Unusual shallow water Devonian coral community from Queensland and its recent analogues from the inshore Great Barrier Reef

Mikołaj K Zapalski,James Daniell,Michał Jakubowicz,Andrew H Baird,Tom Bridge

doi:10.1007/s00338-020-02048-9

Abstract

Palaeozoic coral communities were dominated by two extinct coral groups: Tabulata and Rugosa. Whilst they are not closely related to modern Scleractinia, they are morphologically convergent, displaying many morphological characters that allow comparisons between recent and ancient coral reef communities. The extensive shallow-water reef communities of the Devonian were generally dominated by stromatoporoid sponges, with corals occupying deeper environments. Here, we describe an unusual, shallow water coral reef community from the Middle Devonian (Givetian, approx. 385 Ma) of the Fanning River area, Queensland, Australia. The coral community is dominated by tabulate corals, but also includes solitary and occasionally colonial rugose corals. Tabulate corals most commonly exhibit foliose and massive morphologies, but encrusting and branching growth forms also occur. The depositional environment was characterized by a shallow water depth, moderate hydrodynamic energy, high sedimentation rate, and high turbidity. Since these environmental factors influence the morphological composition of modern coral communities, we hypothesize that similar environments may result in morphologically equivalent coral assemblages throughout the Phanerozoic. To test this idea, we qualitatively compare the Fanning River reefs with modern scleractinian coral assemblages in a similar environmental setting at Magnetic Island. Both reefs are located in a shallow water less than 10 m deep, with high sediment flux, moderate wave energy, and generally high turbidity. Like Fanning River, Magnetic Island coral communities are dominated by foliose morphologies, with contributions from massive and branching forms. The Fanning River reef, together with previously identified Silurian and Devonian mesophotic coral ecosystems, suggest that Palaeozoic coral assemblages may share many functional characteristics with modern scleractinian reefs in similar environments. Therefore, the geological record of inshore, high turbidity-adapted coral communities can be traced back as far as 385 Ma.

Highlights

The Silurian and Devonian periods of the Palaeozoic are characterized by extensive reef development (Copper 2002a)
Palaeozoic coral communities were dominated by two extinct coral groups: Tabulata and Rugosa
The Burdekin River Basin (Queensland, Australia, Fig. 1a) is a Devonian-Carboniferous intracratonic extensional basin developed on the eastern tropical shelf of Gondwana (Fig. 1c), accumulating up to 4500 m of sediments (Lang et al 1990)

Summary

Introduction

The Silurian and Devonian periods of the Palaeozoic are characterized by extensive reef development (Copper 2002a). The peak of reef development occurred during the Givetian stage (* 387–382 Ma) of the Middle Devonian (Burchette 1981; Fagerstrom 1994; Kiessling 2008) These spectacular reefs collapsed during the Late Devonian Frasnian-Famennian extinction event (* 372 Ma), after which metazoan-dominated reef communities were replaced by microbial-dominated communities (e.g. Wood 1999; Copper 2002b, 2011; McGhee et al 2012). The collapse of these reefs was possibly a consequence of rising temperatures and associated widespread bleaching of shallow-water corals (Zapalski et al 2017a). Neither are directly related to modern corals, and their evolutionary lineages most probably diverged in the early Palaeozoic (Scrutton 1997; Quattrini et al 2020)

Methods

Results

Conclusion