Sedimentology and depositional environment of the intraformational flat pebble conglomerates of the lower member of the Elika Formation (Lower Triassic) in the Alborz Mountains

To study intraformational flat pebble conglomerates of the lower member of the Elika Formation (Lower Triassic), four stratigraphic sections in the Alborz Mountains of northern Iran were selected. The thickness of the lower member of the Elika Formation in these sections ranges from 95 meters in the type section to 195 meters in the Veresk section. This member mainly consists of heavily bioturbated thin to thick-bedded limestone and shale intercalations which deposited under fair-weather and storm conditions. The intraformational flat pebble conglomerates are the most important of the storm facies. These conglomerates have sharp or erosional bases and interbedded with the fair-weather facies. These facies rang from a few centimeters to 100 cm thicknesses, and mainly consist of gravel- size intraclasts. The intraclasts are horizontal to sub- horizontal in the thinner beds, but they are imbricated, sometimes opposing orientations in the thicker beds. Their textures are mainly rudstone and sometimes floatstone. Field and microscopic studies indicate that the intraformational flat pebble conglomerates were deposited by powerful storm generated flows in open marine, shoal, lagoon and tidal flat/ beach ridge sub-environments related to carbonate homoclinal ramp platforms.