refrain from killing more than he needs, for these birds are few in number near the desert water holes. Each open body of water, such as the ponds at Quitobaquito, Comovo, Tonukvo, and Buenos Aires, has its share of water fowl. Geese, mallard, and teal duck and the inevitable mud hen were seen on such ponds. Doubtless all these were migrants breaking a long journey at these spots of water on the desert. Of poisonous and venomous animals the desert has its full share. but the number of these animals as well as their deadliness is much exaggerated.41 The rattlesnake is one of the most widely distributed and well advertised poisonous animals of North America. The diamond-back, which includes several species, and the sidewinder, or horned rattlesnake, are found in the Papago country. The sidewinder is small, from 2 to 212 feet in length, and somewhat more active and therefore more to be feared than the other rattlers. Ordinary travelers will, however, seldom see rattlesnakes unless they ramble around in the brush or in rocky places. The bite of a rattlesnake is serious but seldom fatal, except to children and persons in poor health. Proper treatment consists in placing a ligature between the wound and the heart, opening the wound so that the blood will flow freely and if necessary sucking out the blood, and then washing the wound with a strong solution of potassium permanganate. The annulated snake (Libon septentrionalis), a slender snake 21⁄2 feet long, is rarely found. It can not strike but if provoked will seize a finger and embed its poisonous fangs. The Sonoran coral snake (Elaps euryxanthus) is a slender snake, less than 2 feet long, marked with yellow and black bands encircling the body, the black bands being bordered by the yellow, thus distinguishing it from the harmless king and milk snakes, which have black bands between either yellow or red bands. The coral snake has a poison much more deadly than that of the rattlesnake, but it can not strike and must chew in order to insert the fangs. It is said not to bite unless handled. This snake also is rarely found. The Gila monster, a big clumsy lizard, and a similar species in Mexico are the only poisonous lizards known. All the others, however horrible in appearance, are nonpoisonous. The Gila monster is sluggish and difficult to annoy but has a brutish temper and a grip like a bulldog. From around the teeth in the lower jaw poison is excreted which will get in the wound. The bites are fatal to small animals, but there is no recorded case of a human fatality. The "hydrophobia skunk" is more or less of a myth, but it seems true that skunks of all species are subject to rabies or hydrophobia. 41 Vorhies, C. T., Poisonous animals of the desert: Arizona Univ. Agr. Exper. Sta. Bull. 83. 1917. Much of the material here given is drawn from this useful paper. When suffering from the disease they will bite persons sleeping in exposed places and give them the disease. Persons bitten by skunks are advised by Vorhies 42 to take the Pasteur treatment for rabies. The tarantula, a large hairy spider, the scorpion, and the centipede are all poisonous, but their bites or stings are only painful, not deadly. The traveler should shake out his boots in the morning, inspect his blankets before lying on them, and use other reasonable measures to avoid the discomfort of being bitten. Fear is not justified, for no authenticated fatalities among healthy adults have been reported from the desert country. The "niño de la tierra" (child of the earth), which has an evil reputation among the Mexicans, is a burrowing and wingless insect very like a grasshopper and as dangerous. The "velvet ants" or "cow killers" differ from the ants in being hairy and are actually wingless wasps. In the Papago country a red species three-eighths of an inch long is common. Their stings are doubtless no more dangerous than those of ordinary wasps, and they are not nearly so warlike. The praying mantis, common also in the eastern United States, is called "campamocha" by the Mexicans and is thought, without foundation, to bring about the death of any horse or cow that may accidentally eat it. The "mato venado," or killdeer, is also called vinegarroon-a name correctly used only for the scorpion. It is about 1 inch long and resembles a scorpion, though it has no sting but four pointed jaws. It can give a severe bite but is nonpoisonous, though suspected of being a disease carrier. Similarly the Arizona bedbug, or cone-nose bloodsucker, is from half an inch to an inch long, and though apparently harmless, its bite should be avoided for the same reasons as the bite of the ordinary bedbug. Some