Continental rift-setting and evolution of Neoproterozoic Sindreth Basin in NW-India

The Neoproterozoic Sindreth Basin, NW India, and its surrounding area represent a half graben structure situated between the undeformed Malani Igneous Suite (MIS) in the west and a corridor of coeval Cryogenian ductile deformation, anatexis and granite intrusion in the east. The main lithologies observed in the basin are conglomerate, fanglomerate, debris flow and lake deposits derived from a nearby continental provenance, intercalated with concurrent mafic and felsic lava flows. Based on geological traverses across the strike of the basin, we propose a three-fold classification comprising Lower Clastic Unit and an Upper Clastic Unit and a Bimodal (basalt–rhyolite) Volcanic Unit separating the two. Tilting due to basin inversion and faulting has been observed; however, the rocks are unmetamorphosed and show undisturbed primary sedimentary features. The stratigraphic record of the basin is characteristic for deposition and magmatism in a fault-related continental setting. Implications of the findings have been discussed in the context of Neoproterozoic crustal dynamics in NW India. This study provides conclusive evidence for a continental setting for Sindreth Basin evolution and contests the recent models of active subduction setting (either back-arc basin or accretionary sediments over a subduction zone).     

Temporal variations of the magnetic field in sunspots

We obtained simultaneous spectra with a spatial resolution of 1/2 and a temporal resolution of 15 s in H, Ca ii-K, Caii 8542 Å, and three Fei lines of the sunspot group responsible for the large flares of August, 1972 (McMath No. 11976). A time series taken 1972, August 3 in the Fei 6173 Å Zeeman sensitive line was analyzed for oscillations of field strength and the angle between the field and the line of sight, and for changes of the field associated with the Ca ii-K umbral flashes discovered by Beckers and Tallant (1969). The power spectra show no significant peaks, conflicting with the results of Mogilevskii et al. (1972) who reported oscillations in the longitudinal component of the field strength with periods of 56, 90, and 150 s. Changes in the field were not observed to be correlated with the occurrence of umbral flashes. These results place restrictions on magnetic modes of energy transport between the photospheric layers and the chromospheric layers where the umbral flashes are observed.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Mineralogy,chemistry, and noble gas contents of Adzhi-Bogdo– an LL3–6 chondritic breccia with L-chondritic and granitoidal clasts

Abstract— Adzhi-Bogdo is an ordinary chondrite regolith breccia (LL3–6) which fell on 1949 October 30 in Gobi Altay, Mongolia. The rock consists of submm- to cm-sized fragments embedded in a fine-grained clastic matrix. The polymict breccia contains various types of clasts, some of which must be of foreign origin. Components of the breccia include chondrules, melt rock clasts (some of which are K-rich), highly recrystallized rock fragments (“granulites”), breccia clasts, pyroxene-rich fragments with achondritic textures, and alkali-granitoids. The composition of olivine in most fragments is in the range of LL-chondrites. However, olivine in some components has significantly lower fayalite contents, characteristic of L-chondrites. The bulk meteorite is very weakly shocked (S2). Based on the bulk chemical composition, Adzhi-Bogdo is an ordinary chondrite. The concentrations of Fe and Ni are somewhat intermediate between L- and LL-chondrites. The contents of solar gases indicate that Adzhi-Bogdo is a regolith breccia. Most of the solar He and probably a part of the solar Ne of Adzhi-Bogdo has been lost. It is suggested that Adzhi-Bogdo experienced an (impact-induced) thermal event early in its history, because most of the radiogenic ⁴⁰Ar is retained.     

REGIONAL PATTERNS OF FEMALE STATUS IN THE UNITED STATES

Two measures of female status displayed dissimilar spatial distributions. Absolute status, measured by income, education, and occupation, was highest in the West and Northeast and lowest in the South. Female status was high where male status was high. The relative status of women compared to men, however, was high in the West and the rural Middle West and South but low in the Mountain West and industrial Northeast. Nationwide, where men enjoyed high absolute status, the relative status of women compared with men was poor.     

