Flysch trace fossils from the Cretaceous Kodiak Formation of Alaska

• Published in: Journal of Paleontology
• Main Authors: Mccann, Tommy, Pickerill, Ron K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1988
• Subjects: Kodiak; Alaska
• Online Access: http://dx.doi.org/10.1017/s0022336000059138; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000059138

The Cretaceous Kodiak Formation at the northeastern end of Kodiak Island, Alaska, is interpreted to have been deposited in a distal deep-sea fan complex. Facies analysis of the sequence suggests deposition in channels (both major and distributary), lobe fringe (proximal and distal), and interchannel and interchannel/channel mouth environments. The strata contain a diverse and relatively abundant trace fossil assemblage consisting, at the ichnogeneric level, of twenty-six forms: Acanthorhaphe, Chondrites, Circulichnis, Cochlichnus, Cosmorhaphe, Desmograpton, Glockerichnus, Gordia, Helminthoida, Helminthopsis, Muensteria, Neonereites, Nereites, Paleodictyon, Palaeophycus, ?Phycosiphon, Planolites, Protopaleodictyon, Scolicia, Spirophycus, Spirorhaphe, Taenidium, Taphrhelminthopsis, Terebellina, Thalassinoides , and Yakutatia . Thirty-eight ichnospecies are described, three of which ( Acanthorhaphe ichnosp., Cosmorhaphe helicoidea , and Desmograpton fuchsi ) are recorded for the first time in North America. Final channel-fill (levee) and interchannel environments contain the most abundant and diverse ichnoassemblages, a reflection of favorable environmental parameters for inhabitation by benthic organisms, but more importantly the presence of diverse lithotypes conducive to the final preservation of their activity. Channel-fill sequences are devoid of trace fossils, a reflection of substrate mobility and lack of shale interbeds precluding toponomic preservation. Lobe fringe sequences contain only isolated trace fossils, a reflection of their poor exposure and largely monolithologic character. The ichnoassemblage is compared to 20 previously described and taxonomically well-documented deep-water flysch trace fossil studies from the Phanerozoic. Comparison at the ichnogeneric level is favorable with only Acanthorhaphe, Terebellina , and Yakutatia being relatively unique to the Kodiak sequence.