Seasonal sediment storage on mudflats adjacent to the Amazon River

The black sand placer deposits of Kerala beach, southwest India

The dynamics of the unique mudbanks of the southwest coast of India is examined. In situ studies were conducted to understand the processes involved in mud bank formation, sustenance and dissipation. Longterm nearshore wave data show that the pre-mudbank wave intensity and its persistence have a direct bearing on the sustenance and dimensions of the mud banks. Synchronous nearshore and offshore wave measurements indicate that wave energy is almost completely dissipated before it reaches the shoreline in the presence of the mudbank; the dissipation is only on the order of 25% or less in the absence of the mud bank. The role of bottom fluid mud in absorbing surface wave energy is recognized.

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Mudbanks of the Southwest Coast of India. I: Wave Characteristics

Coastal Mudflat Accretion under Energetic Conditions, Louisiana Chenier-Plain Coast, USA

The coastal sediments (129 samples) of central- southwest coast of India, in and around Cochin, the second biggest industrial city along the west coast of India, were analyzed for their textural and geochemical fractions such as Fe, Co, Cr, Cu, Mn, Ni, Pb and Zn on a seasonal basis, which form a first report of this kind. Metal accumulation was found to be highest during the period just after the summer monsoon due to the flushing of previously deposited sediments from the Cochin backwaters; the weak coastal currents favoring deposition in the coastal environment. Cross-shelf transport was found to be insignificant during the other two seasons. The geochemical studies reveal two different processes regulating the regional distribution of trace elements in this environment; viz: (1) The increased monsoonal supply of materials through the Cochin backwaters causing increased metal deposition (2) Effective masking of these metals by incorporation into clay and organic association which follows immediately after the monsoon. As the season progresses, they are further impoverished in metals (normalized) through size segregation of marine sediments. The correlations between various sedimentary parameters are elucidated to interpret the coherence between metallic and carrier phases during each season. While organic associations for most of the metals with seasons are preferential, absence of any correlation for Zn and Mn with organic carbon and clay on all occasion is striking.

Geochemistry of surficial sediments along the central southwest coast of India: Seasonal changes in regional distribution

Mud banks become clearly demarcated as areas of calm water adjoining the Kerala coast,
during the roughest SW monsoon conditions prevailing in the Arabian Sea The appearance
of mud banks is associated with an increase in the constancy and force of wind towards the east
Surface currents at that time run parallel to the coast and record -maximum velocity During
June and July, strong swells approach the SW coast Along the continental shelf, between
Mangalore and Quilon, the nature of bottom from about 3•5 to 18 m depth is largely muddy
Mud banks occur as small elevations of consolidated mud throughout the year

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C K Gopinathan

Papers

Mud Banks of Kerala-Their Formation and Characteristics