Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

B. C. Patro ¹

Affiliations
1 Geology Department, Ravenshaw College. Cuttack, IN

Abstract

No Abstract.

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B. C. Patro ¹, B. K. Sahu ², S. Guru ³

Affiliations
1 Department of Earth Sciences, Sambalpur University, Jyori Vihar, Burla, IN
2 Department of Marine Sciences, Berhumpur University, Bhanj Vihar, Berhumpur, IN
3 G. M. College, Sambalpur, IN

Abstract

Mechanical disintegration of source rocks and selective transport of resulting particles together generate log normally distributed traction, saltation, and suspension sand sub-populations of heavy minerals, ilmenite, zircon, rutile and sillimanite as for quartz. Plots of cumulative weight per cent frequencies in geometric size grades of these heavy mineral sand populations against an arithmetic size grade scale (mm. grade scale with equal class interval) on an arithmetic probability paper gives rise to a more sharply segmented curve than a plot of these frequencies against ∅ scale and hence may be more effective in environmental discrimination. Wadell's shape factor is shown to give satisfactory results in the estimation of equivalent hydraulic sizes of the above heavy minerals from the associated quartz sands in a saltation population. The reported hydraulic inequrvalcncy observed in the case of coarser sand grades of heavy minerals with respect to those of quartz is explained to be due to restricted availability of these sizes rather than to differenual entrainment.

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B. C. Patro ¹

Affiliations
1 Department of Earth Sciences, Sambalpur University, Jyoti Vihar, Burla 768 019, IN

Abstract

The arithmatic probability plots of Size Frequency Distribution (SFD) of untransported in-situ quartz sand accumulations (herein called the 'in-situ sediment'), at the top, slope and foot of a quartzite ridge, generated by thermal disintegration of the source rock (quartzite) show 2 to 4 straight line segments indicating the presence of 2 to 4 log normally distributed sub-populations. The phi standard deviation, σ_φ,increases with decreasing size of the sub-populations indicating a smaller size-spread in coarser sub-populations and wider size-spread in finer sub-populations. These results are shown to be in cornplete consonance with the modus operandi of thermal disintegration. Sand grains of 1.00 mm and finer sizes are shown to be recalcitrant to thermal disintegration. The semblance in the pattern of SFD curves of in-situ sediment as well as those of detrital sediments reader the reliability of the SFD curves as discriminators of transportational/depositional environments questionable.

Keywords

Size Frequency Distribution, In-situ Sediment, Thermal Disintegration, Sedimentology.

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