Abstract Aspects of the isotopic age and stratigraphical databases underpinning Devonian geological time scales are reviewed to assess differences in recent U–Pb zircon-based schemes and older schemes based on Rb–Sr, K–Ar, 40 Ar– 39 Ar dating of minerals and whole-rock samples. The various methods of time-scale construction are described and, with their databases, 14 calibrations of Devonian time are discussed. Finally, the most recent data are collated and compared against current U–Pb-based time scales.

Abstract Boundaries for all the Devonian series and stages have now been proposed by the Subcommission on Devonian Stratigraphy (SDS) of the International Commission on Stratigraphy (ICS) and have been ratified by the International Union of Geological Sciences (IUGS). A summary of these decisions is given. All the defined Global Stratigraphic Section and Points (GSSPs) are in the marine realm, and in pelagic facies. Much work is still needed to correlate the new boundaries into neritic and terrestrial facies.

Abstract The Old Red Sandstone basins of the North Atlantic borderlands provide a record of diverse dynamics in very different settings, related to the Variscan, Caledonian and Ellesmerian orogenies. This paper is a first attempt to review much new information on the basins, including information presented, for the first time, in this book. Five basin groupings are distinguished: (1) Scandinavian basins of, syn- to post-Scandian (Caledonian) age, formed on greatly thickened crust by extension or transtension (Western Norway, East Greenland, Spitsbergen); (2) NE Scotland, Orcadian Basin, mid Caledonian setting, formed by extension; (3) Scotland (Midland Valley) and related Irish basins, north of the Caledonian Iapetus Suture Zone, formed by extension; (4) southern Britain and Ireland, basins south of the Iapetus Suture Zone, related to collision of Eastern Avalonia with Laurentia, and Maritime Canada and the Catskills related to collision of Western Avalonia; these are load-induced flexural basins; (5) Southern margin of Eastern Avalonia, (Munster, South Wales, SW England), of Late Devonian age, extensional basins of various (Early to Late) Devonian ages.

Abstract The Cap-aux-Os Member (of Emsian age) of the Battery Point Formation, Gaspé Bay, Québec, comprises coastal and fluvial deposits containing abundant, well-preserved remains of early land plants (embryophytes). Metres-thick sandstone bodies represent the deposits of the main river channels, including some that were tidally influenced. Thinner sandstone bodies within mudstone successions represent deposits of crevasse splays–levees, lacustrine deltas, tidal channels, flood-tidal deltas and washovers. Mudstone-dominant strata represent backswamps and marshes, lakes, coastal bays and tidal flats. Certain plants (trimerophytes, Huvenia and Sciadophyton) are particularly common on the moist, upper parts of near-coastal channel bars. They apparently germinated and grew rapidly on freshly exposed muds deposited during floods or exceptionally high tides. In situ zosterophylls are most common in backswamp and marshy areas, where they formed extensive, relatively long-lived stands. It is uncertain whether these plants were tolerant of brackish water or killed by it. However, absence of acritarchs in these in situ plant horizons suggests that they occupied primarily freshwater habitats. Transported Prototaxites and Spongiophyton, both interpreted as possible fungi, are the main components of fully non-marine channel deposits. It is no coincidence that the best-preserved plants are those that lived in moist, oxygen-poor settings. However, the occurrence of root traces in palaeosols and sparse fossil evidence suggests that embryophytes also occupied drier settings.

