Showing papers in "American Journal of Science in 1962"

The system H 2 O-NaCl at elevated temperatures and pressures

Abstract: The system H/sub 2/O-NaCI was studied at pressures to 1240 bars and temperatures of 250 to 700 ts C. The temperature and pressure of the gas-solid-liquid boundary curve were determined, and the solubility of solid NaCI in steam up to saturation pressures was measured. The composition of coexisting gases and liquids at pressures above the melting pressure and below the critical pressure was determined for isotherms from 350 to 700 ts C. The critical composition and pressure for various isotherms were determined. The NaCl concentration of saline hot springs is not inconsistent with the postulate that the sodium chloride was transported from the magmatic hearth in gaseous H/ sub 2/O. (auth)

The role of aluminum in igneous clinopyroxenes with relation to their parentage

Abstract: A study of the distribution of Al in soda-poor pyroxenes in the range Ca (super 35-55) MgFe (sub 0-18) is occurring in igneous rocks reveals characteristics which differ in the various magma types. Kushiro has already shown that the more alkaline the magma-type, the more aluminous the clinopyroxene. It is further shown here for groundmass pyroxenes of the above range that the proportion of the Z group filled by Al atoms (Al Z ) decreases with differentiation in tholeiitic and related rocks but increases with differentiation in alkaline rocks, and that the percentage of Al atoms in tetrahedral coordination (Al IV x 100/Al IV + Al VI ), tends to vary inversely with the silica concentration of the host magma. Under solid-solid equilibrium conditions, increased load pressure favors the entry of Al into octahedral rather than tetrahedral sites in the clinopyroxene.

A chemical model for sea water at 25 degrees C and one atmosphere total pressure

Abstract: Dissociation constants involving Ca (super ++) , Mg (super ++) , Na (super +) , K (super +) , SO 4 (super --) , HCO 3 (super -) , and CO 3 (super --) ions, and individual ion activity coefficients have been used to calculate the distribution of dissolved species in sea water at 25 degrees C. and one atmosphere total pressure. The distribution obtained for sea water of chlorinity 19 o /oo and pH 8.1 are given. The activities calculated for free ions are also given.

The upper three-phase region in the system SiO 2 -H 2 O

Abstract: Melting relations in the system SiO_2 – H_2O were studied at high temperatures and pressures. A quadruple point for the equilibrium among quartz, tridymite, and 2 fluids was found at 1160° C. and 1500 bars. A second quadruple point for tridymite, 2 fluids, and cristobalite is estimated to be near 1470° C. and 400 bars. The freezing point of SiO_2 in equilibrium with 2 fluid phases is depressed from 1720° C. at one bar to 1130° C. at 2000 bars. This freezing point is diminished by only an additional 50° C. with a further increase in pressure to 9700 bars. The compositions of coexisting fluids along the upper 3-phase boundary have been determined. A critical end point for the univariant equilibrium curve was found at 1080° C. and 9700 bars with a composition of approximately 75 wt% SiO_2 to 25 wt% H_2O.

