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USGS1951

Stratigraphic sections of the Phosphoria formation in Idaho, 1947-48, Part III

.The U.S. Geological Survey has measured and sampled the Phosphoria formation at many localities in Idaho and other western states. These data will not be fully synthesized and analyzed for several years but segments of the data, accompanied by little or no interpretation, are published as preliminary reports as they are assembled. This report, which contains abstracts of many of the sections in southeastern Idaho (fig. 1), is one of this series and is the third report of data gathered in Idaho during 1947 and 1948. The field and laboratory procedures adopted in these investigations are described rather fully in a companion report (McKelvey and others, 1953). Many people have taken part in this investigation, which was organized and supervised by V. E. McKelvey. D. A. Bostwick, R. M. Campbell, R. A. Gulbrandsen, R. A. Harris, R. L. Parker, R. A. Smart, J. E. Smedley, R. H. Thurston, and R. G. Waring participated in the description of strata and collection of samples referred to in this report. D. B. Dimick, Jack George, W. S. Hunziker, J. E. Jones, H. A. Larsen, and T. K. Rigby assisted in the preparation of trenches and collection, crushing, and splitting of samples in the field. The laboratory preparation of samples for chemical analysis was done in Denver, Colo., under the direction of W. P. Huleatt.

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USGS1948

Monazite in concentrations from Idaho placer operations

During the summer of 1947 the Atomic Energy Commission informally requested the Geological Survey collect sampled of concentrates from Idaho placer operations that might be useful for experimental study of monazite recovery. Some fourteen active gold-dredging operations were examined and sampled by Fred M. Chase during August and September 1947.

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USGS1948

Discharge and sediment loads in the Boise River drainage basin, Idaho 1939-40

The Boise River project is a highly developed agricultural area comprising some 520 square miles of valley and bench lands in southwestern Idaho. Water for irrigation is obtained from the Boise River and its tributaries which are regulated by storage in Arrow Rock and Deer Flat reservoirs. Distribution of water to the farms is effected by 27 principal canals and several small farm laterals which divert directly from the river. The- New York Canal, which is the largest, not only supplies water to smaller canals and farm laterals, but also is used to fill Deer Flat Reservoir near Nampa from which water is furnished to farms in the lower valley. During the past 15 years maintenance costs in a number of those canals have increased due to deposition of sediment in them and in the river channel itself below the mouth of Moore Creek. Interest in determining the runoff and sediment loads from certain areas in the Boise River drainage basin led to an investigation by the Flood Control Coordinating Committee of the Department of Agriculture. Measurements of daily discharge and sediments loads were made by the Geological Survey at 13 stations in the drainage basin during the 18-month period ended June 30, 1940. The stations were on streams in areas having different kinds of vegetative cover and subjected to different kinds of land-use practice. Data obtained during the investigation furnish a basis for certain comparisons of runoff and sediment loads from several areas arid for several periods of time. Runoff measured at stations on the. Boise River near Twin Springs and on Moore Creek near Arrow Rock was smaller during 1939 than during 1940 and was below the average annual runoff for the period of available record. Runoff measured at the other stations on the project also was smaller during 1939 than during 1940 and probably did not exceed the average for the previous 25 years. The sediment loads measured during the spring runoff in 1939 were smaller at most stations than those measured during the spring runoff in 1940. At those stations where the flow was not affected, or only slightly affected, by upstream diversions or by placer-mining operations, the largest sadiment loads per unit of drainage area were measured in Grouse Creek during both 1939 and 1940, amounting to 3,460 and 2,490 tons per square mile, respectively, and the smallest loads per unit of drainage area were measured in Bannock Creek during 1939 and in the Boise River near Twin Springs during 1940, amounting to 14 and 83 tons per square mile, respectively. Size anaylses of a large number of samples of suspended and deposited sediments give an indication of the origin of sediments carried past some of the stations. The analyses show that most of the sediment measured at the five stations in the Moore Creek drainages basin above Idaho City consisted largely of coarse material. They show, also, that the sediment measured at the station on Moore Creek above Thorn Creek consisted almost entirely of fine material during practically the entire period of the investigation. Most of the coarse material passing the stations above Idaho City probably was retained behind the dikes or in the pools usually formed by tailings from dredging operations in the placer-mining area below Idaho City, and much of the fine material measured at the station on Moore Creek above Thorn Creek probably was contributed by placer-mining activity. During the years when the spring runoff is greater than that measured during 1939 and 1940, it is probable that the dikes and pools will be less effective in retaining coarse sediments within the placered area. Records of sediment loads measured in the New York Canal indicate that a negligible amount of sediment was deposited there during 1939, but that in 1940 from 10 to 15 percent of the total load at the gaging station consisted of coarse sediment which was later deposited on the canal bottom. Most of the fine material was doubtless carried through the canal and eventually deposited in diversion ditches and on farm land. Because the sediment carried past the station on Moore Creek above Thorn Creek consisted almost entirely of fine material, it is probable, that a considerable part of the coarse sediment carried in the New York Canal during the 1940 spring runoff period was scoured from the large bed of deposited material in the Boise River above Diversion- Dam, and that the remainder came from Grimes Creek. Arrow Rock Reservoir was not sluiced during the investigation, and it is therefore unlikely that any of the coarse sediment in the New York Canal came from the Boise River above Moore Creek during 1939 and 1940. The average dry weight of 71 samples of deposited sediments collected from several parts of the Boise River drainage basin is about 90 pounds per cubic foot. The average specific gravity of 77 samples of deposited sediments is 2.57.

