Glides, rotational slumps, debris‐ and mud‐flows occur in the Eocene pelagic chalk of the Shefela region, Israel. The pelagic lithofacies are present from the beginning of the Eocene, but mass transport is initiated only in the latest early Eocene and the early middle Eocene. Slight steepening of the palaeoslope, coupled with increased sedimentation rate and early diagenetic changes lowering inherent strength, led to gravity‐induced mass transport in the poorly consolidated pelagic sediments. Instability of the sediment pile was enhanced by underconsolidation and development of spacious packing associated with a relatively high rate of deposition and low initial strength due to high content of siliceous micro‐biota. The palaeogeographic position indicated by the mass‐transport features is the steepened, distal part of the ramp‐like continental margin of the Arabian Platform. Distal steepening of the ramp as part of regional downwarping is coincident with reactivation of Syrian Arc folding, reflecting northward convergence of the Arabian Plate during the Eocene.

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Sixty Upper Cretaceous chalk exposures were examined and sampled in Dorset, the Isle of Wight and Guildford, South England, in order to investigate the effects of tectonic deformation on the chalk fabric. Light and scanning‐electron microscopes were used extensively, and chemical, mineralogical and isotopic analyses ware carried out. Two types of fabric modification were distinguished. The first type involves more than 90% volume loss by mechanical compaction at the early stages of deformation followed by dissolution and removal of calcium carbonate in the advanced stages of deformation. Chalks which have undergone this type of fabric modification are dense and consist of well rounded 0.5–3 μ calcite crystals with well developed pressure‐solution contacts. These chalks contain a high proportion of calcispheres (many of which are plastically deformed) but very few well preserved planktonic foraminifera and coccoliths. They are relatively enriched in insoluble constituents and depleted in strontium. The second type of fabric modification involves introduction of calcium carbonate into the pore spaces. Chalks which have undergone this type of modification are dense and contain a high proportion of 3–5 μ polygonal interlocking calcite crystals. Fossils are virtually never deformed, and delicate foraminifera and coccoliths are well preserved. Insoluble constituents similar to those found in the unmodified chalks occur in low concentrations. Removal of calcium carbonate at crystal contacts has taken place in chalks which have been subjected to high effective tectonic stresses and at crystal peripheries in chalks which have been subjected to high pore fluid pressure. Dissolution at crystal peripheries is responsible for the extensive calcium carbonate losses, and it is termed herein ‘confining pressure solution’. Introduction of calcium carbonate occurs in rocks which were under low tectonic stresses. During deformation calcium carbonate migrates from chalks under high stresses towards those under tow stresses, while some goes into solution in sea water. Well developed joints and high pore fluid pressure might increase the rate of calcium carbonate removal by three orders of magnitude. Petrographic and isotopic data suggest‐that all fabric modifications studied took place in meteoric water.

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