A] Petroluem system includes: a) Source rocks-reservoir rocks-seal rocks. b) Source rocks- organic matter-seal rocks c) Sandstone-reservoir rocks-seal rocks d) Source rocks-shale-seal rocks e) Tarp-reservoir rocks-seal rocks B] Microcrystalline carbonate particles of clay (<1-4 micron) size (sub-translucent matrix) may form by: a) Chemical of biochemical precipitation b) Chemical weathering. c) Transported to the basin by wind action. d) Volcanic eruption..