The Cretaceous Basement of Central Cebu: Does It Really Exist? 

 

Luis Santos-Y˝igo

 

 

 

ABSTRACT

 

Although the original field studies were conducted more than 40 years ago, this paper attempts to resolve some of the controversial issues regarding the Cretaceous and Paleogene rocks, particularly the Pandan Formation and Cansi Volcanics, whose geologic ages must now be reviewed in the light of subsequent findings which have remained unpublished. I take this also as an opportunity to set the records straight with regards to the Paleogene units, the Baye Formation and Lutak Limestone, whose paternity has been unfairly attributed unwittingly to other innocent parties for which I may be held party to blame.

 

The real key to possible solution of the Pandan/Cansi problem was our Baye Formation in Asturias, originally mapped as part of the Pandan but hastily excluded from it toward the culmination of our final mapping of central Cebu in 1956 because of the presence of Eocene (Flosculinabearing) limestone together with Cretaceous (Orbitolina-bearing) limestone clasts in conglomerate beds which placed its approximate age as Late Eocene to Early Oligocene. It was named the Baye Formation accordingly.

 

In my recent review of the geologic literature covering Cebu that has accumulated during the last 4 decades, I found some interesting clues that the situation at Baye was also reflected by similar enigmatic occurrences at the very place cited originally as the type locality for the Pandan Formation, not only from the report of Dr. Balce, but also from those of Japanese and German geoscientists, which therefore leads us to the conclusion that the Pandan and Baye form one integrated unit whose age, in the absence of confirmatory determination of unreworked matrix material, should be Late Eocene to Early Oligocene and not Cretaceous as heretofore believed by all previous workers in central Cebu.

 

The Pandan seems to correspond to the Tabgon Flysch and the Ragas Point Olistostrome in Caramoan Peninsula, Bicol region, which were dated latest Middle Eocene to earliest Late Eocene from nanofossils found in matrix materials (David, 1994).

 

Although McCabe (1985) cited Cebu as a good example of a stratigraphic terrane which he included in his Central Philippine Arc Terrane, our real situation conforms more to the characteristics of a Disrupt Terrane. This would therefore greatly minimize the chances of finding Cretaceous rock units that are truly inplace in the known basement areas of central Cebu.

 

 

 

 

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