Ida Valeton; F. Wilke:

Tertiary bauxites in subsidence areas and associated laterite-derived sediments in northwestern India

1993. III, 104 pages, 43 figures, 15 tables, 3 plates, 16x24cm, 270 g
Language: English

(Contributions to Sedimentary Geology, Volume 18)

ISBN 978-3-510-57018-8, paperback, price: 38.00 €

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Synopsis top ↑

The bauxite-bearing laterites in Kutch/India are presented as an example for bauxites on downwarping platforms along passive shelves. During the tilting of the platform, the marine transgression and the rising of the groundwater level, the bauxite formation started. At the same time, their equivalents in the uplifted hinterlands were reworked, and the resulting products were deposited mainly in flood plains. They formed specific sediments called “laterite-derived facies” = LDF.

The formation of in-situ bauxites and associated laterite-derived sediments was connected with tectonic activities and related marine trans- and regressions. The short period of a few millions of years during the Lower Eocene was sufficient for a very effective mineralogical and geochemical reorganisation of the weathering profiles and sediments producing laterite and finally bauxite.

The results of mineralogical and chemical investigations of saprolite-bauxite profiles and the sedimentary LDF are presented to characterize the unique surface processes occurring in the marine- terrestrial transition zone.

Table of Contents top ↑

1. Introduction 1
2. Geological history of subsiding platforms 4
2.1 Stratigraphic and tectonic evolution in Gujarat 4
2.2 Laterite and bauxite formation in relation to trans- and regressive marine cycles 8
3. Parent rocks of laterites and bauxites 10
3.1 Clay-sandstone formation 10
3.2 Trap basalt 11
4. Planation plains on subsiding platforms and their correlation
with marine regressions 15
4.1 Sequence of planation plains on Kutch peninsula 16
4.2 Ferralite and laterite-derived facies (LDF) in the Paleocene-Eocene “Indian Cycle” 19
5. Three horizons of bauxite-bearing laterites 19
5.1 Bauxite-bearing laterites on top of the basalts 19
5.1.1 Standard profile of bauxite-bearing laterites 19
5.1.2 Lateral variation of the laterite profiles 24
5.2 Second and third horizon of bauxite, both on top
of LDF-associations 24
5.3 Facies patterns of the bauxite-bearing laterite on top of basalt
or LDF-associations 27
6. Mineralogy and chemistry of bauxite-bearing laterites 35
6.1 Mineralogy 35
6.1.1 Initial alteration 42
6.1.2 Saprolite (Btr-horizon) 42
6.1.3 Bauxite-bearing laterite (Box-horizon) 46
6.1.4 Weathering profiles on clastic sediments 51
6.1.5 Late polygenetic overprints 51
6.1.6 Normative mineral content 52
6.2 Chemistry 52
6.2.1 Redistribution of elements 52
6.2.2 Trend diagrams and correlation diagrams 63
6.2.3 Cluster analyses 73
7. Composition of the LDF-sediments 76
8. Interaction of tectonics, lateritic weathering and LDF-sedimentation 87
8.1 Vertical movement of the earth crust (uplift or subsidence of the land surface) 87
8.2 Varying speed and intensity of weathering 88
8.3 “Volume” of weathered material, its input into the marine environment 89
9. Conclusions 89
10. Summary: Comparison of bauxites from uplift- and subsidence areas 92
Acknowledgements 93
References 93