Minute, lamellose concentric micro-frills are described on the external surfaces of the Devonian brachiopod Athyris campomanesi (Verneuil & Archiac). The micro-frills are very regularly spaced with a separation of approximately 0.5 mm, are inclined anteriorly and antero-laterally, and become more or less recurved peripherally down towards the valve surface. These micro-frills must have been secreted by outward extensions of epithelium, presumably resulting from an increase in the rate of cell proliferation or extension in the marginal zone. Extrapolating from the known growth rates of living brachiopods, it seems probable that the micro-frills formed very rapidly, within a matter of days or hours. In life the micro-frills would have formed minute channels around the peripheries of both valves, similar in form and function to rain gutters. As such they probably functioned as baffle chambers, within which excess paniculate material from the inhalant feeding currents would have accumulated. Such particulate material is likely to have been moved laterally from the median axis of the shell down to the sediment surface under the effects of gravity and in vitro shell movements. Each micro-frill may only have functioned in this fashion for a matter of weeks before being rendered ineffective by the forward growth of the valve margin, at which stage it would have been abandoned and replaced by a subsequently formed micro-frill.

Conglomerates from the Lettergesh Formation in the Silurian sequence of N Galway, Ireland, demonstrate palaeocurrents from the NE. Fabric studies demonstrate that the conglomerates were emplaced largely by traction currents and not by down-slope sliding or dispersive currents. Stratigraphic relationships demonstrate that the conglomerates were deposited in an environment which was adjacent to fluviatile, shallow-marine and deeper shelf facies at different times. A fan-delta environment of deposition is suggested, which requires a modification of previous Silurian sea-level curves at, or near, the base of the Wenlock.

The first section of the paper is concerned with a detailed account of the structure of the classic Schiehallion area. The account is extended to the flat belt via the Glen Lyon-Ben Lawers area. It is demonstrated that major D1 folds involve the whole of the Appin and Argyll groups and now face SE. However, the original D1 folds were probably open upward-facing folds which have been refolded and modified by the dominant D2 deformation. D2 is represented by an antiformal complex which culminates downwards in the Boundary Slide, a zone of strong deformation associated with NW translation of Dalradian over the ‘young Moine’ rocks. D3 has been responsible for the rotation of the originally flat D2 structures into their present ‘steep’ attitudes N of Glen Lyon. D4 is represented by the strike-swing of the lower Dalradian formations, possibly related to early movements on the two major faults that bound the area. The concept of a D1 Tay Nappe which roots in the ‘young Moine’ to the N is retained, although the scale and flat attitude of that fold is regarded as in part a product of D2.

Results emerging from the long-term forestry versus upland grassland paired catchment study conducted by the Institute of Hydrology at Plynlimon, mid-Wales, and from studies of the processes controlling the hydrological responses of areas under forest and grassland, have been accepted by the water and forestry industries as a means of determining the probable effects of afforestation in other areas of Britain. When considering proposals in the late 1970s for a further major expansion of forestry, mainly in Highland Scotland, it became apparent that insufficient information was available to predict with confidence the effects in areas where forestry would replace medium height vegetation (heather sp., bracken) or in areas where a significant proportion of the precipitation falls as snow. Against this background a consortium of interested parties (see Hall 1987), agreed in 1981 to fund parallel systems and process studies of the effects in appropriate areas of Scotland. In this paper the initial stages of the systems study, on two catchments in the Balquhidder area of Central Region, are described. Some preliminary results from phase I, in which the catchment water balances under a mature forest and a mixed heather, bracken, grass cover were obtained, are presented. These water balances suggest that water use by the partly forested catchment is lower than that by the control and also lower than Penman ET. These findings are discussed in relation to the Plynlimon results and to information gained in the current process studies. Plans for phase II of the study, in which the mature forest will be clear-felled and part of the heather, bracken, grass control will be planted, are outlined.

