The Great Estuarine Group is a sequence of Middle Jurassic sedimentary rocks deposited in the Inner Hebrides of Scotland.

The sedimentary sequence was originally named the 'Great Estuarine Series' by geologist John Wesley Judd in 1878.

[3] The sediments are equivalent in age to the Inferior and Great Oolite Groups found in southern England.

Above the sandstone is the 'Lealt Shale Formation', a unit in which fossils of creatures which lived in brackish lagoons abound.

The succeeding 'Lonfearn Member' consist of shales and thin shelly and oolitic limestones with conchostracan fossils.