was given on account of the occurrence of this fossil, together with sev eral other species, at or near Fort Ross, Sonoma County, and also at Todos Santos Bay, Lower California, where the best specimens were found. These beds stand in an unknown relation to the other Cretaceous deposits stratigraphically, but have been supposed, on account of the fossils, to indicate a division between the Chico and Shasta groups. I believe, however, that the occurrence of the most important fossil of this supposed division on Point Loma, in the same beds with undoubted Chico fossils, destroys the validity of the supposed Wallala Beds. In a bluff at the northeastern end of the Point Loma peninsula, west of Old Town, there is a stratum of calcareous sandstone, carrying many fossils belonging to the Eocene, or lowest Tertiary. The strata dip northeast at a small angle, and though they cannot be traced continuously west to the outcrops of Cretaceous rocks, yet from the fact that they have the same dip, leads me to the belief that the two beds are conformable. This younger deposit corresponds to the Tejon, or Division B, of Professor Whitney. Everywhere in the State there exists the closest relation between the Chico and the Eocene. Here on Point Loma they are undoubtedly also conformable, but each is distinct as regards its fauna, for they are separated by nearly a thousand feet of unfossiliferous strata. False Bay occupies the basin of a synclinal, for the strata dip north covered by the ocean. It has a course about 30° east of north, and stands vertical. It begins on the north, close in under the high cliffs, but does not extend into them, the only signs being a fault in line with the dike. It is not more than 2 feet wide at the northern point where it is exposed. It is dark and compact and so decayed as to be easily taken for an argillite. The walls of the dike are very smooth and regular, except near the southern point, where it runs into the water. Here it swells to a width of 30 feet. The edges of the dike are compact, while the vesicular portion is in the center, where there is often a flowage structure developed. The central portion is more or less laminated parallel to the wall, and thus is generally a well-pronounced columnar structure developed the whole width. The columns lie horizontally across the dikes and are 12 to 15 inches in diameter. The cavities are wholly or in part filled with calcite. Metamorphism of the adjoining shales is apparent for 2 feet away, but the sea water has so decomposed the shale that it is not so strongly marked as it would otherwise be. The dike projects above the water in places for a distance of 1,000 feet, easterly from Point Loma and south from the Soledad Hills. A violent fossils have been found in the county, but perhaps the most of them have disturbance, forming a great uplifted fold or perhaps a fault, has taken place along a line extending southeast from La Jolla through the Soledad Hills. At the eastern end of False Bay there is a small exposure of Eocene strata, dipping west. Near the mouth of Rose Cañon the strata dip southwest, and at the mouth of the cañon they dip 40° northeast. making its total exposed length about 1,800 feet. In the mesa southe Along the road which leads over the hills to La Jolla the rocks are tilted Rose Cañon and the northern boundary of the county, I do not know at a very high angle to the southwest. The highest point of the Soledad that Miocene fossils have been found, but in Orange County they are Hills, rising 700 feet, lies over this disturbed region. Unconsolidated bowlder deposits lie on the top of the hills. The strata on the east side of Rose Cañon. This fold at La Jolla brings to the surface fossiliferous stratą well characterized. bo de Canon are well exposed, but do not seem to partake of the dis composed, as far as we know, of Quaternary, Pliocene, and perhaps The region occupied by San Diego Bay and the mesa back of it is turbance shown on the west. This is probably no unconformity, as the Miocene strata. Sandstones characterize the lower formation, and loosely turban Eocene fossils, and the Eocene in other spots appears to be COL cemented conglomerates, increasing in thickness toward the mountains, contable with the Chico. Along the coast between False Bay and the upper. These were deposited in a sort of basin, of which Point Loma Jolla the strata dip south at a small angle. At La Jolla, near the caves and the Soledad hills formed the northern and western borders. they have been folded so as to dip very steeply to the southwest for nearly oscillations of level have taken place, the most recent being an elevation Many quarter of a mile across the strike. Near the eastern end of the cliff of 40 feet, shown by an old beach line on Point Loma. The shells in a quartal takes place, and they dip northeast at nearly as great an angle this beach are the same as those now living in the adjoining ocean. It a