Geomorphological evolution of the Merbok estuary area and its impact on the early state of Kedah, northwest peninsular Malaysia

Abstract

The Merbok estuary area was formerly a bay with an elongate bay mouth bar. Regression of sea level during the Late Holocene had caused the disappearance of the bay. Evidence from seismic studies show that the Merbok River was not a river till more recent times. Soil survey and field mapping delineated the former beach inland. An emergent shoreline development model is proposed for the geomorphological development. Historical records and archaeological evidence indicate that the present shoreline configuration was almost in place by about 1400. The regression of the sea level had caused the decrease in importance of early Kedah which was sited in the estuary area. In addition several other problems are also explained or resolved by the emergent shoreline model such as the early geography in relation to early Kedah and identification of Kedah in early records from improved knowledge of the palaeogeography. Considering several lines of evidence from field data to historical and archaeological evidence, it is interpreted that the fall in sea level from 2–3 m to the present level was relatively rapid (200 years or less) compared with periods of still-stand. The reconstruction of the palaeo-shoreline also helps to clarify geographical features described in the ancient Kedah Annals, which appear to contain eye-witness accounts of regression of the sea level and not fairy tales as believed by several eminent commentators.