2.4 Late Glacial

Lowlands Environments

A typical Late Glacial sequence is represented in the Whitlaw Mosses diagrams that derive from Beanrig Moss and Blackpool Moss. At the basal levels of the core at Beanrig Moss there are clays with some organic debris, which were probably introduced by the process of downwashing from the surrounding slopes where vegetation was sparse (Webb and Moore 1982, 370). This is indicative of a cold environment and is consistent with the inference that this deposit represents the close of the Dimlington Stadial. This is succeeded by a phase when marl and ostracods become evident, signalling the advent of warm conditions (Webb and Moore 1982, 370–1). The most likely date for this is the Windermere Interstadial, dated to between c. 13,000 BP and 10,800 BP. The establishment of temperate conditions resulted in afforestation and soil development; this is manifested in the macrofossil sequences by an increase in birch, spruce and juniper remains (Webb and Moore 1982, 372–8). A regressive trend, however, becomes evident after the Windermere Interstadial and is most convincingly correlated with the temperature decline signalling the onset of the Loch Lomond Re-advance.

Photograph of the boardwalk in blackpool moss. The view of the grasses and trees is cut down the middle by a straight plank.
Boardwalk in Blackpool Moss. The boardwalk is to enable biological surveying without damaging the sensitive flora found at the site © James TM Towill (CC BY-SA 2.0)

Less sensitive reconstructions are afforded by pollen studies and sedimentological investigations elsewhere. At Linton Loch, the basal deposits of clay contain little pollen, and thus it is inferred that the environment was florally unproductive – that is to say, that it did not sustain a plant population of any significance (Mannion 1978, 202). This suggests that the deposits here were formed in one of the cold, glacial episodes; this was succeeded by an episode of marl formation. The marl is often seen developing in the earliest phases of the Holocene, immediately following the Younger Dryas (Loch Lomond Re-advance). In short, the sequence at Linton Loch corresponds favourably to the patterns that have been recognised at the aforementioned bog sites. Other pollen diagrams, especially those from the Forth Valley, are of limited value in elucidating the conditions in the Late Glacial because of the lack of radiocarbon dates affixed to specific horizons. Nevertheless, they clearly demonstrate the trend from grasslands and pioneer woodland to closed forests (Newey 1968, 1970). This appears to be a pattern that is common to the region, as opposite the orbit of research for this study, a similar process is seen in Fife at sites such as Black Loch (Whittington et al 1991, 152).

Photograph of green hills, with leafy trees growing along the base and side of the hill.
Linton Loch © James T M Towill (CC BY-SA 2.0)

More widely, studies of marine deposits near Stirling, collected from a series of commercial boreholes, have been focused largely on the molluscan fauna from the Windermere Interstadial. This has suggested a high boreal to low arctic fauna in the marine environment of the Firth of Forth (Peacock 2002). Elsewhere along the Forth, a similar series of faunal studies of Late Glacial horizons in the cores have confirmed this trend in the Windermere Interstadial (Holloway et al 2002). This corresponds too with the diatom collections from Linton Loch (Mannion 1981). The presence of fossils from mammals that are commonly associated with cold conditions is also instructive: woolly mammoth (Mammuthus primigenius) are known from deposits in the region (Kitchener 2014), as are reindeer (Rangifer tarandus) at places such as Edrom (Lawson 1984). Few coleopteran studies have been undertaken – the only ones published are from sites in Corstorphine, which agree with the broad outlines provided by other studies, suggesting that cold and continental conditions developed in the Late Glacial (Coope 1968, 346).

The results of the plant macrofossil studies at the Whitlaw Mosses largely agree with the pollen analytical and chironomid remains from the sedimentary cores at Whitrig Bog and elsewhere (Webb and Moore 1982, 383). Investigation of the chironomid remains from Whitrig Bog, which lies roughly 3km to the north of St. Boswells, permits an extremely sensitive air-temperature reconstruction for the Loch Lomond Re-advance (Younger Dryas) (Brooks et al 1997, 163). The taxa indicate that the temperatures declined very sharply, approximating sub-Arctic conditions, with mean July temperatures at sea-level around 6°C (Brooks and Birks 2000, 763). An increase in minerogenic sediment corroborates the inferences based on the chironomids, inasmuch that this is indicative of vegetation becoming sparser and erosion accelerating as the soil development is arrested and colluvium ran off into ponds and rivers (Brooks et al 1997, 163).

Photograph of the nether whitlaw moss. The foreground of the image shows an area which is mostly under water, with small amounts of the moss poking through. The background has fuller bushes and trees, and a rolling grey sky.
Nether Whitlaw Moss, taken from the boardwalk © Iain Rees (CC BY-SA 2.0)

Faunal evidence from the region is limited and distributed widely amongst institutions. Radiocarbon dates of reindeer remains, and other species associated with the Late Glacial would aid in the understanding of the conditions prevailing in different parts of the SESARF region at this time.

Significant oscillations in temperature, which are now understood to be characteristic of the Late Glacial, are largely elusive in many of the studies apart from the high-resolution investigations at the Whitlaw Mosses. Moreover, there remains the problem of how representative such studies are in a landscape that affords as much relief as that of the SESARF region. Valley and lowland environments were likely to be wetter and more sheltered, providing better conditions for the development of foliage than the more exposed and drier soils of the uplands. Furthermore, this had the effect of soils developing faster in the lower elevation river valleys, lowlands and coastal plain environments and supporting a diverse flora and fauna. The upland environments were therefore also more susceptible to erosion because of the more skeletal soils that could sustain little vegetation capable of arresting or retarding aeolian and solifluction processes that prevailed when the temperatures declined.

Upland Environments

No pollen cores comprising Late Glacial deposits have been recovered from the upland, apart from that at Fala Moor (Young 1966). It is questionable whether deposits from this era survive well here, as there is extensive evidence of solifluction during parts of the Late Glacial. In addition, there are the thin soils that were vulnerable to erosion by aeolian processes as the cold conditions reduced the foliage which helped to support the soils. Almost all the studies at the margins of the hills have demonstrated the prevalence of solifluction in the Late Glacial, probably occurring in different episodes (Harrison 1993; Tipping 1994, 2010; Tipping and Halliday 1994).

A photograph showing the varying colours of the grassy landscape of Fala Moor. The grass in the foreground is green, with the grasses in the background being various shades of orange, yellow and red.
Fala Moor © Richard Webb (CC BY-SA 2.0)