Vigorous Carboniferous extensional tectonism and associated igneous activity is a feature of Ireland and the neighbouring areas of Newfoundland and Britain. In West Connacht, Ireland, dolerite dikes of late Carboniferous age are newly recognised and distinguished from Tertiary dolerites. In the N, the 320 Ma-old Logmor dike trends N–S across the Ordovician South Mayo Trough, and has an evolved, mildly alkaline basalt geochemistry. In the S, in Connemara, a diffuse and arcuate swarm of ENE–NE trending, 305 Ma-old dolerite dikes, the Teach Doite swarm, cuts the Galway Granite batholith and its envelope of Dalradian gneisses. These more tholeiitic dolerites reveal the mineralogical and geochemical effects of varying degrees of pervasive hydrothermal alteration, imposed on an original magmatic composition similar to that of mid-ocean ridge basalts. Variscan overprinting on k–Ar ages from West Connacht dolerites clusters at 300, 245 and 205 Ma. Overprinting is also a feature of much of the Galway Granite. Carboniferous diking in West Connacht may have responded to nascent opening of the proximate North Atlantic, its pattern related to domal uplift adjacent to the rifted zone.

Fifteen specimens of Eristophyton stems from the Lower Carboniferous Cementstone Group of Berwickshire and East Lothian have been examined. Three possess medullary rays comparable to E. waltonii Lacey, the others have rays like E. beinertianum (Göpp.) Zalessky. In one specimen assigned to E. waltonii a leaf-trace subdivides outside the secondary xylem to form an arc of six separate bundles. Another stem of E. waltonii has attached closely spaced petiole bases one of which is clearly identifiable as Lyginorachis with six vascular bundles arranged in an arc. Stems of Eristophyton from five localities occur associated with petioles or rachises possessing a U-shaped vascular bundle with abaxial ridges like L. waltonii Calder. As these may occur mixed with rachises agreeing with L. brownii Calder the latter is regarded as synonymous. Detached petioles found associated with E. beinertianum may possess four or six basal bundles. The evidence suggests that the U-shaped petiolar bundle passes down into four then six basal bundles and such petioles are associated with both E. waltonii and E. beinertianum. Calder (1935, pl. 1, fig. 2) showed dichotomy in the petiole bundle.

In addition different rachises are known possessing a more massive U-shaped bundle but lacking sclerotic nests and sparganum outer cortex. These are assigned to Cladoxylon edromense sp. nov. Cortical nests occur in both E. waltonii and L. waltonii and may be compared with the sclerotic plates in the compressions of Diplotmema dissectum Brongn. and D. patentissimum Ett.. The evidence supports the view that Eristophyton is a pteridosperm with bifurcate fronds known as L. waltonii Calder when petrified and comparable to Diplotmema when compressed.

The Topsails igneous terrane of western Newfoundland contains several intrusive and volcanic suites underlain and separated by screens of older intrusive rocks. The heterogeneous Hungry Mountain complex yielded U-Pb zircon upper and lower intercept ages of 2090 ± 75 Ma and 467 ± 8 Ma, demonstrating a significant inherited component of Aphebian age, while an adjacent suite of relatively massive granodioritic to granitic rocks yielded a slightly discordant U-Pb zircon age of 460 ± 10 Ma. The 438 ± 8 Ma age of the Rainy Lake complex, a suite of island arc type intrusive rocks, suggests it forms part of a Silurian magmatic episode, which also included Springdale Group bimodal volcanics (429 ± 4 Ma), and peralkaline granite and subvolcanic porphyries which intrude the Springdale Group (429 ± 3 Ma and 427 ±3 Ma, respectively). Most igneous units contain a slight component of inherited zircon, but initial 87Sr/86Sr ratios (average 0·704) are similar to calculated ‘Bulk Earth’ values at this time.

Available data suggest that the Topsails terrane formed an oceanic tract with active volcanic island arcs when obduction commenced in early Ordovician time. The subsequent magmatic history, including the major but short-lived early Silurian magmatism, can be directly or indirectly related to obduction processes, including over-riding of the Topsails terrane by ophiolitic allochthons. There is no evidence of any Acadian (Devonian) igneous activity in the Topsails terrane.

Loch Fleet is an upland loch in SW Scotland, distant from significant local pollution, and unlikely to be affected by changes during the five-year project. The underlying geology is granitic. The 111 ha catchment is 90% moorland, dominated by heather and flying bent; 10% is planted with conifers.

Rainfall is approximately 2200 mm per year, predominantly from W and SW. More than half of rain events are pH>4·7; mean pH is 4·84 (1985). Marine salts are the major solutes. Deposition of acidity is about 0·1 g H+ m−2 per year, about twice that of eastern Scotland; deposition of non-seasalt sulphur is 1·6 g S m−2 per year. Soils are shallow and comprise organic peats, peaty gleys, and peaty rankers; base saturation is 3–19%. Soils (pH 2·5 to 4·6) are most acid in the forested area.

