The Quaternary history of Llangorse Lake: implications for conservation

摘要: 1. Llangorse Lake is a relatively recent feature of the landscape—a product Late Quaternary glaciation. It relict proglacial ‘Lake Llangors’, whose water level was once 37 m higher than that present lake. 2. Palaeolimnological studies indicate lake basin started to infill with lacustrine clay in Devensian, cold, steppe-tundra environment. An interlude relative warmth (the Windermere Interstadial) may have prompted accumulations marl, before renewed sedimentation Loch Lomond Stadial. In period increased early Holocene, catchment soils stabilized, and an organic autochthonous nekron mud accumulated slowly central areas, whilst marl deposits northern margins. 3. Sediment later faster, apparently after Neolithic Bronze Age activity led proportion allochthonous material. A major change occurred late Iron Age/Roman times, which troughs has principally been red-brown silty clay, eroded from catchment. 4. eastern trough, nearer principal inflow stream, ca 4 past 2000 years. The depth shallowed some 7–9 deeper parts, compared >20 deglaciation, 15 at start Holocene. (These figures exclude field evidence for having considerably larger, much level, its history.) 5. Several lines show rate accelerated: 90 cm sediment within last 300 years, top 65 (including less-compacted sediment) <150 Unless input curtailed, will become too shallow be sustainable over remainder Copyright © 1999 John Wiley & Sons, Ltd.