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USGS1947

Geology of the Borah Peak quadrangle, Idaho

This report is on result of a long program of geologic investigation in south-central Idaho, undertaken as an aid in the development of the mineral resources of the region. This quadrangle was examined because of the exceptional opportunities for the study of stratigraphy and structure afforded by the Lost River Range, which is the highest in Idaho and contains comparatively few intrusive igneous rocks. The Borah Peak quadrangle differs from the region to the west and northwest in that it contains parts of two sharply defined, narrow ranges elongated in a north-westerly direction, instead of broad, irregular mountain masses, in which the trends of most local topographic units are ill-defined. These ranges, the Lost River and the Lemhi, are flanked by intermontane valleys sparsely populated by stock ranchers. The Lemhi and Swauger quartzites, regarded as of Belt (pre-Cambrian) age, are named. The two Cambrian (?) formations of the Bayhorse region are not recognized in this quadrangle. The Ramshorn slate (Lower Ordovician), widespread and thick there, does not appear to be exposed anywhere in the Borah Peak quadrangle with the possible exception of small areas east of the Elkhorn Ranch, where relations are obscure. The higher Paleozoic formations, named in order of decreasing age, are the Kinnikinic quartzite, Saturday Mountain formation, Laketown dolomite, Jefferson dolomite, Grand View dolomite, Three Forks limestone, Milligen formation, Brazer limestone, and Wood River formation. The Three Forks limestone, nowhere much over 250 feet thick, is the only one of these not recognized farther west. It provides substantial aid in the interpretation of upper Paleozoic stratigraphy. Equivalent beds to the west are presumably grouped with the Milligen. The grit that introduced uncertainties into the correlation of the Wood River and Milligen formations in the southeastern part of the Bayhorse quadrangle is absent here, and both formations have close lithologic resemblances to those in the type localities in the Wood River region. Wood River strata (Pennsylvanian) crop out only in the southwest corner of the quadrangle, and the Brazer may have been the last Paleozoic unit to be deposited over most of the area. Certainly it can have had comparatively little cover over it throughout the Mesozoic. The Brazer is regarded as Mississippian, but some of the fossils in it have Pennsylvania affinities. The carbonate rocks in the Three Forks and later formations are dominantly calcareous, while those in earlier units are dolomitic. Carbonaceous matter is present in most of the formations but is abundant only in the Milligen. The Challis volcanics (Oligocene or Miocene) constitute the first stratified unit to be laid down after Paleozoic deposition ceased, although there was a little intrusive activity late in the Mesozoic. The volcanics were once widely distributed on the flanks of the mountains and are still plentiful in the northwestern corner of the quadrangle, near the head of the valley of the Pahsimeroi, and in smaller areas. They are neither so abundant nor so diversified as they are farther west. They are locally succeeded by an alluvial formation, here termed the Donkey fanglomerate, of possible Pliocene age. Abundant Quaternary glacial and alluvial deposits are present in the larger valleys. The Lemhi and Swauger quartzites were broadly folded before Paleozoic sedimentation began. Apparently the later deformation affected them only enough to render the more impure beds somewhat schistose. The Paleozoic rocks have been folded into closely spaced, asymmetric anticlines, locally broken by thrusts at and near their crests. These folds approximately parallel the trends of the present range, whereas those in the old rocks strike more nearly north. Later deformation twisted some of the folds and produced thrusts of lower dip and greater extent. The folded rocks in the Lost River Range have been arched into an anticlinorium. The original, tight folds may have preceded the emplacement of the Idaho batholith farther west, while the anticlinorium and the late twists and low thrusts result from deformation during the long period in which the batholith came to place and adjusted itself. Local intricately contorted beds in the Brazer limestone are interpreted as the effects of flowage in calcareous material subjected to tangential pressure under comparatively light supercumbent load. The quadrangle contains numerous normal faults of diverse trends. Most of those that can be conclusively demonstrated strike transverse to the trends of the ranges, but especially along parts of the southwest front of the Lemhi Range normal faults along the range fronts may have helped locally to guide erosion of the mountains. Some of the faults have displacements of thousands of feet and are thought to have originated in connection with the low-angle thrusts. Most of these, as well as minor breaks of diverse trends, affect also the Challis volcanics, which shows that renewed movement occurred in Tertiary time. The present mountain masses and broad intermontane valleys are in about the positions occupied by similar features in the early Tertiary. Several incomplete erosion cycles since then have greatly modified the topography but have not obliterated the influence of these ancient land forms. The results of early episodes in the development of the topography are much obscured by the rugged forms that result from active Pleistocene glaciation and later vigorous stream erosion, but modified remnants of the post-Challis and Donkey Hills surfaces can be clearly distinguished. Several less widespread remnants mark intermediate steps in the process. Exceptionally abundant and permeable, coarse alluvial and glacial deposits floor intermontane valleys and choke the larger mountain gorges to such an extent as to interfere with normal erosion and make the surface-water supplies even scantier than might be expected from the climate of the region, which is moderately humid in the mountains and semiarid in the valleys. Active erosion in the high mountains and comparatively static conditions on fans at the range borders result in striking contrasts.

