Clay Mineralogy of the Pleistocene Soil Horizon in Barind Tract, Bangladesh

Abstract

Pleistocene red soil horizons were exposed in different areas of the Barind Tract in north-west Bangladesh. X-ray diffractions of twenty seven samples from different depths of these soil horizons revealed that the soil horizons consisted of kaolinite, illite and chrysotile with significant amount of opal-CT. Samples from Maddhapara, Bogra, and Nachole contain kaolinite, illite, quartz and opal-CT, and the samples from Kantabari contain chrysotile instead of kaolinite. Clay mineral compositions of different soil horizons indicated two different types of clay assemblages, viz. (a) illite-kaolinite and (b) illite-chrysotile. In the village of Kantabari, illite-chrysotile clay mineral assemblage indicate that soil horizons were formed under low temperatures with alkaline and reducing conditions. However, other soil horizons of illite-kaolinite clay mineral assemblage indicate that soils were possibly formed under humid, temperate and well-drained conditions. These two soil horizons were formed under different geochemical, geomorphological and climatic conditions from different parent materials. Scanning Electron Microscopy photographs showing the presence of glass shards and no opal-A were found using XRD, suggesting that the opal-A might not be a precursor to opal-CT in the red soil horizon of the study area. This opal-CT along with the general lack of fossils and presence of glass shards was indicative of a volcanogenic rather than biogenic origin for the Opal-CT in the study area, and X-ray fluorescence data reveals higher percentages of silica which is comparable to the Toba Ash of Toba Caldera, Indonesia of about 75,000 B.P.

Opportunities and challenges for implementing managed aquifer recharge models in drought-prone Barind tract, Bangladesh

“…However, other soil horizons of illite-kaolinite clay mineral assemblage indicate that soils were possibly formed under humid, temperate and well drained conditions. These two soil horizons were formed under different geochemical, geomorphological and climatic conditions from different parent materials (Aftabuzzaman et al 2013). This opal-CT along with the general lack of fossils and presence of glass shards was indicative of a volcanogenic rather than biogenic origin for the Opal-CT in the Barind tract.…”

“…Barind Tract in north-west Bangladesh geomorphologically formed with Pleistocene red soil. Aftabuzzaman et al (2013) carried out detailed investigation on the formation of Barind tract and found that Barind tract consisted of kaolinite, illite and chrysotile with significant amount of opal-CT. The soil sample collected from Nachole and examined by X-ray diffractions showed the composition of kaolinite, illite, quartz and opal-CT while in places it was found chrysotile instead of kaolinite.…”

Terrace formation in the upper Bengal basin since the Middle Pleistocene: Brahmaputra fan delta construction during multiple highstands

“…The average clay content of this facies is ~71%, and clay mineralogy is a suite of inherited minerals that includes chlorite, illite, kaolinite, and smectite phases, with no dominant mineral trends (Fig. a); this mixed composition is similar to clay mineral distributions found in Holocene fluvial overbank deposits throughout the delta (Heroy et al ., ; Tennant, ; Aftabuzzaman et al ., ). Under magnification, these silts display a uniformly euhedral mineral habit with relatively large crystals (up to ~50 μm) (Fig.…”

Mineralogy, geochemistry and monazite U-Th-Pb geochronology of the Hakimpur banded iron formation deposit, Bangladesh: a petrogenetic study

“…2. Upper units consisted of Cenozoic age sediments with the youngest being the Pleistocene Barind clay unit comprising red soils dominated by clay minerals including kaolinite, illite and chrysotile (Aftabuzzaman et al 2013).…”