The loch is more acid (×5) than bulk deposition; additional acidity is mobilised from soils by the predominantly (>90%) superficial drainage. Moorland drainage dominates; that from the forest is more acid, but very variable in quantity and composition.

Catchment interventions in 1986 and 1987 are designed to alter the chemistry of drainage waters and the loch, so that the fishery can be restored. In addition to the work reported, extensive soils, sediment and biological investigations are underway.

A major transcurrent fault in the zone of the Iapetus suture in eastern Ireland separates Ordovician (pre-Ashgill) terranes. The stratigraphy of each terrane belongs to a dismembered volcanic arc system: the northern terrane is characterised by acid plinian eruptions and derivative sediments which are displaced relative to the andesitic southern terrane volcanism. Each was a separate palaeoenvironment with its own lithostratigraphical character and faunal elements which were juxtaposed across the fault. However, the late Ashgill to Silurian sediments in both terranes form part of a regional overstep sequence which links across the suture zone, such that the palaeogeographical contrasts were eliminated by the Silurian. The inference is that the detached terranes were gradually amalgamated by late Ordovician transtensional movements. This occurred when regional scale subduction-related volcanism had ended. Final assembly by early Devonian sinistral transpressive movements juxtaposed a northern terrane, akin to the Lake District/SE Ireland calcalkaline volcanic province, with a southern terrane in the tholeiitic province of eastern Ireland. As distinct from a singular fault trace, the Iapetus suture is regarded as a 100 km wide zone of anastomosing late Caledonian transcurrent faults whose precursors were active during late Ordovician (i.e. Taconic) terrane amalgamation.

Pipe-shaped breccia bodies associated with diorite intrusions are composed mainly of angular clasts of local schists with a few transported clasts of quartzite. Plate shaped fragments are commonly oriented to define planar fabrics in the breccias. These features indicate the operation of gas fluidisation within the pipes and both entrainment and expanded bed conditions are inferred. The fabrics result from the collapse of the fluidised suspensions as the gas flow declined. Dilational fracture patterns in the country rock comparable with the stress release patterns found around mine shafts can be matched with the fractures required to produce the angular schist clasts. It is concluded that fracturing and the introduction of fragments into the fluidised breccia system was a continuous process and that the pipe diameter increased progressively with time. Microdiorite sheets and related stock like bodies of diorite cut and metamorphose the breccias. Compaction, hornfelsing and hydrothermal alteration also contributed to breccia formation.

The Dinantian Lower Oil-Shale Group of the Edinburgh area records the evolution of a SW–NE trending basin within an area of fluvial-dominated deltaic sedimentation, with rare marine incursions from the E. The sequence at Granton records the abandonment of a delta lobe, with deltaic sandstones overlain by lagoonal mud-shales. These thinly-laminated non-bioturbated mud-shales record low-energy, stagnant conditions. Fish, ostracodes and conchostracans inhabited the lagoon at this time.

Within the mud-shale sequence is the dolomitic Granton “shrimp-bed” which contains fenestrae, possible gypsum pseudomorphs and in situ shrinkage breccias suggesting periods of emergence. The “shrimp-bed” contains a number of laminae packed with soft-bodied fossils including marine forms, which resulted from brief marine incursions into the stagnant lagoon. The fluctuating salinity conditions seem to have favoured the development of an unusual fauna of shrimp-like crustaceans, fish, conchostracans, ostracodes and bellerophontid gastropods. This fauna appears to have suffered periodic mass mortalities during marine incursions which brought orthocone cephalopods, polychaete worms and conodonts into the lagoon, according to our current knowledge of the distribution of these marine taxa in the sequence.

The Granton sequence displays a variety of ductile and brittle deformation features most of which can be attributed to local SW-directed extension related to regional dextral strike-slip across the Midland Valley of Scotland.

A description is given of the hydrological regime and associated surface water quality recorded at a multi-disciplinary long-term investigation into the effects of acid precipitation and afforestation. The study catchment at Loch Dee is situated on the margins of the Loch Doon granite complex in SW Scotland. Annual rainfall is in excess of 2200 mm. The three main tributary burns exhibit a rapid response to rainfall with a high percentage of direct runoff. The loch with an average volume of 3650 M1 and a contributing catchment area of 15·6 km2 has an average turn-over of approximately forty days but this has varied from 15 to 100 days. Local physical variations are shown to influence both hydrological response and surface water quality. Generally stream water during spate conditions reflects rainfall chemistry. Occasionally, however, moderately acid rainfall containing large concentrations of sea salts has produced highly acidic runoff through a process of ion-exchange within the surface horizons of the soils. The quality of base flows shows a spatial variation which reflects various lithologies to the extent that pH values ranging from 4·9 to 6·9 have been observed.

