Detailed boring records and surface levels, combined with knowledge of the rate of extension of organic deposits in the lake basin (Part 1), allow the production of a computer-generated contour map and isometric drawings of the microtopography of the area around the Star Carr site of Clark (1954) (figs 1 and 2). The site was at the mouth of a shallow gully on the southern face of a hillock of glacial till which could be reached from the higher ground to the N over dry ground. The hillock extended into the lake basin as a low peninsula ending in a spit, at the entrance to its relatively narrow outflow channel. The occupation area was at a point where the open water most closely approached the shore and extended from the marginal wetland on to the dry slopes of the hillock.

Pollen and lithological analysis, combined with extensive C14 dating, is described at four closely spaced points along a section through the basin deposits close to the Star Carr site. Dated sequences of local vegetation development are established. The results are used to reconstruct pictorially the environmental changes through a period of occupation contemporaneous with, and presumably an extension of, the occupation of the Star Carr site (fig. 9). The dry ground supported birch wood throughout, but natural successional changes in the wetland, on a nominal timescale, were as follows:

(a) At 9800 BP the open water of the lake lapped the shore save for a narrow zone of reeds, sedges and water plants.

(b) By 9650 BP immediately before the occupation, reedswamp dominated by the great reed (Phragmites) had extended well into the basin. There was a narrow drier zone at the landward side of the reedswamp with abundant ferns enclosing a damper patch with fen plants.

(c) At the time of the occupation, around 9600 BP, the inshore reedswamp had largely been replaced by fen dominated by the saw sedge (Cladium). The marginal environment, where artefacts were found, was still dominated by ferns but a wood layer occupied the former damp fen area, presumably having been deliberately emplaced to consolidate the ground. Cladium fen and fringing reedswamp formed an extensive tract to the E of the occupation area behind the spit mentioned above, and probably also to the W.

(d) By 9300 BP (on the nominal timescale used for the reconstruction) the occupation was over and the wood layer and an associated ‘brown layer’ were covered by Cladium deposits on which willows were now growing.

Attention is drawn to the need for detailed work on the taphonomy of artefacts as a component of any further excavation in the organic deposits of the Vale of Pickering.