of the South American relatives of the bedbug are known disease carriers, and the ordinary bedbug is not above suspicion. GEOLOGY The rocks of the Papago country consist of pre-Cambrian schist, gneiss, and intrusive rocks, Paleozoic limestone and quartzite, Mesozoic clastic rocks and granitic intrusives, Tertiary conglomerate and volcanic rocks, and Quaternary alluvium. The pre-Cambrian rocks are a basal complex whose history is as yet unraveled and which is separated by a great unconformity from the succeeding rocks. The Paleozoic rocks now exist as scattered Vorhies, C. T., op. cit., pp. 368–373. patches infaulted into the pre-Cambrian or embedded in later Mesozoic intrusive rocks. The Mesozoic clastic rocks are arkosic sandstone and shale, which are separated from the Paleozoic limestone and quartzite by an unconformity. The Mesozoic igneous rocks occupy large areas, but the granitic intrusives and more or less metamorphosed lava flows are not easily distinguished from the preCambrian, and the undifferentiated rocks of both ages are referred to as the crystalline complex. The Tertiary conglomerate and lava flows are separated from all the rocks previously formed by an unconformity that represents a desert surface in the old age of erosion. The pre-Tertiary and Tertiary rocks form the mountains and hills, but in the valleys lies a great mantle of alluvium, composed of débris derived from the destruction of the older formations. The general distribution of these rocks is shown on the geologic map (Pl. IX, in pocket) and is more particularly described below. PRE-CAMBRIAN BASAL COMPLEX 42a The pre-Cambrian rocks of the region form a highly metamorphosed complex consisting largely of schist and gneiss. No sequence of pre-Cambrian sedimentary rocks such as have been found north of Gila River has yet been determined, but doubtless some of the schist and gneiss are metamorphosed sedimentary rocks. In the northern part of the Salt River Mountains the complex is mostly chloritic schist. In the Sand Tank Mountains chloritic schist has been feldspathized, and there are many transitions from schist to gneiss. Fine-grained biotite granite and phyllite occur also. The northern parts of the Gila Mountains are composed mostly of coarse biotite granite and micaceous and hornblende schist and gneiss. As noted by Blake," near the Fortuna mine the schistosity dips 45° to the south and west and is very even and regular. There hornblende schist predominates, and parallel to the schistosity are quartzose beds in which gold occurs. Blake noted also feldspathic dikes that intersect the schistosity and seem to be connected with great intrusions of pinkish granite, which form the higher peaks. The older gneisses, which are of pre-Cambrian age, in many localities have a very definite sheeting that divides them into layers 42 This geologic map was made in 1917 and first published in 1922 (U. S. Geol. Survey Bull. 730, pl. 9). Equipped with a manuscript copy of it, the authors of the recently published geologic map of Arizona (Darton, N. H., Lausen, C., and Wilson, E. D., Geologic map of Arizona: Arizona Bur. Mines and U. S. Geol. Survey, 1925) did field work in 1921 and the following years that resulted in a new base map on the scale. The geologic boundaries were adjusted to this map and the gaps filled in. Areas of Paleozoic and Mesozoic stratified rocks were discovered and mapped, and the crystalline complex was divided into three parts-pre-Cambrian schist, pre-Cambrian granite, and Mesozoic granite. The later, more basic lava flows of the faulted and dislocated volcanic series, here considered of Tertiary age, were mapped separately and placed with the Quaternary basalt. Ross, C. P., Geology of the lower Gila River region, Ariz. U. S. Geol. Survey Prof. per 129, pp. 184-185, 1922. Blake, W. P., Geology of the Gila Range: Governor of Arizona Rept., 1898, p. 25. from 2 to 4 feet thick. Such gneisses, which are easily distinguished from the later intrusive rocks of supposed Mesozoic age, were observed near Tule Tank, in the Cabeza Prieta Range, and in the Baker Peaks, Sierra Blanca, and Coyote Mountains. In the Coyote Mountains the almost perfect sheeting controls the erosion of the mountain range, which has the topographic form of a monoclinal block of sedimentary rock. PALEOZOIC ROCKS 45 The Paleozoic rocks occur in two situations-as plates or blocks resting on the eroded surface of the pre-Cambrian complex, or as blocks more or less engulfed and metamorphosed by later intrusions. In the western part of the Tucson Mountains, beneath a blanket of lava, mostly Tertiary rhyolite, lie limestone and quartzite of Cambrian and Carboniferous age. At Snyders Hill, just west of Robles Pass, blue limestone has been quarried for burning lime, and also for road metal. Fossils collected at this locality have been identifed by G. H. Girty as follows: Zaphrentis? sp. Pustula aff. P. porrecta. Productus aff. P. subhorridus. 