A method for determining the solubility of water in silicate melts

Abstract: The method described in this paper for determining the solubility of water in silicate melts consists primarily of locating the boundary (or projected boundary) between the field of liquid and the field of liquid+gas in successive isobaric T-X H2O sections for a given system. It involves the sealing of known amounts of water and silicate starting material in noble-metal capsules, the fusing and homogenization of these charges in pressure vessels, equilibration at designated experimental run temperatures and pressures, and quenching after prescribed periods of time. The quenched products are then examined for evidences of excess water. In determining solubility values from the results of critical runs, corrections are made for aqueous bubbles initially trapped and subsequently preserved within the charges, i.e., for water effectively unavailable for solution in the melt. An alternate method involves locating, also in successive isobaric T-X H2O sections for a given system, the boundary (or projected boundary) between the field of liquid and the field of liquid + crystals. This method generally yields results that are less satisfactory, owing chiefly to the moderate slopes of this boundary for many systems and to difficulties in obtaining the precise control and measurements of temperature that are required. The solubility of water in melts derived from albite glass and Harding, New Mexico, pegmatite have been determined by the excess-water method as a function of pressure up to 10,000 bars and at temperatures of the H 2 O-saturated liquidus for each melt. Solubility values for the pegmatite melt are 4.2 wt % at 1000 bars and 655 degrees C., 6.6% at 2000 bars and 635 degrees C., 11.2% at 5000 bars and 650 degrees C., and nearly 20% at 10,000 bars and 675 degrees C. Corresponding values for albite melt are 4.2 wt % (930 degrees C.), 6.4% (850 degrees C.), 9.9% (750 degrees C.), and 16.8% (700 degrees C.). The temperature coefficient of water solubility in Harding pegmatite melt, at a pressure of 1000 bars, is about -0.2 wt % of water per 100 degrees C. rise in temperature through the range 650 degrees to 850 degrees C. The solubility values obtained in these investigations are substantially lower, at pressures up to about 4500 bars, than values reported by Goranson for comparable materials on the basis of his weight-loss-on-ignition method. However, they are much higher, at pressures above 5000 bars, than values derived by the most reasonable extrapolations of Goranson9s results to these higher pressures. The discrepancies are attributed mainly to aqueous bubbles that normally are trapped and preserved in the experimental charges; these bubbles evidently were reckoned as dissolved water in the earlier work on albite and granite melts, which would account for pressure-solubility curves of seemingly incorrect position and shape.

The physical nature of common sandy and pebbly deposits, part I

Abstract: "Plotting of shape functions of clastic particles against size provides strong evidence that most natural sandy and pebbly deposits (particles longer than 0.1 mm) are deposited as composites, whereas they are often assumed in granulometric analysis to represent single homogeneous particle populations. Basic data used were p, q, and r, approximately equivalent to particle length, breadth, and depth respectively. Plots of the elongation function (p/q) against p indicate that samples of water-laid sandy and pebbly deposits taken from single sedimentary laminae consist of natural mixtures of up to three distinct particle populations and that these, named A, B, and C, combine to make four sediment types composed of A, AB, ABC, and AC. Three-dimensional studies of the particles forming these sediments strongly support this interpretation."

Cyclic sedimentation and the origin of analcime-rich Upper Triassic Lockatong Formation, west-central New Jersey and adjacent Pennsylvania

Abstract: The Upper Triassic Lockatong Formation is a huge lens (3500 ft x 25 mi x 90 mi) of lacustrine deposits composed mainly of massive dark gray or reddish brown argillite and subordinate platy dark gray mudstone and black shale arranged in asymmetrical short cycles of 2 kinds. One variety, averaging 17 to 22 ft in thickness, consists of several feet of black shale succeeded by platy carbonate-rich mudstone in the lower part and massive calcareous mudstone (argillite) in the upper part. Lenses of thin-bedded fine-grained sandstone commonly occur in these "detrital" cycles. A second, more common kind of short cycle, averaging 7 to 14 ft in thickness, contains less detrital and more chemical sediment. The lower beds are platy carbonate-rich mudstone and marlstone, some of which are varved. The upper part is massive carbonate- and analcime-rich mudstone (argillite), which contains as much as 7% soda and as little as 47% silica. Analcime, which constitutes as much as 35 to 40% of the argillite, or its Na-rich colloidal precursor were primary products of sedimentation in a lake from whose water calcium and magnesium carbonates had been extracted during deposition of the chemical variety of short cycle. Progressive reduction in water depth and decrease in redox potential associated with the development of a distinctive sequence of sedimentary structures through the course of a short cycle presumably resulted from a cyclic variation in rainfall accompanied by periodically accentuated compaction imposed on lacustrine mud accumulating in a continuously sinking basin. Varve counts of black mudstone suggest control by the 21,000-year precession cycle. Groups of detrital and chemical cycles occur in rhythmic couples 325 to 350 ft thick. These apparently resulted from alternating wetter and drier phases of a long cycle, producing either through-flowing drainage in the lake basin and a group of detrital short cycles, or a closed basin and a group of chemical short cycles characterized by the concentration of Na in the upper part of each cycle. In some chemical cycles reddish brown mud accumulated in an oxidizing environment induced by saline waters that inhibited organic growth.

