Sedimentary rocks exposed at Dob’s Linn, Scotland, have significantly influenced our understanding of how life evolved over the Ordovician to Early Silurian. The current interpreted chronostratigraphic boundary between the Ordovician and Silurian periods is a Global Boundary Stratotype Section and Point (GSSP), calibrated to 443.8 ± 1.5 Ma (Hirnatian–Rhuddanian age), based on biostratigraphic markers, radioisotopic dates and statistical modelling. However, challenges arise due to tectonic disturbances, complex correlation issues and the lack of systematic dating in Ordovician–Silurian stratigraphic sections. Here, hundreds of zircon grains from three metabentonite ash horizons were dated using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). A subset of the grains were re-analyzed using Chemical Abrasion Isotope Dilution Thermal Ionization Mass Spectrometry (CA-ID-TIMS). We present a high-precision CA-ID-TIMS 238U-206Pb weighted mean date of 440.44 ± 0.55/0.56/0.72 Ma (±analytical/with tracer/with U-decay constant) for the Coronagraptus cyphus biozone. However, the study reports younger, and in certain cases, older LA-ICP-MS zircon dates within the Coronagraptus cyphus, Akidograptus ascensus and Dicellograptus anceps zones, suspected as being influenced by Pb loss and LA-ICP-MS matrix mismatch. The study reports concerns about the suitability of Dob’s Linn as a GSSP section and examines various LA-ICP-MS maximum depositional age (MDA) approaches, suggesting the use of the TuffZirc date and the youngest mode weighted mean (YMWM) as suitable MDA calculations consistent with CA-ID-TIMS results.

The chemical composition of unaltered biotites extracted from 18 Lower Palaeozoic metabentonites from Sweden, Norway and Scotland was determined. Discrimination based on FeO, MgO and TiO2 proved able to separate the metabentonites on the basis of their stratigraphical age. A triangular discrimination diagram using MgO, FeO and Al2O3 classified the biotites as calc-alkaline. Independent support for the discriminant power of FeO, MgO and TiO2 in biotite comes from Sr isotope ratios and Sr concentration data from cognate apatite crystals. Within this dataset Caradocian and Llandoverian metabentonites have unique biotite compositions, while Wenlockian samples can be characterized to a lesser degree. Biotite composition also supported the correlation of a pair of metabentonites from Norway known to form part of the same horizon. Biotite in metabentonites preserves the chemical signature of the host magmas in which it crystallized and can be used to discriminate between metabentonites of different ages and provenance.

Fluids trapped inside fluid inclusions in quartz from the multiphase Starav monzogranite in Etive, Argyll, were extracted under vacuum and quantitative data for H2O and CO2 were obtained manometrically. Na and K were determined on an aqueous leach from the decrepitated grains. A bivariate diagram of H2O/CO2 versus Na/K discriminates between magma pulses and mirrors the whole-rock trace-element chemistry. This work shows that compositional variations of fluids in quartz from a weakly mineralised granitoid intrusion are sensitive indicators of its magmatic history and identify subtle changes in its mineralogical composition.

Observations of CO emission (Kutner et al. 1977) have delineated a molecular cloud extending over several square degrees in the Orion region, and extensive surveys have been made of several other molecules (e.g. CN, CS, HCN, H2CO, H2H+) in the densest regions of this cloud.

At the centre of the Parkes 64—m radio telescope a region of diameter 17 m has recently been resurfaced to improve its efficiency at high frequencies. The first measurements using this section have been made at 22 GHz, in observations of both continuum sources and water tfapour masers. For these observations the receiver front-end used a mixer cooled in liquid nitrogen, followed by a 5 GHz cryogenic parametric amplifier as a second stage. The option of switching against an offset horn was available and the total systemnoise temperature was ∽ 750 K.

In this paper we present maps showing the distribution of HCO+ (J= 1→0 transition at 89.18855 GHz) in the direction of NGC 6334 as a function of radial velocity, lhe observations were carried out in May-June 1979 as part of a larger program of HCO+ observations (Batchelor et al. 1980, 1981) using the Epping 4-m millimetre-wave radio telescope.

Ammonia was the first interstellar molecule with more than two atoms to be discovered (Cheung et al. 1968). Since that time it has been observed in many HII regions and dark clouds (Mayer et al. 1973; Morris et al. 1973; Cheung et al. 1973; Kaifu et al. 1975). The molecule has a rich rotation-inversion spectrum with about 10 transitions in the range 23-25 GHz. Each line has hyperfine structure which permits, in principle, the determination of optical depths, filling factors and excitation. Unfortunately line brightness temperatures are low (<1 K) so that a low-noise receiving system and long integration times are required to exploit these possibilities.

A new maser receiver, operating between 20 and 24 GHz and constructed by the radiometer group at the CSIRO Division of Radiophysics, was first scheduled for astronomical observations in December 1981. In good observing conditions the system temperature was as low as 60 K. In conjunction with the versatility of the 1024-channel correlator and the large collecting area of the Parkes telescope (the central 37 m illuminated at 22 GHz yields a ratio of flux density to antenna temperature of 9∼ Jy K-1) the total system is a very powerful new tool. Here we report some observations of naturally occuring celestial H2O masers which we have studied with this system.

A 4-m telescope for mm-wave observations, particularly of spectral lines, was erected in mid-1976 at Epping by Krupp Ltd., Rheinhausen. A cooled mixer receiver was installed on the telescope in April 1977 and a series of test observations made during the remainder of the year, subject to the availability of the receiver and the multi-channel filter bank which were shared with the Parkes 64-m telescope.