Carbonaceous particles are present in superficial sediments and in sedimentary cores of Mejillones del Sur bay (23°S). An analysis of a 44-cm long core based upon petrographical techniques as well as transmitted and reflected light microscopy show that these particles are only present in the upper 1.0 cm of the sequences. Superficial samples (0.5 cm thick) of marine sediments located northeast of the town of Mejillones also contain carbonaceous particles. Due to the total lack of vegetation, which could be burnt in the area, it was inferred that they were originated from industrial activities. Actually, we establish that these particles are related of the transport of carbon to a railway industry, which began to operate in Mejillones in 1910. The superficial sediments reflect the recent development of various industrial plants, which use carbon as source of energy in the bay. Marine superficial circulation is the principal factor that explains the distribution of the carbonaceous particles in the bottom sediments of the bay. Thus, carbonaceous particles present a double potential, as a record of past and present environmental impacts, and as a geochronological tool for sediment columns needed to reconstruct and validate geochronological models for studies on ocean-climate evolution of this zone, in the recent past.