Distribution of titanium between silicates and oxides in igneous rocks

Abstract: Ti commonly occurs in igneous rocks as sphene (or perovskite), in solution in silicates (olivines, pyroxenes), and as iron-titanium oxides. Rocks are known in which there is more Ti in pyroxenes than in the oxides. From thermodynamic considerations it appears that when silicates and iron oxides coexist Ti will occur preferentially in the oxide phases at low partial pressure of O. Entry of Ti into pyroxenes is determined by the free energy of mixing and is therefore possible only at high temperature; the higher t temperature of crystallization of the pyroxene, the more Ti it is likely to contain. Al in 4-coordination (z-sites) in pyroxenes favors introduction of Ti; Al in 6-coordination (y-sites) does not. Other things being equal, more Ti is expected in pyroxenes in undersaturated magmas (low silica activity), and in those containing but little Fe. The assemblage hypersthene-rutile is less likely than enstatite (or clinoenstatite)-ilmenite; magnetite-sphene (or magnetite-perovskite) is more likely than diopside-ilmenite at low temperature and high partial pressure of O.

Zoning in igneous plagioclase; normal and oscillatory zoning

Abstract: A sequence of oscillatory cores and thin, normally zoned, more sodic rims is characteristic of many igneous plagioclases, especially those of quartz diorites and granodiorites. The boundary between the core and rim may be euhedral or somewhat irregular and embayed; the core is commonly corroded, showing a patchy zoning formed by irregular inclusions of rim plagioclase composition. The oscillatory zoning is believed to have formed in response to recurrent supersaturation of the melt in anorthite adjacent to the individual crystals. The abrupt change to normally zoned rims in the zoning sequence is thought to reflect late-stage saturation of the residual melt in volatiles. After saturation, agitation by the escaping volatiles maintains a uniform melt composition equalizing the rates of diffusion and crystallization. This prevents further supersaturation, permitting uninterrupted crystallization of the rims. The occurrence of resorbed oscillatory cores in many plagioclases showing this zonal sequence supports the view that falling pressure accompanying rise of magma was a factor in bringing about saturation. As a result of the diminishing solubility of volatiles, further rise of these magmas led to rapid crystallization of the sodic rims and filling-in of the corroded cores. Formation of the oscillatory zoning through a mechanism of pressure changes due to recurrent release of volatiles cannot be reconciled with either the change in zoning or the timing of this change. This zonal sequence is believed to show that loss of volatiles, even in plutonic rocks, occurs principally as a result of late-stage saturation rather than of leakage or diffusion without saturation. Late saturation in volatiles as recorded in the zonal sequence bears out the generally accepted low water content of granitic magmas.

The system iron oxide-manganese oxide in air

Abstract: Phase relations in the system iron oxide-manganese oxide in air have been determined by the quenching technique. The system is not binary because of varying oxidation states of Fe as well as Mn. The following crystalline phases occur in the temperature interval studied in the present investigation (800 to 1585 degrees C.): Spinel solid solution (approximately Fe 3 O 4 -Mn 3 O 4 ); hematite solid solution (Fe 2 O 3 with some manganese oxide dissolved in its structure); Mn 2 O 3 solid solution (alpha -Mn 2 O 3 with some iron oxide dissolved in its structure); tetragonal Mn 3 O 4 solid solution (Mn 3 O 4 with some iron oxide dissolved in its structure). There are 2 isobaric invariant situations in the system. At 932 + or - 5 degrees C., Mn 2 O 3 solid solution, spinel solid solution, and tetragonal Mn 3 O 4 solid solution are in equilibrium with gas (pO 2 = 0.21 atm). At 997 + or - 5 degrees C., hematite solid solution, Mn 2 O 3 solid solution, and spinel solid solution coexist in equilibrium with gas (pO 2 =0.21 atm). Melting relations of mixtures in this system are characterized by liquidus and solidus curves going through a temperature minimum of 1565 + or - 5 degrees C. A plot of d-spacing versus composition for the spinel solid solution series (Fe 3 O 4 -Mn 3 O 4 ) shows a pronounced change in slope of the curve at approximately 32 wt.% manganese oxide. In the hematite and Mn 2 O 3 solid solution phases the d-spacings change relatively little with composition, and X-ray methods are not practical as tools for determining compositions of these phases.

