Radiometric Studies Research Articles

The stratigraphic evolution of the El Paso basin, southern California: Implications for the Miocene development of the Garlock fault and uplift of the Sierra Nevada

The Ricardo Group is a 1,700-m-thick sequence of Miocene volcanic rocks and continental sedimentary rocks deposited between ∼ 19 and 7 Ma in the El Paso basin, near the junction of the Garlock fault and the Sierra Nevada frontal fault in southern California. The combination of stratigraphic and structural data from the Ricardo Group with chronologic and rotational histories derived from magnetostratigraphic and radiometric studies provides some new constraints for the morphotectonic emergence of the Sierra Nevada, the initiation of strike- slip movement on the Garlock fault, and related east-west extension in the southern Basin and Range region. The Miocene sequence documents (1) volcanism and north-south tension without net extension at 18-15 Ma (2) relative uplift about 15-13.5 Ma, (3) the beginning of sinistral slip on the Garlock fault and east-west extension in the southwestern Basin and Range region about 10-9 Ma, and (4) emergence of the Sierra Nevada as a source area and topographic high by 8 Ma. Stratigraphic evidence from the Ricardo Group does not indicate significant Miocene dip-slip movement along the large-scale, down-to-the-north fault that has been previously hypothesized to have preceded the present Garlock fault in the same location during the early Tertiary. The evolution of this sequence, however, can be explained by tectonic models which propose a time-space linkage between basin evolution, east-west extension in southern California, and the Mendocino triple-junction system.

Subdivision of the Quaternary in Japan

The recent progress of stratigraphical studies on the Japanese Quaternary has led to the establishment of standard geologic sections (Pliocene-Holocene) of representative basins in Japan and the correlation of each one with the others.In the course of compiling the Quaternary Maps of Japan, the geologic sections were chronostratigraphically subdivided into 5 units, i. e. Pliocene, Lower Pleistocene, Middle Pleistocene, Upper Pleistocene, and, Holocene, based on the definitions approved and/or recommended internationally.Unsolved problems, however, still remain in correlating marine sequences with non-marine sequences, and especially in correlating the Pliocene-Pleistocene boundary in the former with that of the latter.The Kazusa Group, a marine sequence of the Boso Peninsula in Kanto basin, is regarded as an expected hypostratotype section of the Pliocene-Pleistocene boundary. Precise correlations of the Kazusa Group with the Osaka Group of nonmarine-marine origin and the Yamato Group of nonmarine origin, which are well studied bio- and magneto-stratigraphically, are of prime importance. The relation between marine and nonmarine sequences are examinable within the Kanto and Niigata basins, because of the coexistence of both sequences in these basins. Bio- and magneto-stratigraphical and radiometric studies on the Pliocene and Pleistocene in the Kanto and Niigata basins are expected to be completed in the near future.

Radiometric studies on the oxidation of (U-14C) L-amino acids by drug-susceptible and drug-resistant mycobacteria.

A radiometric assay system has been used to study oxidation patterns of (U-14C) L-amino acids by drug-susceptible and drug-resistant mycobacteria. Drug-susceptible M. tuberculosis (H37Rv TMC 102 and Erdman) along with the drug-resistant organism M. tuberculosis (H37 Rv TMC 303), M. bovis, M. avium, M. intracellulare, M. kansasii and M. chelonei were used. The organisms were inoculated into a sterile reaction system with liquid 7H9 medium and one of the (U-14C) L-amino acids. Each organism displayed a different pattern of amino acid oxidation, but these patterns were not distinctive enough for identification of the organism. Complex amino acids such as proline, phenylalanine and tyrosine were of no use in identification of mycobacteria, since virtually all organisms failed to oxidize them. There was no combination of substrates able to separate susceptible from resistant organisms.

Radiometric studies on the oxidation of (1-14C) fatty acids by drug-susceptible and drug-resistant mycobacteria.

