Where is Ammonite Fossil in Shale found?
Ammonoidea fossil in shale
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Open the appAmmonite Fossil in Shale occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Ammonite Fossil in Shale
Jurassic Coast, Dorset and East Devon, UK
World Heritage Site famous for abundant and well-preserved ammonites in shales and limestones, particularly from the Lower Jurassic (Lias Group).
Bearpaw Shale, Western Interior Seaway, North America
Extensive Cretaceous marine shale formation across the Great Plains of the USA and Canada, yielding numerous large and often iridescent ammonites (e.g., Placenticeras, Baculites).
Posidonia Shale, Germany
Lower Jurassic (Toarcian) black shale renowned for exceptional preservation of marine fossils, including ammonites, with soft tissues occasionally preserved.
Madagascar
Known for beautifully preserved, often iridescent ammonites (e.g., Cleoniceras, Douvilleiceras) from Cretaceous deposits, frequently found in a shaly or marly matrix.
Kimmeridge Clay, UK
Upper Jurassic black shale formation, particularly in southern England, rich in ammonites and other marine fossils.
Collecting tips
- Target Marine Sedimentary Rocks. Focus on outcrops of fine-grained marine sedimentary rocks, especially shales, mudstones, and marls, that are known to be of Devonian to Cretaceous age.
- Look for Distinctive Shapes. Search for coiled, spiral, or sometimes straight (heteromorph) shapes that stand out from the surrounding rock matrix. Ribbing or ornamentation on the shell surface can also be a key indicator.
- Examine Weathered Surfaces. Weathering can sometimes highlight fossils by eroding the softer matrix or by differential staining. Look for subtle relief or color changes.
- Check for Pyrite or Calcite Infillings. Ammonites are often preserved as internal molds or replaced by minerals like pyrite (golden metallic luster) or calcite (white to clear crystalline). These can be more visible than the original shell material.
- Safety Precautions. Always obtain permission before collecting. Be aware of unstable cliffs and slippery surfaces. Wear appropriate safety gear, including eye protection and sturdy footwear. Some shales can contain pyrite, which can oxidize to sulfuric acid, so wash hands after handling. Avoid inhaling dust if breaking rocks, as shale contains silica.
Quick Check
- Color:
- Dark gray to black shale with a coiled fossil of varying color (white, brown, golden, iridescent).
- Luster:
- Dull to earthy shale, fossil can be dull, vitreous, metallic, or pearly.
- Streak:
- Shale: White, gray, or brown. Fossil: Varies depending on mineral composition (e.g., white for calcite, black for pyrite).
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