268 FANNING. 
Martin ** states that von Drasche found a range of hills near 
Aringay in which layers of tuff are exposed. Farther inland, 
von Drasche found the formation to be of a “hard, crystalline 
and sandstone” nature. On the other hand, Martin found the 
region to consist of marl rather than tuffaceous formations. 
I likewise found the strata to be more of the nature of true 
sediments, for at San Fernando conglomerates were found, and 
along the Naguilian trail, dirty, fine-grained sandstones were in 
evidence. 
Radiolarian cherts.—Just north of Barlo, chert boulders and 
slab fragments are found scattered over the surface of the 
ground, generally lying upon the marls. It is evident that the 
boulders have resulted from the erosion of the strata. The beds 
apparently are very irregular and limited. 
In hand specimen the rock in certain types is exceedingly 
fine-grained and shows banded colors; red, brown, and gray. 
Under the microscope the thin section shows an isotropic ground- 
mass (probably chalcedonic silica) stained with hematite, and 
containing abundant, clear roundish areas which are doubly re- 
fractive under crossed-nicols. These clear spaces are believed to 
be casts of radiolarians from comparison with the radiolarian 
cherts of Ilocos Norte described by Smith,?® specimens and slides 
of which are at hand. 
Lawson?’ has spoken of the gradation, in radiolarian cherts, 
from sections ‘‘composed almost wholly of amorphous or iso- 
tropic silica to those which are holocrystalline aggregates or 
quartz granules.” 
Some of the Pangasinan cherts are of this holocrystalline 
type. The hand specimens are somewhat different from the 
first type as they are coarser-grained, and abundant white or 
yellowish-white quartz is present. This quartz is irregularly 
distributed in the specimen, often as a network of crystals, and 
occasionally filling vugs in the rock. Under the microscope the 
thin section is composed chiefly of interlocking granules of quartz 
(holocrystalline aggregates), often copiously stained with hem- 
atite, and containing magnetite and a few clear radiolarian casts. 
It was interesting to note that the quartz aggregates are second- 
ary to the hematite stain, for blotches of this stain were seen in 
* Becker’s translation, 136. 
* See Plate III, fig. 1. 
* This Journal, Sec. A (1907), 2, 158. 
“715th Ann. Rept. U.S. Geol. Surv. (1893-4), 420-426. 
