Water quality trends at an upland site in wales,UK, 1983–1993

Ten years of detailed upland stream and bulk deposition water quality data from Plynlimon, mid-Wales, are examined for trend. A robust statistical test (the seasonal Kendall test) is applied and data are presented graphically. Smoothing techniques are used to highlight the patterns of change which underlie high data scatter. The graphs show long-term cycles within the data which violate the assumptions of common statistical tests for trend. These cycles relate to fluctuations in the weather patterns at Plynlimon. Even though the seasonal Kendall test is significant for some determinands, the evidence from the graphs suggests that many of these ‘trends’ are unlikely to continue. For solutes in rainfall, there is no convincing long-term trend. There is a possible increase in ammonium concentrations, which may indicate an increasing atmospheric source generated by farming activities, but this will require a longer data series for confirmation. Several trace metal concentrations increased significantly part way through the study period, but later returned to the original levels. The bulk precipitation sea salt input has been uneven over the 10-year sampling period, with the highest inputs occurring during the wetter winters. For solutes in streamwaters, there are clear trends in dissolved organic carbon (DOC), iodine and bromide, which increase over time and may be attributed to an increase in organic decomposition in the catchment. Previous studies in Wales have shown similar behaviour for colour, which is related to DOC, but the corresponding changes for bromide and iodine are new. For most other streamwater determinands, any changes are masked by the effects of year to year variations in the quality and quantity of rainfall. For example, zinc and chromium variations parallel the corresponding rainfall quantity variations. The effect of rainfall quality variation is marked for marine-derived elements such as chloride. For sulphate, streamwater variations are inverted relative to chloride. This suggests that dry deposition may vary with weather conditions: high when the wind direction is from the land and low when weather systems are predominantly frontal and laden with sea salts. Alternatively, high sea salt rainfall may be affecting absorption/solubility reactions in the soils. There are four main conclusions. Firstly, there is no indication of changing acid deposition inputs or changing acidity within the runoff, despite a decline in UK sulphur dioxide emissions. Secondly, streamwater DOC has shown an increase over time, but there is no clear corresponding decrease in pH as might be expected from acidification theory. Thirdly, there are cyclical variations in bulk precipitation inputs and in streamwater quality, which mean that trends cannot be established even with 10 years of data. Long-term cycles are likely to exist in other environmental data and extreme care is required for the interpretation of trend, especially if data sets are short. This aspect strongly supports the continuation of long-term monitoring programmes over several decades. Finally, the graphical application strongly enhances data analysis and should be considered an essential component of trend investigation.     

Palynology of organic beds below Devensian glacigenic sediments at Pen-y-bryn,Gwynedd, North Wales

Pollen diagrams from organic facies overlain by glacigenic sediments at Pen-y-bryn, North Wales (53°7′N, 4°16′W), suggest that it is the first locality in the British Isles to provide evidence for several Devensian interstadials prior to Devensian stadial glaciation(s). The evidence is not, however, unequivocal. At least two main episodes of organic sedimentation are indicated, separated by an interval of uncertain duration. One eposide records a Pinus-Picea-Betula forest. A second, possibly later, event, with tree pollen less than 10% of total land pollen (TLP), suggests a cool, largely unforested environment. A third episode, with tree pollen up to 25% of TLP, may be related to the latter or be of intermediate age, whereas a fourth and later episode of organic accumulation may be of reworked material. Radiocarbon dating of organic deposits and of a wood macrofossil enclosed in basal till is inconclusive, as is preliminary uranium-series dating. The principal biogenic episodes may correlate with Oxygen Isotope Substages 5c and 5a, but as the pollen records reflect facies floras, the correlation remains tentative; it is also possible that other temperate periods are recorded. Further resolution of the chronostratigraphy is required to help clarify the problematic correlation of interstadial and stadial events in northwest Europe and to correlate more accurately the biogenic and glacigenic facies at Pen-y-bryn with their Pleistocene equivalents elsewhere.     

The ordovician (caradoc) volcanic rocks of montgomery,Powys, N. Wales

The Ordovician (Caradoc, Soudleyan) rocks of Montgomery, Powys are shales interbedded with locally conglomeratic volcaniclastic sediments composed of andesitic detritus. New formal lithostratigraphic units are proposed: Montgomery Volcanic Group comprising in ascending order: Castle Hill Shale Formation, Castle Hill Conglomerate Formation and Quarry Sandstone and Shale Formation. The volcaniclastic strata are reinterpreted as deposits of a submarine volcaniclastic fan system sourced by contemporaneous andesitic island volcanism. The observed diagenetic sequence is typical of marine volcanic sandstones and was dominated by hydration reactions related to the degradation of abundant unstable volcanic detritus. Diagenesis has resulted in the virtual destruction of original porosity in the volcaniclastic rocks.     

Late Ordovician island‐arc volcanic rocks,northern Capertee Zone,Lachlan Fold Belt,New South Wales

The Cape Hoskins volcanoes form part of the Quaternary volcanic island arc that extends from Rabaul in the east to the Schouten Islands in the west, and they overlie the northerly dipping New Britain Benioff Zone. The products of the volcanoes range in composition from basalt to rhyolite, and are normative in quartz and hypersthene. They contain phenocrysts of plagioclase and subordinate augite, hypersthene, and in most samples iron‐titanium oxides; some samples also contain olivine or quartz or both, and some pumice contains hornblende and, rarely, biotite.

Chemical analyses of 29 volcanic rocks are presented; 22 were also analysed for 17 minor elements — Rb, Ba, Sr, Pb, Zn, Cu, Zr, Y, Ni, Co, Sc, Cr, V, Ga, B, U, and Th.