The eruption in Askja, 1961; a preliminary report

Abstract: "The 1961 eruption was preceded by the formation of big solfataras on a N-S line along the eastern caldera wall. The eruption started in the same area two weeks later, on October 26, when an E-W-running fissure, 0.7 km long, opened up. The eruption was of the Hawaiian type, and lava fountains rose to a height of 500 m. Within the first 10 hours or so the lava flow reached a length of 7.5 km and an area of nearly 6 km 2 . When the eruption ended five weeks later the area was 11 km 2 . Until November 5 the lava solidified mainly as apalhraun (aa) lava, but from then on it was more fluid and solidified as helluhraun (pahoehoe) lava. The two lava types differ with regard to their mineralogy. The lava produced before November 5 is characterized by relatively few phenocrysts of plagioclase and pyroxene in a groundmass of black glass that is opaque due to precipitation of ore. Olivine is not found. The fluid lava of the second phase contains more phenocrysts. Olivine is present and the glass brown and translucent. Three new analyses od Askja lavas are presented."

Metamorphic aragonite in the glaucophane schists of Cazadero, California

Abstract: Metamorphic aragonite is the dominant polymorph of CaCO 3 within concordant and discordant carbonate-rich lenses and veins in the glaucophane schist belt exposed along Ward Creek, Cazadero, California. This schist sequence is part of a larger metamorphic belt within the Franciscan Formation of Jurassic and Cretaceous age. Petrofabric study shows that the fabric element of the aragonite marbles is compatible with the lineation of the enclosing schists. A careful chemical, optical, and X-ray study of 4 purified aragonite specimens shows that this metamorphic aragonite conforms in every respect with the physical properties recorded from aragonite. The mineral is biaxial negative, 2V approximately 18 degrees , alpha = 1.530 + or - .001, beta = 1.680 + or - .002, and gamma = 1.685 + or - .001. A maximum of 1.26 molecular percent SrCO 3 was found by chemical analysis. The presence of aragonite as a metamorphic mineral within these glaucophane schists suggests that the pressure and temperature conditions for this facies may be unique. Experimental work on the inversion of calcite to aragonite has shown that aragonite is the stable high pressure polymorph of CaCO 3 ; the formation of aragonite in the glaucophane schists indicates that pressures greater than 4000 bars prevailed during metamorphism. Tectonic stresses developed during the formation of the glaucophane schists may have increased the pressure considerably above the lithostatic load pressure and promoted the stable formation of aragonite marbles.

