MICROBIALLY INDUCED SEDIMENTARY STRUCTURES IN THE TRIASSIC LOCKATONG FORMATION NEWARK BASIN, PENNSYLVANIA, USA

Stromatolites are ubiquitously used as proxies for microbial activity in lacustrine settings throughout Earth’s history. The identification of microbially induced sedimentary structures (MISS) is under recognized in ancient lacustrine systems and, hence, provide additional documentation of microbial activity. The Upper Triassic Lockatong Formation, of the Newark Supergroup, is a dominantly lacustrine setting and is producing many diverse MISS.

MISS features, composed of interweaving, microscopic filaments were discovered in thin-bedded heterolithic mudstones, siltstones, and very fine-grained sandstones of the Tumbling Falls Member of the Lockatong Formation. The MISS are best observed on collected slabs and analyzed in thin sections. MISS features recognized include: oriented grains, laminated leveling structures, mat microfabrics, microsequences, wrinkle structures, and microbial spheres. Changes in environment, or static environments, as microorganisms are at work, produce the variations in MISS seen today.

In addition, thin film desiccation, variation in wrinkle textures horizontally and vertically across the sediment surface, and possible gas generation structures are present. SEM analysis shows preservation of tube-like features on the surface and a change in chemical composition from external to internal parts of the filaments. The MISS from the Lockatong Formation demonstrate the importance of recognizing these features, thus adding to the paleontologic diversity inferred from stromatolites and enhancing our understanding of lacustrine paleoecology.