MINERAL RESOURCES OF AROROY DISTRICT. 401 



sediments, largely slates, intruded throughout large areas by diorites and 

 more basic plutonic rocks, and associated with a large amount of later 

 volcanic rocks, of a rather basic t^^pe, ranging from rare dacite, thi-ough 

 andesite to basalt and leucitite, with accompanying pyroclastics. !N^o 

 fossils are found in the early sediments, but from the great discordance 

 between them and the unmetamorphosed Miocene sediments, I believe 

 that it is not unreasonable to class them provisionally as pre-Tertiary. 

 Scattered outcrops of a dark blue limestone are to be found along the 

 shores of Asid Gulf and inland on the flanks of the mountain range. 

 This occurs as a capping unconformably above the older formations. 

 Dr. W. D. Smith has found the characteristic fossil Lithothannium 

 mmos^isimum Eeuss in thin sections of this rock, and considers the 

 formation to be of Middle Miocene age. 



An extensive sedimentary formation of Miocene age, containing coal, 

 occurs between Punta del Este at Port Kataingan and Xaro Bay. This 

 series rests upon a base of schistose quartz diorite and is composed of a 

 basal arkose followed by a sedimentary series containing several coal 

 seams which are overlaid by another slightly unconformable sedimentary 

 series. Between Kataingan and Dinias Alang where the writer has had 

 an opportunity to make a reconnaissance of the coal measures, the sedi- 

 mentary series is found to be bent into a very sharp sracline, the axis 

 of which follows the prevailing northwesterly trend. These sediments 

 in all probability continue northwestward on the unexplored Island of 

 Ticao. 



On the northwest corner of Masbate, a similar formation consisting of 

 shales, limestone, and a large development of conglomerate, but so far 

 as now known without coal, extends southwestward from the western 

 part of Port Barrera to Point Mariveles on Xin Bay. There are occa- 

 sional outliers from these sediments to be found farther inland, but the 

 main boundary shows in a well marked escarpment of limestone and con- 

 glomerate. The dip is quite gentle and generally to the northwest, and 

 the submarine contours along the west coast of the island suggest the 

 continuation of the formation for some distance seaward. 



Limestones and conglomerates, evidently of quite recent date, oc-eur at 

 several places along the northeast coast, such as Points Vigia (Vdiia), 

 Marintok, Bagubau, Kapandan, and Colorada. 



Earthquakes. — The Atlas de Filipinas divides the island between 

 "rather frequent*' and "rare" earthquake areas, the "rather frequent'' 

 zone lying, as would be expected, along the very deep Ticao strait between 

 Masbate and Point Bugui. In a recent catalogue of destructive earth- 

 quakes," six earthquakes above VI of the Kossi-Forel scale are stated to 

 have been felt in the years 1869, 1874, 1893. (two) 1897, 1900. 



" Catalogue of Violent and Destructive Earthquakes in the Philippines. 

 Weather Bur. Manila, P. I. (1910). 