The genera of phytosaurs

Abstract: The long-snouted, crocodile-like, amphibious reptiles of the Late Triassic known as phytosaurs are assigned to 5 genera on the basis of cranial characters. The most primitive genus, Paleorhinus, has external nares well forward of the antorbital fenestrae, the posttemporal arch at level of the skull roof, a slender rostrum without crests, homodont dentition, a low quadrate, and no trace of a posterior squamosal process. Mystriosuchus, which has highly specialized posterior nares, tall quadrate, and depressed posttemporal bar, retains the primitive form of the squamosal, homodont dentition, and slender (much longer) rostrum of Paleorhinus from which it may be derived through Francosuchus (the European subgenus of Paleorhinus). The remaining phytosaur genera are characterized by rounded processes of the squamosal bone projecting well behind the occipital surface of the skull, and by the development of heterodont dentition and generally more robust skulls. Angistorhinus, the most primitive member of this lineage, retains a primitive posttemporal arch at the level of the skull deck, but is advanced over Paleorhinus in its posteriorly placed external nares. Its rostrum is slender and lacks crests; the dentition is only slightly differentiated. Phytosaurus and Rutiodon, the more specialized members of this group, have depressed posttemporal arches and tall quadrates. Rostra of Rutiodon vary from slender and uncrested in small skulls to moderately robust with high dorsal crests in the posterior half in the largest individuals; teeth vary from moderately to strongly heterodont. The squamosal processes are slender and show progressive phyletic elongation. The ratio of rostral to postrostral length varies inversely with size. Phytosaurus skulls are characterized by massive rostra with continuous dorsal crests and have a relatively constant rostral ratio independent of size; the squamosal processes are short and deep; dentition is strongly heterodont; considerable evidence suggests that the dorsal armor plates differed from other phytosaurs.

Widespread occurrence of jadeite, lawsonite, and glaucophane in central California

Abstract: The Pacheco Pass area, 80 mi SE. of San Francisco, has the most extensive development of metamorphic jadeite and lawsonite yet reported. The host rocks are metamorphosed geosynclinal sedimentary and igneous rocks in the Franciscan Formation (Jura-Cretaceous), and are of 2 types: 1) partially recrystallized rocks that appear in hand specimen relatively unaltered ("subcrystalline" rocks); and 2) thoroughly recrystallized schists, gneisses, and hornfelses ("crystalline" rocks). Subcrystalline rocks predominate; crystalline rocks are common locally, especially in major shear zones. Microscopic and X-ray analyses of the subcrystalline rocks indicate a progressive metamorphic sequence not apparent elsewhere. Lawsonite crystallized first, replacing calcium plagioclase, muscovite, biotite, and possibly other minerals. It occurs in almost all samples from the eastern half of the map area (140 sq mi), and in approximately one-half of those from the western part. Jadeite crystallized next, replacing albite in clastic sedimentary rocks, and both albite and augite in greenstones. Glaucophane, replacing chlorite and hornblende, began to crystallize typically before the crystallization of jadeite was completed. Jadeite and glaucophane are present in almost all samples from the eastern half of the area. Jadeite, lawsonite, and glaucophane are common also in the crystalline rocks, along with other minerals characteristic of the glaucophane schist facies. Greenschist facies rocks and eclogite occur locally in shear zones. The consistent distributional pattern of the subcrystalline rock types probably reflects a regional variation in the physical conditions of metamorphism. The local development of crystalline rocks might indicate sharp local changes in temperature, pressure, or solution action, or possibly the carrying in of these rocks by faulting. The high P-T condition of metamorphism may have been caused by rapid subsidence in a deep marine environment, coupled with widespread tectonic pressure. The absence of syntectonic intrusions probably reflects the low temperature condition of metamorphism, but whether this is a cause or effect relationship is not clear. Finally, the widespread nature of this type of metamorphism at Pacheco Pass suggests new possibilities for seismic interpretation of parts of the crust which may have had a similar geologic history.

Thermodynamic calculations on phase equilibria involving fused salts; Part 2, Solid solutions and application to the olivines

Abstract: A theory is developed for ideal solutions of ionic salts giving Roozeboom Type I phase diagrams, based on the assumption that the mole fraction of an ion in a phase is equal to the number of specified ions present divided by the total number of ions of all species in the phase. When applied to solid solutions of fayalite and forsterite the theory predicts for the components heats of fusion, 25,200 and 29,300 cal mole (super -1) respectively, which differ considerably from the value, 14,000 cal mole (super -1) for each component, calculated by Bowen and Schairer, who assumed ideal behavior for the undissociated molecules. Orr found a calorimetric heat of fusion of 22,000 cal mole (super -1) for fayalite. When applied to solid solutions of Mg 2 SiO 4 and Mg 2 GeO 4 , where there is a common cation, the theory predicts that ideal solution theory for undissociated molecules may be used. The data of Ringwood for this system show, however, practically no separation between liquidus and solidus, and do not admit of the calculation of heats of fusion. The behavior of the system Mg 2 GeO 4 +Fe 2 SiO 4 with no common ion is predicted. Mg 2 SiO 4 and Mn 2 SiO 4 , with a common anion, behave like forsterite and fayalite.