reved the little bay there are no exposures, but a mile northward begin is a peculiar fact that the mesas are slightly higher near their western a very high line of cliffs, which extend through to the mouth of Soledad terminations than farther east, indicating a recent uplift along the bearing a number of species similar to those at Point Loma; amb Point Loma there is a strong sulphur spring exposed at low tide. Its them is the Coralliochama Orcutti. The strata of the high cliffs north waters may possess medicinal properties, and should be examined. La Jolla dip northerly at a small angle, and show only a few fossils At the bottom of the cli tufa. The central portion is quite pure and a number of feet thick; just On the southern shore of False Bay is a large deposit of calcareous the Foles, higher up are great beds of conglomerate bowlders, chiefly how thick is not known. It extends along the shore some distance, Eocene age. The cliffs rise fully 400 feet. and often contains bowlders and shells. This is evidently a deposit Coal is reported to outcrop above the water at very low tide some from some former spring of great size. The mesas lying west of the where along this stretch of cliffs. It of course must occur in strata extensive volcanic tuffs have been derived largely from the decay of the coal vein struck in a boring at La Jolla must latter, and have heavier soil. North of Soledad they become more sandy, Cetaceous. About 3 miles up the coast from La Jolla, there appear and maintain this character to the Santa Margarita Creek. This light Idike of basalt cutting the Tertiary shales. At high tide it is near soil, however, is being successfully cultivated in many places and for reddish porphyry. Tertiary age. Water is scarce through this mesa formation. At the end of Fig. 13. certain kinds of fruit, without irrigation. The surface of the higher portion of Point Loma, as well as some of the mesas north, is covered with spherical nodules, a quarter to half an inch in diameter, of sand cemented with red oxide of iron. These literally cover the ground in places so that it is difficult to walk. The origin of these at first seemed very puzzling, but on examining the face of a cliff on the top of which these were found, an explanation was reached. They were seen to grow smaller away from the surface of the ground until a depth of 2 feet was reached, when they cease. Their formation is due to the oxidation of the iron in the sandstone, and its segregation in little nodules on the same principle as the formation of concretions. The cliffs of Eocene sandstone along the ocean grow gradually lower north of Soledad Cañon. At Encinitos the cliffs are higher again and for a short distance the strata dip south, but toward Oceanside they resume the northerly dip and disappear several miles south of that place. Faults grow less numerous the farther we get from Point Loma. The mesa is low about Oceanside; it was either never very prominent On the north bank of the Santa Margarita Creek, near the ranch house, is an interesting cliff of Quaternary sands and gravel, showing a number of strata deposited under different conditions on an old beach (Fig. 13.). or else the erosion has been great. and found to consist entirely of fragmental schists, such as those men- On One mile north and in line of strike near the road at the western foot of the mountains; they also dip west at a high angle. Many of the fragments at the northern end of the range show their derivation from a massive crystalline rock. The hornblende schists are generally garnetiferous. Blue glaucophane schists are also very common. South of Mission Viejo Creek, Orange County, there is an outcrop of rock, apparently in place, which greatly resembles these schists. Good outlines of these mountains, indicative of structure, can be seen to great advantage from the San Luis Rey Mission. the west slope of the San Onofre Mountains, 4 miles north of Los Flores, is an outcrop of a garnetiferous hornblende schist, which certainly appears to be in place. This rises 10 feet above the side of a gulch, and is fully 20 feet across. with the last is another outcrop of similar rock, which is so large that it certainly seems that it must be in place. The only point north of the San Onofre where this breccia appears is at Arch Beach, Orange of County. The Santa Margarita Mountains are bordered by very extensive bowlder deposits, which rise as high as 1,500 feet on their western slope. The topography of the northwestern part of the county between TemeThe Tertiary beds north of the Santa Margarita Creek are very differcula, Elsinore, and the ocean, is very complicated. This section is occuent in outline from those south. Instead of their extending in a gradual pied by rugged, brush-covered mountains and narrow, deep valleys, with the exception of the Santa Rosa plateau, where the configuration of the slope from the older mountains to the ocean, there