Hydrological monitoring of an alluviated landscape in the lower Great Ouse valley at Over,Cambridgeshire: the quarry restoration phase

Abstract

This paper sets out the results of the last phase of the hydrological monitoring programme conducted at the Hanson Over quarry in Cambridgeshire, during the first full year (March 2004 to March 2005) in which the area of the first phase of gravel extraction was reinstated as reed beds under the management of the Royal Society for the Protection of Birds. It follows on from the studies of the pre-extraction and extraction phases, both published previously in Environmental Archaeology (French et al. 1999; French 2004). It is reassuring to report that the groundwater table in the formerly quarried area and the landscape immediately upstream and downstream has ostensibly been restored to pre-extraction levels, along with a return to previous pH, conductivity, redox and dissolved oxygen values in the groundwater system. Significantly, the continuing gradual fall in groundwater levels observed beyond 500 m from the quarry face for a distance of at least 1·5 km was seen to be arrested, although these had not quite recovered to pre-extraction levels downstream to the northeast. In addition, the soil moisture within the alluvial overburden and the buried palaeosol has also almost returned to pre-extraction levels. This indicates that the clay bunding of the formerly quarried areas acts as an effective barrier against further water abstraction, both inside and outside the sealed area, and allows the natural aquifer to begin to return to its previous levels of influence.

The study dramatically indicates that both the mineral operator, drainage authority and archaeological curator need to collaborate from the outset of any quarrying operation to ensure the continuing maintenance of the groundwater and soil moisture system regardless of how well the combined gravel and water abstraction processes are conducted, and how successful the post-quarry conservation is. As every site's landscape dynamics contribute to its individual hydrological setting, each case is different and requires tailored monitoring programmes to protect the archaeological and palaeo-environmental record from the adverse effects of water abstraction associated with development schemes.     

Effects of a New Hydrological Barrier on the Temperatures in the Organic Archaeological Remains at Bryggen in Bergen,Norway

The World Heritage Site of Bryggen in Bergen, Norway, has experienced significant degradation of archaeological deposits as a consequence of changes in the soil water and groundwater balance after urban redevelopment adjacent to the heritage site. Additionally, groundwater temperatures below the heritage site were found to be significantly higher closer to the redeveloped area. One of the main mitigation measures taken to reduce the degradation of the archaeology has been the construction of a hydrological barrier along the sheet piling that divides the redeveloped area and the historic site. A shallow subsurface infiltration system was designed to achieve groundwater levels and flow conditions that are optimal for the preservation of archaeological remains directly along the sheet pile, while reducing drainage and subsidence also further upstream. Monitoring of groundwater level and temperatures after implementation of the hydrological barrier shows that groundwater levels and flow conditions have improved with respect to optimal preservation conditions, and groundwater temperatures have generally been reduced by up to 2 °C.     

The Never-Ending Story? The Lessons of Fifteen Years of Archaeological Monitoring at the Former Island of Schokland

Abstract

The former island of Schokland became part of the mainland of the Netherlands when the Noord-Oost polder was drained in the 1940s. Mesolithic camp sites, Neolithic and Bronze age settlements, and medieval dwelling mounds (terps) on Schokland and in its immediate surroundings now form a UNESCO World Heritage site.

The main threat to the former island and the archaeology is drying out of the soil profiles, causing degradation of organic remains. Because of this, on the island and in its immediate surroundings the groundwater table is kept high in a specially created hydrological zone.

Schokland was one of the first sites in the Netherlands to be monitored in order to assess threats to the archaeological record and ongoing degradation processes. Monitoring started in 1999, and subsequent measurements were taken in 2001, 2006, and 2009/10. This included measurements of groundwater tables, water composition, redox, soil moisture and soil chemistry, micromorphology, and the degradation of botanical remains and bone. This time series of measurements makes it possible — first and foremost — to study long-term effects and changes in the Schokland burial environment, and their effects on the archaeology. In addition, the development of monitoring techniques around Schokland illustrates how the field of archaeological monitoring has evolved over the years.

Since the first monitoring round in 1999, developments in monitoring have included (1) technological developments enabling monitoring of high-frequency variations in groundwater, redox, and moisture contents, for example; (2) growing knowledge of degradation processes and the relevant characteristics of the burial environment; and (3) an increase in easily accessible datasets from third parties. Worries have arisen about the long-term storage and availability of monitoring data.

For future monitoring rounds, the value of the various monitoring techniques need to be critically evaluated, and the purpose of monitoring specific sites need to be reconsidered.     

They did not Live by Grass Alone: the Politics and Palaeoecology of Animal Fodder in the North Atlantic Region

Abstract

A five year research project was set up to monitor soil moisture and groundwater levels of an extensive buried, mainly alluviated landscape located at the interface between the lower Great Ouse valley and the fen-edge in western Cambridgeshire. The intention was to monitor changes in hydrology, soil structure and geochemical status before, during and after large scale gravel extraction. The results presented here concern the pre-extraction monitoring period over three years. The project has identified three major landscape zones – shallowly buried former dryland, several sets of relict palaeochannel systems which still remain waterlogged, and a marginal zone between these where the monitored parameters fluctuate on a seasonal basis. The moisture levels of the alluvial overburden, buried soils and infills of the palaeochannel systems appear to act independently of each other, controlled by a combination of rainfall, agricultural land management, height above sea level and depth of burial. It is predicted that the removal of 1–3m of overburden accompanied by water abstraction when gravel extraction commences will lead to changes in the moisture regime of the immediate area and therefore of any contained archaeological contexts and the superficial sediments in this river valley/fen-edge landscape.     

Quantification and Visualization of In Situ Degradation at the World Heritage Site Bryggen in Bergen,Norway

Abstract

Environmental monitoring at the World Heritage Site of Bryggen in Bergen, Norway, has shown damaging settling rates caused by degradation of underlying archaeological deposits. Measurements of piezometric head, oxygen, and soil moisture content, as well as chemical analyses of water and soil samples are key elements of the environmental monitoring.

Groundwater monitoring and geochemical analyses reveal a complex and dynamic flow through the natural and anthropogenic stratigraphy. The preservation conditions within the organic archaeological deposits are strongly correlated with oxygen and soil moisture content, that are controlled by the groundwater flow conditions at the site. To quantify decay rates, it is thus essential to understand the wider hydrogeological context of the site. This paper presents recent advancements in quantifying decay rates in the saturated zone at Bryggen. The paper also shows that 3D geo-archaeological modelling can contribute to preservation management by visually combining results of geological, archaeological, geochemical, and hydrological investigations. This opens up for improved multidisciplinary understanding of preservation potential, thereby contributing to an improved protection of archaeological deposits in situ.     

DESSICATION AND DESTRUCTION: THE IMMEDIATE EFFECTS OF DE-WATERING AT ETTON, CAMBRIDGESHIRE

This paper presents the first results of a long-term project to monitor changes in ground water conditions in parts of the East Anglian Fenland. So far the project has been concerned with two sites immediately north of Peterborough, at Borough Fen and Etton. The Borough Fen data are still being assessed, but Etton has provided results which warrant prompt publication.
The water levels were monitored in a series of boreholes across the Etton Neolithic enclosure for a period of two years (1982–4), to study the effects of the variation in the local groundwater table on the waterlogged contents of the enclosure ditch.
The first part of the paper (CF) assesses the results of this programme. The ambient water table remained at or above the level of the primary and lower secondary deposits in the ditch, thus accounting for the excellent preservation of botanical remains. Within one month of the adjacent quarry pumps being turned on the water table had fallen by up to one metre below the lowest archaeological deposits, and has not recovered since, to the almost immediate detriment of the botanical record.
The second part of the paper (MT) discusses the observed variation in the preservation of wood in particular, and describes the effects of de-watering on the deposits of wood in the enclosure ditch.     

Exploitation of groundwater in the oasis of Masāfī (UAE): A diachronic perspective

In order to understand the role of water resources in the establishment and long-term evolution of settlements investigated by the French Archaeological Mission in the UAE in the oasis of Masāfī, wells and springs of all periods, identified at the surface and in stratified contexts, were mapped and studied thanks to a multidisciplinary approach combining archaeology, geomorphology, geoarchaeology and ethnography. Our study demonstrates that:

• – The Masāfī oasis was located in a specific geological setting entailing the accumulation of groundwater resources at reachable depth.
• – The groundwater resources remained rather stable from the mid-second millennium BC to the second half of the twentieth century AD. In this respect, the apparent abandonment of the oasis during some periods cannot be explained by water depletion.
• – The groundwater resources have decreased sharply since the second half of the twentieth century AD, due to the introduction of new water extraction technologies, motor pumps and then drillings, as a result of the modernisation and industrialisation of UAE economy.

Our study also stresses the importance of well and spring irrigation in the development of the sedentary settlements in south-eastern Arabia, technologies that have often been neglected in the regional archaeological literature in favour of the qanāt.     

Partial Solutions to Partially Understood Problems — The Experience of In Situ Monitoring and Preservation in Somerset’s Peatlands

Abstract

The peat moors of lowland Somerset contain a wealth of waterlogged archaeological sites, including some of the most significant prehistoric monuments in the country. There has been a long history of attempts to preserve archaeological sites in situ and monitoring of the burial environment began in 1982. The monitoring has become more complex over time, but the results suggest the same continuing problem of a drop in the water table over the summer months across the whole landscape. With the sole exception of the portion of the Neolithic Sweet Track that benefits from an irrigation system, all the other known sites remain at risk of gradual destruction. The solutions must be found on a landscape scale using agri-environment payments to secure sustainable management of the peat resource. Unfortunately, short-term changes to these payments and long-term changes to the climate are likely to worsen the situation and eventually to require a more drastic solution to the problem. Evidence has been generated to support an ecosystems approach to sustainable peatland management.     

Southwest Scottish Crannogs: using in situ studies to assess preservation in wetland archaeological contexts

This paper presents the results of in situ monitoring of waterlogged burial contexts in southwest Scotland. The sites investigated are Iron Age crannogs (lake dwellings) which have a proven waterlogged archaeological component, and which are being assessed as part of a national program of study by the Scottish Wetland Archaeology Programme (SWAP) team. A monthly monitoring program commenced in July of 2004. To date, monitoring of water levels, pH, and redox potential, has been undertaken for a period of 17 months in order to encompass any seasonal variability at the sites studied. The results have proven robust in that an ‘ideal’ site for in situ preservation has been identified from the five sites investigated, and the monitoring has highlighted external variables and seasonal impacts that have the potential to influence the long-term in situ preservation at the remaining sites studied. In general, these results have expanded upon our knowledge of the potential for the preservation of existing archaeological remains within such contexts. This study represents the first stage of monitoring aimed at developing a holistic understanding of in situ conditions at the crannog sites studied in southwest Scotland.     

Response to Wet Season Rainfall of an Alluvial Aquifer System in the Lower Herbert Floodplain,Queensland, Australia

Australia is one of the world's largest exporters of raw sugar. The lower Herbert River floodplain, one of the four main cane growing areas in Queensland, is subject to extremes of rainfall. Some areas are prone to waterlogging, which can lead to reductions in cane and sugar yields. This paper examines the risk of waterlogging and the role of surface drains in the Ripple Creek area, a subcatchment of the lower Herbert River floodplain. Following above‐average rains at the onset of this study, a perched water table developed and remained for the duration of the 19 month study. The responses of the perched watertable and a deeper semi‐confined aquifer following rainfall are examined. The rapid response of the perched water table following rainfall is attributed to the shallow depth of the water table, with soil properties exerting a dominant influence on hydrograph response. In the second year of the study, after above‐average rainfall, the water table of the deeper aquifer was on average 1 m higher than during the former months of the study. This trend, however, did not occur in the perched water table, and this is attributed to the efficiency of the surface drainage network.     

Fusulinoideans from the early Midian (late Middle Permian) Metadoliolina dutkevitchi-Monodiexodina sutchanica Zone of the Senkina Shapka section,South Primorye,Far East Russia

Fusulinoideans from the Metadoliolina dutkevitchi-Monodiexodina sutchanica Zone of the lower part of the Chandalaz Formation in the Senkina Shapka section in South Primorye, Far East Russia, are described. The fusulinoidean zone is assigned to the early Midian (=Capitanian: late Middle Permian) based mainly on the morphologie and biostratigraphic characteristics of Metadoliolina dutkevitchi. Previously, a Midian age has been established for the Metadoliolina dutkevitchi-Monodiexodina sutchanica Zone by the coexistence of Lepidolina species. However, the occurrence of Lepidolina with the two zonal species in this area has not been verified by the illustration of Lepidolina specimens. We examined a fusulinoidean-bearing sample from the Metadoliolina dutkevitchi-Monodiexodina sutchanica Zone, and three fusulinoidean species, Monodiexodina sutchanica, Pseudofusulina sp. and Metadoliolina dutkevitchi, are de-scribed and illustrated.     

THE ROLE AND MAIN FUNCTIONS OF THE OUTER ZONE IN THE TERRITORIAL STRUCTURE OF THE MOSCOW REGION

The proposed basic functions and structure of the “Outer Zone” of the Moscow Region are outlined as part of a long-term physical planning model. The zone, which includes the Transition Zone, Linear Anti-Cores I and II, and Peripheral Zone I of the original model (Soviet Geography, February 1987), is to serve primarily as a check to territorial growth of the Core (a function once assigned to the more centrally located, but now largely developed Buffer Zone) and a potential base for new economic development in the future. A ranking of sites for limited, more immediate development is included (translated by H. L. Haslett, Birmingham, UK).     

