Quaternary deep-sea lebensspuren and their relationship to depositional environments in the Caribbean Sea, the Gulf of Mexico, and the eastern and central North Pacific Ocean
McMillen, Kenneth James
Warme, John E.
Master of Arts
Traces of marine benthos provide evidence of biological activity in the deep sea, even where few animals exist. Traces are not restricted to major ocean basins but some restriction to water depth does occur. The greatest distinction exists between different types of sediment. Burrows are of two types: 1) permanent burrows, and 2) temporary burrows. Permanent burrows tend to occur where sedimentation rates are low, as in pelagic sediments. Temporary burrows occur where sedimentation rates are rapid, as in turbidites. In the Cayman Trough, the relationship between burrowers and sedimentation has been studied in detail. The trough is a deep, linear basin isolated by ridges and islands from surrounding oceanic basins, with pelagic carbonate sedimentation occurring at the present time. Since the Late Pleistocene, sedimentation has consisted of 1) distal turbidites, succeeded by 2) sediments deposited by currents generated by a turnover of bottom water accompanying the post-Pleistocene rise in sea level, and followed by 3) pelagic sedimentation. The traces respond to this succession of sediments. Temporary burrows occur in turbidites and bottom-current sediments, and only permanent burrows occur in pelagic sediments. Permanent burrows are mainly used for protection by filter-feeding organisms, whereas temporary burrows that are actively filled by the organism are produced by sediment-ingesting organisms. These feeding patterns are the result of the way food is distributed in the sediment. Temporary burrows that are actively filled occur where food is buried in the sediment, as it is in turbidity-current sediments, bottom-current sediments, and hemipelagic sediments. Permanent burrows occur where food supply is less so it accumulates near the surface, or is intercepted before it reaches the sea floor, which is the case in pelagic sediments.