On 17 July 1983 heavy rainfall resulted in a flash-flood in the headwaters of the West Grain, a small stream tributary to the River Wear in the northern Pennines. Associated with the flood was a series of three boulder-lobes. The morphology of these lobes and the associated sediment facies are described and used to estimate the hydro-dynamic mode of transport and deposition. Estimates of the shear-strength and viscosity are consistent with the initial conclusion (based on the sedimentology) that the deposits represent low-viscosity debris-flows. The boulder snouts moved as inertial grain-flows with an associated pebbly-core exhibiting a degree of matrix strength imparted by intergranular friction. A degree of reworking of the upper surface of the core by fluidal flow during core motion and immediately upon deposition was also identified. The full sedimentary sequence therefore represents debris-flow core deposits subject to low dispersive pressure evolving into fluidal debris-torrent deposits.

A zircon age of 429 + 6, −5 Ma on felsic volcanic rocks of the Springdale Group, a sequence of bimodal volcanic rocks and redbeds, establishes a Llandovery age for this group. Similar sequences from other parts of the Dunnage and Humber zones of Newfoundland also give Llandovery fossil or radiometric ages, demonstrating temporal correlation among lithologically similar sequences in these zones.

Distinctive sequences of bimodal, subaerial rhyolite and basalt with associated subaerial to shallow marine sedimentary rocks within the Avalon and Meguma zones of Nova Scotia give fossil or radiometric ages demonstrably or arguably very close to the age of the Springdale Group. These sequences suggest an overlap assemblage fixing the minimum age of accretion of the Avalon and Meguma zones to North America. The age and the magmatic and sedimentary character of the assemblage are compatible with origin on or from continental crust, implying that the Iapetus ocean was closed prior to Early Silurian time. If these considerations are correct, the Devonian Acadian orogeny must involve either thermal and mechanical readjustments subsequent to the closing of the Iapetus ocean, or a completely separate episode of plate motion.

The dimensional statistics and proximal development characters of the Llanvirnian pendent didymograptid D. murchisoni are defined using the type material from near Builth Wells (Powys) and other collections from Abereiddi Bay (Dyfed). Population variability (as expressed by variation coefficients) in the undeformed faunas amounts to about 10% for the sicula lengths and thecal spacings, but is over 20% (up to 200%) for stipe lengths and divergences. Characters with low variability have greater species-diagnostic value. Proximal development in the species involves a dicalycal th 11 and a low origin for that theca from the sicula. The taxa Didymograptus amplus, D. nanus, D. geminus, D. geminus latus and D. acutus are varieties within populations of D. murchisoni and are therefore junior synonyms.

The resulting rationalised taxonomy allows advances to be made in the use of the species in stratigraphy and tectonics. For example, an occurrence of undeformed (pyritised) D. murchisoni in full relief at Abereiddi in the same beds as flattened and deformed faunas, allows a calculation of the absolute three-dimensional strains to be made for the slates there. The strains are strongly flattening (K < 0 · 3) and involve volume changes of about −56%. The high dilatation values imply that stylolite and grain-boundary pressure solution operated during the deformations to take the changes in volume beyond what is possible with simple compaction (i.e. porosity reduction).

Deposits of windblown sand up to 4 m thick on the Torridon Sandstone massif of An Teallach are shown to be of predominantly niveo-aeolian origin, a form of sedimentation hitherto unrecognised in upland Britain. Sand grains weathered from bedrock and from exposed clasts on plateau areas are blown on to the winter snowpack on surrounding slopes. When the snow melts, the grains are lowered on to the underlying vegetation, which traps the sand and thus allows a stable deposit to accumulate. The deposits formed in this way are massive, poorly sorted and coarser than most aeolian deposits, comprising mainly medium sand (212–600μm) with a substantial proportion of coarse sand and even very small pebbles. The coarseness and poor sorting of the sands reflect the size of grains available for transportation, the strength of the wind, short transport distances and admixture of different grades of sand during deposition. Sand accumulation began in the Early Flandrian before c. 7900 BP, but was eventually much reduced by the establishment of vegetation cover over the plateau source area. Recent disruption of this vegetation cover triggered either by increased storminess or overgrazing resulted in extensive erosion of sand deposits on the plateau and their redeposition on surrounding slopes. Niveo-aeolian deposition continues on lee slopes at present, but is offset by erosion of unvegetated scarps at the margins of the deposits.

