Where is Ammonite Fossil found?
Ammonoidea fossil in sedimentary rock
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Open the appAmmonite Fossil 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
Western Interior Seaway (North America)
Extensive deposits in states like Montana, Wyoming, South Dakota, and Kansas, particularly rich in Cretaceous ammonites within shale and limestone formations.
Jurassic Coast (England)
A UNESCO World Heritage Site in Dorset and East Devon, famous for abundant Jurassic ammonites in shales and limestones.
Madagascar
Known for beautifully preserved and often iridescent (ammolite) ammonites, particularly from the Cretaceous period, found in various sedimentary rocks.
Morocco
Rich in Devonian and Jurassic ammonites, often found in limestone and shale formations, frequently prepared and sold commercially.
Germany
Significant localities for Jurassic and Cretaceous ammonites, such as the Posidonia Shale (Holzmaden) for exceptionally preserved specimens.
Collecting tips
- Target Sedimentary Rocks. Focus on outcrops of marine sedimentary rocks, especially shales, limestones, marls, and fine-grained sandstones of Devonian to Cretaceous age. Look for areas known for fossil occurrences.
- Look for Distinctive Shapes. Search for the characteristic coiled shell shape, even if partially exposed. Weathering can often reveal the outline of the fossil on rock surfaces.
- Examine Weathered Surfaces. Ammonites are often more visible on weathered rock surfaces where the surrounding matrix has eroded away more quickly, or where the fossil's color contrasts with the rock.
- Check for Suture Lines. If a cross-section or partially exposed specimen is found, look for the complex, wavy suture lines on the internal mold, which are diagnostic of ammonites.
- Tools for Collection. Bring a geological hammer, chisels, safety glasses, and sturdy gloves. For delicate specimens, plaster or consolidants may be necessary for field preservation. Always check local regulations regarding fossil collection.
Quick Check
- Color:
- Variable (white, gray, brown, black, iridescent) against a sedimentary rock matrix.
- Luster:
- Dull, vitreous, pearly, or metallic depending on preservation.
- Streak:
- Not applicable to the fossil itself; streak of the infilling mineral (e.g., white for calcite) or the surrounding rock.
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