Spatio-temporal Analysis of Magnetic Mineral Content as a Tool to Understand the Morphodynamics and Evolutionary History of the Godavari Delta, India: Implications on the Environmental Management of Deltaic Coastal Zones

Abstract

The fluvial delta acts as a unified system wherein the changes in one part of the system affect the other regions and create unique signatures of such events in terms of geomorphic and sediment textural, mineralogical, geochemical and other characteristics in the ensuing deposits. The spatio-temporal variations of the governing factors of the system introduce proportionate changes, which are normally inferred as sub-environments of a delta. An ability to understand the ongoing dynamics in the sub-environments through sensitive parameters of the sediments and developing a capability to interpret the ancient dynamics would be valuable for application of similar technique in other deltaic systems for environmental management. Magnetic mineral contents of the surface samples and vibracore stations collected from the Godavari delta, India were estimated and analyzed for their spatio-temporal variations together with geomorphologic and other characteristics. The magnetic mineral content showed a general increase from inland to coastline and is at its maximum along the river courses. It is concluded that the concentration of magnetic minerals is controlled by erosion and size sorting within a deltaic system and vary according to the spatio-temporal differences of energy conditions in time and space. As each sub-environment within a deltaic system has unique energy conditions, these primary differences reflect in the sediment characteristics and in the magnetic mineral content. Visualizing these differences on a spatio-temporal scale has helped in inferring paleoshorelines and paleochannels in the study area and reconstruct the evolutionary history of the Modern Godavari Delta. Collation of these inferences together with information on neotectonics, geomorphology and land use characteristics suggested that the Godavari delta faces multiple and multi-dimensional natural and anthropogenic environmental threats and urgent mitigation and environmental management programs need to be undertaken based on multi-disciplinary and comprehensive studies.