PALEOZOIC UNDIVIDED. 349 



In the Isle of Pines, associated with the Gerona marble which is described below, and to some 

 extent interbedded with it, is a great mass of crystalline quartz-mica schist, which rarely reaches 

 the surface except in watercourses, as it is nearly everywhere covered by the Malpais gravel. 

 Wherever it reaches the surface it is deeply weathered to a soft yellowish micaceous sand. In 

 addition to the quartz and mica, some portions of the schist also contain numerous garnets and 

 a thoroughly disseminated black mineral, taken to be manganese. The more siliceous portions 

 of the schist are banded and resemble a gneiss. There are also numerous veins of quartz, from 

 several feet in thickness down to mere stringers. It is evident that these quartz veins and the 

 siliceous bands and grains are the sources of the Malpais gravel and of the extensive deposits of 

 beach sand surrounding the island. Some portions of the schist are highly siliceous, forming 

 essentially a quartzite. In the Cerro Siguanea the rock has been extensively fractured and 

 recemented by iron and quartz, rendering it more resistant and thus causing a series of hills of 

 harder material to stand above the surrounding areas underlain by softer material. 



A dark-gray diorite schist has been observed in the Cerro DaguiUa and doubtless occurs 

 elsewhere in the island. It is evidently an intrusive basic rock, probably a diorite which has 

 been rendered schistose along with the inclosing formations. It is extremely tough and com- 

 pact, presenting a high degree of resistance to erosion. Some portions of the rock are rather 

 massive, the schistose structure being most highly developed along the margin of the intrusive 

 mass. 



The ridges on either side of Nueva Gerona are composed of crystalline marble which is 

 known as the Gerona marble. It is probable that the same material also forms the Sierra 

 Pequeiia, which is parallel to the Sierra Caballos, lying a few miles to the east; and to judge from 

 the topography of the Sierra de Canada, which was seen only at a distance, it is composed of the 

 same formation. This marble is everywhere thoroughly crystalline, retaining no trace, so far 

 as observed, of the organisms it may originally have held. The greater portion is rather 

 coarsely crystalline, although there are some beds of fine white statuary marble. The color 

 varies from pure white to dark gray, and in some places there is strongly marked banding. 



Owing to the thoroughly crystalline character of this rock, no evidence was obtained throw- 

 ing light on its probable age. It can, however, scarcely be younger than Paleozoic. In some 

 beds the impurities of the original limestone have recrystaUized to form certain silicate minerals, 

 chiefly fibrous hornblende. This marble was estimated to be not less than 2,000 feet in 

 thickness. 



K 10. KLAMATH MOUNTAINS, OREGON. 



Diller '^^ makes the following statement concerning the Paleozoic rocks of the 

 Klamath Mountains: 



The Paleozoic sediments consist of clay slates, dark sUiceous, locally banded slates, and 

 greenish slates, interbedded with tuffs and lentils of limestone. Near the contact with grano- 

 diorite they are locally metamorphosed into fine-grained mica schist, which usually contains 

 characteristic minerals, such as chiastolite and staurolite. * * * 



Measured directly across the strike the area occupied mainly by Paleozoic rocks, both 

 sedimentary and igneous, in the Applegate region has a width of nearly 30 rmles, in which there 

 are four more or less clearly defined belts of limestone containing about 50 masses, most of 

 which are located on the accompanying map as quarries or prospects. The largest outcrop is 

 not over one-third of a mile in length and 200 feet in thickness. * * * 



The limestones at a number of points are fossiliferous, but the fossUs are too poorly pre- 

 served to permit definite determination. In two lots * * * corals are abundant, and 

 among them E. M. Kindle recognizes with doubt forms that he compares with Favosites nitella 

 and Cladopora robusta, as well as a gastropod resembling Loxonema hella. * * * ^ strildng 

 feature that occurs locally in some of the limestone ledges of the second belt is the inclosure of 

 vesicular volcanic fragments, which indicates that volcanic eruptions occurred in the region at 

 the time the limestones were forming. 



