Clinoptilolite, paragenesis and stratigraphy

Clinoptilolite, a zeolite of the heulandite group, occurs commonly in sediments as an authigenic mineral. In the Middle Eocene of southern Israel, it constitutes from a few per cent up to 80 per cent of the insoluble residue of the chalks and limestones. It is associated with opal C-T, montmorillonite and palygorskite. These chalks and limestones overlie the Danian-Palaeocene Taqiya marls which also contain a well-established clay mineral sequence consisting of opal C-T, montmorillonite, palygorskite, sepiolite, and clinoptilolite. This paragenesis of minerals is shown to be typical of the Upper Cretaceous to Eocene times. It is world-wide, occurs in deep-sea sediments as well as in shallow water sediments, and results from the abundance of silica which probably reflects a warmer climate during this time period. The concentration of magnesium in the sea-water and its ratio to the other cations seem to determine which authigenic silicate will be formed.