Reply to discussion on 'Deglaciation and neotectonics in SE Raasay, Scottish Inner Hebrides’ by Smith et al. 2021 (SJG, 57, 106-116)

We greatly appreciate Dr Morton's interest in our paper and his appreciative comments. The features at Beinn na Leac are, in our opinion, of particular interest to geologists interested in the pattern of deglaciation and neotectonics in this part of western Scotland. The location is unique in Scotland in the magnitude of Younger Dryas/Holocene fault dislocation. We respond to Dr Morton's comments as follows:

Discussion on ‘Deglaciation and neotectonics in SE Raasay, Scottish Inner Hebrides’ by Smith et al. 2021 (SJG, 57, xx-yy)

I congratulate David Smith and his colleagues (2021) on an excellent presentation of their work on the evolution of the morphology and events involved in the evolution of the Beinn na Leac area in south-east Raasay. The summit area is a difficult and even dangerous area to work in, as I know from personal experience – learning to only follow sheep tracks to avoid the many deep fissures with openings often hidden by vegetation.

Radiocarbon dating of a composite multi-period debris cone stratigraphy in the Lochan na Lairige, Ben Lawers

An early stage in formation of a composite debris cone in the glacial trough of the Lochan na Lairige, on Ben Lawers, is 14C dated to 6398–6225 cal BP. A large proportion of the fan comprises a structureless gravel with boulders, possibly deposited in a single event. Blanket peat formed on the fan surface at 3820–3496 cal BP. Sediment slurries are recorded across the peat after this time, at c. 3950 to c. 3100 cal BP, c. 2000 and c. 1400 cal BP, and at c. 1200 to c. 1100 cal BP. They were much less significant events. They can be related to periods of higher effective precipitation in the region.

First report of fish trace fossils (Undichna) from the Middle Devonian Achanarras Limestone, Caithness Flagstone Group

Two newly-discovered specimens of the fish locomotion trace Undichna (U. britannica and Undichna isp.), are described from the Middle Devonian Achanarras Limestone Member (Caithness Flagstone Group, NE Scotland). Fish trace fossils have not previously been reported from the Achanarras Limestone Member, despite decades of study of the unit as a key locality for fish body fossils. The traces comprise discontinuous sinusoidal grooves; one showing multiple parallel incisions, created by the fins of an acanthodian fish swimming close to the substrate. The apparent absence of trace fossils attributable to infaunal or epifaunal benthic organisms suggests that the sediment at the bottom of the lake was relatively inhospitable. The low ichnodiversity of the Achanarras Limestone Member is likely due to low oxygen levels in the depositional environment.Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/cc/SJG-early-career-research

Reply to Discussion on ‘Borehole temperature log from the Glasgow Geothermal Energy Research Field Site: a record of past changes to ground surface temperature caused by urban development’ by Watson and Westaway 2020 (SJG, 56, 134–152, 2020).

Watson and Westaway (2020) (WW) quantified subsurface temperature variations caused by anthropogenic climate change and urban/industrial development in Glasgow, using temperature data from the Glasgow Geothermal Energy Research Field Site (GGERFS) well GGC-01 (at site G-10; Fig. 1), noting implications for the thermal physics of this site. Monaghan, Manning and Shipton (2021) (MMS) have queried points, noted in passing by WW, on other aspects: the GGERFS purpose, location, design, heat resource, and cost.

Deglaciation and neotectonics in South East Raasay, Scottish Inner Hebrides

Changes in the physical landscape of SE Raasay at the end of the last Quaternary glaciation are examined. The area is marked by a major fault system defining the Beinn na Leac Fault Block, and field survey shows this to comprise a rollover anticline in the SW, with extensional movement towards the NE along an oblique transfer fault, the Main Beinn na Leac Fault. The fault system was reactivated after the Last Glacial Maximum (the LGM). Survey of a distinctive ridge of detached scree along the Main Beinn na Leac fault shows it to have involved a single movement of at least 7.12m vertical displacement, arguably the greatest fault movement since before the Younger Dryas in Scotland. The present work confirms that the scree became detached during the Younger Dryas, but finds that it overlies a lacustrine deposit of at least 5.6m of laminated sediments from a lake which had begun to accumulate earlier. Radiocarbon dating of peat overlying the lake sediments gave 10,176 – 10,315 cal. BP, but morphological and stratigraphical evidence indicates that drainage of the lake occurred earlier and only shortly before movement of the scree. Possible causes of displacement at the fault system are briefly discussed.