Gaseous formic and acetic acids in the atmosphere of Yokohama,Japan

Gaseous formic acid (HCOOH_g) and acetic acid (CH₃COOH_g) were measured every 30 minutes during a 10 hour daylight period in August, and a 24 hour period in October, 1990 in the urban atmosphere of Yokohama, Japan. An aqueous nebulizer sampler and ion-chromatography exclusion (ICE) were used for the measurements. In the August experiment (0800–1800 local time) the mean HCOOH_g concentration was found to be 7.3±2.5 ppbv. The mean CH₃COOH_g concentration was 3.8±1.2 ppbv. In the 24 hour experiment in October, concentrations of both acids were lower between 0800–1800 than during the same time-period in August (mean HCOOH_g=4.4±2.7 ppbv, mean CH₃COOH_g=1.4±0.5 ppbv). In October, concentrations of both acids were higher in daylight hours than at night; sporadic high HCOOH_g concentrations were observed. In both experiments the ratio HCOOH_g/CH₃COOH_g of individual samples was usually 2.0 (mean ratio of 2.0 in August, 3.1 in October).     

Seismic effects from major basin formations on the moon and mercury

Grooved and hilly terrains occur at the antipode of major basins on the Moon (Imbrium, Orientale) and Mercury (Caloris). Such terrains may represent extensive landslides and surface disruption produced by impact-generatedP-waves and antipodal convergence of surface waves. Order-of-magnitude calculations for an Imbrium-size impact (10³⁴ erg) on the Moon indicateP-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves would arrive subsequent to secondary ejecta impacts beyond 10³ km and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced ‘fluidization’ of slide material; knobby, pitted terrain around old basins from enhancement of seismic waves in ancient ejecta blankets; and perhaps the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.     

Coalification history of the Stephanian Ciñera-Matallana pull-apart basin,NW Spain: Combining anisotropy of vitrinite reflectance and thermal modelling

The Stephanian Ciñera-Matallana Basin of NW Spain comprises 1,500 m of alluvial to lacustrine coal-bearing sediments, which were deposited in a late Variscan transtensional/transpressional pull-apart setting. The relationship between coalification pattern and rock deformation was evaluated by measurements of the anisotropy of vitrinite reflectance (AVR). The AVR ellipsoids reveal both pre-tectonic elements related to the bedding fabric and syn-tectonic elements related to folding, producing biaxial ellipsoid shapes with the maximum reflectance parallel to fold axes. The mean coalification gradient for the Stephanian succession is about 0.62 %Rr/km. Calculations of the mean palaeo-geothermal gradient are presented on the basis of three different empirical equations. A palaeo-geothermal gradient of 85 °C/km is considered the most realistic, with an overburden of about 1,000 m. 1-D numerical modelling of the burial history results in two possible scenarios, the most preferable involving a palaeo-heat flow of 150 mW/m² and an overburden of ca. 1,050 m. These results indicate that maximum coalification was related to a localised but high palaeo-heat flow/-geothermal gradient. The anisotropy of vitrinite reflectance highlights the interactive and transitional nature of sedimentary compaction and rock deformation on the maturation of organic material within strike-slip fault zones.     

El Niño related interannual variations in biological production in the North Pacific as evidenced by satellite and ship data

A recently proposed method for estimating nitrate and new production from remotely sensed data (Goes and Goes) allowed us to observe significant deviations from the normal in the quantum of winter-time nitrate injected into the euphotic column and its consumption by phytoplankton in the North Pacific following the El Niño event of 1997. Results from this study allowed us to observe large differences in the ways in which the El Niño event affected the western and the eastern margins of the North Pacific basin. For the western North Pacific, a long-term (1972–1992) historical record of oceanographic data provided us with clear evidence supporting of our findings from satellite observations. In the eastern North Pacific Ocean also, our results compared well with those previously reported (Wong, Whitney, Matear, & Iseki, 1998). While it is clear from this study that El Niño/La Niña oscillations can have a major influence on interannual variations in biological processes in the North Pacific, these results also serve to highlight the value of remote sensing as a tool for studying large regional to basin-scale biological oceanographic events.