Interplay between faulting and base level in the development of Himalayan frontal fold topography

Abstract

[1] Fold topography preserves a potentially accessible record of the structure and evolution of an underlying thrust fault system, provided we understand the factors that shape that topography. Here we examine the morphology and fault geometry of two active folds at the northwest Himalayan front. The Chandigarh and Mohand anticlines show the following patterns: (1) most (∼60%-70%) growth in catchment size and relief (across multiple scales) is accomplished within ∼5 km of the fault tips, (2) range-scale relief is divided unevenly between the fold flanks because of base level contrasts, (3) mean gradients of the uplifting catchments correspond to different flank-averaged rock uplift rates, (4) high hillslope-scale relief coincides with areas of fast rock uplift and stronger lithologies, and (5) existing relief represents only ∼15% of the total rock eroded since faulting began, implying significant erosion. The first-order fold topography is developed quickly and asymmetrically as a result of fault-generated rock uplift (which sets the space available for the fold and the distribution of rock uplift rates) with some modulation by base level (which affects the erosional response of the landscape to the uplift). A linear rate of growth in catchment relief with range half-width correlates with catchment-averaged rock uplift rate, suggesting that this metric may be used to infer variations in fault dip at depth. In these frontal fold settings, high slip rates, weak uplifting rocks, and rapid erosion may combine to quickly limit the topographic growth of emerging folds and disconnect their morphology from the displacement field.

Duns: Intermontane Basins in the Himalayan Frontal Zone

“…He also highlighted the prominent differences in slope development between the northern and the southern part of a Dun, the former being generally more steep with geomorphic surfaces formed within the Duns at the foot of the south facing Himalayan slopes. More recently, the tectono-geomorphic implication of this observation has been emphasized by the interpretation that the slopes associated with the Siwalik Hills in the south are related to the hanging wall of the younger Himalayan Frontal Thrust (HFT), and the slopes of the northern part of the Duns are associated with the hanging wall of the MBT or one of its splays (Singh and Tandon 2008;Barnes et al 2011). …”

“…Barnes et al (2011) provided a detailed analysis of the development of Himalayan frontal fold topography, and showed from a study of the Chandigarh and Mohand anticlines that most growth in catchment size and relief is accomplished within 5 km of the fault tips. They suggested that ''high slip rates, weak uplifting rocks, and rapid erosion may combine to quickly limit the topographic growth of the emerging folds and -Donga Fan in Dehra Dun).…”

“…In recent years, much attention has been focused on the Duns including their tectonic geomorphology, active tectonics, drainage development, palaeoseismology of faults in the Duns and the associated earthquake risk, and the evolution of Dun landforms using sedimentological and OSL chronological methods (Singh et al 2001;Malik and Matthew 2005;Delcaillu et al 2006;Malik and Mohanty 2007;Thakur et al 2007;Suresh et al 2007;Tandon 2008, 2010;Barnes et al 2011).…”

Stratigraphy and paleoenvironment during the Late Pliocene at Masol paleonto-archeological site (Siwalik Range, NW India): Preliminary results

“…1a). The Indian plate's northward push resulted in the Himalayan foreland basin uplift, which started in Middle/Late Pleistocene (Barnes et al, 2011). The combined action of tectonics and monsoons resulted in intense erosion and exhumation of sediment rich in fossils of aquatic and terrestrial vertebrata from the Masol anticline, NW of India (Fig.…”

“…(e.g. Barnes et al, 2011;Burbank et al, 2012;Delcaillau et al, 2006;Kumar et al, 2003Kumar et al, , 2007Nanda, 2002;Pilgrim, 1913;Ranga Rao, 1993;Sanyal et al, 2010;Singh and Tandon, 2010;Thomas et al, 2002;Tripathi, 1986). The Siwalik Frontal Range is a result of the folding and uplift of the Siwalik Group, which is a sequence of continental sediments deposited in the Himalayan Siwalik-Ganga-Indus foreland basin from Middle Miocene to Middle Pleistocene (Fig.…”