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USGS1947

Geology of the lead-silver deposits of the Clark Fork district, Bonner County, Idaho

This report gives the results of a reinvestigation of the lead-silver deposits of the Clark Fork district, Bonner County, Idaho, which since the late twenties have been the most important producers of lead-silver ore in northern Idaho outside of the Coeur d'Alene district, their production up to the end of 1941 having been more than $1,200,000. The deposits closely resemble those in the Coeur d'Alene district. They are fillings and replacements along minor low-angle thrust and high-angle reverse faults, which genetically are related to the Hope fault, a great transverse earth fracture, which provides the same sort of structural background for this district that the famous Osburn fault does for the Coeur d'Alene district. The deposits are contained in the Wallace and Striped Peak formations, members of the pre-Cambrian Belt series, and are closely associated with faulting and igneous activity that is probably of early Tertiary age. The mineralization has not been so extensive as in the Coeur d'Alene district, but the deposits, though comparatively small, are rich. Much of the ore is in compact seams and lenses a few inches thick, but stringers of ore and subordinate fractures along which grains of sulfide are disseminated extend across zones that are commonly 2 to 4 feet and exceptionally as much as 8 feet in width. The ore is mainly sulfide ore of the Coeur d'Alene type, consisting dominantly of galena, which is accompanied by lesser quantities of siderite, quartz, and sphalerite and by still smaller quantities of pyrite, arsenopyrite, tetrahedrite, and calcite. Some of the deposits, however, have been substantially enriched by the addition of hypogene silver and antimony minerals, so that much of the ore being mined has a higher silver content than any of that in the Coeur d'Alene district. The hypogene minerals include lead sulfantimonites and sulfarsenites, copper-lead sulfantimonites, and ruby silver. These minerals are absent from only one of the mines, and in one of the mines they form the bulk of the ore that is now being taken out. The high silver content of some of the ore is due in part to the presence of pyrargyrite (3Ag2S.SbS:4). The deposits apparently were formed at moderate depths and at moderate temperatures. It is believed that the ore will persist to depths appreciably greater than those yet reached in mining. The district has not yet been adequately explored, and undiscovered ore bodies may remain hidden beneath glacial and other surface debris.

