Burrowing in recent lime sediments of Florida and the Bachamas

Five organisms, viz. four crustaceans (Alpheus Weber, 1795, Callianassa Leach,1814, Cardisoma Latreille, 1828, and Uca Leach, 1814) and one coelenterate (Phyllactis Milne-Edwards & Haime, 1851), produce extensive and characteristic subsurface burrow complexes. Alpheus, Callianassa, and Phyllactis burrow in marine and intertidal sediments; Cardisoma and Uca burrow in supratidal sediments. Supratidal, intertidal, and subtidal crustacean burrowers produce extensive 3-foot deep open networks in muddy marine sediments which can remain open beneath overburdens exceeding 8 feet. Knowledge of depth of burrowing and relative rate of sea level rise suggests that many inactive burrows have remained open for 1,000 years or more. Burrows commonly become infilled, but compaction of either filled or open burrows has not been observed. Striking resemblances of Recent burrow networks to ancient reef-associated Stromatactis Dupont, 1881 and "reef-tufa" structures suggest burrows as the origin for some of these much debated structures. Burrowing structures can be useful in interpreting ancient rocks. This study shows that "nested-cone" structures in cross-bedded oolite of Pleistocene age were probably produced by an anemone like the Recent form Phyllactis, which makes similar structures in Recent crossbedded marine oolites. Such structures can be used to differentiate between marine- and eolian-deposited sands. Recycling and mixing of sediment by burrowers can produce sediments having grain sizes coarser than the originally deposited sediments. Grain size analyses of extensively burrowed sediments may give little information regarding the energy level of the depositional environment. Polyester plastic casts of burrow networks and other new techniques described in the text have aided greatly in this study