The Causey Pike Fault or Causey Pike Thrust is a major WSW-ENE trending fault within the Lower Paleozoic rocks of the English

Lake District The Lake District, also known as ''the Lakes'' or ''Lakeland'', is a mountainous region and National parks of the United Kingdom, national park in Cumbria, North West England. It is famous for its landscape, including its lakes, coast, and mou ...

. It is named for

Causey Pike Causey Pike is a fell in the English Lake District. It is situated in the Newlands Valley, south-west of the town of Keswick. Even though it has a modest height of it is one of the most distinctive fells when viewed from the Derwent Water a ...

, where the fault was first recognised.

Extent

The Causey Pike Fault has been recognised across the entire outcrop of the Lake District

inlier An inlier is an area of older rocks surrounded by younger rocks. Inliers are typically formed by the erosion of overlying younger rocks to reveal a limited exposure of the older underlying rocks. Faulting or folding may also contribute to the o ...

, extending about 35 km from near Ennerdale Bridge in the west, to near Troutbeck in the east. A possible continuation of the fault to the east has been recognised in the

Cross Fell Cross Fell is the highest mountain in the Pennines of Northern England and the highest point in England outside the Lake District. It is located in the North Pennines Area of Outstanding Natural Beauty. It lies within the county of Cumbria and ...

inlier, where it also juxtaposes two differing parts of the

Skiddaw Group The Skiddaw Group is a group (stratigraphy), group of sedimentary rock formations named after the mountain Skiddaw in the England, English Lake District. The rocks are almost wholly Ordovician in age (Tremadocian, Tremadoc through Arenig to Ord ...

Recognition

It juxtaposes two successions dominated by

mudrock Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

s that are of similar age. To the north of the fault, the

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 ...

Skiddaw Group is represented by the Kirk Stile Formation, to the south by the Buttermere Formation, both of

Arenig In geology, the Arenig (or Arenigian) is a time interval during the Ordovician period and also the suite of rocks which were deposited during this interval. History The term was first used by Adam Sedgwick in 1847 with reference to the "Areni ...

age. The younger sequence of volcanic rocks overlying the Skiddaw Group also differs, with the Eycott Volcanic Group to the north and the

Borrowdale Volcanic Group The Borrowdale Volcanic Group is a group of igneous rock formations named after the Borrowdale area of the Lake District, in England. They are Caradocian (late Ordovician) in age (roughly 450 million years old). It is thought that they represen ...

to the south. The fault is described as a

thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...

near Causey Pike, where metasomatised rocks of the

Crummock Water Crummock Water is a lake in the Lake District in North West England. It is long, wide, deep, and has an area of . The lake's primary inflow is Buttermere Dubs, itself the outflow of Buttermere, and its outflow is the River Cocker, which mee ...

Aureole An aureola or aureole (diminutive of Latin ''aurea'', "golden") is the radiance of luminous cloud which, in paintings of sacred personages, surrounds the whole figure. In Romance languages, the noun Aureola is usually more related to the d ...

are emplaced over

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 ...

olistoliths of the Buttermere Formation, but the overall displacement on this structure is oblique, with a significant component of sinistral (left lateral)

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

motion.

Age of movement

The differences in stratigraphy and interpreted

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will b ...

across the fault may indicate that the fault was originally a normal fault, active during deposition of the Skiddaw Group. The oblique slip movement on the fault occurred during the

Acadian Orogeny The Acadian orogeny is a long-lasting mountain building event which began in the Middle Devonian, reaching a climax in the Late Devonian. It was active for approximately 50 million years, beginning roughly around 375 million years ago (Ma), wi ...

, at least in part postdating the

contact metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of c ...

that caused the development of the Crummock Water Aureole (dated to about 401 Ma -

Emsian The Emsian is one of three faunal stages in the Early Devonian Epoch. It lasted from 410.62 ±1.95 million years ago to 393.47 ±0.99 million years ago. It was preceded by the Pragian Stage and followed by the Eifelian Stage. It is named after ...

), which itself postdates the formation of the regional

cleavage Cleavage may refer to: Science * Cleavage (crystal), the way in which a crystal or mineral tends to split * Cleavage (embryo), the division of cells in an early embryo * Cleavage (geology), foliation of rock perpendicular to stress, a result of ...

seen within the Skiddaw Group.

References

{{Reflist Geology of Cumbria