Abstract The Middle–Upper Devonian strata of New York and Pennsylvania were deposited in a foreland basin adjacent to the Acadian fold thrust belt. Fluvial (Catskill) strata in the east thin to the west into marine (Chemung) strata. The overall sequence is marine regressive, but there were numerous superimposed marine transgressions. The Catskill river channels changed character with distance from the palaeoshoreline. Sinuous,s single-channel rivers (widths tens of metres, maximum bankfull depths 4–5 m, sinuosity 1.1-1.3, mean bankfull flow velocity 0.4–0.7 m s –1 ) occurred near the coast. With increasing distance from the coast, rivers increased in slope, became wider (up to hundreds of metres) and deeper (up to 15 m), coarser grained, and possibly braided. This suggests that rivers were distributive near the coast. Furthermore, muddy floodplain areas were more extensive near the coast than up-valley, such that the proportion of channel deposits increased up-valley. Coastal areas comprised tide-influenced channels and mouth bars, wave-influenced sandy shoals and washovers, sandy and muddy tidal flats, and muddy interdistributary bays and lakes. Major marine transgressions are thus represented in wholly fluvial successions by a decrease in the proportion of channel sandstone bodies, and a decrease in channel size and grain size. Marine transgressions in near-coastal successions are represented in places by an increase in sandstone proportion associated with progradation of coastal sands over muddy backswamps and interdistributary areas. Small-scale marine transgressions and regressions in coastal deposits (i.e. metres-thick parasequences) are probably associated with switching of coastal channels or delta lobes. There is no evidence for the preservation of incised valleys, nor for any changes in coastal channel patterns associated with these parasequences: therefore, major regional sea-level changes were not responsible. However, large-scale (tens to hundreds of metres) transgressive–regressive sequences were due partly to eustatic sea-level change (e.g. in mid-Givetian time) but also due to changes in the balance between sediment supply and subsidence associated with tectonic uplift of the hinterland and peripheral bulge. Such uplift may have induced some kind of climate change. However, climate changes in the depositional basin are not supported by sedimentological evidence. Further understanding of the origin of these strata will require higher precision in the biostratigraphic correlation of marine and non-marine strata (using miospores), and quantitative interpretation of depositional environments from other regions.

Abstract Approximately 250 m of unfossiliferous sediments attributed to the Old Red Sandstone outcrop onshore at Ballymastocker, Donegal in northwest Ireland. Massive sandstones and trough cross-bedded sandstones pass upwards into coarse purple–brown basal conglomerates. The majority of the clast types, which include quartzite, marble, pelite, schist, vein quartz and metadolerite, are derived from the local Dalradian basement. Acid to intermediate porphyry clasts have no local source and may indicate a source to the north-east in the vicinity of the Devonian Lorne Plateau volcanic rocks in Argyll. The rocks are believed to represent an intermontane alluvial fan environment. The sediments occur in an outcrop of 3 km length against the northern flank of Knockalla Mountain, bounded to the southeast by the NE–SW-trending Caledonian Leannan Fault and resting on fractured Argyll Group Dalradian basement. No unconformable contact is observed and all contacts may be tectonic. Coarsening-up cycles within the sediments may reflect syn-sedimentary tectonic activity. The Devonian rocks are transected by a fracture system implying dextral transpressional activity on the Leannan Fault. The Dalradian basement rocks preserve evidence of sinistral strike-slip movement in late Caledonian times. Slickenfibres observed within the sediments and Dalradian rocks provide evidence for oblique dip-slip movement to the northwest. It is considered that these structures represent the last movement of the ORS basin, dropping it below denudation level, which resulted in its preservation. Movement along the Leannan Fault played a major role in the preservation of the offshore basins in the Islay–Donegal Platform region.

Abstract The Dingle Basin of southwest Ireland lies within 40 km of the present-day trace of the Iapetus Suture. Its late Silurian fill (Dunquin Group and lower Dingle Group) is an important and, in many aspects, unique record of late Caledonian development in the Irish and British sector of the orogen. The upper Wenlock–upper Ludlow Dunquin Group comprises shallow-marine to non-marine siliciclastic and volcanic rocks (acid pyroclastic deposits and predominantly andesitic lavas) deposited on and around a volcanic island(s), whereas the lower, upper Ludlow–Přídolí, part of the overlying Dingle Group comprises sandstones, mudstones and minor conglomerates deposited in lacustrine, lake margin and succeeding fluvial systems. The change from marine Dunquin Group to non-marine Dingle Group (Old Red Sandstone) sedimentation is interpreted to have been tectonically driven. The succession is interpreted in terms of four phases of basin evolution: (1) a phase related to active subduction; (2) a phase related to subduction termination; (3) a post-subduction thermal subsidence phase; (4) a phase of strike-slip fault-controlled subsidence. In the broader, late-Caledonian context, the Dunquin Group volcanic rocks and associated sediments are interpreted as representing localized subduction of a final vestigial portion of Iapetus oceanic crust. The later, inferred, strike-slip influence in the basin is believed to be part of the well-documented regional strike-slip regime affecting this sector of the Caledonides.

