North Hertfordshire District Council Museums Service
Archaeology Report 35
Introduction
This assessment of the archaeology of Howard Park and Howard Garden was commissioned on 10 April 2008 by Keith Gayner of North Hertfordshire District Council as part of a Stage 2 submission for Heritage Lottery Funding. The study area is bounded to the west by Norton Way South, to the North by Birds Hill, to the east by Rushby Mead and to the south by Pixmore Way. This report is based purely on existing documentation in the public domain, personal knowledge of the site and its surroundings from the early 1960s to the present, and a detailed site inspection undertaken in April 2008. No original fieldwork was undertaken beyond the site inspection and no original documents held in archives outside North Hertfordshire Museums Service were consulted.
Letchworth Garden City
Geology
Letchworth Garden City lies on deposits of Cretaceous chalk, the Lower Chalk formation in lower- lying parts of the town and Middle Chalk on the higher ground (Figure 2). The study area straddles the boundary between the two. The element of the Lower Chalk found in this area has been termed Grey Chalk, occasionally overlain by a thin deposit of Plenus Marl. The former contains frequent marine fossils, especially of pycnodonteine oysters, while the latter appears to have formed in shallow waters with an abundant macrofaunal fossil assemblage (Hopson et al.1996, 34). These are likely to be the deposits underlying the north-western part of the study area. Above them, the Middle Chalk is represented by Melbourn Rock, an off-white chalk with few fossils (Hopson et al.1996, 43). This is the deposit underlying the south-eastern part of the study area. The Lower Chalk and Grey Clay are impervious and their outcropping at the foot of the hills to the south-east cause springs to form; one of these, Pix Brook, and its tributaries, flows through the centre of Letchworth Garden City and forms the eastern boundary of the study area (Miller 2002, 27).
During the Quaternary, the valley of the Pix Brook was occupied by a river draining south from the Midlands via Stevenage in a palaeochannel known as the Stevenage Channel. The initial advance of the Anglian ice sheet (beginning around 480,000 BP) was through this valley, which was gradually broadened to the west, forming the Hitchin Gap. An early retreat of the glacier left a proglacial lake south of Letchworth Garden City, but the site remained under the glacier (Hopson et al. 1996, 100). The ice sheet was up to a kilometre thick and eroded as much as 70 m or so from the former land surface. Deposits left after its retreat have been classified in the Thames Catchment subgroup of the Britannia Catchments Group (McMillan 2005, 98).
In parts of the valley of the Pix Brook, deposits of a neogene calcareous tufa have been observed (for instance, at Norton Common). It is deposited above the till deposits around three metres above the stream and contains species of mollusca known to have been extinct by about 4000 BP (Hopson et al. 1996, 110). It is not known if these deposits are present in the study area.
During the Quaternary, the valley of the Pix Brook was occupied by a river draining south from the Midlands via Stevenage in a palaeochannel known as the Stevenage Channel. The initial advance of the Anglian ice sheet (beginning around 480,000 BP) was through this valley, which was gradually broadened to the west, forming the Hitchin Gap. An early retreat of the glacier left a proglacial lake south of Letchworth Garden City, but the site remained under the glacier (Hopson et al. 1996, 100). The ice sheet was up to a kilometre thick and eroded as much as 70 m or so from the former land surface. Deposits left after its retreat have been classified in the Thames Catchment subgroup of the Britannia Catchments Group (McMillan 2005, 98).
In parts of the valley of the Pix Brook, deposits of a neogene calcareous tufa have been observed (for instance, at Norton Common). It is deposited above the till deposits around three metres above the stream and contains species of mollusca known to have been extinct by about 4000 BP (Hopson et al. 1996, 110). It is not known if these deposits are present in the study area.
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| Letchworth, image by stevecadman |
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