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USGS1947

Cobalt-copper deposits of the Blackbird district, Lemhi County, Idaho

The Blackbird district is in east-central Idaho, about 20 miles west-southwest of Salmon. The area is one of deeply weathered, flat-topped upland surfaces cut by several steep-walled valleys, which are tributary to the canyon of Panther Creek. Most of the area has a heavy vegetative cover and outcrops are relatively scarce except in the walls of the steeper valleys. The rocks of the district consist mostly of metamorphosed sedimentary rocks of the pre-Cambrian Yellowjacket formation (Belt series); a part of the Cretaceous Idaho batholith cuts across the northern part of the district, and acid porphyry dikes and metamorphosed basic rocks cut the Yellowjacket rocks. Structurally, the sedimentary rocks are divided by faults into three, roughly north-south blocks. The center one (Blackbird structural block) appears to have been more tightly squeezed than the others into relatively tight folds, with the development of widespread schistosity (flow cleavage). The rocks of the two outside blocks are in more open folds. In general they are nonschistose, except for the north end of the western block, where there are schistose rocks cut by several north-dipping thrust faults. The northern parts of the central and western blocks contain considerable garnet, chloritoid, and cordierite. The Blackbird structural block is cut by a number of mineralized shear zones. Those dipping moderately northeast and striking northwest, and those dipping steeply and striking north and northeast; appear to be most important. The mineralized rock contains chalcopyrite, cobaltite, pyrite, and pyrrhotite into a gangue of quartz, biotite, tourmaline, ankerite, and muscovite; the deposits were formed mostly by replacement of the shear zones. In addition, the block is cut by north-dipping thrust faults of west to northwest strike, and a number of high-angle faults. The district was first prospected about 1893; considerable developmont was done at the Brown Bear mine in 1899-1902, at the Haynes-Stellite in l917-1920, and at the Uncle Sam mine in 1938-1941, During World War II, the U.S. Bureau of Mines explored in the district with bulldozer and diamond drill., and the U.S. Geological Survey mapped the district and logged the drill cores. The Howe Sound Co. also did some diamond drilling in the district, and in 1945 the Calera Mining Co., Blackbird Division (subsidiary of Howe Sound Co.), started underground development at the Calera adit. Although the district has had very little production to the present, it is believed that a large tonnage of copper-cobalt ore exists in the district which should permit mining to be continued over a long period. The report contains brief descriptions of all the accessible workings in the district, of which the most important are Calera, Brown Bear, Uncle Sam, and Hawkeye mines. In the Calera adit, about 1,700 feet of the mineralized zone, ranging in width from 3 feet to 40 feet and averaging about 15 feet; have been explored (August 1946); the zone lies on a wide northwest-striking shear zone dipping moderately ( 60° ±) northeast. The Brown Bear adit is in a wide, mineralized, north-south shear zone in which are higher-grade pods plunging 25° to 35° north. The Uncle Sam mine explores a relatively narrow north-south shear zone in which are two or three north-plunging ore shoots. The Hawkeye mine is in a broad zone of mineralized schist in which are several north-plunging lenses of ore.

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USGS1934

Geology and ore deposits of the Casto quadrangle, Idaho

The study of the Casto quadrangle was undertaken as the first item in a project to obtain more thorough knowledge of the general geology of southcentral Idaho on which to base study of the ore deposits of t he region. The quadrangle conta ins fragmentary exposures of Algonkian and Paleozoic sedimentary rocks, extensive deposits of old volcanic strata, presumably Permian, not heretofore recognized in this part of Idaho, and a thick succession of Oligocene(?) lava and pyroclastic rocks. The Idaho batholith and its satellites extend into the quadrangle, and in addition there a re large masses of Tertiary granitic rock, not previously distinguished in Idaho, and many Tertiary dikes, some of which are genetically associated with contact-metamorphic deposits. The area contains injection gneiss of complex origin, largely related to the Idaho batholith but in part resulting from injection by ~he Tertiary granitic rocks under relatively light load. Orogenic movement took place in Algonkian, Paleozoic, and Tertiary time. There is a summit peneplain or par tial peneplain of Tertiary, perhaps Pliocene age, and the erosional history since its elevation has been complex. The ore deposits include lodes and placers. The lodes are related to both the Idaho batholith and the Tert iary intrusive rocks and have yielded gold and copper ore of a total value of about 1,000,000. Placers, largely formed in an interglacial inter val, have yielded about an equal amount. There has been some prospecting but almost no production since 1916.

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USGS1927

A manganese deposit of Pleistocene age in Bannock County, Idaho

Reports of the discovery and exploration of manganese deposits in southeastern Idaho within recent years having come to the Geological Survey, the writer took advantage of an opportunity to spend a day at the deposits in October, 1926. The examination was made in company with V. C. Heikes, of the Bureau of Mines. The local operators, especially Mr. George L. Smith, of the Idaho Manganese Co., courteously gave assistance during the visit.

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