Abstract We propose the name Northwest Dingle Domain for the enigmatic Old Red Sandstone terrane whose tectono-sedimentary evolution has perplexed generations of geologists. The Domain remained largely misinterpreted, unappraised or simply disregarded, and its fundamental impact on regional basin dynamics was grossly overlooked. The Northwest Dingle Domain is largely structurally constrained between two ENE-trending Caledonian structures: the North Kerry Lineament and the Fohernamanagh Fault. It comprises four unconformity-bounded Groups: the Lower Devonian Smerwick Group; the Middle Devonian Pointagare Group; and the Upper Devonian Carrigduff and Ballyroe Groups. Their fluvial–aeolian, and locally tidal, sedimentation patterns profile Late Caledonian transpression to Mid–Late Devonian extension. The inherent primary structural control on basin location, development, geometry, sedimentary-fill and preservation is manifest in the Northwest Dingle Domain. The Acadian emplacement of the Smerwick Group set the foundations of the Northwest Dingle Domain. The Smerwick Group documents sandy and gravelliferous ephemeral-fluvial and erg-margin aeolian processes on an ancient terminal fan(s). The Pointagare Group is cogenetic with the Caherbla Group of south Dingle. Together they record the renewed influx of coarse-grained sediment in the form of transverse alluvial fans and axial braidplains in response to increased tectonism followed by overstep of an erg complex. The Pointagare–Caherbla basin model highlights the fundamental structural control on basin topography, palaeodrainage patterns, provenance, palaeowind directions and sedimentation style in tectonically-active extensional basins.

Abstract The Late Silurian to Mid-Devonian Dingle Basin occupies a central position within the Iapetus Suture Zone of SW Ireland. The basin is believed to have formed from late Silurian times onwards as a product of sinistral transpression along several major faults within this suture zone. Conglomeratic sediments were deposited by moderately large gravelly fans shed into the basin from the NW (Glashabeg Formation) and the SE (Trabeg Conglomerate Formation). The systems fed into a large apparently through-going sandy, axial river (Slea Head Formation) that flowed towards the NE. The lateral, basin-margin systems were sourced from two disparate source terranes. To the NW lay a basic volcanic hinterland with some intermediate volcanic rocks and limestones, mudstones, sandstones and chert. During the Early Devonian time the SE drainage basin was underlain by sandstones, quartzites, phyllites and limestones probably intruded by a granite. Some of these lithologies can be found in outcrop in the pre-Dingle Group of the peninsula. Others need to be correlated with rocks of the oceanic terranes in the northern part of the suture zone. The southerly derived clasts have corollaries in the rocks of the Avalonian Leinster Terrane south of the suture. Following partial inversion of the Dingle Basin, the southerly hinterland was apparently further unroofed during mid-Devonian time, when the Inch Conglomerate Formation was deposited by alluvial fans shed northwards from a source area formed along the Dingle Bay Lineament. The Inch conglomerates are characterized by distinctive clasts of schist, gneiss, mylonite, tourmalinite and granite. The general picture of the Early Devonian deformation, intrusion by granite and unroofing of terranes currently partially exposed in central and southern Ireland within the Iapetus Suture Zone is largely consistent with clast lithotypes. However, some exploratory isotopic data indicate at least two possible vagaries in the interpretation. First, model Nd T DM ages of Trabeg sedimentary clasts yield several results older than typical southern Iapetean or Avalonian crustal material. This suggests a complex history of sedimentary mixing of material across the developing Iapetus Ocean. Second, two of three Rb–Sr muscovite–whole-rock dates of Inch metamorphic clasts indicate Silurian ages. These data are similar to Rb–Sr dates derived from the Carnsore and Saltees granites in the Rosslare Terrane, perhaps extending the geographical spread of this Silurian deformation.

Abstract Three wide-angle seismic profiles were acquired from onshore southern Ireland during VARNET-96. These data provide the only subsurface seismic images of a series of predominantly Late Palaeozoic sedimentary basins. The Dingle Basin is a broadly symmetrical rift on the Dingle peninsula, but assumes a half-graben geometry to the east. The southern syn-rift basin margin is defined by the north-dipping Dingle Bay–Galtee Mountains Line. A south-dipping normal fault at Kerry Head marks the northern basin margin in the west, with displacement on this structure decreasing towards the east. The Dingle Basin is separated from the Munster Basin to the south by a basement horst. Seismic data strongly suggest that the Killarney–Mallow Fault Zone, located on the southern margin of this positive feature, is the Munster Basin northern syn-rift marginal fault. The preserved extensional displacement on this detachment decreases from c. 2.5 km in northern Iveragh, to c. 1 km at Mallow, suggesting that the fault tips out to the east of Mallow. A tilted fault block, possibly cored by shallow granite, is imaged in the northern Munster Basin. This fault terrace is bounded to the south by the Cork–Kenmare Line. The combined Munster Basin and South Munster Basin succession thickens across the Cork–Kenmare Line to a maximum thickness of 8 km on the Beara peninsula. A tectonic thickness of 6 km of sediment is modelled at the Old Head of Kinsale, increasing to 7 km in the southwest.

