Early Liassic Trace Fossil Assemblages from the Holy Cross Mountains, Poland: Their Distribution in Continental and Marginal Marine Environments

In Early Liassic continental deposits from the northern slope of the Holy Cross Mountains, Poland, trace fossils are very rare and the assemblage is not diverse. Only simple feeding structures (fodinichia) and crawling traces (repichnia) are present, and these are mostly associated with levee or distal crevasse deposits.

In brackish-marine deposits, which form the major part of the Holy Cross Lower Liassic sequence, trace fossils are much more numerous and diverse. However, compared to other Jurassic ichnocoenoses from fully marine environments, the Holy Cross Early Liassic brackish water forms are generally smaller and less diverse, and spreiten burrows are rare.

Based on detailed descriptions of 26 boreholes and numerous outcrops, the usefulness of trace fossils in differentiating shore-prograding from barrier-lagoon and deltaic sequences is confirmed. With borehole materials, trace fossils are of primary importance in making this differentiation.