Chemically the rocks have many of the characteristics of the ‘island arc tholeiitic series’, but do not show a pronounced relative enrichment in iron and appear to be relatively enriched in Sr. Compared with volcanic rocks from the northern part of the Willaumez Peninsula, they are lower in K (but not Na), Ti, Rb, Ba, Zr, Pb, Th, Ni, and probably also V, Cu, and Zn: these differences are attributed to the greater depth of the Benioff Zone beneath the Willaumez Peninsula. The more basic of the Cape Hoskins rocks are similar in most respects to lavas of comparable composition from Ulawun volcano to the east.     

Early Ordovician brachiopods from south-west Wales

The Early Ordovician brachiopods of south-west Wales (Pembrokeshire and Carmarthenshire) are identified, in most cases for the first time. That period is termed the local Arenig Stage in Britain, but it is now correlated with the Floian, Dapingian, and earlier half of the Darriwilian, which are more recently established international stages in the system of stratigraphical nomenclature. The rocks in south-west Wales were laid down as turbidites in a backarc basin which formed part of the margin of the relatively small independent microcontinent of Avalonia at that time. However, since the Rheic Ocean between Avalonia and the immense Gondwana continent was relatively narrow in the Arenig, the brachiopods reviewed here can be established to be part of the Mediterranean Province, which was also extensive in the higher-latitude sectors in and around Gondwana in the Early Ordovician. The 17 brachiopod species identified within the Arenig brachiopod faunas of south-west Wales are described, including the new species Aporthophyla prisca, Tritoechia bolohaulensis, Skenidoides pontyfennensis and Paurorthis? llangynogensis.     

Geochemical variation in the Penmaenmawr intrusion (North Wales)

To determine the pattern of geochemical variation within the Penmaenmawr intrusion, 41 rocks were analysed for major oxides and 15 minor elements. The results indicate pulsational emplacement of sheets of magma from a parental body at depth undergoing crystallization differentiation. These sheets now strike NE–SW and dip southeastward. The resultant intrusion shows a range of SiO₂ contents from 57·3% to 65·6% (H₂O-free). Geochemical evidence suggests that it was derived from an intermediate parental magma and is possibly related to parts of the Conwy Rhyolite Formation. © 1997 John Wiley & Sons, Ltd.     

Loch Lomond Stadial glaciers in the Aran and Arenig Mountains,North Wales,Great Britain

Geomorphological evidence for four former local glaciers has been mapped in the Aran and Arenig Mountains, North Wales. Former glacial extent was deduced from the distribution and assemblage of end and lateral moraines, hummocky moraine, boulder limits, drift limits and periglacial trimlines. Comparison of infilled lake sediment stratigraphies inside and outside of the former glacier limits suggests a Loch Lomond Stadial (Late Devensian) age of the former glaciers (c. 12.9–11.5 cal. ka BP ). This finding is also supported by periglacial–landform contrasts between the land inside and outside of the glacier limits. Reconstruction of the four glaciers illustrates a mean equilibrium line altitude (ELA) of c. 504 m. From the reconstructed ELAs and the combination of precipitation and snowblow input for total accumulation, by analogy with Norwegian glaciers, a mean sea‐level July temperature is calculated at 8.4°C. Copyright © 2002 John Wiley & Sons, Ltd.     

Assessing the suitability of OSPAR EcoQOs for eutrophication vs ICES criteria for England and Wales

This paper provides a preliminary evaluation of the suitability of OSPAR Ecological Quality objectives for eutrophication for coastal and offshore waters of England and Wales on the basis of ICES criteria. In principle, EcoQOs are easy to understand, but responses to nutrient enrichment are complex. Few studies provide unequivocal evidence of links between inputs and response. Monitoring is generally feasible and in place, but needs to be improved. The best EcoQO is winter nutrient concentrations. Chlorophyll concentrations are a good indicator in environments susceptible to nutrient enrichment. The EcoQO for zoobenthos/fish kills potentially meets all criteria for a good indicator; EcoQOs for phytoplankton indicator species, oxygen concentrations and zoobenthos changes do not. Greater emphasis needs to be placed on seasonal effects of nutrient inputs and phytoplankton response, natural susceptibility of different water bodies, differences between coastal and offshore environments, and developing longer time series of data.     

Cathodoluminescence study of carbonate cements in the Upper Cambrian conglomerates from the Wonominta Block,northwestern New South Wales

Petrological studies were carried out on the Upper Cambrian conglomerates from the Bilpa and Cupala Creek areas, in the Wonominta Block, northwestern New South Wales. The sediments are post‐orogenic, molasse‐type, shaped in continental and shallow‐marine environments, and deposited in the form of major coarse‐grained deltas. Diagenetic processes caused an extensive lithification of these psephitic deposits. Multistage carbonate cementation is one of the most significant diagenetic changes that occurred. Several generations of carbonate cements have been distinguished based on observations under the polarising microscope, and particularly, using cathodoluminescence analysis. In both areas studied the conglomerates show four types of calcite cements under cathodoluminescence developed in the following order: non‐luminescent (+oscillatory zoned)‐bright orange‐dull orange‐(non‐luminescent). The most likely sequence of carbonate cementation is presented involving eo‐, meso‐ and telo‐ stages of diagenesis. Minor malachite crystallised along with calcite in the telodiagenetic stage.     

Rare cephalopods from the Přídolí of England and Wales

The very rare occurrences of cephalopods in the Přídolí Series of the English and Welsh Silurian are recorded and their taxonomy revised. Apart from one derived form, they constitute a typical relict Ludlow fauna, including Cyrtocycloceras ibex, Leurocycloceras whitcliffense, and Polygrammoceras bullatum. Copyright © 2000 John Wiley & Sons, Ltd.