Transgressive and highstand systems tracts (Ness Formation)

Unit is characterised by parasequences formed
by bay head delta progradation in a lower delta
plain setting. Parasequences in well 211/18-A7 (Fig.
3) reveal a retrogradational parasequence set up
to 8812′ TVDSS, and an overlying progradational
parasequence set to the base of Unit G. The two sets
can be traced across the field and are interpreted as
transgressive and highstand systems tracts separated
by a maximum flooding surface (Fig. 4). The shaleprone
interval that bounds the maximum flooding
surface is the Mid Ness Shale.
In addition to the highstand and transgressive systems
tracts above and below the maximum flooding
surface, the lowermost portion of Unit F may represent
part of the preceding lowstand systems tract.
This possibility results from the difficulty in recognising
the top of the lowstand systems tract, which
is marked in favourable locations by “the transgressive
surface”, i.e. “the first significant marine
flooding surface across the shelf within the sequence”