Ichnotaxonomy and paleoenvironmental analysis of trace fossils in the Late Devonian Catskill Formation, north-central Pennsylvania, USA.

摘要

The purpose of this thesis is to interpret the ichnotaxonomy, paleoenvironmental distribution, and paleoecological ramifications of trace fossils from the Frasnian-Famennian Catskill Formation (CF), north-central Pennsylvania, USA. The CF contains a suite of approximately 14 traces, 11 of which represent animal behavior, and 3 of which represent preservational styles and morphologies of plant roots. CF traces occur in paleosols and strata exhibiting no evidence of pedogenesis. Paleosol traces represent terraphilic to hydrophilic soil biota. Traces in strata with no evidence of pedogenesis represent aquatic organism behavior. Backfilled burrows---Beaconites antarcticus and B. barretti---represent dwelling and feeding by soil-dwelling arthropods. Rhizoliths represent shallow to deep rooting by plants with terraphilic-hydrophilic affinities. Backfilled burrows and rhizoliths form a characteristic ichnofabric that is superimposed on all pedogenically modified deposits. Lungfish estivation burrows---Hyperoeuthys teichonomos---are commonly superimposed on and subsequently overprinted by the dominant ichnofabric. Diplichnites gouldi is present in weakly developed paleosols and represents locomotion of an arthropod of unknown taxonomic affinity. In situ stump casts occur in paleosols of differing maturity and likely represent the life position of an arborescent plant. Camborygma eumekonomos and C. litonomos represent dwelling burrows of terraphilic to hydrophilic arthropods and are also overprinted by the dominant ichnopedofabric. Bivalve resting (Lockeia siliquaria), locomotion (Lockeia ornata), and escape traces, as well as fish swimming traces ( Undichna multiloba), and Sagittichnus lincki----the resting trace of an unknown organism----represent aquatic organism behavior. The presence of terraphilic to hygrophilic and hydrophilic traces in CF paleosols indicates that Late Devonian soil organisms exhibited nearly as much behavioral complexity as Mesozoic-recent soil organisms. The abundance and degree of trace crosscutting increases in increasingly mature paleosols, indicating that CF paleosol ichnoassemblages, despite being controlled by paleohydrology, also represent ecological succession. Continental organisms are known exhibited behaviors that beneficially modify their environment (ecosystem engineering) by modulating resource flow paths (allogenic engineering) or modifying their bodies in ways that create new habitats for themselves (autogenic engineering). The idea that middle Paleozoic continental organisms were ecosystem engineers has not been examined. Our data suggest that the inception of allogenic ecosystem engineering in continental environments had occurred by the Late Devonian.