COAST LINE LOS ANGELES TO SAN FEANCISCO. 



115 



most of it, enter from tlie east and cut througL. the San Luis Range 

 to the sea. 



Edna is built in part on the Paso Robles (ro'blace) formation, of 

 Pleistocene, Pliocene, and late Miocene age. The rocks composing 

 this f ormation, however, are much better exposed farther north. 



From a point 2 miles north of Edna to a point 1 mile beyond the 

 town of San Luis Obispo a set of rocks not hitherto seen on this 

 route, the Franciscan group, is almost continuously exposed.^ 



The most prominent topographic feature in the vicinity of San Luis 

 Obispo (Spanish for St. Louis the bishop) is the row of conical hills 



that begins with Islay (ecs-lie') Hill, on the right (east), 

 San Luis Obispo, ^ little over 2 miles southeast of San Luis Obispo, and 

 Elevation 237 feet. extending to Ccrro Romauldo (ro-mowFdo), about 4 



L^Angei^^2^ miles, milcs uortliwest of the to%vTi. There are eight of these 



hills (Spanish cerros), the four larger northwest and 

 the four smaller southeast of the city* These hihs, of which The 

 Bishop (1,502 feet) is the highest, are composed of igneous rock and 

 are the cores of small volcanoes which broke through the Franciscan 

 sedimentary rocks. The eastern part of Islay Hill consists of a 



surface flow of basaltic lava. 



From San Luis Obispo, which is a division point on the railroad, the 

 Pacific Coast Railway runs to Port Harford on the coast, passing 

 through the resort of Sycamore Warm Sulphur Spruigs. At Port 

 Harford is the end of the Producers' Transportation Co/s pipe line 

 from the San Joaquin Valley oil fields. 



San Luis Obispo is one of the old Spanish towTis of Cahfoi-nia. A 

 mission was founded here in 1772 by Father Junipero Serra, and the 



chiu-ch building is still standing. 



The most important metallic mineral resource in the San Luis 

 region is chromite, which occurs in the serpentine of the San Luis and 

 Santa Lucia ranges. 



Franciscan 



are older than the oil-bearing rocks over 

 which the route has thus far lain and are 

 probably of Jura?pic age. They comprise 

 Bandstones, conglomerates, shale, and 

 local masses of varicolored thin-bedded 

 flinty rocks. The flinty rocks consist 

 lai^ely of the siliceous skeletons of minute 

 marine animals, low in the scale of life, 

 linown as Radiolaria, and on this account 

 they are called radiolariau cherts. All 

 the rocks mentioned have been intmded 

 here and there by dark igneous rocks 

 (diabase, peridotite, etc.), which have in 

 large part undergone a chemical and 

 ciineralogic change into the rock known 



as serpentine 



associated 



most of the serpentine are masses of crys- 

 talline laminated rock consisting largely 

 of the beautiful blue mineral glaucophane 

 and for that reason called glaucophane 



it of this character is known 

 ^'cly few parts of the world, 

 characteristic of the Fran- 

 It has been formed from 



schist 



ciscan group. 



[gh contact 



ma. 



phism 



chemical action set up by adjacent freshly 

 intmded igneous rocks. The Franciscan 

 group is one of the most widespread and 

 interesting assemblages of rocks in the 

 Coast Range. 



