Sequence analysis of the Ecca-Beaufort boundary in the southern Karoo Basin has revealed three separate facies associations spanning the stratigraphic interval between the top of the Fort Brown Formation and the lowermost maroon mudrocks of the Beaufort Group. This sequence was deposited in prodelta, delta front, and delta plain environments respectively. The lithological contact between the rocks deposited in the delta front and delta plain represents the palaeoshoreline, and occurs only once in the stratigraphic sequence, suggesting a continuous normal regression from Ecca to Beaufort times. This diachronous shoreline is associated with deltaic progradation within a highstand systems tract. Sediment deposition was mainly a result of ephemeral flash floods, but perennial rivers also flowed from melting ice-capped highlands to the palaeosouth. Two separate fossil associations have been recognized and correlate with the lithological subdivisions. The lower fossil assemblage occurs in the Fort Brown and Waterford formations and is characterized by silicified wood, comminuted plant material, and fish scales. The upper association occurs only in the lower Beaufort Group and includes in situ equisitalean, and well-preserved Glossopteris plant fossils and tetrapods of the Eodicynodon Assemblage Zone. The Beaufort-Ecca boundary coincides with the position of the palaeoshoreline. This lithological contact also marks a change in depositional style and palaeontological character between the two groups. The new placement of the boundary is some 300-650m below the presently mapped contact in the south of the basin.underlying Ecca Group, also noting that the contact was gradational over a thickness of between 16 to 23 m. This criterion was also used by Venter (1969), who placed the base of the Beaufort Group at the first massive sandstone overlying the Ecca fines. Mountain (1946), Rossouw (1953), and Haughton etal.(1953addedtothislithological distinctionthefirst occurrence of red/maroon mudrocks as the boundary contact. Visser and Loock (1974) recognized the transitional nature of the contact, as suggested by Rogers and Du Toit (1909) and, for this reason, believed that the contact could be better placed via a combination of lithological and interpretative criteria, where there is evidence of a pronounced change of depositional environment from deep water to deltaic and fluvial environments, represented in the field by a zone of slump structures. Lemmer (1977) utilized these criteria in the Britstownarea,howeverNel (1977)feltthattheywerenotapplicable in the Hopetown area, as their use would imply the splitting of two major stratigraphic units. Terblanche (1979), working in the Carnarvon district, incorporated the first major sandstone overlying the Ecca fines into the upper Ecca, and placed the contact above this at the first occurrence of fluvial sandstones. In contrast, Ryan and Whitfield (1979) placed the contact in this region at the base of the first prominent sandstone overlying the Ecca fines. SACS (1980) adopted a co...