page_title: Geology of Malta
section_title: Blue Clay Formation
hierarchical_section_title: Geology of Malta / The geological strata / Miocene / Blue Clay Formation
caption_attribution_description: English: Cliffs at the northern end of Gnejna Bay on west coast of Malta, formed of the Miocene Blue Clay Formation above yellow-weathering limestones of the Upper Globigerina Limestone Formation. (Radisson Blu Hotel in background)
context_page_description: The Geology of Malta consists of a sequence of sedimentary rocks of late Oligocene to late Miocene age cut through by a set of extensional faults of Pliocene age.
context_section_description: The Blue Clay (Maltese: Tafal) is a blue-gray mudstone of Langhian to Tortonian in age (~15–10 million years old) measuring up to 65 m thick. It shows major thickness variations and is missing completely from most of the eastern parts of the islands. It was deposited in a deepwater environment. It forms an impermeable layer beneath the Greensand and Upper Coralline Limestone formations. It is most visible in the northwest of Malta and the northeast of Gozo. It allows the capture of rainfall and the creation of aquifers. Water is extracted through wells or escapes through occasional springs when the topsoil has been eroded.
caption: Blue Clay Formation exposed in the cliffs at the northern end of Ġnejna Bay overlying yellow-weathering Upper Globigerina Limestone
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