Trace Fossil (Burrow)
Thalassinoides isp. • Trace fossil (Ichnofossil); Invertebrate bioturbation structure
Geological Period
Likely Cretaceous to Neogene (common in various periods, but matrix suggests Mesozoic/Cenozoic chalk or limestone)
Estimated Age
Approx. 5 to 145 million years
Preservation Type
Infill cast; the burrow was filled with sediment of a different composition or grain size than the host rock, which later lithified.
Condition Assessment
Fair; the specimen is an incomplete section of a larger burrow network. The matrix is weathered but the structural contrast is clear.
Taxonomic Classification
Ichnogenus: Thalassinoides or Ophiomorpha (Phylum: Arthropoda, Class: Malacostraca, Order: Decapoda, likely produced by Ghost Shrimps or similar crustaceans)
Morphological Description
A cylindrical, partially exposed, slightly curved burrow infill. It exhibits a smooth to slightly granular texture with a distinct color contrast from the surrounding host rock. Lacks the pelleted exterior characteristic of Ophiomorpha, pointing toward Thalassinoides.
Rock Matrix
Finely grained biogenic limestone or chalk, likely containing microscopic calcite and quartz silt; surface shows weathered white patination.
Formation & Location
Likely a marine formation such as the Chalk Group (UK/Europe) or similar calcarenite/marly deposits in coastal regions worldwide.
Size & Dimensions
Approximately 10-15 cm in length for the total matrix block; the burrow section is roughly 1.5-2 cm in diameter, consistent with decapod burrowers.
Value & Rarity
Estimated Market Value
$10.00 - $25.00 USD
Auction Estimate
$20.00 - $40.00 USD (typically sold in bulk lots for educational use)
Rarity Assessment
Common; burrow traces are among the most abundant fossils in marine sedimentary sequences.
Scientific Significance
Provides evidence of paleo-environmental conditions, specifically oxygen-rich marine substrates and the activity of infaunal organisms (bioturbation). Used as an indicator of shallow marine facies.
Preparation Recommendations
No extensive preparation needed. Clean with a soft dry brush. Acids should be avoided as they will dissolve the calcitic matrix. Store in a dry environment.
Notable Features
Features a distinct color differential between the infill and the host rock, highlighting the three-dimensional nature of ancient animal tunnels.