Abstract Flexural cantilever (2D) computer modelling of the palinspastically restored Mid–Late Devonian Munster Basin has been used to appraise quantitatively extensional subsidence and Old Red Sandstone (ORS) stratigraphic geometries. One-dimensional decompaction and (Airy isostatic) backstripping were carried out to constrain syn-rift forward models; these specify the Late Palaeozoic rifting history of the region. Forward modelling showed that listric faults and detachments fail to reproduce restored ORS sediment geometries, but instead indicated that multiple planar, upper-crustal faults are necessary to achieve the correct order of syn-rift subsidence across the basin. Modelled (non-unique) sections transverse to the basin bounding fault (Dingle Bay–Galtree Fault Zone) replicated ORS geometries with cumulative extensions of 27 km in the east (stretching factor β = 1.3) and 59 km in the west (β = 1.48), with effective elastic thicknesses of 7 and 8 km, respectively, starting from a 40 km thick post-Acadian crust. Resultant peak heat-flow anomalies predict well the location of known syn-rift volcano-magmatic centres. Modelling indicated that significant offshore faults are required to achieve subsidence in the west Cork region, implying that the basin continues offshore. Observed ORS (<0.85 km thick) sections on the regional footwall, considered to be the result of thermal (post-rift) subsidence, are not accounted for by modelling, whereas c. 1 km of post-rift ORS is modelled over 5 Ma in the central–southern regions of the basin. These sections buried the principal rift faults during late Famennian time. The ORS of the Munster Basin is dominated by two large-scale transverse fluvial dispersal systems that were largely insensitive to deflection by any extension faults that propagated in the syn-rift fill. A third major system entered in the SW, demarcated by antithetic extension faults south of the depocentre.

Abstract Newly acquired U–Pb magmatic zircon dates from silicic tuffs within the Old Red Sandstone (ORS) magnafacies of the Munster Basin (SW Ireland) are intercalibrated with newly discovered (late Givetian) and reappraised (mid-Frasnian) miospore assemblages to provide the first biostratigraphically constrained numerical ages in the Irish Devonian succession. The weighted mean 207 Pb/ 206 Pb isotopic age determined for the Keel Tuff Bed (385.0 × 2.9 Ma) is indistinguishable from that of the previously investigated Enagh Tuff Bed (384.9 × 0.7 Ma). In conjunction with very similar rare earth element (REE) signatures, this confirms their correlation, placing a minimum age of 384.9 × 0.4 Ma on the newly discovered Reenagaveen microflora, which is assigned to the late Givetian TCo Oppel zone. The equivalence of the Keel and Enagh Tuffs constrains a vertebrate fauna containing Bothriolepis and the Valentia Island tetrapod ichnofauna to pre-date this event. Isotopic dating of thickly bedded subaerial tuffs from the Lough Guitane Volcanic Complex, a major accumulation of rhyolites and silicic volcaniclastic rocks, reveals ages of 384.5 + 1.0 Ma (Killeen Volcanic Centre), indistinguishable from the Keel–Enagh Tuff Bed, and 378.5 × 0.2 Ma from the Horses Glen Volcanic Centre, previously considered to be the oldest of the complex. The Horses Glen Centre post-dates the Moll's Gap Quarry microflora, the only current biostratigraphical control on the age of the early ORS in the east of the basin depocentre, thus indicating a minimum age for the (mid-Frasnian) IV Oppel zone, the revised biostratigraphic age of this assemblage. These controls on the early ORS (1) suggest that Munster Basin initiation occurred before late Givetian time and (2) give time-averaged (compacted) accumulation rates of c. 0.17–0.25 and 0.18 mm a –1 for eastern and western Iveragh, respectively. The minimum basin duration time was c. 23 Ma to the end of the Devonian period. The implications of these data for the depocentre stratigraphy, volcanic events, proposed ORS cyclicities and the geohistory of the Munster Basin are examined.

