Robin Hood's Bay, Yorkshire

Geological time

Triassic Jurassic

Age: 195–180 million years ago
Period: Lower Jurassic (Pliensbachian-Toarcian)
Formation: Cleveland Basin (Whitby Mudstone Formation and Staithes Sandstone Formation)
Depositional environment: Shallow epicontinental sea with alternating offshore mud deposition and nearshore sandy environments
Fossil types: Ammonites, belemnites, bivalves, marine reptiles, crustaceans, trace fossils, driftwood, and occasional plant debris
Paleoecology highlights: A dynamic shallow sea influenced by fluctuating sea levels, with quiet muddy seabeds interrupted by storm-driven sand influxes, oxygen-poor intervals in deeper settings, and periodic input of terrestrial material from nearby landmasses

Picture a broad, shallow sea stretching across what is now northern England, its grey-blue waters gently rippling under a hazy Jurassic sky. The seafloor is a mosaic of soft, dark mud and rippled sand, shaped by shifting currents and occasional storms.

Closer to the ancient shoreline, the water grows slightly shallower and more energetic. Here, sandy bars and patches of firmer ground interrupt the muddy expanse, while fragments of driftwood and plant debris occasionally settle from distant river systems draining nearby land.

The landscape is ever-changing, shaped by cycles of rising and falling sea levels, storms periodically disturbing the seabed, and periods of calm.