P Davies

Evaluating late-Holocene relative sea-level change in the Somerset Levels, southwest Britain

Holocene relative sea-level (RSL) change is investigated at Nyland Hill (Somerset Levels). The lithostratigraphy comprises turfa peat underlying marine clay, both onlapping a sloping Upper Palaeozoic basement. The altitude of the peat-clay contact ranges from 2.42 to 4.52 m OD, becoming lower down basement slope, yet 14C dates of three samples taken laterally along the contact at different altitudes yield similar ages (3640-3330, 3715-3460, 3725-3465 cal. yrs BP), suggesting either very rapid (‘instantaneous’) RSL rise or sediment compaction. Biostratigraphic data indicate a gradual transition to marine conditions across the peat-clay contact. Therefore, the height difference is interpreted as evidence for significant compaction. We consider 4.64 m OD the minimum pre-compaction altitude, indicating maximum observed compaction of 2.22 m. The clay surface, reclaimed during Roman occupation, represents an anthropogenically induced negative tendency and is dated chemostratigraphically to 1776 ± 46, using a datum related to the onset of local Roman lead mining AD 43-49. Sedimentation rates of the marine clay are established: 1.58-1.92 mm yr-1 and 0.8-0.96 mm yr-1 at sites of maximum and less severe compaction respectively. RSL continued to rise throughout the deposition of the clay unit at a rate of 0.41-0.82 mm yr-1, a view that disagrees with previous models that imply stabilised RSL by 3000 BP. These earlier studies underestimate compaction with implications for subsequent studies employing these sea-level data, particularly in crustal studies where the apparent trend of subsidence is overestimated/increased.

Pollen and mollusc records for environmental change in central Spain during the mid- and late Holocene

The central part of the Iberian Peninsula has few radiocarbon dated records of vegetation and climatic history for the Holocene. Extinct and active tufa-forming sites occur along the northwestern margin of the Sierra de Alcaraz. Tufas are often closely associated with the remains of plants and animals, and two extinct systems near the settlements of El Jardin and Alcaraz have yielded a record of environmental history that spans much of the last 6000 years. The record indicates that the present-day sedimentological regime and vegetation are human-induced, and probably extend back to about 2700 yr BP. Before this date, oak-dominated scrub (mattoral) was widespread. Prior to around 5000 yr BP the climate appears to have been relatively humid, and possibly cooler, and the catchments for the two sites were more wooded than today.

Woodland clearance in the Mesolithic: the social aspects

Did Mesolithic people regard the woodland as a wilderness or park? Previous models have portrayed the hunter-gatherers of the Mesolithic as in tune with nature and making use of clearings to attract game. Using equally valid analogies, the authors propose a more hostile landscape that was conceived and managed with clearings and paths to help allay its menacing character.

The Romano-British Exploitation of Coastal Wetlands: Survey and Excavation on the North Somerset Levels, 1993-7

Reproduced with the permission of the publisher and JSTOR. Journal home page http://www.romansociety.org/frame.htm

Scratches in the earth: the underworld as a theme in British prehistory, with particular reference to the neolithic and earlier bronze age

A number of examples where authors have invoked the concept of an underworld in explaining various prehistoric activities are catalogued and considered. In drawing this material together it is hoped that the case for exploring the underworld as a general theme in pre‐Iron Age Britain is made. In addition, the usefulness of looking at various prehistoric activities from the perspective of the underworld is considered. In particular, the phenomenon of inversion is examined.

Later Neolithic Woodland and Regeneration in the Long Barrow Ditch Fills of the Avebury Area: The Molluscan Evidence

Modern data on molluscan migration rates are applied to the sub-fossil record obtained from Neolithic long barrow ditch fills of the Averbury region. It is demonstrated that it is theoretically possible to consider the maximum and minimum distances of woodland from a number of long barrow sites. The problems and potential of such calculations are addressed.

The Importance of Re-Creating Realistic Reservoir Architecture in 3-D Sub-Surface Models: Lessons from Outcrop Studies

The objective of this study is to define the best approach to recreate realistic reservoir architecture in sub-surface models of wave-dominated shoreface/deltaic deposits. To achieve this goal, a fullydeterministic 3-D model based on 10 measured sections and fully continuous photo-panoramas was first created which exactly matches the sand and shale architecture in a well-exposed series of outcrops in Utah, USA. This model would be used as the benchmark against which all test model results could then be judged. The exceptionally well-exposed, near-horizontal Campanian strata of the Book Cliffs in eastern Utah were chosen as the basis for this study as they provide ideal outcrop analogues which have previously been used to develop, test and refine many sedimentary and stratigraphic models, including the principles and concepts of sequence stratigraphy. To approximate the sparsity of real sub-surface data, only three input well data points were used in all the models. Three different stochastic modelling techniques have been tested to try and capture the sediment body continuity and architecture observed in the outcrop. In addition, a deterministic model was built using only the same three log sections, supplemented only by geological knowledge about the palaeogeography, but strictly following a set of correlation rules and guidelines derived from the outcrop.