Late Quaternary river terrace developments in the Macgillycuddy's Reeks, Southwest Ireland

E. Anderson, S. Harrison, D. Passmore, Timothy Michael Mighall, S. Withan

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

Geomorphological, sedimentological, pedostratigraphical and palaeoecological analyses of fluvial and glacigenic deposits infilling the Gaddagh valley, Macgillycuddy's Reeks, southwest Ireland, are used to elucidate the patterns and controls of Late Quaternary valley floor development in a 3 km reach of the catchment lying immediately downvalley of two mid-basin lakes, Lough Gouragh and Lough Callee. A total of four Holocene alluvial terraces (Terrace Level, TL 2-5) and a modern floodplain (TL 6) have been identified and lie inset within a strath terrace comprising Late Quaternary (Midlandian) till (TL 1). The combination of mid-basin lakes and flanking strath terraces acted to decouple the Gaddagh channel from upper catchment and valley-side debris sources shortly after regional deglaciation. Postglacial fluvial terrace development in the study reach has therefore occurred primarily in response to hydrological changes and reworking of local valley floor deposits rather than catchment-wide debris supply changes.

Pollen analyses of valley floor peat deposits interbedded with minerogenic alluvium indicate that anthropogenic disturbance of catchment tree cover had commenced by c.a 1690-1450 cal BC and that the catchment was largely cleared of woodland by later prehistoric times. Major phases of incision and alluviation represented by terraces TL 3-5, however, have been radiocarbon dated to the period after 250-530 cal AD and broadly correspond with Holocene fluvial records elsewhere in the region, upland Britain and northwest Europe. Although fluvial system responses to hydrological changes will have been promoted by anthropogenic disturbances of catchment vegetation cover, the timing of late Holocene incision and alluviation episodes are interpreted as reflecting enhanced flood frequencies and (or) magnitudes associated with late Holocene climatic shifts. In the Gaddagh Valley, however, we hypothesise that the headwater lakes Lough Gouragh and Lough Callee may also have exerted a critical control on the postglacial evolution of the valley floor. In particular, high-magnitude flooding is likely to have been instrumental in valley floor entrenchment and formation of TL 3, TL 4 and TL 5 terraces. (C) 2004 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)1785-1801
Number of pages16
JournalQuaternary Science Reviews
Volume23
Issue number16-17
DOIs
Publication statusPublished - 2004

Keywords

  • HOLOCENE ALLUVIAL-FAN
  • NORTHERN ENGLAND
  • NORTHWEST ENGLAND
  • AGE CALIBRATION
  • CLIMATE-CHANGE
  • SCOTLAND
  • ATLANTIC
  • CHANNEL
  • RECORDS
  • UPLANDS

Cite this

Late Quaternary river terrace developments in the Macgillycuddy's Reeks, Southwest Ireland. / Anderson, E.; Harrison, S.; Passmore, D.; Mighall, Timothy Michael; Withan, S.

In: Quaternary Science Reviews, Vol. 23, No. 16-17, 2004, p. 1785-1801.

Research output: Contribution to journalArticle

Anderson, E. ; Harrison, S. ; Passmore, D. ; Mighall, Timothy Michael ; Withan, S. / Late Quaternary river terrace developments in the Macgillycuddy's Reeks, Southwest Ireland. In: Quaternary Science Reviews. 2004 ; Vol. 23, No. 16-17. pp. 1785-1801.
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AU - Anderson, E.

AU - Harrison, S.

AU - Passmore, D.

AU - Mighall, Timothy Michael

AU - Withan, S.

