Abundance and morphology of Paleodictyon nodosum, observed at the Clarion-Clipperton Zone

Jennifer M Durden,Daniel O B Jones,Erik Simon-Lledo,Andrew J Gooday

doi:10.1007/s12526-017-0636-0

Jennifer M Durden, Daniel O B Jones + Show 2 more

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https://doi.org/10.1007/s12526-017-0636-0

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Abstract

Paleodictyon is an important trace fossil characterised by a regular hexagonal structure and typical of ancient deep-ocean habitats as far back as the Ordovician. It is represented in modern deep-sea settings by Paleodictyon nodosum, known from the Mid-Atlantic Ridge, the South Atlantic, and off eastern Australia. Here we report the occurrence of P. nodosum in the Clarion Clipperton Zone (CCZ), abyssal equatorial Pacific, an area characterised by polymetallic nodule fields. At the study site within the International Seabed Authority northeastern Area of Particular Environmental Interest (APEI-6), P. nodosum appeared as a compact, regular pattern of small circular openings on the seafloor, each pattern interpreted as reflecting the activity of an individual organism. The patterns had a mean size (maximum dimension) of 45 mm ± 16 mm SD (n = 841) and occurred at a density of 0.33 individuals m−2. Most (82%) were interrupted by nodules, but those that were not displayed both regular (59%) and irregular (41%) forms, the former having equal numbers of rows along the three axes (6 x 6 x 6 and 8 x 8 x 8). In both size and morphology, our Paleodictyon traces were more similar to the Australian examples than to those from the Mid-Atlantic Ridge.

Highlights

Paleodictyon encompasses an important group of graphoglyptid trace fossils, because it is common and found in fossilised sediments globally
Modern Paleodictyon traces resembling these were first photographed on the seabed at the Mid-Atlantic Ridge (MAR) by Rona and Merrill (1978) and have been assigned to the Eocene species Paleodictyon nodosum (Seilacher 1977; Ekdale 1980; Rona et al 2009)
A total of 841 specimens of Paleodictyon nodosum were observed in the photographs, equivalent to 0.33 individuals m−2

Summary

Introduction

Paleodictyon encompasses an important group of graphoglyptid trace fossils, because it is common and found in fossilised sediments globally. Both the fossil and modern forms are known only from deep-sea sediments, including further observations (Fig. 1) at the MAR (Rona et al 2009; ∼3500 m water depth), the South Atlantic (Ekdale 1980; ∼1400 and 4000 m water depth), and on the eastern margin of Australia (Przeslawski et al 2012; 1300-2200 m water depth).

Results

Conclusion