5. REPORT ON FIELDWORK IN BAC NINH PROVINCE, VIETNAM, JULY 1999
Bernard Maloney*, G. Sleeman*, Nguyen Mai Huong, Trinh Hoang Hiep, Vu The Long and Pham Minh Huyen,
*The Queen's University, Belfast BT7 1NN, Northern Ireland and Institute of Archaeology, Hanoi, Vietnam.

This is a shortened version of a longer report submitted by B.K.M.to the Institute of Archaeology, Hanoi, and its contents will be disseminated within that institution at their annual conference, which is to be held at the end of September 1999, by Miss Nguyen Mai Huong.

During July 1999 collaborators from the Institute of Archaeology, Hanoi, University of Pittsburgh, Pennsylvania, U.S.A, and The Queen's University, Belfast, Northern Ireland, participated in fieldwork aimed at investigation of the Quaternary geology of an area in Bac Ninh Province north west of Hanoi. This region had been identified by Dr. Brian Vincent, University of Otago, New Zealand, and Dr. Francis Allard, University of Pittsburgh, in 1998 as showing potential for a study of the environmental background to the origin of the Bronze Age Dongson culture in the northern part of the (Song-koi) Red River Delta. Research was funded by grants made by the British Academy and the Royal Society of London to Dr. Bernard Maloney, Palaeoecology Centre, The Queen's University, Belfast.

Emphasis was placed upon investigation of the geological evolution of the landscape during the last 4000 years. Numerous borings were made to a depth of 2 m using a split spoon soil auger to determine the sediment texture, its colour, delineate the stratigraphy, and assess the possible origins of deposits. Work concentrated on trying to establish the limits of the middle Holocene marine sediments and more recent fluvial deposits in relation to archaeological sites, that of Dinh To, in particular. The present path of the Duong River, which dissects the 12m2 study area, appears to follow a track largely initiated by faulting during the period of prehistoric occupation of the region. So it was decided to try and locate other former river channels and associated features, i.e. levees, point bars, flood plains, etc., situated both to its north and south and to try and find infilled meander lakes to collect samples for pollen analysis and radiocarbon dating from..

Meander lakes may infill rapidly but the pollen is likely to be largely from more local sources than that to be found in open riverine sediments, and erosion and redeposition is unlikely to be a problem. Unfortunately no such sites were found in the areas investigated, although they might be present elsewhere, in places which we had neither the time nor necessary permissions to visit.

In the end we had to make do with samples taken from former river channel,s and some reasonably undisturbed short cores were obtained from sediments comprised of gleyed soil horizons, non-indurated lateritic valley fill and organic and minerogenic fluvial sediments using lengths of split bamboo bound together with wire, but we do not yet know how hold these are.

It is known that human use of the land in part of this area has led to disruption of the natural hydrological regime through canalization from at least the 11th century A.D. Canalization, artificial heightening of natural levees, digging of both major and minor irrigation and drainage ditches, and creation of bunded fields, which has intensified especially from the late 19th century onwards, has drastically changed the landscape from that of prehistoric times. So this is not an easy area for the Quaternary geologist or the pollen analyst to work on, but that makes it all the more interesting!

Apart from relocating naturally deposited sediments, this manipulation of the landscape has almost certainly disrupted many archaeological sites. Added to this, there have been natural changes in the river courses and alterations due to variations in sea level and, possibly, typhoon events.

It is hoped that fieldwork aimed at probing more deeply using a D-shaped borer to further flesh out the mid-late Holocene geological history and collect better material for pollen analysis will continue in 2000. In the meantime, preliminary investigations of the pollen content will be made to establish its range and identify any possible problems of pollen determination. Attempts are also being made to trace historical documentation relating to modification of the natural hydrology.

It may be noted, that in addition to the cores, wood from the haft of a bronze Dongson axe was collected for identification and possible AMS dating, as was soil from the interior of a socketed arrowhead. Copper in bronze normally inhibits microbial action; therefore it is possible that the soil will contain pollen dating to the time of burial, which may be used to reconstruct the past vegetation. Unfortunately it is unlikely that there will be enough organic material left after extraction of the pollen for AMS dating. Soil was present in a second arrowhead but this was not collected because there was less of it, and because contamination with atmospheric pollen seemed certain.