Incorporation of uranium in modern corals

Uranium occurs in corals at three sites: 1, in organic matter; 2, adsorbed on the surfaces of skeletal aragonite; and 3, in the aragonite lattice. Organic matter incorporates from sea water by chelation 40–70 ppm uranium; skeletal aragonite incorporates only 3 ppm. However, as the organic fraction is low (0·1%), its high concentration of uranium does not significantly affect the total concentration of uranium in the coral. A negligible concentration of uranium, 40–60 ppb, is adsorbed on skeletal aragonite from which it is readily leached or exchanged. This low concentration of adsorbed uranium (<2% of the total uranium in skeletal aragonite) is related to the very small specific surface area (1·5–1·8 m²/g of the corals.     

WHEN THE LIGHTS GO OUT IN CHESHIRE*

ABSTRACT. The purchase and subsequent demolition of Cheshire, Ohio‐located in the shadow of the General James M. Gavin Power Plant‐has attracted national attention. According to a New York Times report, “the deal … is believed to be the first by a company to dissolve an entire town.” In this article we consider historical precedents for the case, explore the thirty‐year history of community‐plant relations in Cheshire, and recount the series of incidents that ultimately led to the town's sale. We discuss the impact that the town's sale has had on the local community and the larger implications of American Electric Power's actions.     

The high-level marine shell beds of Scotland and the build-up of the last Scottish ice sheet

It is argued that high-level shell beds buried by till at various localities around the Scottish coast are in situ and represent a marine transgression immediately prior to and consequent upon loading of the earth's crust by the build-up of the last Scottish ice sheet. The high-level rock platforms of the Hebrides may also have been eroded at this time. A relationship between the build-up of the last Scottish ice sheet and world sea-level is suggested and it is further argued that the Scottish ice sheet was a more sensitive indicator of the onset (and termination) of a period of northern hemispheric glaciation than either the Laurentide or Scandinavian ice sheets. It is suggested that the build-up of the last Scottish ice sheet took place in the Early Devensian and a tentative correlation is proposed between the Scottish evidence and the deep-sea evidence for glacier build-up at ca. 75,000 years B.P     

Flow properties of turbidity currents in Bute Inlet, British Columbia

Bute Inlet, a fiord along the southwestern coast of British Columbia, Canada, includes a sea-floor sedimentation system 70 km in length which resembles those developed on some large submarine fans. Turbidity currents originate at the head of the flord on the submerged delta fronts of the Homathko and Southgate rivers. They move downslope for about 30 km within a single large incised channel, spill onto a depositional area termed the channel lobe complex, and finally spread out over a low-relief distal splay area that passes 55 km downslope into a flat basin floor. During the present study, turbidity currents in Bute Inlet were studied using sea-floor morphology, bottom sediment distribution, and in-situ instrument packages. The mean velocities of the most recent flows, estimated from surface sediment grain size, has varied between 100–120 cm s^–1 in the incised channel, 20–50 cms^–1 in the channel lobe complex, and < 5 cm s^–1 on the basin floor. Velocities based on channel morphology are poorly constrained but are in the range of 160-425 cm s^–1 in the upper part of the incised channel and 66 cm s^–1 in the lower channel. Calculated flow densities range from 1.049 to 1.028g cm^–3. Turbidity flows monitored in 1986 using submerged instrument packages exceeded 32 m in thickness in the upper part of the incised channel, where the maximum measured velocity was 330 cm s^–1. At the head of the channel lobe complex the maximum velocity had declined to 75 cm s^–1. The density of the monitored flows is estimated at 1.025-1.03g cm^–3. The cored sediments and channel morphology yield estimates of mean flow velocities that are generally greater than those measured by the in-situ instrument packages and estimated from modern surface sediments. The former suggest past flow velocities up to 500 cm s^–1 in the incised channel, about 20 cm s^–1 in spillover deposits along the lower part of the incised channel, and 100-140 cm s^–1 in the distal splay. The contrast between the velocities of modern and past flows suggests that past flows may have been considerably larger and more energetic than those presently occurring in Bute Inlet. The size properties of sediments in the monitored turbidity flows suggest a strong vertical size gradient in the suspended load during transport. The surface and cored sediments fine downslope from the channel lobe complex to distal splay area. Distinctive sedimentary sequences are recognized in cores from the spillover lobes, channel lobe complex, distal splay, and basin floor depositional areas. Many individual turbidites grade downslope from massive T_a divisions in the channel lobe complex and probably in the incised channel to T_a divisions overlain by slurried divisions on the distal splay and largely slurried beds on the basin floor. These facies suggest that individual currents commonly evolve from largely cohesionless suspensions in the incised channel and channel lobe complex to dilute cohesive slurries downslope on the distal splay and basin floor. Many flows in Bute Inlet fail to develop a traction state of sedimentation and the resulting turbidites lack well-developed T_b. T_c, and T_d divisions.     

Diffusion of sediment on the lee of dune-like bedforms: theoretical and numerical analysis

Theoretical and empirical analyses of flow structure, sediment transport, and sediment size characteristics at the crest of dune-like bedforms indicate that it is possible to describe, at least semi-quantitatively, the diffusion and deposition of sediment on the leeside of such structures. A numerical program based on this analysis simulates the grain-size distribution and deposition rate on the leeside of dunes for specified flow conditions and bed material. Evaluation of flow and sediment variables through the numerical simulation program shows that flow velocity, flow depth and sediment size have a strong influence on the deposition rate and texture of leeside sediment before avalanching. Sorting of the bed material, in particular, appears to exert a strong control on both the grain-size and the deposition-rate gradients.     

Minor-element and Revised Major-element Contents of Some Mediterranean Pantellerites and Comendites

Optical emission spectrographic analysis of three pantelleritesfrom Pantelleria and two comendites from Sardinia show highconcentrations of B, Be, Ga, La, Mo, Nb, Sn, Y, Yb, and Zt andlow contents of Ba, Co, Cr, Ni, Sr, and V. Minor-element trendsof these specimens are very similar to those of pantelleritesfrom southern Nevada and New Zealand and other peralkaline silicicrocks from various localities. Fluorine contents of the Pantellerianspecimens range from 0.19 to 0.32 per cent by weight resultingin abnormally high Cl to F ratios. New analyses for MgO, Na₂O,and K₂O are almost identical with the values obtained by Zies.Revised major-element compositions and calculated glass-phasecompositions for the three Pantellerian specimens are given.