Abstract The following paper is intended as a review of the magmatism in the Munster Basin and an initial attempt to link it with the basin's history. During the initiation, evolution and inversion of the Devono-Carboniferous Munster Basin magmatic activity was widespread, although small in volume. The episodic occurrence and diversity of the magmatism gives insights into the basement involvement and structural controls relating to the basin's history. The differences in composition, location and structural relationship of the magmatic bodies are used as indicators for the timing of their emplacement and their relationship to the basin's evolution. On the western Beara Peninsula in SW Ireland alone, more than 160 sheet-like intrusions, a wide variety of tuff bands and a deep-seated pipe-like structure of lamprophyric affinity occur. Other centres of magmatism in the basin are the Lough Guitane area, where rhyolitic lava flows and acidic pyroclastic rocks are associated with contemporaneous basin faults, and the Valentia Harbour area, where doleritic sills are associated with a volcanic breccia. A rhyodacitic tuff can be traced as far as St Finan's Bay on the western shore of the Iveragh Peninsula. The chemical composition of the extrusive and intrusive magmatic bodies ranges from tholeiitic dolerites (Valentia Harbour) and subalkaline rhyolites (Lough Guitane) in Mid-Devonian time to subalkaline basalts and tuffs (e.g. Beara Peninsula) in Late Devonian time. In Late Carboniferous and possibly Permian time alkali basalts, trachytes and phonolites (e.g. Beara Peninsula) occur. The igneous activity in the Munster Basin is linked to the basin's history by the interaction between active faults and fractures opening up during various stages of stress imposed on the basin and exploitation of these faults and fractures by rising magma.

Abstract The Munster Basin of southern Ireland contains a thick (7 km +) succession of Old Red Sandstone sediments interpreted as the product of various alluvial processes. The present study presents a preliminary sedimentological and palynological analysis of a grey succession informally known as the Foilcoagh Bay Beds, which is the lowest unit of the Sherkin Formation exposed in the southern part of the basin. Sedimentological analysis of the succession suggests that it is the product of sinuous distributary channels, flanked by permanently flooded overbank areas that endured occasional crevasse splay floods. These conditions evolved into a protected lagoon or lake that received periodic high energy floodings from an adjacent marine environment. Palynological study has refined the age of the Foilcoagh Bay Beds as mid-Frasnian time. Palynofacies analysis has provided direct evidence of marine influence as revealed by the presence of marine microfossils and abundant amorphous organic matter at some dark grey mudrock levels. This suggests deposition in a well-established lacustrine or lagoonal environment in which anoxic conditions prevailed at intervals and which was subjected to a period of marine incursion. The recognition of a marine influence in the Munster Basin at an early stage in its history has several important implications, including the following (1) previous models for the basin that suggested an enclosed centripetally draining entirely non-marine system have to be re-evaluated; (2) the drainage pattern and direction of the marine incursion were probably controlled by localized subsidence along an east–east direction; initiation of subsidence associated with the development of the east–west-trending South Munster Basin may have commenced much earlier than previously considered; (3) the occurrence of marine conditions has been tentatively correlated with the Rhinestreet mid-Frasnian sea-level highstand; (4) the recognition of marine conditions early in the known history of the basin provides a pathway for fish to have entered the basin; (5) the basin may have had a marine connection throughout much of Late Devonian time, opening the possibility for base-level control of the alluvial systems within the basin by external eustatic factors.

Abstract The environment of deposition of the plant-bearing horizons of the Devonian– Carboniferous Kiltorcan Formation in Co. Kilkenny is poorly known. Previous studies suggested a possible lacustrine palaeoenvironment with plant material being swept in and fluvial conditions. Reinvestigation of the plant-rich localities on Kiltorcan Hill using both sedimentological facies and palynofacies suggests that there were high-sinuosity streams carrying fine-grained sediments with the plant fossils preserved on point bars, and marginal back-swamp conditions with plant material deposited close to the growth site.

