CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY OF NGALANG RIVER SECTION, SOUTHERN MOUNTAIN AREA, GUNUNG KIDUL, YOGYAKARTA

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

CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY
OF NGALANG RIVER SECTION, SOUTHERN MOUNTAIN AREA, GUNUNG KIDUL, YOGYAKARTA

Akmaluddin^', T. Susio^', and W. Rahardjo^'
'Department of Geology, Gadjah Mada University
ABSTRACT

Total of 46 samples were collected from Miocene age of Ngalang River section. Those samples yield abundant calcareous nannofossils contents which belong to Sambibitu and Oyo Formation. Biozonation were done based on standard procedure of first and last occurrences of taxa which are widely known as standard zone indicators. The result of this study shows that there are 59 taxa known on Sambipitu and Oyo Formation and can be sub-divided into seven interval zone and one range zone.

Sambipitu formation shows 5 zones (NN2-NN6) which equals to Early Miocene to Middle Miocene while Oyo Formation shows 3 zone (NN8-NN10) which are equals to Middle Miocene to Late Miocene. These results indicated that there is a gap between Sambipitu and Oyo Formation with the absence of NN7 not founded. That means there is an unconformity between of them. Based on nannofossils date, it appears that all of the formations show younger age than which has been dated previously.