Informatics Publishing Limited

Joyanto Routh ¹

Affiliations
1 Department of Earth Sciences, University of Roorkee, Roorkee 247667, IN

Abstract

Herren in 1987, reported normal faults resulted in the telescoping of metamorphic isograds within a 200 meter zone between Sumche Topko to Mulung Topko in the Zanskar Shear Zone NW Himalaya. However petrographic study-of sections obtained from Mulung Topko and surrounding areas (pensila-padarn section) indicate that the rocks belong to the kyanite-sillimanite-starurolite grade only. Extension crenulation cleavage and other shear criteria show an initial NESW movement after which a layer parallel extension occurred and the shear zone developed. Minieralogical assemblage and mapping indicate that the isograds run paralleI to each other before they possibly truncate against the shear zone along the Pensila-Padam section. A probable model has been proposed to explain the features.

Keywords

Metamorphic Isograds, Structure, Zanskar Shear Zone, Himalaya.

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Supriyo Kumar Das ¹, Joyanto Routh ², Alakendra N. Roychoudhury ³

Affiliations
1 Department of Geology, Presidency University, 86/1 College Street, Kolkata 700 073, IN
2 Department of Water and Environmental Studies, Linköping University, 581 83 Linköping, SE
3 Department of Earth Sciences, Stellenbosch University, Private Bag X1, Maiteland 7602, ZA

Abstract

Studying the biogeochemistry of shallow lake sediments, especially the source of sedimentary organic matter (OM), is challenging because of the low preservation of OM in shallow lake sediments. Here we report the source of sedimentary OM in a shallow freshwater lake, Verlorenvlei, in South Africa using a number of biogeochemical proxies. Elemental carbon and nitrogen ratio (C/N), and stable C and N isotopes (δ ¹³C andδ ¹⁵N) indicate algal source of the sedimentary OM. Total organic and inorganic C, different phosphorus fractions, δ¹³C and δ¹⁵N values indicate repetitive presence of non-N-fixing cyanobacteria under moderate N-limited conditions. Cyanobacterial population in Verlorenvlei is likely influenced by the availability of dissolved inorganic C. Cyanobacterial proliferation in the lake has ceased with accelerated N input as recorded at the top of the core.

Keywords

Carbon, Cyanobacteria, Nitrogen, Organic Phosphorus, Shallow Lakes, Stable Isotopes.

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