Invertebrate trace fossil assemblages from the Lower Hettangian of Sołtyków, Holy Cross Mountains, Poland

Abstract

Invertebrate trace fossil assemblages from the Hettangian (Early Jurassic) alluvial plain deposits of Sołtyków (Holy Cross Mts, Poland) represent three terrestrial ichnofacies: the Mermia ichnofacies (entirely aquatic), Scoyenia ichnofacies, and Coprinisphaera ichnofacies. They span environments from shallow lacustrine to different subaerial fluvial environments. Bivalve burrows and traces, oligochaetae, insect and crayfishes burrows, plant roots, vertebrate tracks and other types of trace fossils record information on biodiversity and palaeoecological conditions. The Sołtyków ichnoassemblages confirm that terrestrial ichnocoenoses were quite diversified, chiefly a result of a changing water table and food availability. Diversity of trace fossils was supported by the strongly mosaic character of local environments. Bivalve burrows are very diversified, and several ichnogenera have been distinguished. Trace fossil producers as well as functional, taphonomic and preservational aspects of ichnofossils are discussed. The following ichnotaxa have been recognized: Lockeia siliquaria James, 1879; L. amygdaloides (Seilacher, 1953); L. czarnockii (Karaszewski, 1974); Scalichnus isp.; Scoyenia isp.; Spongeliomorpha isp.; Spongeliomorpha carlsbergi (Bromley and Asgaard, 1979); Cruziana problematica (Schindewolf, 1921); cf. Cruziana isp.; Rusophycus isp.; Diplichnites isp.; cf. Kouphichnium sp.; Planolites isp.; Palaeophycus isp.; Cochlichnus isp.; cf. Helminthoidichnites isp.; cf. Xylonichnus isp., and Linckichnus terebrans Schlirf, 2006. Various structures attributed to arthropod burrows (vertical to subvertical tunnels), chambered insect nests of Pallichnidae affinity or othernests with septa, earthworm burrows as well as enigmatic radial chambers, likely made by crayfishes, are illustrated. The new bivalve dwelling ichnotaxon Calceoformites uchmani igen. et isp. n. is described.