The interval contains abundant trace fossils such as Skolithos, Cruziana, Cochlichnus, Monomorphichnus, Catenichnus, Thalassinoides
, Helminthodoichnites and Planolites.
Many of the organic-rich intervals show a multi-episodic origin, indicated by the presence of more calcareous horizons and surfaces which were colonized mainly by Chondrites, Thalassinoides
ichnocoenosis of Pickerill and Donovan (1991; see also Pickerill et al.
The sandstone/siltstone-claystone heteroliths that underlie and overlie such thick claystone beds are often characterized by sparse to abundant trace fossil associations, dominantly Planolites isp., Thalassinoides
isp., and Paleophycus isp., along with abundant plant fossils.
The large burrows that form the mottles are assigned to the ichnogenus Thalassinoides
; these were probably produced by arthropods (Kendall, 1977; Coniglio, 1999).
It contains abundant trace fossils including Thalassinoides
, Planolites, Chondrites, Teichichnus, and Zoophycos.
Most beds are visibly bioturbated at various scales and some bedding surfaces are underlain by dense networks of borings and burrows reminiscent of Balanoglossites and/or Thalassinoides