Department of Botany, University of Leeds, Leeds LS2 9JT, UNITED KINGDOM.
Five sites were investigated, in the Ingleborough region of Yorkshire, Helwith Moss, Thieves Moss, Scar Close, Moughton, and Howrake Rocks. Samples of peat were extracted by means of a borer, or taken from monoliths, and their structure and pollen content examined. Profiles and pollen diagrams were produced for each site.
Helwith Moss was found to have developed from a former lake which became invaded by aquatic mosses, then reed swamps and finally raised bog. Peat formation began in zone V, and raised bog was initiated at the Boreal-Atlantic transition, when the climate became wetter. An important recurrence surface was found in, sub-zone VIIb, where the peat changes noticeably from a relatively humified Eriophorum-Spaghum type to light brown less humified Sphagnum imbricatum. As this did not coincide with the suggested position of the VII/VIII boundary of the pollen diagram, a transition zone was postulated from the recurrence surface at 235 cms. to the start of zone VIII at 120 cms.
Thieves Moss also was found to have developed from a former lake which became colonised by Carex swamp, hypnoid moss, and then Sphagnum bog. The upper layer is of a mixed peat including monocotyledonous material. Pollen is preserved from zones II to VII, the latter zone being the latest to which any of the peat belongs. The change from swamp to bog took place at the end of sub-zone VIa, when a lowering of the water table took place probably caused by the removal of a barrier at the southern side of the Moss. This would lessen considerably the influence of calcareous drainage water allowing more acid conditions to develop with a corresponding vegetational change. The surface of the bog appears to be affected by erosion and peat formation is not actively taking place, probably because of the well developed drainage system of a limestone area.
At Scar Close the peat lies in a continuous layer on slopes above the limestone pavement but only in patches on the pavement itself. Profiles and pollen diagrams from eight sites suggest that this peat cover was once continuous over the whole pavement area. The peat belongs to zone VIII. On the slopes above the pavement it has formed on a layer of drift which covers the limestone The peat on the pavement is in actual contact with the limestone. It may have formed on a thin drift layer which has now been washed into the grykes, or directly on the limestone with a later widening of grykes under peat, because of an increase in the rate of solution of the limestone. The series of pollen diagrams from the upper to the lower sites show a progressive truncation from below. These may be interpreted, either as a gradual spreading of the peat onto the pavement from the slopes above, or the result of oxidation of the lower peat layers in contact with the limestone.
The information from Moughton and Howrake Rocks suggests that the peat on the limestone pavement at Scar Close has formed in situ, and has not slipped down from the slopes above.