base level

corelative conformity

forced regression

highstand systems tract

lowstand systems tract

maximum flooding surface

ravinement erosion surface

regressive surface of erosion

regressive systems tract

transgressive surface

transgressive systems tract

unconformity

This is the surface that marks the top of the regression associated with a lowstand system tract and the base of the overlying transgressive system tract (Helland-Hansen and Martinsen, 1996). Traditionally most sequence stratigraphers follow the lead of Posamentier and Vail (1988) and call this surface the transgressive surface. In shallower marine successions this surface often marks the upper surface of coarsening-upward (regressive) sediments (Catuneanu, 2002), an important point that helps enhance the recognition of this surface on logs.

As can be seen in Catuneanu's (2002) diagram this surface marks the between the underlying regressive system tract and the overlying transgressive system tract. On the diagram Catuneanu (2002) shows the maximum regressive surface as conformable. However in shallower settings the transgression that accompanies a base level rise may erode the upper surface of the underlying regressive sequence (Loutit et al., 1988; Galloway, 1989). It was for this reason that Posamentier and Vail, (1988) thought this surface should be named the transgressive surface. Others like Nummedal et al., (1993) call it the initial transgressive surface, while Embry, (1995) refers to it as the conformable transgressive surface, and Emery and Myers, (1996) call it the maximum progradation surface. This surface lies over the youngest clinoform (paleoseafloor) of regression and is onlapped by transgressive strata (Catuneanu, 2006).

References
Catuneanu,O., 2002, sequence stratigraphy of clastic systems: concepts, merits, and pitfalls Journal of African Earth Sciences, Volume 35, Issue 1, Pages 1-43
Catuneanu, Octavian (2006), Principles of sequence stratigraphy, Elsevier pp 375
Embry, A.F., 1995, sequence boundaries and sequence hierarchies: problems and proposals. In: Steel, R.J., Felt, V.L., Johannessen, E.P., Mathieu, C. (Eds.), sequence stratigraphy on the Northwest European Margin, vol. 5 (Special Publication). Norwegian Petroleum Society (NPF), pp. 1–11.
Galloway, W.E., 1989, Genetic stratigraphic sequences in basin analysis. I. Architecture and genesis of flooding-surface bounded depositional units. American Association of Petroleum Geologists Bulletin 73, 125–142.
Helland-Hansen, W., Martinsen, O.J., 1996, shoreline trajectories and sequences: description of variable depositional-dip scenarios. Journal of Sedimentary Research 66 (4), 670–688.
Loutit, T.S., Hardenbol, J., Vail, P.R., Baum, G.R., 1988, condensed sections: the key to age-dating and correlation of continental margin sequences. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G.St.C., Posamentier, H.W., Ross, C.A., Van Wagoner, J.C. (Eds.), Sea Level Changes––An Integrated Approach, vol. 42. SEPM Special Publication, pp. 183–213.
Nummedal, D., Riley, G.W., Templet, P.L., 1993, High-resolution sequence architecture: a chronostratigraphic model based on equilibrium profile studies. In: Posamentier, H.W., Summerhayes, C.P., Haq, B.U., Allen, G.P. (Eds.), sequence stratigraphy and Facies Associations, vol. 18. International Association of Sedimentologists Special Publication, pp. 55–68.
Posamentier, H.W., Vail, P.R., 1988, eustatic controls on clastic deposition. II. sequence and systems tract models. In: Wilgus, C.K., Hastings, B.S., Kendall, C.G.St.C., Posamentier, H.W., Ross, C.A., Van Wagoner, J.C. (Eds.), Sea Level Changes––An Integrated Approach, vol. 42. SEPM Special Publication, pp. 125– 154.