THE REEF-CORAL FAUNA OF CARRIZO CREEK, IMPERIAL COUNTY, CALIFORNIA, AND ITS SIGNIFICANCE . .By THOMAS WAYLAND VAUGHAN . INTRODUCTION. occur has been determined by Drs . Arnold and Dall to be lower Miocene . The following conclusions seem warranted : Knowledge of the existence of the unusually (1) There was water connection between the Atlantic and interesting coral fauna here discussed dates Pacific across Central America not much previous to the from the exploration of Coyote Mountain (also upper Oligocene or lower Miocene-that is, during the known as Carrizo Mountain) by H . W. Fair- upper Eocene or lower Oligocene . This conclusion is the same as that reached by Messrs. Hill and Dall, theirs, how- banks in the early nineties.' Dr. Fairbanks ever, being based upon a study of the fossil mollusks . (2) sent the specimens of corals he collected to During lower Miocene time the West Indian type of coral Prof. John C. Merriam, at the University of fauna extended westward into the Pacific, and it was sub- California, who in turn sent them to me . sequent to that time that the Pacific and Atlantic faunas There were in the collection representatives of have become so markedly differentiated . two species and one variety, which I described As it will be made evident on subsequent under the names Favia merriami, 2 Stephano- pages that this fauna is much younger than ctenia fairbanksi,3 and Stephanoccenia fair- lower Miocene, the inference as to the date of banksi var. columnaris .4 As the geologic hori- the interoceanic connection given in the fore- zon was not even approximately known at that going quotation must be modified . time, I gave it as "doubtfully Cretaceous" in After receiving the specimens from Dr . Bow- the paper cited . ers and recognizing the need of more careful Late in 1903 Dr. Stephen Bowers sent to me geologic studies in the Carrizo Creek area, I for examination a small collection of fossils brought the matter to the attention of C . W. obtained by him in the Carrizo Creek area dur- Hayes, then chief geologist of the Survey, and ing June and July, 1901 .5 This collection con- in January, 1904, arrangements were made for tained corals whose affinities are undoubtedly an expedition to the region, in charge of W . C. with Pliocene, Pleistocene, and Recent species Mendenhall, who was accompanied by Dr . of the western Atlantic region, and not with Bowers. Mr. Mendenhall conducted the phys- any known living Indo-Pacific fauna . The fol- iographic and stratigraphic studies and Dr . lowing statement was made in a paper based on Bowers made a large collection of fossils . this collection .' As it was my intention to publish promptly In the collection that has so far been made from the an account of the fossil corals, I furnished to California fossil reef five genera are represented, all of Ralph Arnold, for publication in his paper which occur in the fossil and recent faunas of the Antilles entitled "The Tertiary and Quaternary pectens and not one of which is at present known to occur on . the of California," 7 a list which contained three Pacific coast . The age of the beds in which these fossils nomina nuda, but other duties prevented my I California State Min. Bur. Eleventh Ann. Rept., pp . 88-9.0,1893 . completing a report until the summer of 1916 . s Vaughan, T. W ., The Eocene and lower Oligocene coral faunas of the United States : U . S . Geol . Survey Mon. 39, p . 142, p1 .15, figs. 5,5a, 5b, 5c, The list furnished and published was based oil 1900. the collection submitted by Dr . Bowers before Idem, p . 151, pl . 17, figs . 11, lla. he made the expedition with Mr . Mendenhall. 4 Idem, pp . 151, 152, pl. 17, figs . 10, 10a. ' A brief report on his field observations was made by Dr . Bowers in It is given in the first column of the list on . an article entitled "Reconnaissance of the Colorad9 Desert mining The second column gives the names district," 19 pp., California State Min . Bur ., 1901 . page 356 . 6 Vaughan, T . W ., A Californian Tertiary coral reef and its bearing on applied in this paper . American recent coral faunas : Science, new sor., vol. 19, p . 503, Mar. 24, 1904. 7 U . S . Geol . Survey Prof. Paper 47, p. 22, 1906 . 355 356 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1916 . Fossil corals from Carrizo Creek, Cal . some of the photographs. The illustratio,14 Name in Prof. Paper 47, p . 22 . Revised name. showing the geologic conditions under which Diploria bowersi Vaughan Mmandra bowersi Vaughan . the fossil corals occur are reproductions of (MS. ). photographs taken by Mr. Mendenhall, and Favia merriami Vaughan. Dichoceenia merriami I am making extensive quotations from hi,; (Vaughan) . article entitled "Notes on Plesiastrea c a l i f o r n i c a Solenastrea f a i r b a n k e i the geology Of Vaughan (MS.). (Vaughan) . Carrizo Mountain and vicinity, San Diego Siderastrea californica Siderastrea c a l i f o r n i c a County, Cal ." I Vaughan (MS .) . Vaughan. Stephanoccenia fairbanksi Solenastrea f a i r b a n k e i GEOGRAPHIC RELATIONS. Vaughan . (Vaughan) . Stephanoccenia fairbankei Solenastrea fairbanksi var . The accompanying sketch map (fig. 43) f, var . columnaris Vaughan . columnaris (Vaughan) . taken from the article by Mr . Mendenhall, who corals were FIGURE 43.