Chalk (Phosphatic)
“Enriched by ancient ocean upwelling”
Phosphatic chalk is a variety of chalk enriched in phosphate minerals, typically forming where nutrient-rich ocean upwelling zones intersected chalk-producing seas. The phosphate content gives the rock a brownish tinge and makes it a valuable record of ancient ocean productivity and nutrient cycling.
calcite (coccolith plates), francolite (carbonate-fluorapatite), glauconite, clay minerals, fish debris
Ciply (Belgium), Taplow (England), Cambridge (England), Negev (Israel), North Africa
2-3
Phosphatic chalk deposits often contain abundant shark teeth and fish bones — the same nutrient-rich conditions that concentrated phosphate also supported dense marine food chains.
Test Your Knowledge
Why do phosphatic chalk deposits typically contain abundant shark teeth and fish bones?
Related Specimens
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