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| Titel |
Along strike variation of active fault arrays and their effect on landscape morphology of the northwestern Himalaya |
| VerfasserIn |
Markus Nennewitz, Rasmus Thiede, Bodo Bookhagen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143902
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| Publikation (Nr.) |
 EGU/EGU2017-7668.pdf |
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| Zusammenfassung |
| The location and magnitude of the active deformation of the Himalaya has been debated for
decades, but several aspects remain unknown. For instance, the spatial distribution of the
deformation and the shortening that ultimately sustains Himalayan topography and
the activity of major fault zones are not well constrained neither for the present
day and nor for Holocene and Quarternary timescales. Because of these weakly
constrained factors, many previous studies have assumed that the structural setting and
the fault geometry of the Himalaya is continuous along strike and similar to fault
geometries of central Nepal. Thus, the sub-surface structural information from
central Nepal have been projected along strike, but have not been verified at other
locations.
In this study we use digital topographic analysis of the NW Himalaya. We obtained
catchment-averaged, normalized steepness indexes of longitudinal river profiles with drainage
basins ranging between 5 and 250km2 and analyzed the relative change in their spatial
distribution both along and across strike. More specific, we analyzed the relative changes of
basins located in the footwall and in the hanging wall of major fault zones. Under the
assumption that along strike changes in the normalized steepness index are primarily
controlled by the activity of thrust segments, we revealed new insights in the tectonic
deformation and uplift pattern.
Our results show three different segments along the northwest Himalaya, which are
located, from east to west, in Garwhal, Chamba and Kashmir Himalaya. These
have formed independent orogenic segments characterized by significant changes
in their structural architecture and fault geometry. Moreover, their topographic
changes indicate strong variations on fault displacement rates across first-order fault
zones. With the help of along- and across-strike profiles, we were able to identify
fault segments of pronounced fault activity across MFT, MBT, and the PT2 and
identify the location of along strike changes which are interpreted as their segment
boundaries.
In addition to the steepness indices we use the accumulation of elevation data as a proxy
for the strain that has been accumulated over a specific distance. Thus, despite the changes in
topography, structural setting, and kinematics along the NW Himalaya we observe that the
topography of the orogen is in good agreement with recently measured convergence rates
obtained from GPS campaigns. These data suggest reduced crustal shortening towards the
northwest.
Deformation in the Central Himalaya has been explained either by in-sequence thrusting
along the MFT that localize the entire Holocene shortening or a combination of this with
out-of-sequence thrusting in the vicinity of the PT2. In contrast to these conceptual models,
we propose that the segmented NW Himalaya is a product of the synchronous activity of
different fault segments, accommodating the crustal shortening along three independently
deforming organic segments. The lateral discontinuity of these segments is responsible for the
accommodation of the variation in the deformation and the maintenance of the topography of
the Himalaya in NW India. |
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