A radiometric assay system has been used to study oxidation patterns of (1-14C) fatty acids by drug-susceptible and drug-resistant organisms of the genus Mycobacterium. Two strains of M. tuberculosis susceptible to all drugs, H37Rv and Erdman, were used. Drug-resistant organisms included in this investigation were M. tuberculosis H37Rv resistant to 5 ug/ml isoniazid, M. bovis, M. avium, M. intracellular, M. kansasii and M. chelonei. The organisms were inoculated in sterile reaction vials containing liquid 7H9 medium, 10% ADC enrichment and 1.0 uCi of one of the (1-14C) fatty acids (butyric, hexánoic, octanoic, decanoic, lauric, myristic, palmitic, stearic, oleic, linoleic, linolenic). Vials were incubated at 37°C and the 14CO2 envolved was measured daily for 3 days with a Bactec R-301 instrument. Although each individual organism displayed a different pattern of fatty oxidation, these patterns were not distinctive enough for identification of the organism. No combination of fatty acids nor preferential oxidation of long chain or of short chain fatty acids were able to separate susceptible from resistant organisms. Further investigation with a larger number of drug susceptible mycobacteria including assimilation studies and oxidation of other substrates may be required to achieve a distinction between drug-susceptible and drug-resistant mycobacteria.

A coupled voltammetric and radiometric (voltradiometric) study of the simultaneous adsorption of hydrogen and anions at platinized platinum electrodes

Donnees sur l'adsorption des ions HSO 4 − et Cl − au cours des variations cycliques du potentiel. Essai d'etablissement d'une relation entre l'adsorption de l'hydrogene et des anions

Radiometric studies on the oxidation of [1- 14C]fatty acids and [U- 14C] l-amino acids by mycobacteria

A radiometric assay system has been used to study oxidation patterns of [1- 14C]fatty acids and [U- 14C] l-amino acids by drug-susceptible and drug-resistant organisms of the genus Mycobacterium. Two strains of M. tuberculosis susceptible to all drugs, H 37Rv TMC 102 and Erdman, were used. Drug-resistant organisms included in this investigation were M. tuberculosis H 37Rv TMC 303, M. bovis, M. avium, M. intracellulare, M. kansasii and M. chelonei. The organisms were inoculated into a sterile system containing liquid 7H9 medium along with one of the [1- 14C]fatty acids or [U- 14C] l-amino acids. Although each individual organism displayed a different pattern of fatty acid oxidation, these patterns were not distinctive enough for identification of the organism. Susceptible and resistant mycobacteria did not display any preferential oxidation of long chain or of short chain fatty acids that might help to distinguish these organisms. As with the fatty acid series, differential oxidation patterns for amino acids could be recognized, but again these patterns were not distinctive enough to identify each organism. Complex amino acids such as proline, phenylalanine and tyrosine were of no use in identification of mycobacteria, since virtually all organisms failed to oxidize them. Identification of each individual organism was feasible using a combination of fatty acids and amino acids which included butyric, octanoic, oleic, glycine and alanine. There was no combination of substrates able to separate susceptible and resistant organisms.

Recent data quality and earth science results from the landsat thematic mapper

The Landsat Thematic Mapper (TM) provides high-quality observations for earth science studies in regional and global resources assessments. A considerable body of research results shows that TM data can meet geodetic requirements for map products of 1:100,000 scale and smaller. As a coordinate reference system for multiple data sets or indicating where changes have occurred, TM image data may be useful at larger scales up to 1:24,000. For multispectral radiometric studies of earth surface features, TM data provide band-to-band registration for the seven bands extending from 0.45 to 12.5 micrometers of at least 0.3 pixel and often to 0.1 pixel accuracies. Although several scanning and electronic effects have been observed in TM data, the relative radiometry for the bands monitoring reflected solar radiation has limits of uncertainty of less than 1 percent. The uncertainty in the absolute radiometry of the TM system must still be considered to be near 10 percent of full scale, and therefore the uncertainty in bidirectional reflectance values should not exceed 6 percent. A group of 31 investigation teams are in the initial period of analyzing TM data for a wide variety of studies in the earth sciences. Early exemplary results show TM data to be quite useful in geologically related studies such as regional, tectonic, and volcanic processes, mapping landforms and assessing surficial characteristics of glaciers. Other investigations are just beginning to accumulate results related to properties of the hydrosphere, biosphere, and animal habitats.

