Lateral coherence of longitudinal wind components in strong winds

A combination of lateral coherence measurements of wind speed at five locations suggests that the decay constant is a monotonically increasing function of the ratio of separation to height, under neutral conditions.     

Growth of Mytilus edulis in net bags transferred to different localities in a eutrophicated Danish fjord

The growth rate has been measured in Mytilus edulis transferred in net bags to seven localities in the brackish Danish fjord, Limfjorden, in which certain areas are heavily eutrophicated. The increase in shell length, shell weight and flesh body weight was measured after growth periods of 14–18 days. The increase in, e.g., flesh dry weight ranged from twice the start weight to a four-fold increase of the start weight. The net growth efficiencies were estimated to be between 54 and 73%. Algal concentration was in no case the limiting growth factor, but low growth rates were observed in areas with seasonal oxygen depletion and release of toxic H₂S from the sediments. It is suggested that measurements of actual growth in M. edulis can be a useful technique in the study of biological effects in marine recipients.     

Mesozoic ophiolites,sutures, and arge-scale tectonic movements in Afghanistan

The tectonic history of Afghanistan appears to be the result of successive accretion of fragments of Gondwana to the active margin of Laurasia since the end of the Paleozoic. The margin, in Afghanistan, lies along the present Herat and Panjshir faults, south of Hindu Kush, swings around the central Pamirs and can presumably be traced along the present western Altyn Tagh and Kunlun faults in Tibet. North of this boundary, Paleozoic rocks have been deformed in the Upper Paleozoic, whereas south of it, there is no trace of the Hercynian orogeny. The first collision of Gondwanian fragments with Laurasia probably occurred in the early Mesozoic along the Hindu Kush and Kunlun. To the south, ophiolites along the Panjao and Pangong-Nu Chiang sutures (respectively in central Afghanistan and central Tibet) testify for another suturing event in the Upper Jurassic or Lower Cretaceous. The Indus-Tsangpo suture between India and Tibet corresponds, in eastern Afghanistan, to two ophiolite subbelts, near Kabul and Khost. Both ophiolite complexes have been emplaced between Maestrichtian and Lower Eocene by choking of two northward-dipping subduction zones. After complete contact between the Indian and Asian continents was achieved, presumably in the end of Eocene, the penetration of India into Asia caused large-scale intra-continental shortening. A large part of the shortening was accommodated by strike-slip faulting along Mesozoic and more ancient sutures. Central Afghanistan, in particular, was extruded to the west along the Herat suture by the protrusion of the Pamir wedge. It subsequently collided with the Lut block.     

Hydrochemistry of the Lake Magadi basin,Kenya

New and more complete compositional data are presented for a large number of water samples from the Lake Magadi area, Kenya. These water samples range from dilute inflow (<0.1 g/kg dissolved solids) to very concentrated brines (>300 g/kg dissolved solids). Five distinct hydrologic stages can be recognized in the evolution of the water compositions: dilute streamflow, dilute ground water, saline ground water (or hot spring reservoir), saturated brines, and residual brines. Based on the assumption that chloride is conserved in the waters during evaporative concentration, these stages are related to each other by the concentration factors of about 1:28:870:7600:16,800.Dilute streamflow is represented by perennial streams entering the Rift Valley from the west. All but one (Ewaso Ngiro) of these streams disappear in the alluvium and do not reach the valley floor. Dilute ground water was collected from shallow pits and wells dug into lake sediments and alluvial channels. Saline ground water is roughly equivalent to the hot springs reservoir postulated by Eugster (1970) and is represented by the hottest of the major springs. Saturated brines represent surficial lake brines just at the point of saturation with respect to trona (Na₂CO₃.NaHCO₃.2H₂O), while residual brines are essentially interstitial to the evaporite deposit and have been subjected to a complex history of precipitation and re-solution.The new data confirm the basic hydrologic model presented by Eugster (1970) which has now been refined, particularly with respect to the early stages of evaporative concentration. Budget calculations show that only bromide is conserved as completely as chloride. Sodium follows chloride closely until trona precipitation, whereas silica and sulfate are largely lost during the very first concentration' step (dilute streamflow-dilute ground water). A large fraction of potassium and all calcium plus magnesium are removed during the first two concentration steps (dilute streamflow-dilute ground water-saline ground water). Carbonate and bicarbonate are the dominant anions, and mechanisms by which they are extracted from the solution include precipitation of alkali and alkaline-earth carbonates, and degassing, as well as precipitation and re-solution of efflorescent crusts. Much sulfate is apparently lost from solution by sorption as well as subsurface reduction.Seasonal runoff, principally from the valley floor north of Lake Magadi, is considered to be the principal recharge to the Magadi ground water system. Evaporative concentration is the overall process responsible for the chemical evolution of the brines. This includes not only simple evaporation, but also mineral precipitation as films and cements in the unsaturated zone, re-solution, and reprecipitation of efflorescent crusts, with consequent recycling of salts. In fact, a large fraction of the solutes are acquired through dissolution of efflorescent crusts.Data were obtained for borehole brines from as deep as 297 m. They show the existence of two distinct brine bodies below the present lake, one shallow, coexistent with bedded salts, and highly concentrated (260 g/kg average dissolved solids), and the other deeper in lacustrine sediments or fractured lavas, and only half as concentrated.