
seismic slip on the subsurface fault planes which are important for understanding the state of
stress accommodated within the deforming crust as well as for analysing the mechanics and
kinematics of post seismic slip also reported from post seismic deformation investigations in
the viscous accretionary prism of Makran complex at the Iran-Pakistan border on the east of
Zagros.
Fiscal Year: 2023