Combined cyclic voltammetric and radiometric study of polymer film electrodes

Etudes de la formation de sites actifs sur des electrodes d'or recouvertes d'un film de polyvinylferrocene. Donnees sur l'adsorption d'ions antagonistes au cours de mesures de voltammetrie cyclique, associees a des mesures radiometriques en presence de H 2 SO 4 dilue, marque par 35 S

Radiometric Dating of Ochoan (Permian) Evaporites, Wipp Site, Delaware Basin, New Mexico, Usa

AbstractWe have attempted radiometric dating of halide-sulfate salts and clay minerals from the Delaware Basin, New Mexico, USA, as part of geochemical study of the stability of the evaporite sequence at the WIPP (Waste Isolation Pilot Plant--a US DOE facility) site. We undertook this dating to determine: (1) primary age of evaporite genesis or time(s) of recrystallization, (2) if previously undated evaporite minerals (leonite, polyhalite, kieserite) give useful data, and (3) if the detrital clay minerals have been radiometrically reset at any time following their incorporation into the evaporite medium. We have shown earlier that polyhalites can indeed be successfully dated by the K-Ar method, and once corrections are applied for admixed halide minerals, dates of 210-230 Ma for the Delaware Basin are obtained. Rb-Sr isochrons from early stage sylvites-polyhalites- anhydrites yield 220 ± 10 Ma, even when some sylvites yield lower K-Ar dates due to l1s of 40Ar*. K-Ar dates on leonites and kieserites are also low due to 40Ar* loss, but their Rb-Sr dates are higher. Detrital clay minerals from the Delaware Basin collectively yield a highly scattered isochron (390 ± 77 Ma), but samples from a local area, such as the WIPP Site, give a much better age of 428 ± 7 Ma. These dates show that the interaction between the clay minerals and the evaporitic brines was insufficient to reset the clay minerals Rb-Sr systematics. In a related study, we note that a dike emplaced into the evaporite at 34 Ma had only very limited effect on the intruded rocks; contact phenomena were all within 2 m of the dike. All of our geochemical (radio-metric and trace element) studies of the WIPP site argue for preservation of the isotopic and chemical integrity of the major minerals for the past 200 Ma.

Daylight illumination from radiometric studies made at Pune

Actual measurements of daylight illumination- the radiant energy in the visible part of electromagnetic spectrum causing the sensation of sight are not being made in the network of radiation stations in India. Following the method discussed by Drummond and Angstrom, daylight illuminations have been derived from the global radiation measurements made at Pune during 1974 in the spectral ranges 300-400 nm and 710-2700 nm and the data presented. The importf!nt factor, luminous efficiency has also been worked out for Pune. The results are discussed.

A review of radiometric studies in Macaronesia [North Atlantic]: Mitchell-Thomé, R.C., 1985. Bolm Mus. munic. Funchal, 37(167):52–85. 29, Rue de la Liberation, Mamer, Luxenbourg.

A review of radiometric studies in Macaronesia [North Atlantic]: Mitchell-Thomé, R.C., 1985. Bolm Mus. munic. Funchal, 37(167):52–85. 29, Rue de la Liberation, Mamer, Luxenbourg.

KAr biotite data for Ludlovian bentonites from Great Britain

A mineralogical and KAr radiometric study has been undertaken on biotites from Ludlovian bentonites from Great Britain. Some biotites are chloritized. Preliminary apparent ages of 417 ± 10, 423 ± 9 and 424 ± 8 Ma have been obtained. These ages are considered significant for the Ludlovian series, the base of which appears older than 420 Ma as concluded previously from recent studies in the U.K. and Australia.

Age and significance of magnetizations in dolerite dykes from the Northampton Block, Western Australia

Samples from nine dolerite dykes that outcrop in the Northampton Block, Western Australia, have been analysed to investigate the palaeomagnetic constraints that may be placed on the timing of magmatic events in relation to the widespread lead and zinc mineralization in the Northampton Mineral Field. The palaeomagnetic directions are consistent with a group of pole positions obtained from independent studies of formations of latest Precambrian and very earliest Cambrian age. The pole for the dykes lies at latitude 47.1°S, longitude 317.3°E (A95=7.9°). A comparison with the palaeomagnetic catalogue suggests that the dykes cannot be younger. Results from radiometric studies yield ages for two dykes at 550 Ma and a third dyke at 750 Ma. The results indicate that the dykes were intruded considerably earlier than the mineralization age (late‐Early to early‐Mid Paleozoic) and hence cast doubt on the role of the intrusive event as either the source of mineralization or the principal catalyst for the mobilization of pre‐existing mineral deposits.

