Loch of Park - locality, Cainozoic of north-east Scotland

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From: Merritt, J W, Auton, C A, Connell, E R, Hall, A M, and Peacock, J D. 2003. Cainozoic geology and landscape evolution of north-east Scotland. Memoir of the British Geological Survey, sheets 66E, 67, 76E, 77, 86E, 87W, 87E, 95, 96W, 96E and 97 (Scotland).

Loch of Park

Glacial and glaciofluvial features and the distribution of glacigenic deposits on Sheet 66E Banchory. P915380.

The organic sediments preserved within the large ice-scoured rock basin at Loch of Park, north-east of Banchory (P915380), provide evidence of typical climate and vegetation changes that have occurred within the district since deglaciation. Pollen data and radiocarbon dates from the site indicate that a ‘tripartite’ Late-glacial sequence is preserved that passes upwards into Holocene deposits.

Loch of Park locality, near Banchory. P915327.

The Loch of Park (P915327 a) is the site of a freshwater lake that was drained during the 19th century and is now a local nature reserve. It occurs at the south-eastern end of the basin, which extends for about 4 km along the northern margin of Sheet 66E Banchory and across the southern margin of Sheet 76E Inverurie. The basin was formed by ice that flowed eastwards from the Grampian Highlands, scouring the underlying decomposed Crathes Granodiorite. The ice deposited a thin spread of till on the basin floor. It also laid down morainic mounds at the eastern margin of the basin during its westward retreat. These moraines blocked the subsequent drainage of the lake eastwards and an interbedded sequence of organic muds, peats and fine-grained lacustrine sediments were laid down on top of the basal till. Mounds and narrow terraced spreads of sand and gravel were also laid down around the southern margin of the lake.

The organic sediments in the basin were first described by Vasari and Vasari (1968), who analysed the pollen content from a narrow diameter piston-cored borehole. The borehole, at about 70 m above OD, near the eastern end of the former lake (P915327 a), penetrated interbedded peats, clays and organic muds to a depth of 5.6 m. The lowermost 1.70 m of the core was recorded as bluish clay, almost entirely devoid of pollen. Above this unit occurred 0.5 m of organic mud, 0.35 m of nutrient-rich silty peat (gyttja) and 0.53 m of clay. The upper clay was overlain by peat, which became increasingly sandy upwards. The three units above the basal blue clay (and their pollen assemblages) were interpreted as being of Late-glacial age and the upper peat as being Holocene.

The pollen spectrum (P915327 b), between 2.10 and 3.85 m depth was assigned to the classical Late-glacial pollen zones I (cold), II (warm), III (cold), a combined zone III–IV, coinciding with the transition from cold to warm conditions, and the Postglacial (Holocene) IV (warm). The Late-glacial sediments, which were subdivided in to three subzones, Ia–Ic, are characterised by a dominance of non-arboreal pollen and the Holocene sediments by a marked increase in the proportion of Betula (birch), Pinus (pine) and Juniperus (juniper) pollen. A corresponding decrease was recorded in the proportions of grass and herb pollen in the Holocene deposits. Subzone Ia (mainly almost barren blue clay) and subzone Ib, (the organic mud) were thought to reflect progressive climatic amelioration. This was followed by a colder episode (subzone Ic).

The sequence was subsequently reinvestigated in 1972 (Vasari, 1977), when samples of organic sediment were taken for radiocarbon dating from a second boring. The borehole was sited immediately adjacent to the first and a similar stratigraphical sequence was proved. The lower sample, HEL–417, taken at the boundary between the top of subzone Ic and the base of zone II (Empetrum {crowberry} rise/Rumex {docks} fall), yielded a radiocarbon age of 11 900 ± 260 BP (see table below). This was said by Vasari (1977) to correspond closely with the accepted radiocarbon age for the I/II boundary for much of north-western Europe. The upper sample, HEL–416 (at the combined zone III–IV boundary; between the Rumex and Empetrum maxima), yielded a radiocarbon age of 10 280 ± 220 BP. This was seen by Varasri (1977) as compatible with the generally accepted radiocarbon age of the Late-glacial/Holocene boundary in Britain (about 10 250 BP).

Radiocarbon dates from Late-glacial sites in the district
Site Grid reference Laboratory number Age (year BP) Dated material and setting Reference
Rothes cutting NJ 277 498 Beta 8653 11 110 ± 70 peat under remobilised till Appendix 1
Garral Hill, Keith NJ 444 551 Q-104 10 808 ± 230 peat under remobilised till Godwin and Willis (1959)
Garral Hill, Keith NJ 444 551 Q-103 11 098 ± 235 peat under remobilised till Godwin and Willis (1959)
Garral Hill, Keith NJ 444 551 Q-102 11 308 ± 245 peat under remobilised till Godwin and Willis (1959)
Garral Hill, Keith NJ 444 551 Q-101 11 888 ± 225 peat under remobilised till Godwin and Willis (1959)
Garral Hill, Keith NJ 444 551 Q-100 11 358 ± 300 peat under remobilised till Godwin and Willis (1959)
Woodhead, Fyvie NJ 788 384 SRR-1723 10 780 ± 50 peat under remobilised till Connell and Hall (1987)
Howe of Byth NJ 822 571 SRR-4830 11320 peat beneath gravel Hall et al. (1995)
Moss-side, Tarves NJ 833 318 I-6969 12 200 ± 170 peat under remobilised till Clapperton and Sugden (1977)
Loch of Park NO 772 988 HEL-416 10 280 ± 220 kettlehole infill Vasari and Vasari (1968)
Loch of Park HEL-417 11 900 ± 260 kettlehole infill Vasari and Vasari (1968)
Mill of Dyce NJ 8713 1496 SRR-762 11 550 ± 80 kettlehole infill Harkness and Wilson (1979)
Mill of Dyce NJ 8713 1496 SRR-763 11 640 ± 70 kettlehole infill Harkness and Wilson (1979)
Glenbervie NO 767 801 GX-14723 12 460 ± 130 peat under remobilised till Appendix 1
Glenbervie NO 767 801 SRR-3687a. (humic) 12 305 ± 50 peat under remobilised till Appendix 1
Glenbervie NO 767 801 SRR-368Th (humin) 12 340 ± 50 peat under remobilised till Appendix 1
Brinzieshill Farm NO 7936 7918 SRR-387 12 390 ± 100 peat under remobilised till Auton et al. (2000)
Rothens NJ 688 171 SRR-3803 10 680 ± 100 kettlehole infill Appendix 1
Rothens NJ 688 171 SRR-3804 11 640 ± 160 kettlehole infill Appendix 1
Rothens NJ 688 171 SRR-3805 11 760 ± 140 kettlehole infill Appendix 1

References

Full reference list