DEPOSITIONAL EVENTS AND THEIR RECORDS - AN INTRODUCTION

Event deposits of some lateral extent as defined here occur almost in all types of sedimentary basins. They reflect either local, intra-basi nal processes, or they are associated with regional or global mechanis ms. Some types of event beds, such as sediment gravity flows, sandy an d muddy turbidites, are common and usually well preserved. They make u p large proportions of basin fills, whereas others (e.g., tsunami depo sits and in-situ earthquake structures) appear to be less frequent or rare in the geological record. Volume, frequency, and facies of event deposits are controlled by several processes: pre-event sediment accum ulation, triggering and transport mechanisms, and mode of final deposi tion.