Snowmelt modelling is of potential value in flood forecasting, reservoir management, and understanding stream acidification. It involves meteorological extrapolation, snowmelt calculation, meltwater routing, and snowpack depletion. A simple conceptual model using air temperature can reproduce the general pattern of daily streamflow in basins of >100 km2 but is prone to parameter instability. At a point scale and with the benefit of automatic weather station data the energy balance approach is superior to temperature index methods, but the roughness length parameter is again unstable in time and space. Even in a small (0·4 km2) basin this approach has to be coupled with an adequate flow routing model. Current research is comparing alternative models and data inputs in an intermediate-sized basin.

The quartz-sillimanite-garnet rocks of the Precambrian khondalite assemblage of Orissa consist dominantly of SiO2 + Al2O3 + Fe2O3 + FeO (average c. 95%) with Fe2O3 > FeO. An average analysis (H2O and CO2 free) also shows MgO, CaO and Na2O having 1·0, 0·5 and 0·4%, respectively. Compared with average crustal abundances, enrichment is shown in SiO2, Al2O3 and Fetot and depletion shown in MgO, CaO, Na2O and P2O5 with that for CaO being more than an order of magnitude and that for Na2O being a factor of >7. On an SiO2–Al2O3–Fetot plot a clearly defined field, elongate nearly parallel to the SiO2–Al2O3 sideline, is similar to that for deeply weathered soil profiles in Brazil. This correspondence also extends to enrichment, stability or depletion, compared to crustal averages, for Ce, Co, Cu, Ga, La, Ni, Nb, Th, U, Y, Zn and Zr, but not for Ba, Cr and Rb. In addition comparison of the proportions and ratios of alkalis and alkaline earths in average khondalite and in a weathering profile over a granodiorite, considered to be typical of the weathering of continents, shows remarkable similarities.

The major and trace element data are consistent with the khondalites being granulite facies—upper amphibolite facies metamorphic equivalents of a deeply weathered soil profile. Associated quartzites and calc-silicate granulites are interpreted as having been silcretes and calcretes, respectively. This interpretation implies (1) the previous existence of a large stable cratonic mass on which the soil profile formed, (2) climatic conditions suitable for the development of such a profile, (3) topography, drainage systems and groundwater movement in Precambrian times similar to those of present day peneplane regions, (4) the presence of free oxygen in the atmosphere, (5) rapid covering (e.g. by products of volcanism) to preclude mass wasting, (6) a Precambrian stratigraphy in the crystalline rocks of the Eastern Ghats region similar to that of South India, and (7) orogenesis that involved tectonic repetition of lithological units and a mechanism for taking products of surface weathering down to granulite facies P–T conditions and subsequently elevating them.

Anthraconaia lived on clay grade sediments. In highly variable life assemblages of the A.prolifera group of the E German Wettin Shales (Stephanian C) organic carbon percentage of the host sediment correlates with wu/m and A/L ratios of the shell (where wu is the maximum width ventral to the line of maximum growth, m, L the maximum length measured parallel to the line of the hinge, and A the length anterior to the umbo). Decrease in the organic carbon of the sediment is associated with decrease in umbonal development, elongation of the shell along the m axis, and straightening and reflection of the ventral margin; the latter becomes subparallel to the dorsum or to the m axis with a concomitant decrease in size. These results confirm and amplify earlier work on Anthraconaia in the Appalachian coalfields. The same morphological trends in relation to organic carbon characterise the Anthraconaia modiolaris group of Britain, both within a single succession in upper Westphalian A sediments in Yorkshire, and also in three shell bands of Lower Westphalian B age in S Wales, Yorkshire and central Scotland. In the last named, above the Musselband Coal, statistical formulae (of Leitch 1940) for the species A.salteri are shown to define neither the type assemblage nor its stratigraphical position. The shell-shape/organic carbon relationship has been broadly confirmed on other horizons of lower Westphalian B age in the Scottish and Pennine coalfields. Far from embarrassing the stratigrapher, the relationship, which reflects ultimately trophic level of deltaic palaeoenvironments, contributes to our understanding of non-marine bivalve faunas, especially of the apparent regional distribution of ‘species’ of Anthraconaia.