Natuurhistorisch Museum Maastricht

Aken sands
In the earliest coastal swamps, clay layers with plant remains were deposited. Where the sea swept away dunes, sand was distributed over vast areas. Uprooted trees drifted on the waves and were subsequently covered by sand, which explains why they survived as silicified fossils.

Vaals greensands
Gradually almost all of southern Limburg became flooded by a shallow sea. The green colour of deposits of this age is caused by the mineral glauconite. In the Vaals Greensands the oldest remains of mosasaurs have been found, in addition to beautifully preserved shells, snails , squid-like molluscs and echinoderms.

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Gulpen chalks
Changes in ocean currents caused the character of the Cretaceous sea to change too. In the originally cold waters squid-like molluscs in particular flourished. Eventually a shallow, clear, subtropical sea with sea lilies and dozens of sea-urchin species came into being.

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Kunrade chalks
In the north-east of southern Limburg the proximity of the coast was very apparent. In the Kunrade Chalks many land-based erosional products occur: sand, clay and even small pieces of coal. The occurrence of brittle starfish indicates this must have been a turbulent environment in a mud-dominated, shallow-water setting.

Maastricht chalks
These deposits formed in the quieter south-westerly part of the Cretaceous sea. Crinoids and serpulid worms, in particular, indicate these deposits must have formed in slightly deeper and less muddy water. The Cretaceous sea was also inhabited by: seagrasses, foraminifers, sponges, corals, molluscs, brachiopods, bryozoans, echinoderms, crabs and lobsters, seaturtles and fishes inhabited the Cretaceous sea. Mosasaurs were the largest carnivores and the terror of the oceans.

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