NORTHWESTERN PANGASINAN. 969 
places to be cleanly fractured and the cleavages filled with the 
quartz. 
Lawson in discussing the silica of the radiolarian cherts of the 
San Franciscan formation believed it to have originated from 
“siliceous springs in the bottom of the ocean.” As stated :18 
The hypothesis of the derivation of the silica from siliceous springs 
and its precipitation in the bed of the ocean in local accumulations in 
which radiolarian remains became embedded as they dropped to the bottom, 
seems, therefore, the most adequate to explain the facts, and there is 
nothing adverse to it so far as the writer is aware. 
The above hypothesis appears strikingly applicable to the 
cherts of Pangasinan. Almost directly beneath the cherts, 
where the Barlo Creek cuts deeply into the underlying forma- 
tions, the andesite has been extensively silicified by the action of 
circulating waters, and it would seem that during the deposition 
of the sedimentaries these waters discharged from the bottom 
of the ocean, and their silica content was deposited to the 
formation of the cherts. 
Cherts recently have been found in many different parts of 
the Philippines such as Bulacan, Palawan, Mindoro, and Min- 
danao. All show great similarity, and it is possible that they 
may form an exceedingly valuable means of correlation. The 
cherts of Ilocos Norte were provisionally placed in the pre-Ter- 
tiary,!® while the cherts of Pangasinan occur at the base of the 
Miocene-Pliocene formation. The provisional age determina- 
tion of pre-Tertiary for the Ilocos Norte formation was made on 
a basis of similarity to the Mesozoic cherts of California, U.S. A., 
and the Moluccas; and in the absence of evidence to the contrary 
it is a possible supposition even though it marks the only pre- 
Tertiary formation as yet found in the Philippines. Concerning 
the field relations of the Ilocos Norte cherts it is stated that: ° 
“It is exceedingly limited in its outcroppings and quite variable in its 
phases, never being encountered as a continuous formation but only as 
isolated outcrops which reveal little or nothing as to its position.” Con- 
cerning the paleontological evidence it is stated, “as yet I have been unable 
to make any specific determinations from these slides.” 
It is positively known that, during the Tertiary, siliceous 
springs were very active throughout the length of Luzon. This 
is Shown by the quartz veins which are found in numerous places 
™* Tbid., 424. 
* Smith, This Journal, Sec. A (1910), 5, 319. 
# Smith, This Journal, Sec. A (1907), 2, 158. 