Discussion on ‘The geological collection from the Scottish National Antarctic Expedition (1902–04) in the Museo de La Plata, Argentina’ by Carrasquero 2021 (Scottish Journal of Geology, 57, 60– 66)

The informative paper by Carrasquero (2021) reveals the personal contribution made by Francisco Moreno to the success of the 1902-04 Scottish National Antarctic Expedition (SNAE) during the time it spent in Buenos Aires, Argentina. It was a crucial intervention, and for the hospitality and generous assistance that Moreno arranged for the expedition's leader, William Speirs Bruce (Fig. 1), the presentation of a few rock specimens might seem scant reward, although as an additional mark of respect Bruce named Point Moreno on the expedition's published map of Laurie Island (Brown et al. 1906, p. 145): the name is still valid – 60° 44’ S, 44° 41’ W. Bruce would have been deeply satisfied by the knowledge that his donation of specimens from the South Orkney Islands had initiated the development of an Antarctic collection at the Museo de La Plata. His scientific outlook was always international and collaborative.

A new geological map and review of the Middle Devonian rocks of Westray and Papa Westray, Orkney, Scotland

The Middle Devonian lacustrine sediments of Orkney, off the northeast Scottish mainland, are composed largely of the Lower and Upper Stromness Formations and overlying Rousay Formation. These three formations have been subdivided and defined by vertebrate biostratigraphic biozones with recent division of the Rousay Formation into three further units based on characteristic fish fossils. The division of the Rousay Formation has enabled a map to be constructed of the solid geology of the island of Westray, Orkney, based on fish identification, detailed logging of sedimentary cycles throughout the Rousay succession, parameters of divisional boundaries, and a survey of faults marking sinistral transtensional movement parallel to the Great Glen Fault. Post-Carboniferous shortening and basin inversion led to uplift, folding and reactivation of normal faults as reverse faults, to form a positive strike-slip flower structure in Westray. A suite of Permian igneous dykes intruded across Orkney include three minor offshoots in Westray. The resulting map is the first to make use of biostratigraphic units within the Rousay Flagstone which are now regarded as Members.

The geological collection from the Scottish National Antarctic Expedition (1902–04) in the Museo de La Plata, Argentina

In December 1903, Williams Speirs Bruce, leader of the Scottish National Antarctic Expedition, arrived in Buenos Aires and contacted Francisco Moreno, director of the Museo de La Plata to request his assistance. Bruce asked Moreno to be an intermediary with the Argentine government and to facilitate Bruce's wish for Argentina to take over the meteorological station that the Scottish expedition had established on Laurie Island (South Orkney Islands). Moreno was please to provide the necessary assistance and was instrumental in Bruce achieving his ambition. As a gesture of appreciation, before leaving Buenos Aires Bruce presented a small collection of Laurie Island rock specimens to Moreno as a donation to the Museo de La Plata. This donation initiated the museum's Antarctic collection.

Volcaniclastic deposit (tonstein) in the Balcomie Beds, Lower Carboniferous, East Fife

A volcanogenic clay bed (tonstein) has been identified in the Balcomie Beds of the Inverclyde Group near Crail, East Fife. Its chemical composition suggests an undersaturated alkaline magma source. This horizon may be contemporaneous with the early Carboniferous Garleton Hills trachytic lavas of East Lothian (346 Ma). This would make it the earliest expression of Carboniferous volcanism preserved in Fife, and also the earliest occurrence of a tonstein in Fife.