The preservation of planktonic foraminiferal shell assemblages in sediments can be characterized by their degree of fragmentation. The amount of carbonate removed from the shells can easily be estimated and it is therefore possible to calculate their total loss of CaCO3. Arctic deep water today reaches the abyssal plains off Portugal, resulting in high carbonate solution rates and therefore intensive shell fragmentation, while shells from similar depths off Morocco are nearly unfragmented. Late Pleistocene sediments in both areas yield well-preserved planktonic Foraminifera. This is important for the reconstruction of Pleistocene North Atlantic deep-water hydrography. In both areas continental-slope assemblages are better preserved with decreasing water depth, with the exception of its uppermost part where the rate of carbonate solution increases.