A Stable Isotope Test for the Origin of Fossil Brown Bodies in Trepostome Bryozoans from the Ordovician of Estonia

Document Type

Book Chapter

Publication Date



Earth Sciences



Publication Title

Bryozoan Studies 2007: Proceedings of the 14th International Bryozoology Association Conference, Boone, North Carolina, July 1-8, 2007


This study provides a novel test of the brown body origin of brown deposits in fossil bryozoans. We use C stable isotopes of inorganic carbonate from separate samples of brown deposits, skeletal walls, matrix, and diagenetic cements from trepostome bryozoans from the Ordovician of Estonia. Our sampling technology improves on the spatial resolution of previous studies to minimize contamination from the various carbonate sources. Samples from brown deposits display lower δ13C values indicating the presence of originally organic material. The granular texture, reddish-brown color, 80 μm diameter size, and circular cross-sectional shape of the deposits as well as their location in the zooecial chambers relative to diaphragms support the isotope results in demonstrating the brown deposits are the diagenetic remnants of original brown bodies.


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