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Mercury and copper inventories are low in central Lake Superior and increase markedly towards the Keweenaw Peninsula. Total copper flux to Lake Superior sediments averages 5.0 ± 2.5 μg cm-2 year-1(mean ± 95% confidence limits), whereas mercury flux averages 7.5 ± 4.2 ng cm-2 year-1. In the Keweenaw Peninsula region, copper, mercury and silver inventories are elevated and highly correlated. High copper, silver and mercury inventories can be traced back to shoreline stamp sand piles, the parent ores and to smelters. Mercury occurs in elemental form, probably as a natural amalgam, in native metal (copper, silver, gold) deposits and was liberated as volatile Hg0during on-site copper smelting. Stamp mills discharged at least 364 Mt of ‘stamp sand’ tailings, whereas smelters refined 5 Mt of native copper, liberating together at least 42 t of mercury. The Keweenaw situation is not unique, as mineral-bound mercury is commonplace in US and Canadian Greenstone Belts and is of worldwide occurrence in massive base metal ores.

Field observations and experimental measurements of the partitioning coefficient (Kd) of7Be in fresh water show that it varies inversely with the solids concentration at typical environmental values (up to 30 mg/1). This behavior is similar to that of many other metals and organic pollutants, which means that 7Be may be useful as a tracer of the movement of these substances in the water column. However, the wide range in the percentage of 7Be adsorbed by solids over this range of concentrations (over 50%) means that in order to use 7Be either to measure total sedimentation rates or to trace lateral sediment movement it will be necessary to monitor changes in sediment concentration over the area and time period of interest. The wide scatter in our data at both high and low solids concentrations suggests that other factors also affect Kd. Until these factors are identified, application of our results to other systems will be risky. At high (greater than 100 mg/1) solids concentrations over 90% of 7Be is associated with the solid phase, so it may be a useful tracer of reworking rates in bottom sediments. 7Be has a slightly greater affinity for the solid phase in fresh water than in seawater.

Interpretation of regional seismic data and analysis of available well data from the North Viking Graben suggest that a significant phase of structural inversion took place in the Late Jurassic and also in the early Cretaceous. It is believed that this inversion may be a consequence either of compression of the basin as a whole or alternatively, transpressional uplift along offset NW-SE fault systems.The north-south trending Penguin Ridge in UKCS quadrant 211 is interpreted as being such an inversion feature. The Penguin Ridge may well be an extreme example of apparent compression within the context of the Northern North Sea. However, it is clear that less well-developed structures of a similar type have previously been interpreted as simple extensional fault blocks. A compressional or transpressional mode of formation has implications for both reservoir diagenesis and faulting and thus important consequences for exploration play evaluation.It is also proposed that the Penguin Ridge is the northerly limit of a north-south trend or fairway in which compressional features can be observed from regional and field specific seismic data. Certainly there are many anomalous structures within the complex crestal areas of the majority of the Brent Province fields.The impact of such a model is the subject of continuing studies, but it is clear that as the search for more subtle plays intensifies in mature exploration areas such as the North Sea, it is important that the explorationist keeps an open mind, especially when confronted with apparently anomalous data.

The large volume of water, approximately one-fifth of the total surface fresh water on the planet, contained in Lake Baikal in southeastern Siberia is distinguished by having a relatively high concentration of uranium (ca. 2 nM), and, together with the surface sediments, an unusually high234U238Ualpha activity ratio of 1.95. About 80% of the input of uranium to the lake, with a234U238Uratio of 2.0, comes from the Selenga River. Profiles of uranium, as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on Academic Ridge, generally show high values during interglacial periods corresponding to high diatom frustule numbers (DiFr) and biogenic silica (BSi) data that have been reported elsewhere. During glacial periods (low DiFr and BSi), uranium progeny (234U and230Th) were in secular equilibrium with low concentrations of their parent238U. Radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing238U232Thratios and uranium progeny in secular equilibrium. If the234U238Uactivity ratio of adsorbed uranium has remained constant, mean sedimentation rates can be independently estimated as 3.6 ± 0.6 and 3.7 ± 0.9 cm · kyr−1for the decay of234U and in-growth of230Th, respectively. These rates are consistent with a mean rate of 3.76 cm · kyr−1, calculated by optimization of the correspondence between adsorbed238U and δ18O in dated oceanic sediments. The adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation. Evidently, uranium has not been significantly redistributed within Baikal sediments over at least the past 250 kyr and is a unique, biologically non-essential, tracer for climate-sensitive processes, which provide their own internal geochronometers, potentially useful for ages up to 1 Myr BP.

