FOSSILIZED MICROBIAL AND ALGAL TEXTURES IN POST EOCENE LACUSTRINE ZEOLITE TUFF SEQUENCE, G. ABU TREIFIYA, CAIRO-SUEZ ROAD, EGYPT
FOSSILIZED MICROBIAL AND ALGAL TEXTURES IN POST EOCENE LACUSTRINE ZEOLITE TUFF SEQUENCE, G. ABU TREIFIYA, CAIRO-SUEZ ROAD, EGYPT

Summary/Abstract: Alteration textures observed in the volcaniclastic deposits – hyaloclastites – exposed in G. Abu Treifiya area suggest bioalteration processes acting upon basaltic glass clasts and vitric tuff matrix due to their interaction with water where they were laid. Calcimicrobes and microorganisms as algae seem to play an important role in the processes of palagonitization and alteration of volcanic glass, as well as in the cementation and lithification of hyaloclastite tuffs. Biogenic alteration textures observed in the glass fragments suggested that microbes accelerated their dissolution and alteration. Green algae, microbial aggregates, calcispheres, pellets and peloidal forms described in the tuff matrix greatly influenced alteration and cementation of the tuffs. The investigated green algae and other recorded microbes and framboidal pyrite clusters indicate the deposition of the investigated tuffs in brackish- lacustrine environment and alkaline/ calcium rich lakes with fluctuation of water level, due to post Eocene–Oligocene rift tectonics contemporaneous with the processes of basalt eruptions.

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