arises in them, near their western border, a range of mountains, known as the San Onofre county has been entirely changed by extensive lava eruptions, stretching Mountains. These extend parallel to the ocean at an average distance over a distance of 10 miles. This mountain region narrows toward the of 2 miles. They rise north of the Santa Margarita Creek and extend north to form the Santa Ana range. The variety of rock formations is to the San Onofre Creek. They have a gradual slope on the west, rising very large. The northern portion is unsurveyed. On the south are the Los two large grants, the Santa Margarita and the Santa Rosa. Between to an elevation of 1,400 feet, but are quite abrupt on the east. Flores Creek cuts through the southern end of this range, showing that these lies De Luz Valley. The Santa Margarita Mountains extend with north while the soft, clayey sandstones between it and the Santa Margarita and south, forming the eastern borders of the grant and rising to un Mountains slope only 5° to 10° southwest, the rocks of the range itself elevation of 3,100 feet. The granite of the region about De Luz Valley dip west at an angle of 35° to 40°. The formation is a breccia, the far from being homogeneous. A part of it is undoubtedly intrusive, fragments of which are argillitic, micaceous, and hornblendic schists and a part may represent an original sedimentary formation. Bedding Some of these fragments are of great size, one bowlder of hornblende planes are present in much of this supposed metamorphic granite, but and other hard generally The soft, coarse sandstone in which springs is perhaps due to a dike of dark, aphanitic diorite, which has cut the fragments are imbedded show no traces of any granitic matter through the granite in an irregular manag A very interesting breccia The range was ascended 2 miles north of the Los Flores ranch house outcrops in the bed of the creek below the warm springs. (Fig. 14.) metamorphics are also present. Fig. 14. The fragments are chiefly granite and an aphanitic rock. They are quite angular, showing only a slight rounding of the corners. Some of the larger fragments are a foot in diameter. The boundaries are very irregular. Long arms of the inclosing granite project into the breccia. The base or matrix varies from a coarse syenitic rock to an aphanite. It often seems to present a blending of different kinds of fragments. Besides the large inclusions there are scattered through the matrix small angular pieces, which are so regular in outline and distribution as to give to the rock the appearance of a porphyritic structure. The granite in the hills west of the valley contains much biotite and quartz in long, rounded grains, presenting a pseudo-porphyritic aspect. This appearance is characteristic of much of the granite of this section. Imbedded in the granite are masses of dark aphanitic rock. The lower granite hills are covered with considerable sandy soil. There are isolated peaks of a coarse white granite, much like that of the Sierra Nevada, arranged in some sort of regularity in north and south lines. One rugged peak of this coarse granite rises 2,500 feet west of the valley. At the northern end of the valley the bedding planes in the finer grained granites are very regular; strike north 45° west, dip 65° southwest. There is, however, no schistose structure present. A half mile above the warm springs is another conglomerate or tuff, which seems so related to the granite that the latter must really be eruptive. In a little valley southwest of De Luz and just east of the Santa Margarita grant there is a large outcrop of diabase. It has been intruded in a fine-grained, jointed granite. Farther down the valley, on the road to De Luz Station, there is a narrow outcrop of black quartz feldspar porphyry, followed on the east by a dark felsitic mica schist; strike northwest, dip 60° southwest. Immediately west of the deep cañons which lead down to De Luz Creek, rises the Santa Margarita Mountains. They consist of a fine-grained granite, verging at times on a quartz porphyry. The main crest is 2 miles long, the highest peak of which is nearly 3,200 feet. The rock is perfectly massive, but shows apparent bedding planes; strike north 30° west, dip 80° northeast. The On the porphyritic facies of this formation occur in the western slope. western slope of the main range, at an altitude of 2,500 feet, there is a dotted with white oak trees. The western slope of this plateau is very abrupt and brushy. The formation is partly porphyry and partly dark diabase and diorite. The most interesting fact connected with the Santa Margarita range is the occurrence of sandstone at an elevation of 2,600 feet on its western slope. The sandstone occupies very limited detached areas in the heads of the gulches, and is evidently the remnant of a once far more extensive formation. The sandstone is largely kaolinitic, and has evidently been derived from