HR: 1330h
AN: OS32A-0241    [PDF]
TI: Paleodictyon, a Living Fossil on the Deepsea Floor
AU: * Rona, P A
EM: rona@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AU: Seilacher, A
EM: geodolf@tuebingen.netsurf.de
AF: Institut fur Geologie und Palaeontologie der Universitat, Sigwartstrasse 10, Tuebingen, 74 Germany
AU: Luginsland, H
AF: Institut fur Geologie und Palaeontologie der Universitat, Sigwartstrasse 10, Tuebingen, 74 Germany
AU: Seilacher, E
AF: Institut fur Geologie und Palaeontologie der Universitat, Sigwartstrasse 10, Tuebingen, 74 Germany
AU: de Vargas, C
EM: vargas@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AU: Vetriani, C
EM: vetriani@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AU: Bernhard, J M
EM: jmbernha@gwm.sc.edu
AF: School of Public Health, University of South Carolina, Columbia, SC 29208 United States
AU: Sherrell, R M
EM: sherrell@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AU: Grassle, J F
EM: grassle@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AU: Low, S
EM: slow@videotron.ca
AF: The Stephen Low Company, 795 Carson, Suite 6, Dorval, QC H9S1L9 Canada
AU: Lutz, R A
EM: rlutz@imcs.rutgers.edu
AF: IMCS and Geological Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521 United States
AB: We report new observations based on high resolution imagery, in situ experiments, and recovery of samples made in conjunction with filming of the IMAX movie, "Volcanoes of the Deep Sea", which reveal hitherto unknown features of an enigmatic form on the deep seafloor. Thousands of strikingly hexagonal patterns (typically 5 to 7 cm diameter) formed by intersecting rows of tiny black dots were originally imaged on a veneer of calcareous lutite along 3 km of a camera tow up the lower east wall of the rift valley of the Mid-Atlantic Ridge between water depths of 3600 m and 3200m at 26o 09'N, 44o48'W (Rona and Merrill, 1976). Defying classification into either a known invertebrate phylum or as the product of a known organism, the hexagonal pattern was tentatively interpreted as the surface expression of a trace fossil (Paleodictyon nodosum) found in deepsea flysch sediments of Eocene age (Seilacher, 1977). Subsequent discoveries revealed that the modern Paleodictyon occurs in an outlying area of the Trans-Atlantic Geotraverse (TAG) hydrothermal field, where high-temperature activity ceased some hundreds of years ago and the veneer of lutite overlies metalliferous sediments. In situ observations show that the black dots are indeed vertical shafts about 1 mm in diameter, each of which connect to the midpoint of a strikingly regular network of horizontal tunnels or tubes 2 to 3 mm beneath the sediment surface. The surface patterns range from sharp shield-like forms several millimeters high that expose underlying metalliferous sediments and are surrounded by shallow moat-like depressions, to flat forms with rounded edges entirely in lutite. This variation suggests a degradation sequence under prevailing (c. 5 cm/s) or episodic near-bottom currents over hundreds of years based on the radiometrically measured regional sedimentation rate. The 3D morphology revealed by artificial erosion confirms identity with the fossil Paleodictyon nodosum. Biological studies of core samples recovered on a recent DSV Alvin dive are underway to test alternative hypotheses for the origin of the Paleodictyon pattern. In the paleontological view, the pattern is a tunnel system constructed as part of the feeding strategy (bacterial farming) of an unknown benthic invertebrate. Another hypothesis claims that we deal with the tubular body of an infaunal member of the Xenophyophorea, a poorly known group of foraminifera, like protozoans
DE: 0400 Biogeosciences
DE: 3299 General or miscellaneous
DE: 4200 OCEANOGRAPHY: GENERAL
DE: 4804 Benthic processes/benthos
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting