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  • Septarian Nodule


    DPS Ammonite


    Septarian Nodule

    Kingdom: n/a
    Phylum: n/a
    Class: n/a
    Order: n/a
    Family: n/a
    Genus: n/a
    Species: n/a

    Geological Time Scale

    Eon: Phanerozoic
    Era: Mesozoic
    Period: Cretaceous
    Epoch: Late
    International Age: Turonian


    Eagle Ford Group
    Arcadia Park Formation


    Collector: me
    Acquired by: Field Collection


    Thickness: 5 "
    Diameter: 9.5 "


    Collin County
    United States


    Septarian nodules sometimes are misidentified as turtles, coprolites and other fossils. Septarian nodules are hardened mudballs that dehydrate, crack and fill with minerals. The cracks in this one filled with fluorescent calcite. The ribs that stick out are the calcite that filled the cracks in the mudball. 


    This nodule was found in calcareous shale from the Late Cretaceous Arcadia Park Formation. The exact age of its formation is unknown but probably occured in the Late Cretaceous. Septarian nodules from the Arcadia Park Formation are common in north Texas. Some contain spectacular calcite crystals when cracked open. 

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