Turnpike Bluff () is a conspicuous rock formation in the Shackleton Mountains of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

Exploration

First mapped in 1957 by the

Commonwealth Trans-Antarctic Expedition The Commonwealth Trans-Antarctic Expedition (CTAE) of 1955–1958 was a Commonwealth-sponsored expedition that successfully completed the first overland crossing of Antarctica, via the South Pole. It was the first expedition to reach the South ...

, and so named because it marks entry to a crevassed area of

Recovery Glacier The Recovery Glacier () is a glacier, at least long and wide at its mouth, flowing west along the southern side of the Shackleton Range in Antarctica. Discovery and name The Recovery Glacier was first seen from the air and examined from the ...

through which the Expedition's vehicles had difficulty in passing on their journey from Shackleton Base to the

South Pole The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish ...

in 1957.

Location

Turnpike Bluff is in the south of the Otter Highlands, to the north of the

. It lies five nautical miles (9 km) southwest of

Mount Homard Mount Homard () is a mountain high, near the head of Blaiklock Glacier, south of the Trey Peaks in the western part of the Shackleton Range, Antarctica. It was first mapped in 1957 by the Commonwealth Trans-Antarctic Expedition The Commonw ...

, at the southwest extremity of the

Shackleton Range The Shackleton Range () is a mountain range in Antarctica that rises to and extends in an east–west direction for about between the Slessor and Recovery Glaciers. Surveys The Commonwealth Trans-Antarctic Expedition (CTAE), which in 1956 s ...

Geology

The Turnpike Bluff Group is a

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

sequence of rocks exposed on the south flank of the Shackleton Range. The sequence includes basal

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks by ...

s and

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

, followed by

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

-bearing clastics with Riphean age

stromatolite Stromatolites ( ) or stromatoliths () are layered Sedimentary rock, sedimentary formation of rocks, formations (microbialite) that are created mainly by Photosynthesis, photosynthetic microorganisms such as cyanobacteria, sulfate-reducing micr ...

colonies, and capped by over 1 km of

greywacke Greywacke or graywacke ( ) is a variety of sandstone generally characterized by its hardness (6–7 on Mohs scale), dark color, and Sorting (sediment), poorly sorted angular grains of quartz, feldspar, and small rock fragments or sand-size Lith ...

and quartzitic

arenite Arenite (from the Latin ''arena'', "sand") is a sedimentary clastic rock with sand grain size between 0.0625 mm (0.00245 in) and 2 mm (0.08 in) and containing less than 15% matrix. The related adjective is ''arenaceous''. The e ...

, alternating with

pelite A pelite () or metapelite is a metamorphism, metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary rock, i.e. mud or ...

. The sequence is underlain

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

by an

Archean The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and t ...

granitoid A granitoid is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental ...

basement A basement is any Storey, floor of a building that is not above the grade plane. Especially in residential buildings, it often is used as a utility space for a building, where such items as the Furnace (house heating), furnace, water heating, ...

(1400 Ma).

Metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

occurred at 526 Ma. The group contains four formations, named after Wyeth Heights, Stephenson Bastion, Flett Crags and

Mount Wegener Read Mountains is a group of rocky summits, the highest being Holmes Summit at , lying east of Glen Glacier in the south-central part of the Shackleton Range. Name The Read Mountains were first mapped in 1957 by the Commonwealth Trans-Antarctic ...

. These are features along the southern margin of the Shackleton Mountains, from west to east.

References

Sources

* * * * {{refend Cliffs of Coats Land