The upper boundary of this Systems Tract is marked by the first occurrence of sediments that onlap onto the underlying prograding clinoforms (see animated gif associated with the Lowstand Systems Tract). This change in sediment geometry occurs when accommodation starts to expand in response to a relative rise in sea level that occurs when a rise in eustasy exceeds the rate of subsidence. On seismic data the upper boundary is a potentially definable horizon but when well logs and outcrops are used instead it is recognized as a marine-flooding surface that may be marked by a time transgressive ravinement surface overlain by a sediment lag.

Stacking patterns exhibit the downward stepping prograding clinoforms of a forced regression.

Posamentier and Allen (1999) divided a Lowstand Systems Tract into Early and Late Phases. They indicated that during early lowstand, relative sea level is falling, forced regression takes place, and an unconformity forms a sequence boundary on the exposed surface landward of the shoreline, representing a surface of sedimentary bypass. Incised valleys may form in the interfluve lows. Vail et al 1977, like many other referenced authors, also equate this Systems Tract to the accumulation of sediments as basin floor fans. However Posamentier and Allen (1999) suggest that care should be taken with this interpretation since the formation of these fans may often be independent of a relative fall in sea level and are instead tied to higher rates of sedimentation and the character of the updip slope! Since this Systems Tract is equated with the relative fall in sea level, Plint and Nummedal, (2000) and Coe et al (2002) believe that it should be called the Falling Stage Systems Tract and this is the terminology this web site tends to favour.