Flexural Modeling of the Himalayan Foreland Basin: Implications for the Presence of a Forebulge and Formation of Basement Ridges



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The purpose of this study is to evaluate the formation and shape of the Himalayan Foreland Basin system as it responds to lithospheric thrusting and loading. The study area is an elongate trough with an arcuate shape that mimics the shape of the Himalayan arc. The Eocene Himalayan Foreland Basin formed on the Indian Plate following subduction and continent-continent collision between the Indian and Eurasian Plates. The deepest part of the foreland basin adjacent to the Himalayan Main Frontal Thrust is covered with about 6 km of sediments.

The basement is characterized by several basement ridges; elongated structures oriented perpendicular to the plate boundary. The origin of these basement ridges is unknown. In a foreland basin system, a forebulge is expected to form when a plate has strength. There are some indications that a forebulge may have developed in the Himalayan Foreland Basin, but its exact location and amplitude are debated.

Three-dimensional flexural models were produced to determine the effective elastic thickness and flexural strength of the Indian Plate. Preferred models using realistic parameters predict that a low, broad forebulge has developed on the Indian Plate. The forebulge has an amplitude of about 30-50 m, and the lack of forebulge observed in the field and in stratigraphic columns is probably a result of the small amplitude of the forebulge.

The formation of the basement ridges was addressed by along-strike variations in the load with 3D flexural models, and by modeling compression of an elastic plate using Abaqus. Lateral variations in the load did produce basement ridges, but did not produce realistic basin depths. In the compression model, forces were applied to the sides of the Indian Plate to simulate compression as the Plate continues to be subducted beneath the Eurasian Plate. The model produced basement ridges using realistic values of plate rigidity. It is proposed that the basement ridges observed in the Himalayan Foreland Basin are the result of compression of the Indian Plate, and lateral variation of load is the result of non-uniform basin depths and subsequent sediment in-fill.



Himalayan foreland basin, Himalayas, Foreland basin, Flexural rigidity, Effective elastic, Forebulge, Basement ridges, Lithospheric buckling, Lithosphere, Lithospheric thrusting