EARLY DIAGENETIC LIME "MUD" BALLS IN MIDDLE
EOCENE LIMESTONE, MOKATTAM AREA, CAIRO, EGYPT.
AHMED M. ELSHISHTAWY
Geology Dept., Fac. Sciences, Tanta Univ., Egypt
|
Irregular limestone mud balls in the lower part of the Upper Building Stone Member of Gebel Mokattam appear to have undergone early marine lithification. Several different forms of such segregation structures can be distinguished from the succession. They range in size from 0.5 cm to more than 50 cm and vary from fairly rounded sub-elliptical forms to irregular elongated forms. Such structures form more-or-less continuous alignment in beds or layers with irregular upper and lower surfaces. The lime mud balls are composed mainly of fossils and calcite microspars varying from a few microns to ab. 20 microns in size, together with Some minor components of dolomite, silica and argillaceous materials. Mud balls are thought to have been formed soon after deposition in the carbonate mud by segregation and sporadic diagenetic precipitation of calcium carbonate and was subsequently modified by differential compaction and minor flowage.
|
|