A Study on Evolution of Koggala Lagoon during the Holocene
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Date
2013
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Uva Wellassa University of Sri Lanka
Abstract
Climate change will have significant impacts on the oceans and on the coastal zone at a global
scale. It will introduce new hazards and increase existing hazard potential, both with respect to
magnitude and frequency of occurrence, in coastal regions. The hazards would be sea level rise,
storm and tsunami events. Sea level rise is one of the major problems experienced by many
nations including Sri Lanka
Sediment entrainment in the coastal environment is changed according to the climate changes.
So their sedimentation rates also change, depending on the type and its magnitude. Therefore,
the past depositional environments of sediments and their provenance can be identified by
studying the physical, chemical, biological and textural properties of sediments preserved in
coastal environments. This helps to understand the past environmental changes, which can also
be expressed as “studying the paleo-coastal environmental evolution”. Indeed this evolutionary
history can be used to interpret past and future environmental aspects in order to build a more
comprehensive framework to understand the behavior of the natural system. This study attempts
modeling the evolution of the Koggala Lagoon in Southern Sri Lanka in the said context.
Methodology
Two continuous sediment cores KG 1 and KG 2 were extracted from the Koggala Lagoon. KG
1 was extracted closer to the sea side (1100 m) and KG 2 further 1900m inland from the sea.
Both cores were logged and photographed. Organic matter content was analyzed by Loss on
Ignition (LOI) method and dry sand percentage was calculated by wet sieving with 63 μm sieve.
Geochemical variation of sediment cores was analyzed using handheld X-ray fluorescence
analyzer (Bruker S1). Gamma ray intensity and concentration were analyzed using gamma ray
spectrometer for the two cores. Sub-samples taken from different depositional environments and
recognized events were identified through the binocular polarized microscope. Data were
plotted using Pan Plot software. The ages for the boundaries of mid-Holocene sea level
variations and recognized events were approximately calculated using the published regional
age models equation (Ranasingheet al., 2013.).
Description
Keywords
Mineral Sciences, Mineral, Science and Technology, Materials Sciences, Biodiversity – Sri Lanka, Climate Change