The Manx Group is an

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

lithostratigraphic group (a sequence of rock strata) in the

Isle of Man The Isle of Man ( , also ), or Mann ( ), is a self-governing British Crown Dependency in the Irish Sea, between Great Britain and Ireland. As head of state, Charles III holds the title Lord of Mann and is represented by a Lieutenant Govern ...

in the

Irish Sea The Irish Sea is a body of water that separates the islands of Ireland and Great Britain. It is linked to the Celtic Sea in the south by St George's Channel and to the Inner Seas off the West Coast of Scotland in the north by the North Ch ...

. The name is derived from the name of the island which is largely formed from them; these rocks have also previously been referred to as the Manx Slates or Manx Slates Series. The group comprises dark mudstones with siltstone laminae and some

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and which exceed a thickness of 3000m. It is divided into a lowermost Glen Dhoo Formation which is overlain by (though the entire known boundary is faulted) the Lonan, Mull Hill, Creg Agneash and Maughold formations in ascending order. A fault separates these from the overlying Barrule, Injebreck, Glen Rushen and Creggan Mooar formations which are in turn separated by a fault from an overlying Ladyport Formation. In stratigraphic order (youngest at top) the formations are: *Ladyport—faulted boundary-- *Creggan Mooar *Glen Rushen *Injebreck *Barrule—faulted boundary-- *Maughold *Creg Agneash *Mull Hill *Lonan **Ny Garvain member **Santon member **Keristal member—faulted boundary-- *Glen Dhoo

References

* {{Refend Geological groups of the United Kingdom Ordovician System of Europe Geology of the Isle of Man Mudstone groups Siltstone groups Sandstone groups