Morphotectonic study of warm climatic terminal fans in the Yamuna-Ganga Interfluve of the Ganga plain, India
Abstract
The terminal fans in the Ganga plain ranging age from early Holocene to present provide important informations regarding climate change and tectonism. Optically stimulated luminescence chronology of the terminal fan ranging from 2.4 Ka to 9.1 Ka suggests that, these terminal fans were formed in warm climatic conditions. Numerous calcrete layers within fan sequence, limonitised soil horizons and the associated clay mineralogy support their formation in warm climatic regime. These terminal fans preserve a number of paleochannels characterised by salt efflorescence, characteristics of arid climate.
Clay mineral studies by scanning electron microscope (SEM) from the terminal fans reveals that Illite as the most dominant mineral. Calcrete is ubiquitous and occurs in a variety of forms within the fan sequence and indicate arid environments during fan formation. Three calcrete horizons have been identified between 6.4 to 5.3 Ka attended different stages of development, indicating three warm climatic episodes within the 1100 year duration. Morphotectonic parameters such as sinuosity, directional shift of channels on the terminal fans suggests these channels were tectonically influenced. Morphotectonic parameters of the present channels suggest the influence of neotectonism. Therefore, it is believed that not only the tectonics is responsible for formation of the terminal fans, but also influences its channel morphology even after their formation. In the otherward, it can be explained as the response of the channels to the tectonic events irrespective to prevailing climate. Climatic response on channel morphology has been studied through the gradual change in channel-bed facies from proximal to the distal end of the fans. Due to increasing aridity, as evapotranspiration increases the channel strength decreases gradually. Due to lowering of channel competency the channels become weak and finally get segmented into numerous ponds aligned to the paleo courses of the channels. In the present study, numerous aligned ponds have been marked representing the paleo courses of the channels on the terminal fans. Preliminary study of paleochannels and present channels indicate most of the channels are shifting towards NE direction which supports neotectonic activity in the interfluve.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP31C2319P
- Keywords:
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- 1815 Erosion;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS;
- 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS