Jackie Hatton

The development of high moorland on Dartmoor: fire and the influence of Mesolithic activity on vegetation change

1. Results of pollen and charcoal analysis of blanket peat sites from northern Dartmoor demonstrate the influence of burning and grazing on the transition from hazel woodland to blanket peat during the early and mid Holocene. 2. Within a general phase of enhanced burning between 7700 and 6300 BP the site at Pinswell at an altitude of 461 m shows how woodland was transformed over a period of 600–1000 years into blanket peat via a phase of acid grassland, in some ways similar to heath-derived grassland found on Dartmoor today 3. The results clearly implicate Mesolithic communities, and their use of the high moorland, in the development of the open peat-covered landscape that is so characteristic of the present Dartmoor environment.

Assessing the impact of volcanic activity on mid-Holocene climate in Ireland: the need for replicate data

Analyses of pollen, tephra, mineral input and degree of peat humification from three neighbouring raised peat profiles at Corlea, central Ireland, covering the period of the deposition of a tephra layer dated to just before 2290 cal. BC, and thought to represent Hekla-4 (2310±20 BC), are used to show the problems of relying on data from a single profile when invoking relationships between volcanic activity, climate and ecosys-tem response. While there appears to be a strong correlation between tephra deposition and flooding of the bog surface in one profile, with a short-lived increase in the rate of peat accumulation, comparison with the other two records suggests that peat had already begun a trend to a less humified condition before tephra deposition, and that evidence of local bog surface flooding was neither consistent nor synchronous.

Life by the river: a prehistoric landscape at Grendon, Northamptonshire

This paper describes the development of a prehistoric landscape by the river Nene at Grendon Lakes, partly revealed in the 1970s and partly during excavations in 1998 and 2001, which are reported in full. Two major phases of archaeological activity are evident, one interpreted as Neolithic–Early Bronze Age, the other as Iron Age. The gap between these is bridged by an environmental sequence reconstructed with the aid of a pollen core from an adjacent palaeochannel, which shows that human activity continued in the intervening period. The landscape is comparable in form, though not in scale, with that investigated 13 km downstream at Raunds, and helps shed light on the distinctive features of Midlands river valleys like the Nene in prehistory. In conclusion it is suggested that the different characters of the Neolithic and Iron Age features at Grendon mask some underlying similarities in the way they structured people’s movements and encounters.

A Cromerian Complex stalagmite from the Mendip Hills, England

In order to provide a better chronological constraint on a British Middle Pleistocene interglacial, a large stalagmite boss from the Mendip Hills was selected for palaeoclimate data using pollen analysis. Dating analyses by thermal ionisation mass spectrometry (TIMS) of uranium–thorium ratios and by magnetostratigraphy constrain the age of the sample to 450–780 ka. The isotopic consistency of the TIMS analyses, plus the presence of luminescence laminations, suggest that the sample has been preserved under closed-system conditions. Pollen assemblages have been recovered from the speleothems, despite the fact that the pH of calcite deposition is usually greater than 7. Furthermore the evidence presented here indicates that the pollen was probably transported by the speleothem feedwater, rather than entering the cave aerially. The pollen record contained within the stalagmite is interpreted as early–mid-interglacial but does not have clear Cromerian affinity.

Controls on lake level in the early to mid Holocene, Hawes Water, Lancashire, UK

This study presents a new interpretation of the evidence for Holocene lake-level changes from Hawes Water in NW England constrained by detailed stratigraphic data, radiocarbon chronology and palaeo-environmental evidence. Lake levels are seen to decline gradually from the start of the Holocene through to 9960 cal. yr BP, in response to lake infilling and the prevailing dry climatic conditions. Low lake levels then persist until 6000 cal. yr BP, punctuated by two transgressive phases. Rising sea levels during the Holocene high-level sea stand are thought to be responsible for a major rise in lake level at 6000 cal. yr BP driven by changes in the local water-table. The rise in lake level is coincident with a rise in anthropogenic activity across the site, possibly reflecting the migration of coastal Mesolithic communities inland in response to rising sea levels.

Evidence for increased expression of the Amundsen Sea Low over the South Atlantic during the late Holocene

The Amundsen Sea Low (ASL) plays a major role in the climate and environment of Antarctica and the Southern Ocean, including surface air temperature and sea ice concentration changes. Unfortunately, a relative dearth of observational data across the Amundsen and Bellingshausen seas prior to the satellite era (post-1979) limits our understanding of the past behaviour and impact of the ASL. The limited proxy evidence for changes in the ASL are primarily restricted to the Antarctic where ice core evidence suggests a deepening of the atmospheric pressure system during the late Holocene. However, no data have previously been reported from the northern side of the ASL. Here we report a highresolution, multi-proxy study of a 5000-year-long peat record from the Falkland Islands, a location sensitive to contemporary ASL dynamics which modulates northerly and westerly airflow across the southwestern South Atlantic sector of the Southern Ocean. In combination with climate reanalysis, we find a marked period of wetter, colder conditions most likely the result of enhanced southerly airflow between 5000 and 2500 years ago, suggesting limited ASL influence over the region. After 2500 years ago, drier and warmer conditions were established, implying more westerly airflow and the increased projection of the ASL onto the South Atlantic. The possible role of the equatorial Pacific via atmospheric teleconnections in driving this change is discussed. Our results are in agreement with Antarctic ice core records and fjord sediments from the southern South American coast, and suggest that the Falkland Islands provide a valuable location for reconstructing high southern latitude atmospheric circulation changes on multi-decadal to millennial timescales.