ICHNOLOGY OF THE SILURIAN RED MOUNTAIN FORMATION OF ALABAMA AND GEORGIA (USA)

Trace fossils are diverse and well preserved in the Red Mountain Formation, historically the chief source of iron ore for the smelters of Birmingham. Bioturbation occurred in probable estuarine to distal shelf environments, with shoreface and proximal shelf being especially well represented. Among the most interesting finds are specimens of W-shaped burrows, Dictyodora major, Scotolithus mirabilis, and Arthrophycus brongniartii. W-shaped burrows consist of U-shaped dwelling burrows that were later extended by an additional U, as in the burrows of the living polychaete Chaetopterus variopedatus. This behavior has not been previously reported from ancient strata. Dictyodora major is a spreite burrow made by an animal that fed on sediment as it moved laterally through the substrate; in one case it is connected with Lockeia, which is interpreted as a probable bivalve resting trace. The tracemakers of Dictyodora are otherwise unknown. Scotolithus mirabilis is another feeding burrow, made by an animal that probably lived in a vertical shaft and extended itself downward to feed, curving radially outward; the burrows were later packed with sediment. This behavior has previously been recorded only in the Lower Cambrian of Sweden. The feeding burrow Arthrophycus brongniartii is abundant in some beds, with one specimen including resting traces of a probable trilobite. These and other distinctive trace fossils make the Red Mountain Formation a valuable source of information on the behavior of Silurian infauna.