The large volume of water, approximately one-fifth of the total surface fresh water on the planet, contained in Lake Baikal in southeastern Siberia is distinguished by having a relatively high concentration of uranium (ca. 2 nM), and, together with the surface sediments, an unusually high234U238U alpha activity ratio of 1.95. About 80% of the input of uranium to the lake, with a234U238U ratio of 2.0, comes from the Selenga River. Profiles of uranium, as well as the extent of isotopic disequilibrium in a 9 m sediment core collected on Academic Ridge, generally show high values during interglacial periods corresponding to high diatom frustule numbers (DiFr) and biogenic silica (BSi) data that have been reported elsewhere. During glacial periods (low DiFr and BSi), uranium progeny (234U and230Th) were in secular equilibrium with low concentrations of their parent238U. Radionuclide distributions were interpreted in terms of a quantitative model allowing for adsorption of riverine inputs of uranium onto two classes of sedimenting particles with differing238U232Th ratios and uranium progeny in secular equilibrium. If the234U238U activity ratio of adsorbed uranium has remained constant, mean sedimentation rates can be independently estimated as 3.6 ± 0.6 and 3.7 ± 0.9 cm · kyr−1 for the decay of234U and in-growth of230Th, respectively. These rates are consistent with a mean rate of 3.76 cm · kyr−1, calculated by optimization of the correspondence between adsorbed238U and δ18O in dated oceanic sediments. The adsorbed uranium apparently tracks variable river flow during interglacials and is drastically reduced during periods of glaciation. Evidently, uranium has not been significantly redistributed within Baikal sediments over at least the past 250 kyr and is a unique, biologically non-essential, tracer for climate-sensitive processes, which provide their own internal geochronometers, potentially useful for ages up to 1 Myr BP.

The distribution of 210Pb, 137Cs, and Ambrosia(ragweed) pollen in two sediment cores from Lake Ontario and in three cores from Lake Erie provides independent estimates of sediment accumulation rates. Geochronology with 210Pb is based on radioactive decay of the isotope following burial in sediments. The method can reveal with precision changes in sedimentation occurring over the past 100 yr or so. Geochronologies with 137Cs and Ambrosiaare based on the occurrence of a horizon corresponding, respectively, to the onset of nuclear testing 25 yr ago and to regional forest clearance in the middle 1800s. These methods provide estimates of long-term average sediment accumulation rates. In all but one core, the distributions of 137Cs and 210Pb indicate no physical mixing of near-surface sediments. In two cores, including one from central Lake Erie collected by diver, all three estimates of sedimentation rates are in excellent agreement. In two other cores, rates based on 210Pb are significantly higher than those inferred from Ambrosiapollen profiles. Lower average rates appear to result from occasional massive losses of sediments. Such events, apparent in the distribution of 210Pb but not in pollen records, correlate with the occurrence of major storm surges on the lakes during this century. In one core from western Lake Erie, exponential distributions of both 210Pb and Ambrosiaappear to be artifacts which may result from extensive biological or physical reworking of sediments in shallow water (11 m). Previous indications of increased sedimentation in Lake Erie since about 1935 based on Castanea(chestnut) pollen data are not substantiated.

The 12C(d, n)13N reaction has been studied in the region of the 4 MeV resoance. Measured excitation and angular distribution curves have been analysed on the assumption that the reaction proceeds principally in two modes, one resonant, the other non-resonant. The total reaction amplitude is written as the sum of a stripping theory and a amplitude resonnance amplitude having a Breit-Wigner denominator. Satisfactory fits to the experimental data are obtained with a resonance energy of 4.02 MeV and a level width of about 235 keV. The analysis shows that the resonant state probably has spin 1 with even parity. The relationship of these results to others bearing on this level and the possible nature of the level are both discussed.