Dictionary:Lowstand system tract (LST)

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The earliest (lowermost) system tract within a sequence, bounded below by a sequence boundary and above by the first major flooding surface, or transgressive surface (Van Wagoner, 1995). It is deposited during a rapid eustatic fall and generally can be separated into three units by downlap surfaces. A lowstand (or basin-floor) fan lies on the lower slope or basin floor and is associated with canyons incised into the slope through which siliciclastic sediments are fed to the fan, thus bypassing the shelf; it is deposited during a rapid eustatic fall. A slope fan is characterized by turbidite and debris flow deposition. A lowstand wedge (prograding wedge) is characterized by fill into incised valleys and progradation with wedge-shaped geometry. See Figure S-32.