A systematic approach to radiometric and paleomagnetic studies in a mobile orogenic belt: I. The waning phase of activity in the southern Appalachians of South Carolina

The survey of radiometric and paleomagnetic work on the mafic rocks of South Carolina is consistent with, and amplifies the studies on the acidic rocks of the southeast by Ellwood (1982). The westerly post-early Mesozoic tilt of the southeastern Appalachians proposed by Dooley and Smith (1982) over most of the Piedmont balances out the post-late Paleozoic southeastern tilt of Ellwood (1982). Only in the Elberton-Sparta block is the tilting important and here the interpretation proposed is of a greater initial tilt (approximately 25-30°) reduced by the post-early Mesozoic tilt.

Evidence for a hot spot origin of the Caroline Islands

The results of paleomagnetic, petrographic, and radiometric studies of the Eastern Caroline Islands in the western Pacific indicate that the islands were formed by a hot spot located near the paleoequator between 1 and 11 Ma. The islands show a linear progression of mean ages from 1 Ma in the east (Kusaie) to 11 Ma in the west (Truk). The results of volumetric measurements and geochemical studies suggest that the hot spot source is waning and perhaps was slowly dying during the time Truk, Ponape, and Kusaie were being formed. The dominant shield‐building magmas in the Caroline Islands are part of a differentiated alkalic series. The posterosional lavas are highly silica undersaturated and trace element enriched nephelinites. The latter were erupted subsequent to the cessation of the main shield phase of volcanism. The petrography and geochemical evolution of Truk are strongly reminiscent of that of the Hawaiian chain; however, the shield‐building lavas are compositionally similar to the alkalic lavas that typically form only thin, late‐stage caps on many Hawaiian volcanos. No tholeiitic rocks were found despite sampling deep within the eroded volcanic structure of the islands. This absence of tholeiitic lavas and dominance of alkalic lavas stand in contrast with Hawaii, where tholeiitic volcanism dominates and alkalic lavas form only a minor component of the exposed lavas. The absence of tholeiitic lavas in the main shield‐building phase of construction, however, is not unique to the Caroline Islands. Dominant alkalic volcanism appears characteristic of other seamounts in the Pacific, including the Samoan, Austral‐Cook, and Line Islands.

A unique magnesiochloritoid-bearing, high-pressure assemblage from the Monte Rosa, Western Alps: petrologic and 40Ar-39Ar radiometric study

A phengite-talc-chloritoid-chlorite-kyanite-quartz assemblage is reported from a nearly undeformed quartz-rich metapelite found in the Monte Rosa massif (Western Alps). Chloritoid contains up to 74 mol % of the Mg end member and is the most magnesian ever reported. Textural relationships and mineral compositions suggest equilibrium and therefore a low-variance assemblage which represents the high-pressure stability limit of chlorite+quartz according to the terminal reaction $${\text{chlorite + quartz }} \rightleftarrows {\text{ talc + chloritoid + kyanite + H}}_{\text{2}} {\text{O}}{\text{.}}$$ Mineral compositions combined with new experimental data on the stability of the Mg-chloritoid end member lead, for a temperature close to 500° C, to a pressure estimate of 16 kbar and a water activity of 0.6 which is supported by fluid inclusions study. Chloritoid composition is in fact a fine metamorphic indicator which opens new ways for barometry in high-grade blueschists. It demonstrates here the existence of a high-pressure metamorphism in the Monte Rosa massif. The assemblage remained mineralogically unaffected during the subsequent lower-pressure evolution. Two size fractions of the single phengite generation were analysed by the 39Ar-40Ar incremental release method. Both spectra are identical with a plateau at 110±3 Ma representing over 96% of the 39Ar degassed. The ages of the first heating steps are discordant and increase with increasing temperature from values near 70 Ma to the plateau age. Isotope correlation diagrams show two 36Ar components, one released at high temperature and correlated with 40Ar and 39Ar, the other released at low temperature in a mixture of atmospheric argon and of a loosely held argon of 70 Ma apparent age. The 110 Ma plateau age may reflect the presence of homogeneously incorporated excess argon, the 70 Ma value might then be a true age. However we favour the alternative hypothesis that the 110 Ma plateau age is a true age, implying that the internal crystalline massifs of the Western Alps have endured high-pressure metamorphism as early as mid-Cretaceous. Whatever the interpretation chosen, the preserved high-pressure mineral assemblage remained isotopically unaffected during the low-pressure mid-Tertiary event which is recorded by the 37 Ma plateau age of phengite from a foliated, recrystallised quartzite collected in the same, westernmost part of the massif. The contrasting behaviour of the two samples shows that even at temperatures as high as 400–450° C deformation and recrystallisation are also major controlling factors of isotope mobility.

