MODEL OF REEF DEVELOPMENT IN RESPONSE TO SEA LEVEL FLUCTUATION AND ISOTOPE STRATIGRAPHY OF PACIRAN FORMATION, EAST–JAVA

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

MODEL OF REEF DEVELOPMENT IN RESPONSE TO SEA LEVEL FLUCTUATION
AND ISOTOPE STRATIGRAPHY OF PACIRAN FORMATION, EAST–JAVA

Premonowati ¹, Koesoemadinata, R.P. ² , Pringgoprawiro, H. 2 &
Hantoro, W, S.³.

¹ Department of Geological Engineering, FTM, UPN Yogyakarta,
E-mail: premonowati_geo@yahoo.com
² Prof. Emiritus – Dept. of Geo. Engineering. - Institut Teknologi Bandung, Indonesia.
³ Puslitbang Geoteknologi LIPI, Indonesia.

ABSTRACT

25 samples have been choose on non deformed calcite and analyzed by (oxygen and carbon) stable isotope. It used to validizing a sea level changes during Reef 1 to Reef 12 formation (since 4 Ma to Recent) from Paciran formation with sea surface temperature (SST).

On early forming of Reef 1 to Reef 3 (since 4 – 2.88 Ma), sea level occurred marine flooding surface or temperature warmer. Since Reef 4 formation (2.59 Ma) to Reef 8 formation (1.4 Ma) occurred stagnant temperature and almost to warmer condition. Then, δ¹⁸O drop drastically to 5‰ and shows warmer condition to reef 8 formation or sea level rise, even to Reef 10 formation (0.7 Ma). The temperature have been fluctuated between 0.5^o and 1^oC until Reef 12 forming (Early Holocene) and continue to Reef 12 formation at 2^oC based on the rapidity sampling of Porites sp.

Wholly, curve of oxygen stable isotope shows decreasing or cooler condition since Reef 7 and Reef 8 formation. Recently, a curve of oxygen isotope reveals warmer drastically or sea level have been arisen.