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    GIANTS AMONG MICROMORPHS: WERE CINCINNATIAN (ORDOVICIAN, KATIAN) SMALL SHELLY PHOSPHATIC FAUNAS DWARFED? (2016)
    Society for Sedimentary Geology (SEPM)
    In: PALAIOS
    Details
    Publication Date: 2016-04-02
    Description: Small fossils are preserved as phosphatic (carbonate fluorapatite) micro-steinkerns (~ 0.5 mm diameter) in Upper Ordovician beds of the Cincinnati area. Mollusks are common, along with bryozoan zooecia, echinoderm ossicles, and other taxa. Similar occurrences of Ordovician micromorphic mollusks have been interpreted as ecologically dwarfed and adapted to oxygen-starved conditions, an interpretation with implications for ocean anoxia. An alternative explanation for small phosphatic steinkerns is taphonomic. Stable carbonate fluorapatite selectively filled small voids, thus preserving small fossils, including larval/young mollusks. Reworking concentrated small phosphatic steinkerns from multiple generations while larger, unfilled calcareous shells were destroyed, resulting in small fossils progressively replacing larger fossils. With thin sections and insoluble residues, we document evidence that many of these steinkerns are incomplete ("teilsteinkerns") recording small parts of larger, normal-sized animals, or juveniles, along with smaller species. This finding suggests that these fossil assemblages are taphonomically, not ecologically, size-limited. Based on the ecology of modern oxygen minimum zones in which shelled mollusks are rare, the presence of abundant shelled organisms actually argues against severe oxygen stress. Our results also imply that the process by which the "small shelly fossils" of the Cambrian were preserved continued into the Ordovician.
    Print ISSN: 0883-1351
    Electronic ISSN: 0883-1351
    Topics: Geosciences
    Published by Society for Sedimentary Geology (SEPM)
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  • 2
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    Aerobic microbial respiration in 86-million-year-old deep-sea red clay (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-05-19
    Description: Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O(2) liter(-1) year(-1) near the sediment-water interface to 0.001 micromoles of O(2) liter(-1) year(-1) at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10(-3) femtomoles of O(2) cell(-1) day(-1) 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Roy, Hans -- Kallmeyer, Jens -- Adhikari, Rishi Ram -- Pockalny, Robert -- Jorgensen, Bo Barker -- D'Hondt, Steven -- New York, N.Y. -- Science. 2012 May 18;336(6083):922-5. doi: 10.1126/science.1219424.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Center for Geomicrobiology, Department of Bioscience, Aarhus University, Ny Munkegade 116, 8000 Aarhus C, Denmark. hans.roy@biology.au.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22605778" target="_blank"〉PubMed〈/a〉
    Keywords: Aerobiosis ; Aluminum Silicates ; Bacteria/*metabolism ; Bacterial Load ; Bacterial Physiological Phenomena ; Carbon/analysis/metabolism ; Computer Simulation ; *Ecosystem ; Energy Metabolism ; Geologic Sediments/*chemistry/*microbiology ; Oxidation-Reduction ; Oxygen/*analysis ; *Oxygen Consumption ; Pacific Ocean ; Prokaryotic Cells/*metabolism/physiology ; Seawater/chemistry/microbiology ; Time ; Water Movements
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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