Ablation Point, also known as Punta Ablación, is the eastern extremity of a hook-shaped rock ridge marking the north side of the entrance to

Ablation Valley Ablation Valley, also known as Ablation Bay, is a mainly ice-free valley on the east coast of Alexander Island, long, which is entered immediately south of Ablation Point, opens on George VI Sound and lies immediately north of Ganymede Heights. I ...

, on the east coast of

Alexander Island Alexander Island, which is also known as Alexander I Island, Alexander I Land, Alexander Land, Alexander I Archipelago, and Zemlja Alexandra I, is the largest island of Antarctica. It lies in the Bellingshausen Sea west of Palmer Land, Antarc ...

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

. It was first photographed from the air on 23 November 1935 by

Lincoln Ellsworth Lincoln Ellsworth (May 12, 1880 – May 26, 1951) was a polar explorer from the United States and a major benefactor of the American Museum of Natural History. Biography Lincoln Ellsworth was born on May 12, 1880, to James Ellsworth and Eva F ...

and mapped from these photographs by W.L.G. Joerg. It was roughly surveyed in 1936 by the British Graham Land Expedition (BGLE) and resurveyed in 1949 by the

Falkland Islands Dependencies Survey The British Antarctic Survey (BAS) is the United Kingdom's national polar research institute. It has a dual purpose, to conduct polar science, enabling better understanding of global issues, and to provide an active presence in the Antarctic o ...

(FIDS). It was named by FIDS for nearby Ablation Valley.Stewart, J., 2011. ''Antarctica: An Encyclopedia,'' 2nd ed. Jefferson, North Carolina and London, McFarland & Company, Inc. 1771 pp. The site lies within Antarctic Specially Protected Area (ASPA) No.147.

Geology

Ablation Point is the namesake and type locality of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Ablation Point Formation. At the type section,

cliff In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on co ...

s on the east facing scarp of Ablation Point, expose a minimum thickness of of the Ablation Point Formation. As elsewhere in the region, the base of it is not exposed. At Ablation Point, this formation is characterized by a wide range of slump- folded and rafted blocks of

sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

and

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

strata that occur chaotic, laterally discontinuous

beds A bed is an item of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many be ...

that are part of the deposits a single, large, deep-sea submarine slump. The blocks consist largely of

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s, interbedded sandstones and mudstones,

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

volcaniclastic Volcaniclastics are geologic materials composed of broken fragments ( clasts) of volcanic rock. These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it ...

sandstones, rare

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...

s and conglomerates. Intercalated with the blocks are sedimentary

mélange In geology, a mélange is a large-scale breccia, a mappable body of rock characterized by a lack of continuous bedding and the inclusion of fragments of rock of all sizes, contained in a fine-grained deformed matrix. The mélange typically cons ...

s consisting of sandstone blocks surrounded by a sheared mudstone matrix. These mélanges occur as layers that are as much as thick and in lateral extent. They contain coherent blocks of interbedded sedimentary and volcanic rocks that are as much as thick and in lateral extent. The Ablation Point Formation exhibits numerous internal unconformities and irregular, erosional contacts. Exposures of this formation are limited to the eastern and central area of the

Ganymede Heights The Ganymede Heights consist of rounded ridges with extensive rock outcrops rising to about , between Jupiter Glacier and Ablation Valley on the eastern side of Alexander Island, Antarctica. They were mapped by the Directorate of Overseas Survey ...

, including of Ablation Point and

Belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

points.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of ammonites,

belemnite Belemnitida (or the belemnite) is an extinct order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous. Unlike squid, belemnites had an internal skeleton that made up the cone. The parts are, from the arms-most ...

s, and bivalves are sparse and poorly preserved within the Ablation Point Formation. Base on these fossils, this formation was originally interpreted as being late Oxfordian-

Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...

(Late

Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

). However, it is now regarded to be Kimmeridgian.Butterworth, P.J., Crame, J.A., Howlett, P.J. and Macdonald, D.I.M., 1988. ''Lithostratigraphy of Upper Jurassic-Lower Cretaceous strata of eastern Alexander Island, Antarctica.'' ''Cretaceous Research'', 9(3), pp.249-264.Butterworth, P.J. 1991. ''The role of eustasy in the development of a regional shallowing event in a tectonically active basin: Fossil Bluff Group (Jurassic-Cretaceous), Alexander Island, Antarctica.'' In: Macdonald, D.I.M., ed., pp. 307-329. ''Sedimentation, Tectonics and Eustasy: sea-level changes at active margins.'' ''Special Publications of the International Association of Sedimentologists'', 12. At Ablation Point, the Ablation Point Formation is conformitably overlain by a few tens of meters of the Himalia Ridge Formation. It consists of conglomerates, immature arkosic sandstones, and mudstones which were deposited in deep sea fans. The strata of Himalia Ridge Formation is only the base of a thick sequence of Late Jurassic to Early Cretaceous sediments deposited in a north–south elongate forearc basin and sourced from a andesitic volcanic arc.Butterworth, P.J. and Macdonald, D.I., 2007. ''Channel-levee Complexes of the Fossil Bluff Group, Alexander Island, Antarctica.'' in Nilsen, H., Shew, R.D., and Steffens, G.S., eds., pp. 36-41. ''Atlas of Deep-Water Outcrops: AAPG Studies in Geology'' 56. Tulsa, Oklahoma, American Association of Petroleum Geologists. 504 pp.

References

Headlands of Alexander Island Antarctic Specially Protected Areas Paleontological sites of Antarctica {{AlexanderIsland-geo-stub

Geology

See also

References