A new trace fossil assemblage from the Middle Permian Broughton Formation, southern Sydney Basin (southeastern Australia): Ichnology and palaeoenvironmental significance

摘要

AbstractThe Permian-Triassic sedimentary succession of the southern Sydney Basin in southeastern Australia contains a wealth of well-preserved trace fossils that are important for systematic ichnological, palaeoecological, and palaeoenvironmental interpretations. In this study, a new ichnofossil assemblage comprisingMacaronichnus,Palaeophycus,Psammichnites,Protovirgularia,Rosselia, andTeichichnusis documented from the tide-influenced shoreface deposit of the Middle Permian Jamberoo Sandstone Member of the Broughton Formation. Two distinct ichnofabrics are recognized: i) thePsammichnitesichnofabric characteristic of the upper–middle shoreface deposit; and ii) the crowdedRosseliaichnofabric (CRI) representing the lower shoreface. ThePsammichnites-dominated ichnofabric is interpreted to have resulted from opportunistic behaviours of unknown trace makers, whereas the CRI is interpreted to represent possible strategic behaviours of stress-tolerant polychaetes (e.g., terebellid, spionid, and cirratulid polychaetes) in a distal shoreface with high sedimentation rate. Thus, thePsammichnites–crowdedRosseliaichnofabric succession can be considered to represent a response to an environmental shift from proximal to distal shoreface. As such, this study highlights the utility of these two ichnofabrics as stressed environmental indicators.展开▼