the adjoining rocks. At the foot of the southern end of the mountains appears very quartzose rocks, probably of metamorphic origin. Coarse granite has been intruded into them in small bunches. Granite extends southwesterly in the form of a wedge as far as the Santa Margarita ranch house, and is there covered by modern deposits. Between De Luz and Fallbrook the country is gently rolling, with knobs of granitic rocks projecting here and there. About Fallbrook, and for some distance east, the granite does not outcrop much, owing to its easy decomposition. A little east of De Luz Station is a small body of mica schist; dip 30° east, strike north 15° west. The road from Fallbrook to Temecula leads through a long, narrow valley. On either hand rise high mountains of bare granite. Immense bowlders, 20 to 30 feet across, line the valley, having fallen from the cliffs. The granite here is a coarse rock, rich in biotite, and though great masses could be obtained free from checks, yet does not seem durable. The valley owes its origin to a difference in rapidity of decay along certain lines. On this section there appears no trace of the schist belt extending northwest from Julian. This coarse granite is undoubtedly intrusive and has cut it off. of A wholly different series of rocks is exposed in the Temecula Cañon, not more than 2 miles north of the country just described. This cañon is deep and rocky, taking a very direct course from Temecula to the ocean. At the upper entrance there is a narrow exposure of granite. This is followed by quartzite, dipping 45° southwest. The rocks shortly become massive and are replaced by dark syenitic ones with an excess of hornblende. Two miles down, granite appears for a short distance, and in it a quarry has been opened. The rock can be obtained in blocks any size from great masses which have broken off and rolled into the cañon. Gneissoid rocks soon replace the granite, and these are followed by hornblendic rocks, which vary from a schistose to a massive structure. In places they contain feldspar and pass into syenites; in others the rock is almost pure hornblende. The greater portion of these rocks are of metamorphic origin. The dip is generally vertical, strike east and west to northwest. The syenites are followed by mica schists, and these by coarse biotite granite about 5 miles above Howe Station. In the granite are many pegmatitic veins, carrying biotite, garnets, and tourmaline. Fine-grained granite, varying at times to syenite, forms the rock along the cañon for many miles below this point. The most interesting geological feature about this northwestern part of San Diego County is the long plateau, confined chiefly to the Santa Rosa grant. This plateau lies near the western corner of the grant, and extends east nearly to Murrieta. The lava is broken up into detached tables by erosion, which become very strongly pronounced toward the western end of the flow. The western body of lava is the highest. It has a length of nearly 2 miles and is broken into three plateau-like area of a thousand acres or more of fine grass land. It is peaks or ridges, sloping generally a few degrees to the east; height ་ 2,850 feet. There are two terrace-like tables lower down its southern slope. The lava is, perhaps, a hundred feet thick at its eastern end, and has been so much eroded toward the western portion that the underlying sandstone is exposed along the crest of the ridge, with lava lying in broken masses along its sides. The sandstones form quite an extensive bed under the lava flow, being 200 or 300 feet thick, and horizontally bedded, wherever bedding is present. The upper part is very soft and granular, the lower portion is hard and stained reddish. It carries many bowlders 6 to 8 inches in diameter, different from any other rock seen in the adjacent mountains: quartzite mica schist, aphanitic rocks, and some granitic ones. These are washed smooth. The sandstones contain much kaolinitic matter, and at one spot show an incipient crystallization. A number of contiguous grains, over a space half an inch in diameter, show the same orientation. Near the bottom the sandstones are impregnated with iron. The western ridge in particular shows a great amount of erosion. The lava is nearly gone in places, but occurs southward in scattered outcrops for half a mile. At the northern end the sandstone rises fully 300 feet above the lava. Lava is present on its sides. Much of the sandstone closely resembles a granite decomposed in situ. Fragments of the mica schist resemble that in the hills west of Temecula. Northward half a mile is the deep cañon of the San Mateo. The country descends very rapidly from the lava ridge, especially so on the north, where the cañon is fully 1,500 feet deep. It is a number of miles in any direction to mountains which are as high as this lava-capped sandstone ridge, and the amount of erosion must have been enormous since it was