Abstract

Late Mesozoic Franciscan turbidite deposits, examined along the Pacific Coast of northern California, contain a locally varied and abundant assemblage of trace fossils. These include (1) open burrow systems that may have functioned as microbial “farms” or traps (graphoglyptids, such as Cosmoraphe, Paleodictyon, and Megagrapton); (2) burrows constructed as back-filled probes and spreiten by infaunal deposit-feeders (Chondrites, Lophoctenium, Taenidium, and ?Micatuba); (3) shallow infaunal burrows made by foraging deposit-feeders (Gordia, Helminthopsis, and ?Neonereites); (4) a widespread, infaunal locomotion trace fossil (Planolites); (5) burrow-mottled zones; (6) burrows with dark halos; (7) wispy, indistinct burrows delineated by stringers of carbonaceous material; and (8) fecal pellets that appear to be the products of polychaete worms. These trace fossils make up a rich assemblage from rocks that heretofore have been considered to be essentially unfossiliferous, and may be the only in situ macrofaunal remains preserved in Franciscan turbidites of the Central Belt.

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