Abstract Deposition of the Silurian (Wenlock) siliciclastic Gray Sandstone Group of south-west Pembrokeshire took place within littoral environments close to the palaeogeographical shelf-margin of the Welsh Basin. Sedimentation described a northerly, basinward progradation across an earlier Late Ordovician? to Aeronian rift basin. Changes in relative sea level (rs1) had profound effects on depositional environments, and five depositional sequences are recognized. During highstands of rs1, the area was influenced by wave-dominated, shallow-marine conditions. During lowstands of rs1, shelf incision and sediment bypass occurred. Associated valley fills vary in nature from high-sinuosity estuarine channels, tidal flats and tidally-influenced, high-sinuosity fluvial channels. The last of these predominate within the youngest sequence, with abundant subaerial emergence indicators heralding the onset of true continental deposition, and the conformable transition into the overlying Old Red Sandstone Red Cliff Formation within the Marloes Peninsula. A renewal of tectonic activity ensued within the Lower Old Red Sandstone, with pebbly low-sinuosity alluvium of the Albion Sands Formation, and fanglomerates of the Lindsway Bay Formation reflecting reactivation of earlier rift-margin faults, probably within a transtensional tectonic regime.

Abstract Small coalified fossils (mesofossils) have yielded new insights into vegetation of the Old Red Sandstone Continent in early Devonian times. Particularly useful are those containing spores that can be placed in dispersed spore taxa, although patinate and emphanoid spores have not hitherto been found in situ. Emphanisporites cf. micrornatus Richardson & Lister is described in a bifurcating cylindrical sporangium preserved as a cuticular sheath. A terminal dehiscence feature is compared with that in Horneophyton. The sporangium is encased in amorphous detritus with some tubular fragments. Similar associations occur on other sporangia, e.g. Tortilicaulis and axes at this North Brown Clee Hill locality, and they are interpreted as remains of a microbial or fungal film. Fragmentary cuticles, interpreted as isolated sporangial valves, bear an undescribed species of Emphanisporites with fine interdigitating proximal muri and laevigate distal surfaces referred to Emphanisporites sp. A Richardson & Lister. Analysis of dispersed spore assemblages from the locality and others in the Welsh Borderland indicate that the two emphanoid taxa were not common components of the spore ‘rain’. This evidence, coupled with the dearth of mesofossils of the producers, suggests that the plants grew at the upper reaches of the drainage basin of the river that deposited the sediment, although the paucity of sporangia may also be attributed to their low fossilization potential.

Abstract The high-quality, laterally continuous coastal exposures of the Moor Cliffs Formation have allowed a highly detailed 2D reconstruction of the floodplain sediments and their contained pedogenic horizons to be made. The thick siltstone packages were actively deposited as finely laminated and rippled sheets, or as intraformational clasts forming larger bedforms. It is proposed that the unusual sediment geometries preserved are intimately related to the timing of land plant colonization of the Old Red Sandstone continent. Channels were extremely broad with low relief and flow over interfluvial areas was common. Evidence for ephemerality and regular desiccation is also closely related to the lack of rooted vegetation and not to palaeoclimate, which is postulated to be warm and seasonally wet. The low net sandstone (< 10%) fluvial sediments are the product of deposition by shallow, high width to depth fluvial ‘channels’ flanked by broad, low-relief silty plains on which Vertisols formed. The reconstructions of this fluvial system reveal distinctive and systematic vertical and lateral variations in floodplain architecture and palaeosol development. Pedogenic maturity consistently increases with distance both vertically and laterally from channels. The vertical patterns of palaeosol development and maturity suggest that autocyclic processes of aggradation and avulsion predominated.

Abstract The 200 m long face of Pantymaes Quarry, central South Wales, exposes part of the upper (Dittonian) Red Marl Group (Lower Old Red Sandstone). A lower Sandstone Facies Association (up to 15m thick) comprises interbedded grey–green micaceous sandstones, pebbly intraformational conglomerates, and grey siltstones. Major bounding surfaces define stacked channel complexes, representing the deposits of braided river systems. An erosively overlying Mudstone Facies Association (up to 15 m thick) comprises tabular-bedded, bioturbated and calcretized red siltstones and fine sandstones representing overbank deposits, possibly from a meandering system. The change in fluvial style is interpreted as a local response to pulses of oblique-slip movement on nearby fault systems. The period of fault activity resulted in the braided Sandstone Facies Association, the Mudstone Facies Association recording a gradual return to a meandering system. Individual pulses of activity produced the stacked channels within the Sandstone Facies Association. The Sandstone Facies Association is similar in character to the overlying Senni Beds, suggesting that ‘Senni Beds’ may describe a recurring, possibly tectonically controlled, braided channel facies in the Lower Old Red Sandstone.