The system Ni-As-S; phase relations and mineralogical significance

Abstract: Phase relations in the ternary system Ni-As-S were determined in rigid silica-glass tubes between 700 degrees and 450 degrees C., with some additional data at lower temperatures. The only ternary phase in the system, corresponding to the mineral gersdorffite for which the accepted formula is NiAsS, has a large variation in its As/S ratio. It is homogeneous from Ni-As (sub 1.77) S (sub 0.23) to NiAs (sub 0.77) S (sub 1.23) at 700 degrees C. Gersdorffite in equilibrium with NiAs 2 (rammelsbergite or pararammelsbergite) has the composition NiAs (sub 1.80) S (sub 0.20) and NiAs (sub 1.72) S (sub 0.28) at 660 degrees and 450 degrees C., respectively. This is a difference of only 2 wt % As. The unit cell edge of gersdorffite between stoichiometric NiAsS and NiAs (sub 1.80) S (sub 0.209 is given by the equation: a = 5.6939 + 0.00047OX, where a is the unit cell edge of gersdorffite (in Aa) containing X weight percent NiAs 2 . Gersdorffite analyses from the literature are reviewed and several new specimens examined to demonstrate that natural gersdorffite also has a large variation in its As/S ratio. Complete solid solution exists between niccolite (Ni (sub 1+ or -x) As) and alpha Ni (sub 1-x) S (the high-temperature modification of millerite) above 595 degrees + or - 5 degrees C. The solvus was determined from 595 degrees to 400 degrees C. along the join from NiAs to NiS. Approximately 1 wt % S substituting for As lowers the polymorphic inversion of rammelsbergite to pararammelsbergite from 590 degrees + or - 10 degrees C. to 475 degrees + or - 25 degrees C. Stable assemblages in the synthetic system correspond closely to the associations found in nature.

Some aspects of drumlin geometry

Abstract: Measurements of form, orientation, and spacing of drumlins were made from topographic maps and aerial photographs of areas 1) near Boston, Massachusetts, 2) near Weedsport, New York, and 3) in Blaine County, Montana, and Pierre County, North Dakota. It was found that individual drumlins depart slightly from the ideal ellipsoidal form. Orientations of drumlins within small areas are characterized by normal distributions. Spacing between drumlins is characterized by multimodal distributions with some indications of periodicity.

A late-glacial pollen diagram from Madelia, south-central Minnesota

Abstract: Late-glacial and early postglacial pollen stratigraphy is described for a gyttja and peat section overlying Mankato drift, in the center of the Des Moines glacial lobe near Madelia. Five pollen zones are distinguished; the oldest may represent pioneer vegetation shortly after the retreat of the ice. The transition from zone I to II is likely to be the beginning of the Two Creeks interstadial. The Two Creeks vegetation shows up in the pollen diagram as a spruce-ash forest. During zone III, the Valders stadial, a shrub forest with birch, alder, spruce, and Artemesia seems to have been present. The postglacial starts with a rapid decline of spruce and a strong rise of birch (zone IV) followed by elm and oak (zone V). The diagram is controlled by 2 radiocarbon dates: the transition from zone I to 11 is dated at 12,650+ or -350 B.P. (W-824); the top of zone IV at 9300+ or -350 B.P. (W-825). The locality lies less than 200 mi. outside the presumed margin of the Valders ice. It is therefore worth noting that the Valders readvance did not produce tundra or park tundra at the site but merely increased the proportion of shrubs in the forest.

