The University of Southampton
University of Southampton Institutional Repository

Late pleistocene–holocene river dynamics at the Trent-Soar confluence, England, UK

Late pleistocene–holocene river dynamics at the Trent-Soar confluence, England, UK
Late pleistocene–holocene river dynamics at the Trent-Soar confluence, England, UK
Although river confluences have received geomorphic attention in recent years it is difficult to upscale these studies, so confluence-dominated reaches are commonly presumed to be either: (1) braided; or (2) meandering and characterized by laterally migrating channels. If the geomorphology of a confluence zone is to be considered over longer timescales, changes in river style need to be taken into account. This paper uses a combination of remote sensing techniques (LiDAR, GPR, ER), borehole survey
and chronometric dating to test this differentiation in the confluence-zone of a medium-sized, mixed-load, temperate river system (Trent, UK), which on the basis of planform evidence appears to conform to the meandering model. However, the analysis of ‘confluence sediment body stratigraphy’ demonstrates that the confluence does not correspond with a simple meander migration model
and chronostratigraphic data suggests it has undergone two major transformations. Firstly, from a high-energy braid-plain confluence in the Lateglacial (25–13 K yrs cal BP), to a lower-energy braided confluence in the early to middle Holocene (early Holocene-2.4 kyr BP), which created a compound terrace. Second, incision into this terrace, creating a single-channel confluence (2.4–0.5 kyr cal BP)
with a high sinuosity south bank tributary (the River Soar). The confluence sediment-body stratigraphy is characterized by a basal suite of Late Pleistocene gravels bisected by younger channel fills, which grade into the intervening levee and overbank sediments. The best explanation for the confluence sediment body stratigraphy encountered is that frequent switching (soft-avulsionssensu) of the tributary are responsible for the downstream movement of the channel confluence (at an average rate of approximately 0.5m per year) dissecting and reworking older braid-plain sediments. The late Holocene evolution of the confluence can be seen as a variant
of the incisional-frequent channel reorganization(soft-avulsion sensu Edmonds et al., 2011) model with sequential downstream migration of the reattachment point.
0197-9337
Brown, A.G.
c51f9d3e-02b0-47da-a483-41c354e78fab
Toms, P.S.
323a4b9c-2e67-4dce-b0fe-f966ada75b99
Carey, C.J.
b53b6e6e-543d-4492-b491-2644da392249
Howard, A.J.
fbbad830-c039-44e3-be1a-cef130dfe26c
Challis, K.
c83bdce9-c124-4261-a973-733b03e54357
Brown, A.G.
c51f9d3e-02b0-47da-a483-41c354e78fab
Toms, P.S.
323a4b9c-2e67-4dce-b0fe-f966ada75b99
Carey, C.J.
b53b6e6e-543d-4492-b491-2644da392249
Howard, A.J.
fbbad830-c039-44e3-be1a-cef130dfe26c
Challis, K.
c83bdce9-c124-4261-a973-733b03e54357

Brown, A.G., Toms, P.S., Carey, C.J., Howard, A.J. and Challis, K. (2012) Late pleistocene–holocene river dynamics at the Trent-Soar confluence, England, UK. Earth Surface Processes and Landforms. (doi:10.1002/esp.3270). (In Press)

Record type: Article

Abstract

Although river confluences have received geomorphic attention in recent years it is difficult to upscale these studies, so confluence-dominated reaches are commonly presumed to be either: (1) braided; or (2) meandering and characterized by laterally migrating channels. If the geomorphology of a confluence zone is to be considered over longer timescales, changes in river style need to be taken into account. This paper uses a combination of remote sensing techniques (LiDAR, GPR, ER), borehole survey
and chronometric dating to test this differentiation in the confluence-zone of a medium-sized, mixed-load, temperate river system (Trent, UK), which on the basis of planform evidence appears to conform to the meandering model. However, the analysis of ‘confluence sediment body stratigraphy’ demonstrates that the confluence does not correspond with a simple meander migration model
and chronostratigraphic data suggests it has undergone two major transformations. Firstly, from a high-energy braid-plain confluence in the Lateglacial (25–13 K yrs cal BP), to a lower-energy braided confluence in the early to middle Holocene (early Holocene-2.4 kyr BP), which created a compound terrace. Second, incision into this terrace, creating a single-channel confluence (2.4–0.5 kyr cal BP)
with a high sinuosity south bank tributary (the River Soar). The confluence sediment-body stratigraphy is characterized by a basal suite of Late Pleistocene gravels bisected by younger channel fills, which grade into the intervening levee and overbank sediments. The best explanation for the confluence sediment body stratigraphy encountered is that frequent switching (soft-avulsionssensu) of the tributary are responsible for the downstream movement of the channel confluence (at an average rate of approximately 0.5m per year) dissecting and reworking older braid-plain sediments. The late Holocene evolution of the confluence can be seen as a variant
of the incisional-frequent channel reorganization(soft-avulsion sensu Edmonds et al., 2011) model with sequential downstream migration of the reattachment point.

Text
esp_3270_to_author.pdf - Author's Original
Restricted to Repository staff only
Request a copy

More information

Accepted/In Press date: 5 May 2012
Organisations: Palaeoenvironment Laboratory (PLUS)

Identifiers

Local EPrints ID: 340577
URI: http://eprints.soton.ac.uk/id/eprint/340577
ISSN: 0197-9337
PURE UUID: ec15005c-fa49-4753-b7c4-9d24ba869728
ORCID for A.G. Brown: ORCID iD orcid.org/0000-0002-1990-4654

Catalogue record

Date deposited: 26 Jun 2012 13:44
Last modified: 15 Mar 2024 03:27

Export record

Altmetrics

Contributors

Author: A.G. Brown ORCID iD
Author: P.S. Toms
Author: C.J. Carey
Author: A.J. Howard
Author: K. Challis

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×