Prehistoric Activity in the Lower Medway Valley: Evidence from Excavations in the Development of Peters Village and the Medway Crossing

Following the publication of the main article in Archaeologia Cantiana, vol. 146 below are the supplementary pollen analysis and Appendix C.

Geoarchaeological investigations (including pollen analysis) by Rob Scaife

Prior to the main excavations, a borehole (ABH01; Fig 2, reproduced below) near the western bank of the River Medway, opposite Area 2a and in an area known as the Holborough Marshes found a sequence of undisturbed sediments that provided an outline of the changing local depositional environments from the Mesolithic to the historic period (MoLAS 2007).

[fg]png|Fig. 2 Areas of excavations (Areas 2a, 2b, 3, 5a, 5b, 5c, 6 and 8a).|Image[/fg]

Floodplain river terrace gravels carried by the flux of meltwater from the last glaciation were recorded as the lowest deposit in the borehole sequence overlain by tufa-rich organic sandy silty clays. The clays represented a vegetated swamp near an active tufa spring and were dated [pg1]within the Mesolithic (7270–7150 cal BC; Poz20043, 6250±40 BP; Appendix C, Table 1). Ostracod fauna, earthworm granules and slug plates presented a picture of freshwater environments. However, fragments of brackish and marine diatoms, at a time when the sea was a long way from the present day coastline, suggested the rapid sea-level rise in the early Holocene produced large-scale floods or surges that pushed salt water environments up major river valleys like the Medway.

Overlying deposits represented the development of a tufa spring-fed pool and the advance of colonising vegetation that formed an area of alder-dominated swamp at the margins of the river, with oak and mixed woodland in the wider landscape. The onset of tidal conditions was marked by a sharp contact between peat and clay dated to the late Neolithic (2760-2560 cal BC, Poz-20041, 4090±35 BP; Appendix C, Table 1). Pollen retrieved from the overlying detrital peats indicated that conditions became progressively wetter with an expansion of fen herbs, arable species, and cereal pollen. This provided the first clear evidence for human activity.

During the site excavations, vertical monolith columns were taken from a trench cut into the floodplain alluvium that covered the south-west of Area 2a (see Archaeologia Cantiana, vol. 146, Fig. 13, p. 82) and subsequently sub-sampled for pollen. The recovered pollen numbers were low and preservation was generally poor with preservation in favour of the more robust taxa and spores including derived material from earlier, eroded sediments (Fig. 15).

[fg]jpg|Fig. 15 Pollen diagram from geo-arch trench in Area 2A (section 127, Tr 3).|Image[/fg]

[pg2]Overall, the pollen assemblages were dominated by herbs with a paucity of trees and shrubs. The former comprised a range of taxa derived both from the floodplain and from the drier surroundings. The former, on-site habitat appeared to have been from a wet grass-sedge fen and the latter from grassland and areas of arable cultivation. There were only relatively minor changes in the pollen assemblages throughout the profile which may have resulted from changing sedimentology rather than from changes in the character of the past vegetation. In the upper samples, especially at the top, Lactucoideae (dandelion types) were dominant and there were increased pre-Quaternary palynomorphs. That is, geological palynomorphs derived from the erosion of the bedrock, earlier alluvium and eroded soil. These were subsequently fluvially transported and deposited through over-bank deposition. The geological palynomorphs and later dandelion type pollen are also prominent as a result of differential preservation of these robust taxa in the poor pollen preserving conditions. In the lower samples herbs were dominant with grass (Poaceae), cereal pollen, ribwort plantain (Plantago lanceolata) and Lactucoideae being most important. The on-site wetland taxa comprise sedges (Cyperaceae) with marsh pennywort (Hydrocotyle vulgaris), Typha angustifolia type (lesser bulrush and/or bur reed) and the Royal Fern (Osmunda regalis) at the middle of the sample profile. Overall, the importance of the wetland taxa noted suggests that the depositional habitat was throughout, an open herb fen or wet floodplain habitat. It was clear, from the absence of alder (Alnus) pollen in any notable quantity, that carr woodland was not present in the vicinity.

