ASSESSMENT OF CONTINENTAL TRACE FOSSILS IN THE FRASNIAN–FAMENNIAN CATSKILL FORMATION, NORTH-CENTRAL PENNSYLVANIA: INITIATION OF DEVONIAN ECOSYSTEM ENGINEERING BY SOIL BIOTAS

The Catksill Formation (CF) contains a moderately diverse trace-fossil suite interpreted as rooting by various sized plants and the traces of surface-, soil-, and aquatic-dwelling animals with terraphilic to hydrophilic affinities that represent transient, temporary, and periodic presence in soils. These traces are unique from those produced by marine organisms as they reflect such physicochemical factors as the groundwater profile, depositional energy, sedimentation rate, and medium typical of continental depositional environments. Traces of soil-dwelling organisms occur in weakly developed to moderately and well-developed paleosols that reflect compound, composite, and cumulic soil profiles. Aquatic traces occur in pointbar deposits and include Lockeia siliquaria and Sagittichnus lincki that likely represent mollusks (e.g., bivavles) and crustaceans (e.g., ostracodes), respectively. Also present are fish-swimming traces assigned to Undichna multiloba. Subaerial trackways assigned to Diplichnites gouldi occur in weakly developed paleosols and represent locomotion traces of myriapods as epigeon in proximal fluvial deposits. Lungfish burrows are abundant in proximal floodplain deposits and represent aestivation behavior, which reflects a transient presence in soil. Beaconites antarcticus and B. barretti occur in paleosols and represent behaviors of terraphilic to hygrophilic organisms similar to beetle larvae and soil bug nymphs that likely had a temporary to periodic presence in CF soils. Camborygma litonomos and C. eumekonomos likely represent hydrophilic organisms (similar to crayfish) that had a periodic presence in floodplain deposits. Trace-fossil distribution in the CF represents the inception of allogenic ecosystem engineering in continental environments of the Late Devonian, as burrowing organisms beneficially modified the physicochemical environment in which they lived by developing the detritivore nutrient cycling system that modulated resource flow paths.