The Oslo Rift: new palaeomagnetic and 40Ar/39Ar age constraints

⁴⁰Ar/³⁹Ar whole-rock and alkali feldspar ages demonstrate that dioritic to monzonitic dykes from Bøverbru and Lunner belong to the youngest recorded magmatic activity in the Oslo Rift region, southeast Norway. These dykes represent the terminal phase of rift and magmatic activity in the Oslo Graben, at the dawn of the Triassic (246–238 Ma).
  The Bøverbru and Lunner dyke ages are statistically concordant. However, the palaeomagnetic signature of the Bøverbru dyke is complex, and directions from the margins and the interior of the dyke differ in polarity. Therefore, the new Early Triassic palaeomagnetic pole for Baltica (Eurasia) is exclusively based on the less complex Lunner dykes and contacts (palaeomagnetic pole: latitude=52.9°N, longitude=164.4°E, dp / dm =4.5 ° /7.3°). The early Triassic palaeomagnetic pole [mean age: 243±5 Ma (2 σ )] is slightly different from the Upper Carboniferous–Permian (294–274 Ma) and Kiaman-aged poles from the Oslo Rift.     

The relationship between phytolith- and plant-water δO values in grasses

Information regarding climatic conditions during plant growth is preserved by the oxygen-isotope composition of biogenic silica (phytoliths) deposited in grasses. The O-isotope compositions of phytoliths and the plant water from which they precipitate are dependent on soil-water δ¹⁸O values, relative humidity, evapotranspiration rates, and temperature. Plant water and phytoliths from two grass species, Ammophila breviligulata (C₃) and Calamovilfa longifolia (C₄) at Pinery Provincial Park in southwestern Ontario, Canada, were examined to determine the variability in their δ¹⁸O values. Stem water was unfractionated from soil-water in oxygen isotopic composition and the δ¹⁸O values of stem silica provide a good proxy for the soil water available to roots during the growing season. Greater spatial and temporal variation in the δ¹⁸O values of water in the top 5 cm of the soil, and their enhanced sensitivity to evaporative ¹⁸O enrichment, are reflected in the generally higher δ¹⁸O values of water in the shallow roots and rhizomes of these grasses. Water within the sheath and lower and upper leaf tissues experiences continual evaporation, becoming progressively enriched in ¹⁸O as it moves towards the tip of the leaf. However, the water from which leaf silica precipitates has not acquired the extreme ¹⁸O enrichment predicted using steady-state models, or measured for midday or average daily leaf water. Possible explanations for this behaviour include preferential deposition of silica at night; the existence of a secluded water fraction within the leaf, which experiences smaller diurnal variations in isotopic composition than leaf water at sites of evaporation; kinetic isotope effects during rapid precipitation of leaf silica; and incomplete exchange between the oxygen in the silicic acid and the leaf water.     

Application of a sensitive chemiluminescent technique for comparison of cytochrome P4501A induction in hepatic and intestinal tissues of fish exposed to bleached kraft mill effluent

In conjunction with an environmental assessment of biologically-treated bleached kraft mill effluent (BKME) in a Western Canadian river, data indicated that lipophilic compounds were transferred to the mountain whitefish Prosopium williamsoni through ingestion of filter-feeding benthic caddisflies. P4501A induction was correlated with lipophilic body burdens, not with indices of recent BKME exposure. P4501A contents in hepatic and intestinal tissues of BKME-exposed whitefish were compared during a follow-up collection. Ethoxyresorufin O-deethylase (EROD) activity was not detectable in intestines; P-450 spectral analysis indicated denaturation had occurred. Use of enhanced chemiluminescence (ECL) immunoblotting achieved at least 10-fold greater sensitivity over colorimetric methods and indicated that some intestines did contain P4501A protein. No correlation of intestinal P4501A with hepatic EROD activity or P4501A content was found. Application of the ECL technique significantly improves the analytical detection limits of P4501A immunoblotting. Analysis of historical samples from this site will further probe water-borne versus dietary routes of uptake of BKME-related P4501A inducers in this species.