GEOMORPHOLOGICAL DEVELOPMENT OF THE MURIA PALAEOSTRAIT IN RELATION TO THE MORPHODYNAMICS OF THE WULAN DELTA, CENTRAL JAVA

• Main Author: Sunarto .
• Format: Article
• Language: English
• Published: Universitas Gadjah Mada 2013-07-01
• Series: Indonesian Journal of Geography
• Online Access: https://jurnal.ugm.ac.id/ijg/article/view/2257
• ISSN: 0024-9521; 2354-9114

The research area is situated in the Demak, Jepara, Pati and Kudus regencies of the CentralJava Province. The objectives of the research are: (1) the investigation of the geomorphologic development of the Muria Palaeo-Strait in Central Java and (2) the analysis of the morphodynamicsof the WulanDelta. A morphographic- morphogeneticapproach was used to interpret the genesJsand subsequent evolution of the coastal lowlands in the surroundings of the Muria Volcano. The data analysis techniques, based on cause-effect assessment and analogy, were implemented in four steps, such as: (a) descriptive, (b) comparative, .(c) associative and (d) causative stages. The results of the research can be summarized as follows: The coastal plain situated to the south of the Muria Volcano was originally a shallow strait and subsequently became a mangrovecovered tidal flat with many creeks. Ultimately this tidal flat evolved into an alluvial/coastal plain with natural levees and back swamps. The coastal area in the west was still inundated by the sea around 6,000 yrs BP. This is evidenced by the 14C-dating 6,530 + 120 yrs BP of a coral reef situated at 25 cms a.s.l. The present beach ridge has an age 4,600 + 100 yrs BP and originated as a barrier bar. The coastal area in the east is characterized by the occurrence of four sequential beach ridge complexes at elevations of 580, 520, 220 and 125 cms respectively. They have been 14C-dated 5,860 + 110 yrs BP, 5,090 + 100 yrs BP, 3,530 + 100 yrs BP and 1,760 + 120 yrs BP. Since 1,760 yrs BP nofurther beach ridges wereformed, a tidal flat developed instead. The shape of the Wulan Delta changed from actuate to digit ate in the period of 1925 - 1995, mainly due to human interference with the river for purposes of irrigation. The growth of the Wulan Delta affected the hydro dynamical situation offshore of Jepara. These hydrodynamic changes resulted in marine erosion in the rural areas in the Jepara Regency and chewier formation in the rural areas of the Demak Regency.