LIMESTONE WEATHERING IN EASTERN AUSTRALIA .1. EROSION RATES

A traversing microerosion meter (MEM) was used to measure the rates of surface weathering of limestones in southeastern Australia. There wer e two groups of MEM sites installed in 1978/9. The aim of the experime ntal design for the first type, the 13 sites at Cooleman Plain and Yar rangobilly Caves, was to obtain erosion rates for limestones of simila r lithology exposed under comparable climate conditions. The sites wer e positioned to measure erosion over a range of microsolutional forms and with exposure to differing forms of erosion, i.e. subaerial, subso il and instream. The second set, at Ginninderra close to Canberra, con sists of nine limestone slabs of differing lithology, collected from d ifferent locations but exposed under identical climatic conditions. Th e number of individual measurement points at each MEM site varied from 24 to 68. There were major differences in erosion rates between subae rial bedrock and instream sites at Yarrangobilly and Cooleman Plain, b ut no evidence of differential erosion across the micro-forms. There w ere differences in the weathering rate for bedrock sites, due to clima tic differences, and between the limestone lithologies exposed at Ginn inderra. The average rate of erosion for the subaerial bedrock sites a t Cooleman Plain and Yarrangobilly over the 13 years was 0.013 mm a(-1 ) and at Ginninderra 0.006 mm a(-1). At some of the sites microflora ( lichens and mosses) caused problems for field measurement. The weather ing processes that contribute to the surface lowering are discussed in the accompanying paper by Moses ef al.