Abstract

Uppermost Cretaceous to Pleistocene deep and shallow water sediments were deposited in the fore arc area of Costa Rica and Nicaragua. Outcrop data show successions of depositional sequences bounded by unconformities. Strong structural activity and increased volcanic sediment supply overprint the effects of global sea-level changes. During long-term periods of subsidence sufficient space was available to store large amounts of shallow marine sands. Strong tectonic uplift reduced accommodation space and erosion of shelf deposits occurred.

Depositional sequences in the deep water sediments developed mainly as channel-lobe-systems and slope-apron-systems. The coarse grained, sand-rich channel-lobe-systems reflect a fast lowering of the sea level and strong removal of shelf sands. Canyons cut toward the shelf edge which formed point source feeding systems. Slope-apron-systems developed during slow lowering of the sea level. Depending on differential tectonic style a relative rise of the sea level caused either the development of coastal embayments or equilibrium coastlines. Strong tectonic uplift resulted in the initiation of fan deltas.