258 FANNING. 
sion has been accomplished by sea-action, in which case it repre- 
sents an uplifted shore-line. 
Valleys.—With the exception of the Alaminos, all valleys are 
very narrow and deeply cut toward the source of the rivers, and 
gradually broaden into the flood-plains contiguous to the sea. 
The Alaminos flood-plain is the largest in the area and contains 
some 75 square kilometers. 
Deltas.——The southwest corner of the area includes part of 
the great Agno delta which still is advancing northward into 
Lingayen Gulf. Drill holes put down at Dagupan and other 
places show many hundred meters of river silt. 
The Dagupan well No. 32, bored in 1908, showed the follow- 
ing section: 
' Depth in feet. Material. 
0 to 40 Blackish sandy to stiff mud. 
40 to 60 Fine gray sand, probably quartz. 
60 to 184 Blackish mud with fragments of shells; pebbles at various 
depths. 
184 to 189 Yellowish sand; stained by iron, probably by circulating water. 
189 to 233 Blackish sandy to sticky mud with shell and a few pebbles. 
233 to 328 Gray sand grading to finer sand containing some mud. 
328 to 374 Blackish mud containing some shell and pebbles at various 
depths. 
374 to 385 Gray sand, rather fine. 
385 to 395 Blackish mud. 
395 to 410 Gray sand with flow of water. 
Deltas of large size are absent from the remainder of the 
area. Along the China Sea the rivers empty directly into the 
ocean where wave action has prevented delta growth. 
Coral reefs.—Coral reefs, recent and living, fringe the shore- 
lines to-day as in the Pliocene. As in other parts of the Phil- 
ippines, uplifted Pliocene coral may be traced from the land 
into the sea where the living forms are found. 
Rivers and drainage.—The main drainage is northwestward 
along the Alaminos, Bani, Balincaguin, and Balingasay Rivers. 
The parallelism of the river courses is a feature structurally 
accounted for by the monoclinal northwest slope of the sedi- 
mentaries. Some minor drainage occurs southwestward down 
the Dasol River, and eastward down the east flank of the east- 
ern range of hills. 
The Agno River, one of the largest rivers in the Philippines, 
originates high in the mountains of north-central Luzon, flows 
southwestward to the great central plain of Luzon, then swings 
northward and empties into the ocean at the southeast corner 
of the region. All of the rivers, with the exception of the Agno, 
