154 The Philippine Journal of Science im 



Calcareous materials 35, 37, and 39. — The Pliocene and 

 Pleistocene limestones form a terrace which rises abruptly from 

 sea level at the coast to an elevation of about 30 meters and 

 thence continues inland at a gentle slope to the crest of 

 Magdagoog Range (Plate I). The upper or latest portion 

 consists of fragmental coral in beds which dip very gently 

 toward the coast and do not persist inland more than 1 kilometer. 

 Mingled with the coral in different beds (fig, 3) are marine 

 shells, coral sand, chalky limestone, and a fine conglomerate of 

 various other rocks. Parts of the beds are entirely coralline, and 

 the corals often remain almost intact in the position assumed 

 during growth, but more generally the rock consists of large and 

 small fragments of coral in utter disorder. Evidently the 

 formation resulted from the intermingling of fragments eroded 

 from adjacent raised coral reefs and of material carried down 



Fig. 3. East-west geologic section through limestones 36, 37, and 39, Naga, Cebu ; length of 

 section 1,500 meters. (A) Coralline limestone: (B) coral shells and fine conglomerate; (C) 

 fragmental coralline limestone; (D) coralline limestone and fine conglomerate; (E) chalky 

 limestone; (F) calcareous, sandy clay. 



periodically from farther inland, with growing coral near the 

 shore line. 



Beneath the fragmental coral beds, the maximum aggregate 

 thickness of which is perhaps 60 meters, is a soft yellowish 

 gray limestone very much like chalk in character. A few 

 hundred meters inland where the upper beds, by reason of 

 their tendency to thin out, are no longer encountered, the chalky 

 limestone is exposed without overburden at the surface. The 

 material is uniform, and occurs in heavy beds with a total 

 thickness of about 30 meters. Minute fossil forms are to be 

 observed, but the character of the grains is essentially that of 

 very finely divided, amorphous calcium carbonate with ac- 

 companying traces of clay. This uniform extreme fineness of 

 grain makes it appear improbable that the chalk originated 

 as coral sand; a more plausible suggestion is that it represents 