46 Rhynchopora?n. sp. Mr. Girty considers that this fauna is probably younger than that found at the Vekol mine and indicates later Pennsylvanian, perhaps even Permian time. South of this locality, on the east side of the Sierrita Mountains, limestone and quartzite, in which Pennsylvanian fossils were found, occur at Mineral Hill and Twin Butte.47 The ore deposits of Silver Bell occur in blocks of limestone embedded in post-Paleozoic intrusive rocks.48 In the near-by Silver Bell Mountains Tolman 9 found 3,700 feet of alternating quartzite, shaly quartzite, and limestone, of which the massive limestone contains Carboniferous fossils. North of Pozo Blanco, at the east foot of the Sierra Blanca, the galena ore of the Black Prince mine is found in blocks of blue limestone which, with some red shale, are embedded in intrusive rocks. No fossils were found at this locality. Tolman, C. F., The geology of the vicinity of the Tumamoc Hills: Carnegie Inst. Washington Pub. 113, p. 76, 1909. "Blake, W. P., Geologic sketch of the region of Tucson, Ariz.: Carnegie Inst. WashIngton Pub. 99, pp. 45-68, 1908. Jenkins, O. P., and Wilson, E. D., A geological reconnaissance of the Tucson and Amole mountains: Arizona Univ. Bur. Mines Bull., Geol. ser. 2, p. 11, 1920. Ransome, F. L., Ore deposits of the Sierrita Mountains, Pima County, Ariz.: U. S. Geol. Survey Bull. 725, p. 412, 1922. Stewart, C. A., The geology and ore deposits of the Silver Bell mining district, Ariz.: Am. Inst. Min. Eng. Trans., vol. 43, pp. 240-290, 1913. Tolman, C. F., Copper deposits of Silverbell, Ariz.: Min. and Sci. Press, vol. 99, pp. 710-712, 1909. The northern part of the Vekol Mountains consists of a monocline of limestone, quartzite, and shale, extending from the Vekol mine to the Reward mine. These sedimentary rocks rest on a basal complex of schist, granite, and diorite and have been faulted and intruded by granitic masses and later siliceous porphyry dikes and plugs.50 On the south side of the monocline, near the Vekol mine, fossils were collected in three lots from a thickness of about 200 feet of thick-bedded gray limestone. The surface of this limestone is marked by brown siliceous concretions, and the lower beds are cherty. Near the mine the same limestone is red. The fossils were submitted to G. H. Girty, who reports the following combined list: Cladochonus sp. Campophyllum torquium. Rhombopora lepidodendroides. Schizophoria? sp. Chonetes verneuilianus. Productus semireticulatus. Spirifer cameratus. Spirifer rockymontanus. Mr. Girty states that the beds are "Pennsylvanian, apparently lower Pennsylvanian." They thus correspond in age to the lower part of the Naco limestone of the Bisbee district.51 About 14 miles northwest of the Vekol mine and 3 miles east of Stouts Well is a small hill composed of massive gray limestone, which dips gently to the southeast. About 100 feet of limestone is exposed. This mass appears to be an infaulted fragment of the great limestone series exposed in the Vekol Mountains. A few fossils were collected and submitted to Edwin Kirk, who reports as follows: There are no determinable fossils in the lot that definitely fix the stratigraphic horizon. The crinoid fragments, however, are of such a nature that they could not be older than Devonian nor younger than Carboniferous. There is little doubt in my mind that the material is of Carboniferous age. West of this hill only one other outcrop of limestone was found. At the east side of Growler Pass is a high, irregular hill composed of limestone and quartzite which appear to have been mashed and the limestone later silicified. Because of this alteration fossils seem to be rare; none were found by the writer in the short time available. The remnants of Paleozoic rocks occurring at widely scattered places in the Papago country indicate that the Paleozoic seas were limited on the west by land. The Cambrian and Devonian rocks. extend no farther west than the Santa Rita and Tucson mountains; the later Paleozoic (Pennsylvanian) has a wider extent. Earth movements following the Paleozoic era, with consequent erosion, con 50 Higgins, Edwin, Vekol copper deposits (Pinal County, Ariz.): Eng. and Min. Jour., vol. 91, pp. 473-474, 1911. 1 Ransome, F. L., Some Paleozoic sections in Arizona and their correlation: U. S. Geol. Survey Prof. Paper 98, p. 148, 1916. |