Paleoproterozoic quartz-pebble conglomerate type uranium mineralisation in Mankarhachua area,Angul district,Orissa

Ground Radiometric survey of Paleoproterozoic pyritiferous quartz-pebble conglomerate (QPC) occurring to the north of Pallahara area led to the discovery of a QPC type uranium mineralisation near Mankarhachua village. Significant radioactivity is recorded in three sub-parallel uraniferous QPC horizons with metamorphosed pebbly to medium grained recrystallised massive sandstones. Detrital grains of uranothorite, thorite, radioactive allanite, monazite, zircon, minute uraninite grains in carbonaceous matter and thucolite contributes to the radioactive phases present in QPC matrix. Adsorbed U on limonite and goethite, secondary uranyl minerals in matrix, along bedding planes and fractures are commonly observed. This discovery has opened up a new horizon for future exploration for QPC type uranium mineralization in the area. The paper presents observations on geology, radioactivity, petrological and geochemical nature of the uraniferous QPC horizons.     

Nonlinear dynamic analysis of deep water risers

The paper presents a theoretical and numerical approach to the dynamical behaviour of risers in deep water which takes into account two types of nonlinearity; that due to viscous drag forces and that due to the large displacements of the riser when submitted to strong axial loads. As the second nonlinearity may have a significant influence upon the behaviour of risers in deep water, a method for automatically updating the structural geometry during the dynamic analysis is given. A computer programme has been written for this purpose.     

The Biology of Upogebia pusilla (Petagna) (Decapoda, Thalassinidea) I. The Burrows

Abstract. The biology of the thalassinidean shrimp Upogebia pusilla was studied on a tidal flat in the Lagoon of Grado (Northern Adriatic). Burrows were investigated using in situ resin casting and with additional in situ and laboratory observations. Burrows show a basic pattern consisting of a U or a double U with turning chambers and a vertical shaft. Mean burrow diameter depends on animal size, it is smaller than the rigid carapace of the animal. Dimensions, distance between openings, depth of U, total depth, volume and surface are size dependent. The burrow wall is smooth and oxidized. Burrows are always inhabited by a single shrimp. Although they overlap, they are never interconnected. They are mainly constructed by compression of the sediment and are relatively permanent structures. A comparison of the burrows of Thalassinidea with regard to shape, number and appearance of openings, dimensions, properties of the burrow wall and dynamics is given.     

Upper Jurassic overlapping-fans slope-apron system: Brae oilfield,North Sea

The Brae oilfield reservoir in the North Sea comprises Upper Jurassic resedimented conglomerates and sandstones interbedded with organic-rich silstone and mudstone thin-bedded turbidites. The system represents a series of small overlapping fans that form a thick (300 m) slope-apron accumulation of sediments deposited in a narrow (<10 km wide) belt along an active fault zone. The complex lateral and vertical distribution of facies was due mainly to variable tectonic activity, and partly also to sediment supply and sea-level changes.     

A sonic well log of the basement complex of the Walvis Ridge

A sonic well log was obtained within the basement complex of the Walvis Ridge during Deep Sea Drilling Project Leg 74. The top of the basement complex is characterized by smooth acoustic reflectors. The rocks recovered within the basement complex consist of basalts with intercalated sediments. According to the log ～-50% of the upper 75 m of basement are igneous rocks and the other 50% sedimentary. Sonobuoy results indicate that the ratio of sediments to basalt increases with depth for an additional 225 m until a typical oceanic velocity structure is observed. Paleontological results suggest that the processes forming this upper 300 m of the basement complex was accomplished within a short time interval.     

Diatoms and aquatic palynomorphs in surface sediments of the White Sea bays as indicators of sedimentation in marginal filters of rivers

Diatom algae, aquatic palynomorphs, and the grain-size of surface sediments from bays of the White Sea were investigated in a program dedicated to the study of marginal filters (MF) in the Severnaya Dvina, Onega, and Kem rivers. Three microalgal assemblages are established in surface sediments, which replace each other successively with distance from river mouths and are characterized by a gradual decrease in a share of freshwater species of diatoms and Chlorophyceae algae, significantly varying concentrations of marine diatoms and dinocysts due to changes in water salinity, grain-size composition of sediments, quantitative distribution of suspended particulate matter (SPM), and water productivity at different marginal filter stages.     

Tectonic evolution of the Siberian Platform during the Vendian and Phanerozoic

This paper presents characteristics of the structural regions surrounding the Siberian Platform and discusses the Vendian-present time evolution of the Siberian Paleocontinent with the Siberian Craton making up its nucleus. It shows that the paleocontinent underwent significant intraplate compressional deformations with vertical movements and formation of inversion structural features within broad areas. Such epochs of deformation took place at the Riphean-Vendian time boundary, during the Late Paleozoic, Late Triassic, Early Cretaceous, and during the Late Cenozoic. The principal rifting events took place during the Middle-Late Devonian. The paper presents paleotectonic reconstructions of East Siberia at several key time intervals.     

Mineralogy and geochemistry of lateritic soil profiles in Kerala, India

Lateritic soils near Calicut, Kerala, contain halloysite of intermediate hydration, kaolinite, goethite, gibbsite and quartz. The presence of halloysite is responsible for relatively high plasticity and cation-exchange capacity. Fe-hydroxide colloids along with halloysite contribute to significant phosphate uptake by this soil. Composition of local groundwater is consistent with weathering of sodic plagioclase to gibbsite, kaolinite and metastable halloysite.     

Recognition of the Cambrian Timan–Severnaya Zemlya orogen and timing of geological evolution of the North Kara sedimentary basin based on detrital zircon dating

New data on the ages of detrital zircons from folded basement rocks and cover sediments of the Severnaya Zemlya archipelago and Izvestiy TSIK islands have been obtained. The basement age is defined as Cambrian (pre-Ordovician). The Ordovician and Silurian sandstones were mainly formed by erosion of the basement rocks. The Devonian sandstones were formed by debris sourced from the Caledonian orogen. The Carboniferous–Early Permian molasse was formed simultaneously with the erosion of the Carboniferous granitoids and weathering of the Ordovician volcanic arc rocks and the Cambrian basement. The North Kara basin was formed in the Ordovician as a back-arc basin. It experienced its main compression deformations at the boundary of the Devonian and Carboniferous and in the Carboniferous.