Radiometric studies with gas-liquid and thin-layer chromatography for rapid demonstration of hemin dependence and characterization of Mycobacterium haemophilum.

Eight isolates of Mycobacterium haemophilum were evaluated by radiometric methods to determine whether this test system could support the growth of these organisms as well as demonstrate their growth requirements for iron complexes such as hemin, ferric ammonium citrate, and blood. In addition, gas-liquid and thin-layer chromatography were evaluated to determine whether these procedures could further differentiate M. haemophilum from other mycobacteria. During the initial 24 to 48 h, there was no significant difference between the radiometric test broths containing iron complexes and control broths without iron supplementation. After 48 h, the test growth index readings rapidly increased, and control broth readings leveled off and declined. The mean growth index reading of the test broths after 6 days of incubation was 100 times that of the controls. The mean incubation time with supplemented 7H10 agar was 17 days. The use of radiometric media resulted in the demonstration of hemin dependence by M. haemophilum significantly earlier than with 7H10 agar. Of the three supplements studied, whole blood provided the greatest growth rate, followed by ferric ammonium citrate and hemin. When 12 species of mycobacteria other than M. haemophilum were radiometrically evaluated, no isolate demonstrated an iron complex requirement. Gas-liquid and thin-layer chromatography procedures were able to rapidly differentiate M. haemophilum from the other 12 Mycobacterium species.

Distribution of radioactivity at North Wadi Kareim area and correlation with the surrounding areas, Central Eastern Desert, Egypt

North Wadi Kareim area, Central Eastern Desert of Egypt, covers about 130 km 2 of basement complex composed of a sequence of igneous and metamorphic rocks of late Precambrian age. The present study deals with the distribution of radioactivity amongst the different lithological units, especially in bostonites and trachyandesites, the structural control of radioactivity and geological studies. Radiometric measurements were carried out for each rock unit, with comparative studies of the surrounding areas. The relationship between radioactivity and the age of rocks, according to their chronological sequence, revealed that the younger rocks had a higher intensity of radioactivity compared with the older ones. Significant radioactive anomalies were discovered in the younger alkaline volcanics, namely bostonites and trachyandesites. Radiometric studies carried out along structural features showed that bostonites and trachyandesites were invaded along fault zones and that faults devoid of bostonites and trachyandesites were barren of radioactivity. Radioactivity is connected with joints normal to the contact of buff bostonite bodies with the country rock, while the radioactivity of trachyandesite is due to mass effect. Radioactive joints cutting the bostonite bodies were measured and the trends of radioactive fractures are N45°E and N15°W. Bostonite dykes and sills were plotted on an equal area stereographic projection and they have a semicircular shape.

Interactions between proteins and synthetic polypeptides adsorbed at solid-liquid interfaces

The forces acting between two atomically smooth mica surfaces immersed in aqueous electrolyte have been measured, in the range of surface separations D, 0 ∼ 1000 nm, both in the absence and in the presence of macromolecules adsorbed onto the surfaces from solution. In this way the interactions between the adsorbed macromolecular layers themselves were determined. Interactions between the bare mica surfaces were short-range and in good accord with DLVO (electrostatic-double layer) theory for both electrolyte concentrations (10 −1 and 10 −3 M KNO 3). Two macromolecular systems were used as adsorbing species; (i) soluble calf-skin collagen and (ii) synthetic poly-L-lysine (MW = 77,000). The forces between adsorbed layers of collagen were monotonically repulsive, with interactions starting at D ∼ 650 nm. This indicates an adsorbed layer extending some 300 nm from each surface, and suggests the rod-like collagen monomers (of length 300 nm and diameter 1.5 nm) are adsorbed end-on normal to the mica substrate. This finding is in accord with recent independent viscometric and radiometric studies of monomeric collagen adsorbed onto glass substrates. For the case of the adsorbed polylysine layers, the forces are again monotonically repulsive, and onset of interactions occurs at D ∼ 120–140 nm. As the surfaces approach, irreversible changes in the surface structure of the adsorbed polyelectrolyte take place and the final quasi-equilibrium adsorption configuration is that of a dense, flat surface layer. A close analysis of the force—distance profiles reveals that the interaction is a combination of both reversible, repulsive field-type (DLVO) forces, and a repulsive steric component which is largely irreversible.

Microwave radiometric study of ferro–paraelectric phase transitions in KNO3

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