PY - 2004

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N2 - Geomorphological, sedimentological, pedostratigraphical and palaeoecological analyses of fluvial and glacigenic deposits infilling the Gaddagh valley, Macgillycuddy's Reeks, southwest Ireland, are used to elucidate the patterns and controls of Late Quaternary valley floor development in a 3 km reach of the catchment lying immediately downvalley of two mid-basin lakes, Lough Gouragh and Lough Callee. A total of four Holocene alluvial terraces (Terrace Level, TL 2-5) and a modern floodplain (TL 6) have been identified and lie inset within a strath terrace comprising Late Quaternary (Midlandian) till (TL 1). The combination of mid-basin lakes and flanking strath terraces acted to decouple the Gaddagh channel from upper catchment and valley-side debris sources shortly after regional deglaciation. Postglacial fluvial terrace development in the study reach has therefore occurred primarily in response to hydrological changes and reworking of local valley floor deposits rather than catchment-wide debris supply changes.Pollen analyses of valley floor peat deposits interbedded with minerogenic alluvium indicate that anthropogenic disturbance of catchment tree cover had commenced by c.a 1690-1450 cal BC and that the catchment was largely cleared of woodland by later prehistoric times. Major phases of incision and alluviation represented by terraces TL 3-5, however, have been radiocarbon dated to the period after 250-530 cal AD and broadly correspond with Holocene fluvial records elsewhere in the region, upland Britain and northwest Europe. Although fluvial system responses to hydrological changes will have been promoted by anthropogenic disturbances of catchment vegetation cover, the timing of late Holocene incision and alluviation episodes are interpreted as reflecting enhanced flood frequencies and (or) magnitudes associated with late Holocene climatic shifts. In the Gaddagh Valley, however, we hypothesise that the headwater lakes Lough Gouragh and Lough Callee may also have exerted a critical control on the postglacial evolution of the valley floor. In particular, high-magnitude flooding is likely to have been instrumental in valley floor entrenchment and formation of TL 3, TL 4 and TL 5 terraces. (C) 2004 Elsevier Ltd. All rights reserved.

AB - Geomorphological, sedimentological, pedostratigraphical and palaeoecological analyses of fluvial and glacigenic deposits infilling the Gaddagh valley, Macgillycuddy's Reeks, southwest Ireland, are used to elucidate the patterns and controls of Late Quaternary valley floor development in a 3 km reach of the catchment lying immediately downvalley of two mid-basin lakes, Lough Gouragh and Lough Callee. A total of four Holocene alluvial terraces (Terrace Level, TL 2-5) and a modern floodplain (TL 6) have been identified and lie inset within a strath terrace comprising Late Quaternary (Midlandian) till (TL 1). The combination of mid-basin lakes and flanking strath terraces acted to decouple the Gaddagh channel from upper catchment and valley-side debris sources shortly after regional deglaciation. Postglacial fluvial terrace development in the study reach has therefore occurred primarily in response to hydrological changes and reworking of local valley floor deposits rather than catchment-wide debris supply changes.Pollen analyses of valley floor peat deposits interbedded with minerogenic alluvium indicate that anthropogenic disturbance of catchment tree cover had commenced by c.a 1690-1450 cal BC and that the catchment was largely cleared of woodland by later prehistoric times. Major phases of incision and alluviation represented by terraces TL 3-5, however, have been radiocarbon dated to the period after 250-530 cal AD and broadly correspond with Holocene fluvial records elsewhere in the region, upland Britain and northwest Europe. Although fluvial system responses to hydrological changes will have been promoted by anthropogenic disturbances of catchment vegetation cover, the timing of late Holocene incision and alluviation episodes are interpreted as reflecting enhanced flood frequencies and (or) magnitudes associated with late Holocene climatic shifts. In the Gaddagh Valley, however, we hypothesise that the headwater lakes Lough Gouragh and Lough Callee may also have exerted a critical control on the postglacial evolution of the valley floor. In particular, high-magnitude flooding is likely to have been instrumental in valley floor entrenchment and formation of TL 3, TL 4 and TL 5 terraces. (C) 2004 Elsevier Ltd. All rights reserved.

KW - HOLOCENE ALLUVIAL-FAN

KW - NORTHERN ENGLAND

KW - NORTHWEST ENGLAND

KW - AGE CALIBRATION

KW - CLIMATE-CHANGE

KW - SCOTLAND

KW - ATLANTIC

KW - CHANNEL

KW - RECORDS

KW - UPLANDS

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DO - 10.1016/j.quascirev.2003.12.001

M3 - Article

VL - 23

SP - 1785

EP - 1801

JO - Quaternary Science Reviews

JF - Quaternary Science Reviews

SN - 0277-3791

IS - 16-17

ER -