deposited. Mesa Redonda has an elevation of 2,750 feet, and is separated from the lava just described by a valley fully 800 feet deep, and nearly a mile broad. Mesa Redonda is formed by a lava table, probably basalt, 150 to 200 feet thick. It is quite precipitous on three sides. The lava is bedded, dipping 5° to 8° northeast. Underneath is a body of coarse, friable sandstone, similar to that just described. Some pebbles and bowlders of lava lie in the upper portion of the sandstone. The sandstone consists of angular quartz grains and kaolinic matter, and often presents the appearance as if it had been partly fused by the lava. In the top of the sandstones are pebbles of quartz, feldspar, and mica schist. The sandstone shows no bedded structure, but seems to form a mantle over the hill, following the irregularities of the underlying granite. It descends 700 feet on the southern slope of the mountains which rise so abruptly from De Luz Valley. The lava has spread out in thin sheets on the southern slope of the mountain, descending more than a thousand feet on the east side of Cottonwood Creek. These thin beds are not massive, but are formed of angular lava bowlders. The flows were so thin that they either broke up on cooling, or later through atmospheric agencies. Fig. 15 is a sketch of Mesa Redonda from the north. Cienega Peak lies east of Mesa Redonda and is separated from it by two gulches opening in opposite directions. It has an elevation of 2,400 feet, and the mesas east rise still less. Sandstone underlies this as it. does the other lava flows. Near the eastern end of the southern slope, a lava flow has broken out from a basin-like depression which opens southward, and flowed down the mountain for a mile, descending & vertical distance of 1,800 feet. It appears to have broken up entirely into angular bowlders. The stream was probably very liquid, like the others, and formed a thin flow. It takes a slightly winding course and slopes often 30°. One short branch appears on the western side about half way down, and another on the east near the bottom. The lava descends in successive terraces, like steps, from the crater depression. The width varies from 500 to 700 feet, terminating in a straight line about a hundred feet above the bed of the cañon at the head of De Luz Valley. This distance may represent the amount of erosion since the stream flowed. There are also cañons worn to some depth on each side. The surface of the flow is rounding, and appearances indicate that.it descended over a surface not much different from the one now shown. A large part of the bowlders in the creek for several miles are lava. they flowed. It is possible that the mesas, with the high precipitous cliffs, represent remnants of an older flow, and yet the lithological character of the lava seems to point to a single origin. With the exception of the long southerly flow and another short one west of it, the lava everywhere presents bluffs on its southern side, with deep gulches between them. Toward the northeast and east there is а gentle slope. A large part is coarsely vesicular; dense massive portions are mixed irregularly in places with the vesicular. The lava tablelands lie nearly 2,000 feet above De Luz Valley. This abrupt escarp ment extends east as far as the lava does, though less marked. There has either been an enormous erosion in the region lying south, or a great fault elevating the plateau. A detached portion of the lava plateau caps the hills west of Murrieta, extending in a north and south line for a distance of 2 miles. Whether these detached portions all had their source in one great flow and have been separated by erosion, or were formed from different sources, was not fully determined. It seems probable, however, that the main portions did belong to one flow, from the fact that they have a uniform slope and are underlaid by similar sandstone, which may once have been the bed of a stream. GEOLOGY OF SAN DIEGO, ORANGE, AND SAN BERNARDINO. 105 into deep cañons, which lead down to the coast. A dark dioritic granite is included in the usual light-colored variety, sometimes in bowlder-like masses and sometimes in dike form. The metamorphic rocks extend 2 miles west of Parker Deer's house. They include mica felsite and dark vitreous quartzite. They are often intruded by granite bosses and dikes of quartz porphyry. The lava table-land lies just south of the ranch house. It is about 40 feet thick, and has underneath a kaolinic stratum 12 to 14 feet thick, which is impregnated with bog iron; one assay has shown 10 per cent. This is quite similar to the sandstone under the table-land farther west, but is less quartzose. A similar deposit, impregnated with iron, was seen north of Mesa Redonda. The Santa Rosa grant consists chiefly of broad, open valleys, having an altitude of 1,700 to 1,800 feet, with rocky ridges between them. On the trail from Santa Rosa to Howe Station, the metamorphic