Bioturbation in marine sediments has basically two aspects of interest for paleo-environmental studies. First, the traces left by the burrowing organisms reflect the prevailing environmental conditions at the seafloor and thus can be used to reconstruct the ecologic and paleoceanographic situation. Secondly, for high-resolution stratigraphy, bioturbation is a nuisance due to the stirring and mixing processes that destroy the stratigraphic record. In order to evaluate the applicability of biogenic traces as paleoenvironmental indicators, a number of gravity cores from the Portuguese continental slope, covering the period from the last glacial to the present were investigated through X-ray radiographs. A number of traces could be recognized, the most important being: Thalassinoides, Planolites, Zoophycos, Chondrites, Palaeophycus, and the pyritized traces Trichichnus and Mycellia. The shifts between the different ichnofabrics agree strikingly well with the variations in ocean circulation caused by the changing climate. On the upper and middle slope, variations in intensity and oxygenation of the Mediterranean Outflow Water were responsible for shifts in the ichnofabric. In contrast, on the lower slope where calm, steady sedimentation conditions prevail, changes in sedimentation rate and nutrient flux have controlled variations in the distribution of the traces. Additionally, distinct layers of Chondrites corresponded to the reduced thermohaline circulation during Heinrich events 1, 2, and 4. A first attempt to automatize a part of the recognition and quantification of the ichnofabric was performed using the DIAna image analysis program on digitized X-ray radiographs. The results show that enhanced abundance of pyritized microburrows appears to be coupled to fine grained, organic rich sediments deposited under dysoxic conditions. Radiocarbon dating of sample pairs from Zoophycos spreiten and surrounding sediment revealed that the spreiten material was up to 3,320 years younger than the surrounding sediment. Together with detailed X-ray radiograph studies this shows that the trace maker collected the material on the seafloor, and then transported it downward deep in to the underlying sediment. This clearly shows that age reversals of several thousands of years can be expected if Zoophycos is unknowingly sampled. These results also render the hitherto proposed ethological models proposed for Zoophycos as largely implausible. Therefore, a combination of surface detritus feeding, short time caching, and probably also gardening of chemosymbiontic microorganisms, is suggested here as an explanation for this complicated burrow.