Monument record 2425/0/21 - Palaeochannels and glacial lake, Stanwick Quarry

An oval feature that may be a late-glacial lake. As typically exposed beneath the alluvial overburden, the gravels fills comprised variations of clean yellow to orange-yellow sand and gravel. These gravels are of Devensian date, 11000 to 10000 BP, and are fluvioperiglacial deposits dating to the mid- and late Devensian. A minor palaeochannel system that branched off from the main channel to the south-west and ran for some 500m before linking back into the main river channel. A sample of bark from one the channels has been radiocarbon dated to the late 6th/early 5th millennium.

{1} An oval feature that may be a late-glacial lake. As typically exposed beneath the alluvial overburden, the gravels fills comprised variations of clean yellow to orange-yellow sand and gravel. These gravels are of Devensian date, 11000 to 10000 BP, and are fluvioperiglacial deposits dating to the mid- and late Devensian.
The lake was roughly oval in plan, measuring c160m north-east to south-west by 100m wide, and was aligned along the floodplain. It comprised a shallow bowl-shaped depression in the top of the main mass of the gravels, with very shallowly-sloping sides and it was no more than c1m deep. It was filled with very mixed deposits of mottled dark grey to grey-black coarse gritty sand containing varying amounts of gravel pebbles, but always with a less dense gravel component than the surrounding clean gravels. These distinctive dark, coarse silts were exposed around the margins of the feature, and defined its limits. Across the central area the dark silts had been sealed by a final deposition of clean orange sand and gravel, up to 0.30m thick and at least 90m long.
The coarse silts would appear to have been deposited by an incoming body of water containing reworked sands and some gravel. The absence of any finer silt, which would be expected to have accumulated above the coarser component within such a lake, can only be accounted for by assuming a further stage of reworking that truncated the upper levels and culminated in the deposition of the final deposit of clean gravels. These events are undated, but by analogy with work elsewhere in the Nene valley the process had probably been completed by around 10000BP.
The exposed surface of the gravels and the glacial lake deposits sloped down to the south-east as they dipped towards the palaeochannel defining the eastern edge of Irthlingborough island. This indicates that there was discontinuity and an episode of remodelling between the final phase of Devensian gravel deposition and the establishment of the overlying Flandrian river channel system.

A minor palaeochannel system that branched off from the main channel to the south-west and ran for some 500m before linking back into the main river channel. The surrounding area had probably stood at least 1m above the surface of the palaeochannel. This emphasises that the prehistoric landscape comprised a series of dry gravel islands that stood above well above the water levels of the contemporary river channels.
Palaeochannel 1 was consistently around 10m wide by up to 1m deep. The bottom 0.3-0.5m of the channel fill comprised mixed silts and gravel. Above this there was a grey/black firm silty loam, with a buttery texture. Quantities of waterlogged wood were present in the upper fills of this palaeochannel at some observed locations, while in other lengths such deposits were absent, suggesting that wood debris had accumulated in discrete areas of tree growth along the silted-up channel, possibly in and around a chain of shallow ponds within the former channel. A sample of bark has been radiocarbon dated to the late 6th/early 5th millennium (5280-4850 cal BC, 95% confidence, 6140+/-60 BP, Beta-188366), suggesting that this channel had fully silted well before the advent of the first Neolithic monuments.
A second shallower palaeochannel (2) lay to the east of palaeochannel 1, and was buried beneath up to 2m of alluvial clays. The western end had been lost, presumably as a result of later water action prior to the deposition of the alluvium, but it would appear to have branched from the corner of the dog-legged turn in palaeochannel 1. It then ran more directly eastward to link back with the main palaeochannel. At the western end it became visible as a band of dirty gravel, but steadily broadened and deepened to the east, where it reached 10m wide by up to 1.0m deep as it approached the main river channel. It was filled with mixed grey black clayey silts. The chronology of this channel is unknown. It may have been a contemporary side channel to paleochannel 1, but it is also possible that it may have taken the full water flow following the silting of the northern half of palaeochannel 1. As it was generally shallower than channel 1, there would have been a reduced water flow, perhaps reflecting the progressive process of silting and reduced water flow along this minor channel system.

<1> Chapman, A., 2004, Prehistoric palaeochannels and a ring ditch at Stanwick Quarry, Northamptonshire (watching brief 2002-2004) (Article). SNN112189.

<1> Chapman, A., 2004, Prehistoric palaeochannels and a ring ditch at Stanwick Quarry, Northamptonshire (watching brief 2002-2004), p.9-11 (checked) (Full Report). SNN105065.

<2> CBA South Midlands Group, 2003, South Midlands Archaeology: CBA Group 9 Newsletter, 33-55 (checked) (Journal). SNN103380.

Record last edited

Jan 8 2021 1:54PM