There was a notable paucity of tree and shrub pollen. The few arboreal taxa which occur sporadically (birch, pine, oak, alder, and hazel) are all wind pollinated, produce copious quantities of pollen thus giving potential for long distance transport. As such, the pollen here probably derived from regional rather than local sources. In contrast, herbs were important and, from the limited data here, indicated that an open, probably mixed agricultural environment existed in the vicinity. Taxa from this habitat included taxa of pastoral affinity including grasses (Poaceae), ribwort plantain (Plantago lanceolata), possibly buttercups (Ranunculus-type), clover/vetch (Trifolium-type) and Scrophulariaceae spp (Rhinanthus- type).

Cereal pollen is, in general, under-represented in pollen spectra. However, associated herbs of disturbed ground, here included black-bindweed (Fallopia convolvulus), knotgrass (Polygonum aviculare) and possibly goosefoot and/or orache (Chenopodiaceae), suggesting the possibility that there was local arable cultivation. However, it may also be considered that the pollen might have derived from pollen liberated during nearby crop processing (threshing and winnowing) or from dumped waste deposits. Overall, it is suggested that pastoral arable economy was clearly important in the vicinity. When compared to the results from the borehole (ABH01) on the opposite side of the river, the floodplain alluvium in Area 2a appears to have accumulation after the Neolithic, with the cutting of the Roman features suggesting the reclamation of the floodplain during this period.

Appendix C: Radiocarbon Dating

Four sub-samples taken from the core (ABH01) were submitted to Poznan Radiocarbon Laboratory, Poland for dating by accelerator mass spectrometry (AMS).[pg3]

Table 1 Radiocarbon samples taken from ABH01

[tb][th]Sample number|Lab. No.|Sample depth (m bgl)|Height OD (m)|Radiocarbon determination|Calibrated date[/th]

[tr]14C 1|Poz-20040|4.65|-0.20|990±30|AD 980–1060[/tr]

[tr]14C 4|Poz-20041|6.16|-1.71|4090±35|2760–2560 cal BC (4710–4510 cal BP)[/tr]

[tr]14C 7|Poz-20042|7.00|-2.55|6320±40|7330–7160 cal BP[/tr]

[tr]14C 8|Poz-20043|8.23|-3.78|6250±40|7270–7150 cal BP[/tr]

[/tb]

Following the excavations, a programme of radiocarbon dating refined the dating of skeletons [2040] and [3090] (Bronk Ramsey 1995, 1998 & 2001; Reimer et al 2013).

Table 2 Radiocarbon samples taken from skeletal remains

[tb][th]Context|Lab. No.|δ13C|δ14N|Radiocarbon determination|Calibrated date (cal yr BC/AD) (95% probability)[/th]

[tr]2040|Beta-397063|-21.3‰|8.5|2770±30 BP|1003–834 cal BC[/tr]

[tr]3090|Beta-397064|-20.6‰|9.5|2150±30 BP|354–95 cal BC[/tr]

[/tb]

Bibliography

Bronk Ramsey, C, 1995, Radiocarbon calibration and analysis of stratigraphy: the OxCal program, Radiocarbon 37, 425–30.

Bronk Ramsey, C, 1998, Probability and dating, Radiocarbon 40, 461–74.

Bronk Ramsey, C, 2001, Development of the radiocarbon calibration program OxCal, Radiocarbon 43, 355–63.

MoLAS, 2007, Peters Village, Wouldham, Kent: an archaeological evaluation report, unpub MOL rep.

Reimer, P J, Bard, E, Bayliss, A, Beck, J W, Blackwell, P G, Bronk Ramsey, C, Buck, C E, Cheng, H, Edwards, R L, Friedrich, M, Grootes, P M, Guilderson, T P, Haflidason, H, Hajdas, I, Hatté, C, Heaton, T J, Hoffmann, D L, Hogg, A G, Hughen, K A, Kaiser, K F, Kromer, B, Manning, S W, Niu, M, Reimer, R W, Richards, D A, Scott, E M, Southon, J R, Staff, R A, Turney, C S M, and van der Plicht, J, 2013 IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal BP, Radiocarbon 55, 1869–87.[pg4]