rocks extend to within a mile and a half of the latter place. They are chiefly light-colored, granular quartzites. Dikes of diabase and gabbro appear in many places on the Santa Rosa grant, Ores of gold, silver, and copper are found in the metamorphic rocks of the grant, but they have never been developed. Selected samples of galena assay several hundred dollars to the ton in silver. The veins are, however, small and bunchy, and it is not probable that they can be profitably worked. The granite varies from one with mica, as the only dark constituent, to one with much hornblende. It is uniformly coarse and of undoubted eruptive origin, judging from the manner in which it has broken through the metamorphic rocks. The range of mountains lying west of the valley which extends from Temecula to Elsinore, also has the appearance of having been elevated by a fault. From the entrance to the Temecula Cañon, northward past Elsinore, and along the eastern base of the Santa Ana Mountains, these abrupt escarpments and indications of a fault become more pronounced. The eastern part of the Santa Rosa plateau, with its lava fields, forms the southern end of the escarpment. The valley in which are located The table-land west of Murrieta is about a mile broad and fully as the towns of Temecula, Murrieta, and Wildomar, rises gradually toward high as that near Parker Deer's house. the east. The western portion is very fertile. Artesian water is found farther west by a mile of brush-covered hills. The lava was supposed It is separated from the lava at Murrieta. The eastern portion, which rises toward the granite mount- to extend no farther than the big cañon west of Murrieta, but a close ains, is more gravelly, while east of Temescal there is a stretch of many examination revealed a small outcrop on the hills about a mile south of miles of these dry gravel hills, probably of Quaternary age. The town Wildomar. The elevation is about 600 feet above the valley. It is of Temecula has an elevation of 1,000 feet. Immediately west and north perhaps one fourth of a mile across. In places it extends down the hill of the cañon there arise hills of metamorphic rocks, having an elevation nearly one third of its elevation above the valley. It presents the of 1,800 feet. They are covered with dense brush on their eastern appearance of having flowed out of the summit of the hill when it had slopes, but contain some fertile valleys to the west. For several miles much the same form as now, and down over its sloping surface. This the rock is almost wholly matamorphic. It extends south to the cañon eruption is fine-grained, and not vesicular. Much of it has a conand north to the lava plateau. It is chiefly a fine, dark mica schist; glomeritic character, appearing to have been broken up when almost strike indistinct but north 60° west, to east and west, dip vertical. On solid, and then cemented. The fragments are more or less rounded and the west it changes to a quartzite. Dikes of granite cut this rock; one elongated, and are at times almost blended in the matrix. There are is noticeable for several miles by its more pronounced croppings over the signs of former solfataric action on the summit, there being a considerable deposit of a light yellowish material, consisting chiefly of alumina East of Murrieta the granite begins near the boundary of the grant, and magnesia. Under the lava is sandstone 10 to 20 feet thick, comand forms a line of barren hills extending northerly. East of these the posed of quartz grains and kaolinic matter, exactly similar to that under country is less rocky and quite fertile. Many springs abound in the Mesa Redonda. It would be easily taken for granite decomposed in situ, granite through this section. Near the Hot Springs is a dike of granite but for the large quartz grains. The sandstone has an apparent southerly porphyry. Numerous bunches of a dark, coarse, dioritic rock are scat-dip. It is very difficult to account for the presence of the sandstone tered through the light-colored country granite. They weather away under the lava, unless we suppose it covered the adjacent country, and more slowly than the granite. The metamorphic rocks of the Santa was only preserved by the greater permanency of the lava. Another Rosa plateau extend north to the entrance to the cañon, up which the hill of lava was found 200 feet lower, about a mile south of this, and road passes to Parker Deer's. The strike in the cañon is a little east of West of the cañon leading up to Parker Deer's. It occupies a sort of north. The metamorphic rocks terminate in a range of hills which form depression between three hills, with gulches cutting into it between the southern boundary of the Rinconada. Northward the country is them. The lava is very similar to that just described. formed of rugged granite mountains. The Los Alamos opens westward A long, high ridge running northwest and southeast, adjoining the hills. |