Namibia's southwestern coast, the Sperrgebiet, hosts one of the world's largest gem diamond placer deposits consisting of fluvial, marine and desert deflation/aeolian placer types. To date, the richest onshore placer discovered in the Sperrgebiet comprises several, Plio-Pleistocene to Holocene, littoral marine packages distributed northwards from the Orange River mouth for some 120 km to Chameis Bay. In this zone, known as Mining Area No. 1 (MA1), these Quaternary marine deposits are floored predominantly by siliciclastic rocks of the Late Proterozoic Gariep Belt that have been bevelled into a number of marine-cut platforms during the different Quaternary high sea level stands (notably, at + 30 m, + 8 m, + 4 m and + 2 m). In many places, these bedrock platforms are extensively gullied and potholed, forming abundant fixed trapsites that promote diamond concentration in the Late Cainozoic littoral sediments. Some observations on the distribution, orientation and incision of bedrock gullies in MA1 are presented here. Keywords: Alluvial diamonds, Bedrock gully trapsites, Marine platforms, Late Cainozoic, Sperrgebiet, Namibia.