DEEP-SEA BENTHIC FOOD CONTENT RECORDED BY ICHNOFABRICS - A CONCEPTUAL-MODEL BASED ON OBSERVATIONS FROM PALEOGENE FLYSCH, CARPATHIANS, POLAND

Fluctuations in the input of organic matter into a deep-sea environmen t can be deciphered from ichnofabrics if the continuous processes of h emipelagic sedimentation and bioturbation are episodically interrupted by turbidite deposition. Below turbidites, the bioturbated zone may b e preserved almost intact; the benthic food content in such frozen tie rs can be interpreted from the ethology, size, penetration depth, and density of trace fossils. Especially high benthic food content is char acterized by (1) dark sediment color, (2) complete bioturbation, (3) h igh density of burrows produced near-surface in several levels, (4) ra rity or absence of graphoglyptids, and (5) deep tiers completely biotu rbated by feeding burrows having an open connection to the surface. Ox ygen-deficiency can. be eliminated as a reason for the black color of the sediment; the size, diversity, and penetration depth of the trace fossils are similar to that of modern and fossil counterparts formed u nder well-oxygenated settings that are not restricted in benthic food. An increase in sedimentation rate enhances the burial of benthic food and is indicated by the downward ex:tension of the bioturbated zone a nd by increasing burrow density. Our analysis suggests that several ot her black shale occurrences may result from increased organic matter i nput rather than from water-column anoxia due to sluggish circulation. Our model is supported by similarities with other deposits that conta in many frozen tiers.