-Sketch map of Coyote Mountain, Cal., and vicinity, showing localities in Alverson and Barrett canyons where fossil collected . (After Mendenhall.) Messrs. Mendenhall and Bowers shipped to gives the following graphic description of the Washington over 400 specimens of corals, and general geographic relations : it is on this large collection that the present Black and Carrizo mountains, known also as Fish Creek bp paper is mostly based . All the photographs of and Coyote mountains, are eastern outliers of the Penmsu Range that separates the depression occupied in corals herein illustrated were made by Mr . W. pan am the Gulf of California from the Pacific Ocean. 0. Hazard, except those for Plate XCIX, which e the were contributed by Dr . Charles Gravier, of in southeastern California near the western a dge Paris. Miss Frances Wieser has retouched REEF-CORAL FAUNA OF CARRIZO CREEK, IMPERIAL COUNTY, CAL . 357 Colorado Desert and from 15 to 30 miles north of the inter- representatives in this region . Either the Carrizo and national boundary. East of them the Colorado Desert, Black Mountain areas were land masses subject to erosion much of it below sea level, extends to the Colorado River, during this interval or the evidence of such periods of while to the west low ridges extend to the base of the main deposition as intervened was later removed by erosional Peninsula Range . processes . The two masses are separated by the valley of Carrizo The Miocene seems to have been inaugurated by vol- Creek . This stream rises in Mexico, flows north for several canic activity . On the southern slopes of both Carrizo and miles, through a high valley in the Peninsular Mountains, Black Mountains are bedded tuffs, volcanic conglomerates, then descends to the desert level through a precipitous and less extensive masses of dark lavas of andesitic aspect . canyon . Nearly all of that part of its channel that lies On Black Mountain there are distinct sandstones inter- within the desert is dry except during rare flood periods, bedded with these and directly upon them lie the Miocene when its waters join those of San Felipe Creek, north of coral reefs . In Alverson Canyon, which drains south from Black Mountain, and eventually reach the Salton depres- Carrizo Mountain, red vesicular lavas are succeeded by sion . At Carrizo Station, one of the relief stations of the green and lavender sandstones and conglomerates, whose old Butterfield stage line, a series of springs rise, and for 1 constituent materials are volcanic, and these in turn grade to 2 miles below this point flowing water is found in the into conglomerates with a diminishing proportion of vol- creek bed except during the hottest period of summer. canic pebbles . Above them are quartz conglomerates, The desert floor at the eastern base of the peaks is gen- tawny sandstones, and finally soft greenish-yellow clay erally from 100 to 200 feet above sea level, but on the north shales . side of Black Mountain the sea-level contour and the old An unconformity which is not especially conspicuous beach of Lake Cahuill'a, 40 feet above sea level, swing exists in the Miocene between the sandy shell-bearing in against the mountain base. In the past the region beds, 100 feet or less in thickness, which immediately over- has been rather difficult of access because of its remoteness from settlements and its aridity . With the colonization of the Imperial Valley since 1900 and the building of the branch railroad from Old Beach to Calexico, however, this PLEISTOCENE MIOCENE PALEOZOIC condition has been greatly modified . Now Carrizo Station or Coyote ONE,? 9llhLa1j Alluvium Shale Sandstone Tuff Limestone with Well may be reached by one day's F7 and conglomerate intrusive granites, both metamorphosed drive from Imperial or El Centro, FIGURE 44 .-Diagrammatic section across Coyote Mountain, Cal., by way of Alverson and Garnet and supplies are readily secured at canyons . (After Mendenhall .) many points in the valley . The old roads from the desert to San Diego, the one running lie the volcanics or the metamorphics, and the great mass north of Carrizo Mountain byway of Julian and the other of shales, greenish or yellowish at base, pink or pale red in south of the mountain by way of Jacumba and Campo, general color tone toward the top, which form the badland are still much used for direct communication between area that is especially well developed between Black and the Imperial Valley and the coast, although the Campo Carrizo mountains .