ABSTRACT

The uranium content of diverse pelletal phosphorite beds of Maestrichtian age in Egypt, as indicated by alpha radioactivity determined by autoradiographic nuclear emulsion techniques, is usually unequally distributed among the constituents of the phosphate rock. The most radioactive parts are those dark, almost opaque bituminous, blackish, brownish or reddish pellets, probably after original fecal pellets with a relatively high content of organic matter. Bone fragments, chiefly after fish and reptilian teeth, are less radioactive, but the amorphous (mostly isotropic under crossed nicols) clear or zonally to patchily colored collophanite pellets have intermediate radioactivities. Non-phosphatic limestone or chert lithoclasts as well as epigenetic intergranular carbonate cements or late diagenetic theft cements in the pelletal phosphorites are the least radioactive. External surfaces of a minority of large phosphatic pellets, and particularly of large reptilian bones are more radioactive than their interiors. Average specific radioactivity values are given for the different constituents of some pelletal phosphate beds near Port Safaga.