SYNSEDIMENTARY SEISMIC ACTIVITY IN AN IMMATURE PASSIVE MARGIN BASIN (LOWER MEMBER OF THE KATROL FORMATION, UPPER JURASSIC, KUTCH, INDIA)

Seismites are difficult to identify in a sedimentary sequence that has been exposed to a number of other synsedimentary disturbances. The paper identifies some possible signatures of earthquakes in a lower submarine fan complex that formed in an extensional basin at the northwestern margin of the Indian plate. Dying growth faults, preferential basal brecciation of shale beds, frequent local intraformational unconformities, reverse grading attributed to mechanical sieving and intrabasinal mass flows through sand volcanoes bear the distinctive records of seismicity. Abundant synsedimentary grabens and horsts and profuse signs of liquifaction are suggestive. In this association, the thinning and fining up channel-fill sequences with evidence of gradually declining mass flow regimes also corroborate. © 1990.