Abstract Fluvial point-bar deposits are described from the c. 1 Ga Diabaig Formation, representing some of the most compelling architectural evidence of planform sinuosity recognized in pre-vegetation sedimentary strata to date. The stratigraphical architecture of the deposits indicates different planform transformations in response to meander-bend expansion and downstream migration. Point-bar architectural motifs are locally abundant in the unit and this is attributed to elevated amounts of mud-calibre cohesive sediment. Mud afforded landscape stability that, together with limited stream power, was sufficient to corral sediment into single-thread, sinuous channels. Significant volumes of fine-grained sediment were encouraged to accumulate by the local basin setting of several topographically confined endorheic depressions. These conditions ceased once the hydrologically closed valleys were filled, with the overlying sandstone-dominated Applecross Formation subsequently deposited by low-sinuosity, braided rivers that bypassed fine-grained sediment oceanward. Other endorheic basins conducive to the formation of depositional meanders should be expected to have been relatively widespread on pre-vegetation Earth, though many individually limited in size, confined by their inherited topographies. Depositional architectures representative of sinuous channel planforms remain scarce within more extensive, externally drained basins.

Abstract Dashwoods is a composite peri-Laurentian terrane in Newfoundland and forms the basement to the Early Ordovician to Silurian Notre Dame arc. The southern part of Dashwoods is characterized by paragneiss that is intruded by Early Ordovician to Late Silurian plutons and affected by polyphase Taconic to Salinic deformation and high-grade metamorphism. The crystalline basement of Dashwoods is not exposed and pre-Middle Ordovician paragneiss is investigated herein to constrain the provenance of Dashwoods. SHRIMP U–Pb zircon analysis of the paragneiss yielded metamorphic rims ranging from c. 500 to 395 Ma and abundant detrital grain cores ranging from c. 1853 to 546 Ma. The presence of abundant Tonian dates differentiates Dashwoods from the adjacent Humber Margin in Newfoundland, and Hebridean and Grampian terranes in the British Isles. The detrital provenance of Dashwoods is most similar to the Baie Verte Margin in Newfoundland, and Tyrone Complex and Dalradian Supergroup in Ireland. These data suggest that Dashwoods and the Baie Verte Margin originated near the Rockall promontory and were subsequently emplaced outboard of the Humber Margin by Ordovician to Carboniferous motion along the Baie Verte–Brompton Line.

Abstract The Moine Thrust Belt in NW Scotland is fundamental for developing an understanding of complex fault systems and continental tectonics. The high-quality geological mapping, exceptional structural interpretation and insight of the late nineteenth century that underpins this is chronicled here. The Geological Survey of Great Britain mapped the thrust belt over a 14 year period, at 1:10 560, but it took five decades for the individual 1:63 360 map sheets to be published. The mapping itself was hampered by access problems, illness and prevailing weather. The deployment of expert staff to this region of few apparent economic resources threatened the status of the Geological Survey. Map publication was hindered by the transition from hand-coloured to full-colour printing, together with the restrictions of publishing to a strict grid that incorporated complex geology outside the thrust belt itself. This history of fieldwork, publication and outreach by the Geological Survey is placed in an environmental and logistical context to identify the challenges not only for the mapping itself but also in sharing the results in publication. The execution of these activities provides lessons for developing coherent interpretation in complex geology and the challenges in charting their uncertainties and alternative explanations.

Abstract Paragenetic interpretation, defined as the process of constraining the order in which the phases (minerals) comprising a rock formed, are fundamental in all disciplines requiring a detailed mapping of the genetic relationships between the investigated crystal(s) and their surrounding phases. Ore geology, geochronology, petrological and fluid inclusion studies are underpinned by a robust interpretation of the paragenesis. Without this understanding, the interpretation of the analytical data will be greatly restricted and potentially wrong. Textural mapping is particularly useful for studying phases precipitated into hydrothermal veins because the host many metallic ore deposits. Understanding the paragenesis and the association of ore minerals feeds directly into the approach taken towards exploration, mining operation and ore processing. Apart from ore deposits, precipitation of hydrothermal phases occurs in any setting where hot fluids interact with rock or sediment (e.g. CCS storage; geothermal facilities). This paper summarizes the principles for developing a robust paragenetic interpretation, including demonstrating the practical workflow via a case study from a sulfide-bearing vein near Loch Tay, Scotland. The principles and the workflow outlined in this paper are applicable to any discipline and route of investigation that necessitates a robust understanding of the relationships of the phases in a rock.

Abstract Since the term was coined in 1873, palaeogeography has provided a powerful map-based tool for synthesizing, visualizing, and testing diverse regional data and hypotheses, but there are problems in deducing the palaeogeography of areas with few data points. As an example, the Scottish Highlands are better mapped and more studied than almost any other ancient orogen, yet questions remain on the persistence of topography since the Caledonian orogeny and the possibility of Cretaceous marine inundation. This paper reviews the data available on Scottish Cretaceous outcrops using published geological maps and memoirs to extract data: outcrop length, stratigraphic thickness and component units, elevation range of the outcrop and subcrop formations. All Cretaceous rocks in western Scotland were deposited in shallow marine and shoreline environments; deposits thin northwards and appear to be close to a feather edge. Elevation data are used to construct a Cretaceous surface which intersects present-day topography at low to intermediate altitudes. It is concluded that the Scottish Highlands were largely emergent during the Late Cretaceous, confirming previous palaeogeographic studies.