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Sclerosponges: Potential High-Resolution Recorders of Marine Paleotemperatures

By
Gary B. Hughes
Gary B. Hughes
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Charles W. Thayer
Charles W. Thayer
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Published:
January 01, 2001

Abstract

Sclerosponges have great potential as seawater temperature recorders. These animals precipitate their skeletons in carbon and oxygen isotopic equilibrium with the surrounding seawater (Druffel and Benavides, 1986). Their skeletons also display chemical properties that vary directly with changes in environmental conditions. Lack of photosynthetic symbionts allows sclerosponges to live below the photic zone, providing the potential to investigate past marine conditions beyond the range of corals. Individual sponges live for several centuries, preserving archives of pre- and postindustrial seawater variations within single specimens (Hartman and Reiswig, 1980). Crosscorrelation of successively older specimens could yield up to 2000 years of marine history. Extracting environmental information can be accomplished by determining elemental characteristics preserved in skeletal growth bands. A method is presented here that utilizes energy dispersive spectroscopy (EDS) to provide inexpensive assessment of magnesium (Mg): calcium (Ca) and chlorine (Cl): calcium (Ca) ratios at high spatial resolution, yielding environmental data with correspondingly high temporal resolution. The relationship between environmental conditions and skeletal characteristics is defined by a spectral transfer function, which can then be applied to skeletal carbonate data from ancient sponges to reconstruct past environmental conditions. Accurate reconstruction of seawater temperature and salinity variations is demonstrated here at submonthly resolution. The technique’s efficiency is ideal for documenting long, high-resolution records of marine paleoenvironments.

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AAPG Studies in Geology

Geological Perspectives of Global Climate Change

Lee C. Gerhard
Lee C. Gerhard
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William E. Harrison
William E. Harrison
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Bernold M. Hanson
Bernold M. Hanson
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American Association of Petroleum Geologists
Volume
47
ISBN electronic:
9781629810669
Publication date:
January 01, 2001

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