Monitoring the burial environment of terrestrial wet archaeological sites in The Netherlands

Abstract

Monitoring the burial environment of archaeological sites is necessary to assess the success of their preservation in situ. Also, monitoring the state of preservation of actual archaeological remains together with that of their burial environment will further our understanding of the degradation processes acting on archaeological remains in situ. These remains consist not only of objects made from wood, metal, stone, etc., but also of pollen, soil features and even micromorphological features. Although, to date, the precise degradation mechanisms of archaeological remains in situ are not yet fully understood, general agreement exists on which parameters should be monitored in wet terrestrial environments. Also, it has been established that in situ measurements are preferable to laboratory analyses of soil (water) samples. In practice, it is difficult to find suitable monitoring equipment for in situ measurement as it must meet many requirements: an in situ measuring principle; stable for a period of at least several months; robust for use in the field; and equipped with a datalogger. A suitable principle exists for measuring the redox potential, however a simple, robust field instrument with datalogger is not yet available. Monitoring of the water table level, temperature and oxygen content is possible with recently developed, commercially available instruments. Monitoring of acidity is less complex as it does not vary as rapidly as, for example, the redox potential; however, the recommended method is still based on analysing soil samples, which is not acceptable in the long term at archaeological sites.     

Impact of Roots and Rhizomes on Wetland Archaeology: A Review

The general premise for successful archaeological in situ preservation in wetlands is that raising the water table will ‘seal the grave’ by preventing oxygen from reaching the deposit. The present review reveals that this may not be the entire picture, as a change in habitat may introduce new plant species that can damage site stratigraphy and artefacts. However, reviews on the types and degree of damage caused by vegetation to archaeological remains preserved in situ in wetlands have hitherto only been sporadically treated in the literature. Thus, this paper provides an overview of the adverse effects that various plants species have on the preservation status of wetland archaeology.Disturbance, due to growth of roots and rhizomes of the surrounding soil is denoted contextual disturbance, whereas deterioration of archaeological remains per se acts by several root-related factors that may be spatially and temporally concomitant. In waterlogged anoxic environments, deterioration is mainly related to (i) preferential growth of roots/rhizomes due to nutrient uptake and lesser soil resistance, (ii) root etching due to organic acid exudates, (iii) microbial growth due to root release of oxygen and labile organic compounds, and/or (iv) precipitation of hydroxides due to root release of oxygen. For example, roots of some wetland plants, such as marsh horsetail (Equisetum palustre), have been documented to penetrate archaeological artefacts down to c. 2 m in waterlogged anoxic soils. Here, we demonstrate that cultural heritage site management may unintentionally introduce deep-rooted or exudate aggressive plants by invoking change in hydrological conditions. Moreover, the implementation of biomass energy utilization and agricultural root depth optimization on a worldwide basis stresses the need for more research within root and rhizome impact on archaeological remains in wetlands. In conclusion, the worst-case scenario may be in situ deterioration instead of preservation, and one essential threat to archaeological wetland sites is the impact of wetland vegetation.     

Surface controls on the characteristics of natural CO2 seeps: implications for engineered CO2 stores

CO₂ injected into rock formations for deep geological storage must not leak to surface, since this would be economically and environmentally unfavourable, and could present a human health hazard. In Italy natural CO₂ degassing to the surface via seeps is widespread, providing an insight into the various styles of subsurface ‘plumbing’ as well as surface expression of CO₂ fluids. Here we investigate surface controls on the distribution of CO₂ seep characteristics (type, flux and temperature) using a large geographical and historical data set. When the locations of documented seeps are compared to a synthetic statistically random data set, we find that the nature of the CO₂ seeps is most strongly governed by the flow properties of the outcropping rocks, and local topography. Where low‐permeability rocks outcrop, numerous dry seeps occur and have a range of fluxes. Aqueous fluid flow will be limited in these low‐permeability rocks, and so relative permeability effects may enable preferential CO₂ flow. CO₂ vents typically occur along faults in rocks that are located above the water table or are low permeability. Diffuse seeps develop where CO₂ (laterally supplied by these faults) emerges from the vadose zone and where CO₂ degassing from groundwater follows a different flow path due to flow differences for water and CO₂ gas. Bubbling water seeps (characterized by water bubbling with CO₂) arise where CO₂ supply enters the phreatic zone or an aquifer. CO₂‐rich springs often emerge where valleys erode into CO₂ aquifers, and these are typically high flux seeps. Seep type is known to influence human health risk at CO₂ seeps in Italy, as well as the topography surrounding the seep which affects the rate of gas dispersion by wind. Identifying the physical controls on potential seep locations and seep type above engineered CO₂ storage operations is therefore crucial to targeted site monitoring strategy and risk assessment. The surface geology and topography above a CO₂ store must therefore be characterized in order to design the most effective monitoring strategy.     

