Natural to anthropogenic influence of environmental change of Jakarta Bay: seismic reflection and sediment coring studies

Abstract

The shallow of high resolution seismic reflection profiles recorded dynamicdevelopment of Jakarta Bay. The interpretation results suggest least four transgression events andthree events of regression. The last regression event characterized by rough erosional surface, deepand wide channel of fluvial or shallow marine environment. This event indicates strong energysedimentation accompanied by high density material flow like as laharic flows or dense andfrequent wet season. Upper part of seismic profile characterized by continues, parallel and thinsedimentation layer indicates gradual sea transgression event. The shallow sediment coring data,100 cm to 160 cm length, indicates significant anthropogenic influences. At the depth 50 cm, thesediment core shows decreasing sharply of Si, Ca, Ti and Fe content interpreted as decreasing ofvolcanic source rocks. While to the near sediment surface was indicated by increasing of majorelement content such as Cu, Ti and Fe and also the heavy metals content such as Pb, Cr, Cd, Snand Zn. The presence of major or heavy metals were possible related to human activities such asdeforestation, industry, transportation and agriculture while in depth, the heavy metal contentrelated to volcanic rocks as source rocks The environmental degradation in modern period detectedat the sediment surface indicated by increasing sharply of Ammonia.