Presentation of paleomagnetic data, polar wandering, and continental drift

Abstract: "A method is proposed for presenting paleomagnetic data by means of isoclines on paleomagnetic maps. These maps offer a more detailed picture of ancient magnetic fields than is given by a single virtual pole position. The isoclines of these maps restore the original connection between the continental forms and their ancient magnetic--and geographic--latitude. This is of importance particularly when we want to investigate the mutual relative positions of different continents or tectonic units of the past: from the maps we can easily see where continentalcoasts were opposite one another, and what rotations and translations have occurred since. Paleomagnetic data make the assumption of continental drift and polar wandering necessary; the data do not appear to be in conflict with themajor hypotheses on continental drift, which are based on geological, morphological, and climatological grounds."

Thermodynamic calculations on phase equilibria involving fused salts; part I, General theory and application to equilibria involving calcium carbonate at high pressure

Abstract: A theory is developed for determining melting-point curves of salt mixtures and of salt mixtures containing small amounts of other ions. Depression of the curves is illustrated for NaCl + NaF and CaO + CaCl 2 at atmospheric pressure and then applied at 1000 bars to the system Ca(OH) 2 -CaCO 3 . The presence of 1.35 weight percent of water is calculated to lower the eutectic temperature in this system by 10 degrees C.

On the relative stability of talc, anthophyllite, and enstatite

Abstract: Over a limited range of conditions between 670 degrees to 800 degrees C. at 2000 bars it has been found possible to convert talc to anthophyllite + quartz, and enstatite + quartz to anthophyllite, in the presence of water. The concept that anthophyllite can be formed only in the water-deficient region is thus untenable.

Precambrian and Cambrian rocks of south-central Esmeralda County, Nevada

Abstract: More than 13,000 ft of Precambrian and Cambrian sedimentary rocks occur in S.-central Esmeralda County. The succession contains upper Precambrian to Upper Cambrian strata in conformable sequence and appears to be unconformably overlain by the Middle Ordovician Palmetto Formation. The Cambrian rocks are considered to include the oldest Cambrian strata in North America because of the presence of the olenellid trilobite Fallotaspis. Approximately two-thirds of the Precambrian and Lower Cambrian sedimentary rocks are quartzose detrital deposits, similar in thickness and lithologic character to strata of equivalent age in the Inyo Mountains, California. Carbonate rocks dominate the Middle and Upper Cambrian.

Metasomatic quartz keratophyre in central Oregon

Abstract: Altered tuff having the composition of quartz keratophyre is intercalated within a Jurassic formation composed dominantly of black marine mudstone near Izee in central Oregon. The tuff was deposited originally as a thin yet extensive accumulation of rhyodacitic vitric ash. Shortly after burial, the ash was devitrified and altered, with loss of soda and acquisition of lime, to heulandite and associated diagenetic minerals. After deep burial, heulandite and volcanic plagioclase were recrystallized locally to laumontite. Still later, soda metasomatism that was apparently accomplished by connate waters expressed from nearby mudstones by compaction, and that was accompanied by dehydration and leaching of lime, magnesia, and potash, converted most of the tuff to quartz keratophyric felsite composed dominantly of albite and quartz. Local potash enrichment was a terminal(?) phase of the metasomatic alteration. Relict textures and stratigraphic continuity clearly demonstrate the sequence of alteration.

New meteorite localities in the Rub' al Khali, Saudi Arabia

Abstract: "Sixteen localities in the Rub9 al Khali of southern Arabia are known to have produced meteoritic materials. Of these, only the centrally located al-Hadida has craters. The rest of the specimens must be assumed to have fallen as fragments of meteoritic showers. Many of the specimens are thoroughly oxidized, but several specimens of Ni-Fe metallic meteorites occur. Eight of the localities fall on a straight line oriented 300 degrees . Others fall on either side of the line but not all at random."