The age of alluvial fan deposition at a site in the southern uplands of scotland

Abstract

The age of a large alluvial fan debouching onto the valley floor of the River Tweed, in southern Scotland, and the sequence of events relating to this, are investigated using geomorphological, sedimentological, palynological, archaeological and radiocarbon dating evidence. Prior to fan deposition, the Tweed valley floor seems to have been covered by a wooded peat at a time of low fluvial activity. The fan commenced deposition in the 11 th century AD, and appears to have been a local event, the Tweed showing no response to this accelerated sedimentation. Later, perhaps 200 years later, the Tweed commenced overbank deposition of the only Flandrian terrace preserved. Local proxy data are examined in order to define the causes of these events, but difficulties in temporal correlation, despite the good resolution of the radiocarbon chronology, mean that the causes of these events remain unknown. KEY WORDS Alluvial fan Fluvial aggradation Radiocarbon dating Historic period changes Proxy data and causal inference

Holocene river development and environmental change in Upper Wharfedale, Yorkshire Dales, England

“…7), including the Tweed (Tipping and Halliday, 1994), the Southern Uplands (Tipping, 1995b), and the Northern Pennines (Macklin et al, 1994). This time period also marks the onset of renewed alluvial fan deposition, notably in the Western Grampian Highlands (Brazier et al, 1988), Southern Uplands (Tipping and Halliday, 1994), the Howgill Fells (Harvey et al, 1981), the Bowland Fells (Harvey and Renwick, 1987) and on the North York Moors (Richards et al, 1987), suggesting increased slope instability.…”

“…3a, Tweed Valley, Southern Uplands (Tipping & Halliday, 1994). 3b, Hopecarton Burn, Southern Uplands (Tipping and Halliday, 1994). 4, Breamish Valley, Cheviot Hills (Tipping, 1992).…”

“…2, Glen Etive, Western Grampian Highlands (Brazier et al, 1988). 3a, Tweed Valley, Southern Uplands (Tipping & Halliday, 1994). 3b, Hopecarton Burn, Southern Uplands (Tipping and Halliday, 1994).…”

“…The late Pleistocene and Holocene development of upland river systems in northern and western Britain has received growing attention over the past two decades (Harvey et al, 1981;Richards, 1981;Macklin and Lewin, 1986;RobertsonRintoul, 1986;Harvey and Renwick, 1987;Richards et al, 1987;Brazier et al, 1988;Macklin et al, 1991;Macklin et al, 1992a, b;Passmore et al, 1993;Tipping, 1994Tipping, , 1995aTipping and Halliday, 1994;Taylor and Lewin, 1997). The majority of these studies have illustrated how declining sediment supply in response to deglaciation and isostatic rebound has resulted in the development of flights of river terraces rising above the contemporary channel.…”

Late Holocene floodplain incision and alluvial fan formation in the central Grampian Highlands, Scotland: chronology, environment and implications

“…There is growing evidence, however, that many relict debris cones and alluvial fans in upland Britain were deposited in the mid-or late Holocene, several millennia after final deglaciation (e.g. Harvey et al, 1981;Harvey and Renwick, 1987;Brazier et al, 1988;Brazier and Ballantyne, 1989;Tipping and Halliday, 1994). Many alluvial basins in upland Britain also exhibit evidence for successive episodes of mid-or late Holocene valley-floor accumulation and incision, reflecting complex changes in sediment delivery and storage (e.g.…”