Upper crustal fluid flow in the outboard region of the Southern Alps,New Zealand

The currently active fluid regime within the outboard region of the Southern Alps, New Zealand was investigated using a combination of field observations, carbon‐ and oxygen‐stable isotopes from fault‐hosted calcites and interpretation of magnetotelluric (MT) data. Active faulting in the region is dominated by NE striking and N striking, oppositely dipping thrust fault pairs. Stable isotopic analyses of calcites hosted within these fault zones range from 10 to 25‰δ¹⁸O and from ?33 to 0‰δ¹³C. These values reflect mixing of three parent fluids: meteoric water, carbon‐exchanged groundwater and minor deeper rock‐exchanged fluids, at temperatures of 10–90°C in the upper 3–4 km of the crust. A broad, ‘U‐shaped’ zone of high electrical conductivity (maximum depth c. 28 km) underlies the central Southern Alps. In the ductile region of the crust, the high‐conductivity zone is subhorizontal. Near‐vertical zones of high conductivity extend upward to the surface on both sides of the conductive zone. On the outboard side of the orogen, the conductive zone reaches the surface coincident with the trace of the active Forest Creek Faults. Near‐surface flow is shown to dominate the outboard region. Topographically driven meteoric water interacts, on a kilometre scale, with either carbon‐exchanged groundwater or directly with organic material within Pliocene gravels, resulting in a distinctive low ¹³C signal within fault‐hosted calcites of the outboard region. The high‐strain zone in the lower crust focuses the migration of deeply sourced fluids upward to the base of the brittle–ductile transition. Interconnected fluid is imaged as a narrow vertical zone of high conductivity in the upper crust, implying continuous permeability and possibly buoyancy‐driven flow of deeply sourced fluids to higher levels of the crust where they are detected by the isotopic analysis of the fault‐hosted calcites.     

Underground drainage at Mole Creek,Tasmania

Complex patterns of groundwater flow exist in the Mole Creek karst area, Tasmania. Many surface drainage divides are breached underground The evolution of the drainage has been dominated by (I) the deflection of streams along the strike of the limestone beds; (2) progressive changes to hydraulic gradients; and (3) a history of climate change during the Quaternary that has seen drainage diverted underground by glaciers and/or by proglacial and periglacial sedimentation     

Preservation Status and Priorities for In Situ Monitoring of the Weapon Sacrifice in Illerup Ådal,Denmark

Abstract

Excavations of the southern part of a very rich sacri?cial bog in Illerup Ådal, Denmark between 1950 and 1985 recovered approximately 15,000 Iron Age artefacts. At the time, 60 per cent of the area was left unexcavated and thousands of objects are now preserved in situ, but the present preservation status has not been investigated for approximately twenty-?ve years. Extensive in situ monitoring was carried out for one year in order to present a prioritized plan for further monitoring of the unexcavated areas, producing documentation of groundwater table variations, water quality and vegetation in the area. Results show that the remaining artefacts are generally well preserved in a waterlogged and anaerobic environment. However, in the north-eastern part of the bog, the groundwater table is too low even in a year when net precipitation and hydrological conditions were near normal. In the centre of the bog elevated salt concentrations have been measured in the groundwater.     

An Assessment of the Status and Condition of Archaeological Remains Preserved In Situ in the Medieval Town of Trondheim Based on Archeochemical Investigations Conducted During the Period 2007–2010

Abstract

In recent years systematic archeochemical investigations in the medieval town of Trondheim have provided the heritage management authorities with a rich and complex set of data concerning the status and condition of the cultural deposits in the anthropogenic material. The collected data raises important questions for the long-time management of in situ preservation for archaeological material in non-saturated zones. In this paper we present the standardized scientific methods used in these archeochemical investiga- tions. We examine the results from several sites in the town and discuss the challenges facing modern heritage management in its efforts to protect a complex body of archaeological material in the non-saturated zone. We show that sediments with a thickness of 1–2 m have low levels of moisture and organic matter, and most of the inorganic parameters analysed are found in oxidized form with low preservations. The 2–3 m thick anthropogenic sediments showed better preservation conditions.     

REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ¹⁸O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ¹⁸O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ¹⁸O_shell appears to be strongly influenced by seasonal inputs of very low δ¹⁸O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.