Geologic map of Seymour Island, Antarctica

Seymour Island or Marambio Island, is an island in the chain of 16 major islands around the tip of the

Graham Land Graham Land is the portion of the Antarctic Peninsula that lies north of a line joining Cape Jeremy and Cape Agassiz. This description of Graham Land is consistent with the 1964 agreement between the British Antarctic Place-names Committee a ...

on the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

. Graham Land is the closest part of Antarctica to South America. It lies within the section of the island chain that resides off the west side of the peninsula's northernmost tip. Within that section, it is separated from

Snow Hill Island Snow Hill Island is an almost completely snowcapped island, long and wide, lying off the east coast of the Antarctic Peninsula. It is separated from James Ross Island to the north-east by Admiralty Sound and from Seymour Island to the north b ...

Picnic Passage Picnic Passage () is a marine channel, 1.5 nautical miles (2.8 km) long and 0.5 nautical miles (0.9 km) wide, between Snow Hill Island and Seymour Island in the James Ross Island group. First surveyed in 1902 by Swedish Antarctic Expediti ...

, and sits just east of the larger key,

James Ross Island James Ross Island is a large island off the southeast side and near the northeastern extremity of the Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to , it is irregularly shaped and extends in a north–south ...

, and its smaller, neighboring island,

Vega Island Vega Island is a small island to the northwest of James Ross Island, on the Antarctic Peninsula. It is separated from James Ross Island by Herbert Sound. The island was named by Otto Nordenskjold, leader of the Swedish Antarctic Expedition (190 ...

. Seymour Island is sometimes called Marambio Island or Seymour-Marambio Island, taking its resident Argentine base as its namesake (see section, Base Antárctica Marambio, below).

Historic site

A wooden plaque and rock cairn stand at Penguins Bay, on the southern coast of Seymour Island. The plaque was placed on 10 November 1903 by the crew of the Argentinian Corvette ''Uruguay'' on a mission to rescue the members of the Swedish expedition led by

Otto Nordenskiöld Otto is a masculine German given name and a surname. It originates as an Old High German short form (variants ''Audo'', '' Odo'', '' Udo'') of Germanic names beginning in ''aud-'', an element meaning "wealth, prosperity". The name is recorde ...

. The inscription on the plaque, placed where the two parties met, reads:

“10.XI.1903 ''Uruguay'' (Argentine Navy) in its journey to give assistance to the Swedish Antarctic expedition”.

The cairn was erected in January 1990 by Argentina at the site of the plaque in commemoration of the same event. The site has been designated a Historic Site or Monument (HSM 60), following a proposal by Argentina to the

Antarctic Treaty Consultative Meeting russian: link=no, Договор об Антарктике es, link=no, Tratado Antártico , name = Antarctic Treaty System , image = Flag of the Antarctic Treaty.svgborder , image_width = 180px , caption ...

Base Antárctica Marambio

Located in the island is the Marambio Base which is the main

Argentine Argentines (mistakenly translated Argentineans in the past; in Spanish ( masculine) or ( feminine)) are people identified with the country of Argentina. This connection may be residential, legal, historical or cultural. For most Argentines ...

base in

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 co ...

operating an airfield (

ICAO The International Civil Aviation Organization (ICAO, ) is a specialized agency of the United Nations that coordinates the principles and techniques of international air navigation, and fosters the planning and development of international ...

SAWB) for wheeled landing the whole year. In winter the base has an average of 55 crew members, but in summer the population of the base can grow to 180.

Climate

The average temperatures on Seymour Island, as measured at Base Antárctica Marambio, are during the summer and during the winter. In the wintertime, however, strong winds can lower the wind chill temperature feeling to as low as on exposed skin. On 9 February 2020, a temperature of was recorded on the island. However, on 1 July 2021, the World Meteorological Organization invalidated the reading because based on the analysis of the data, the air temperature was recorded in non-standard conditions, leading to bias and errors in the temperature sensor and readings.

Paleontological significance

The rocks making up Seymour Island date mainly from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

to the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

. Successively younger rock

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

s found on the island are the López de Bertodano Formation (Cretaceous to early

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

) Sobral Formation and Cross Valley Formation (Paleocene) and La Meseta Formation (Eocene). Seymour Island has been referred to as the

Rosetta Stone The Rosetta Stone is a stele composed of granodiorite inscribed with three versions of a decree issued in Memphis, Egypt, in 196 BC during the Ptolemaic dynasty on behalf of King Ptolemy V Epiphanes. The top and middle texts are in Ancient ...

of Antarctic palaeontology, due to the unparalleled insight it provides into the geological and palaeontological history of the continent. In December 1892 when Norwegian Captain, Carl Anton Larsen landed his ship, the ''Jason'', on Seymour Island, he returned with more than maps of the territory, he found

fossils 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 ...

of long- extinct species. Larsen's trip aboard the ''Jason'' was significantly more successful than his

Swedish Antarctic Expedition The Swedish Antarctic Expedition of 1901–1903 was a scientific expedition led by Otto Nordenskjöld and Carl Anton Larsen. It was the first Swedish endeavour to Antarctica in the Heroic Age of Antarctic Exploration. Background Otto Nord ...

journey between 1901 and 1904. During that trip, his ship, the ''Antarctic'', was crushed and sunk by

icebergs An iceberg is a piece of freshwater ice more than 15 m long that has broken off a glacier or an ice shelf and is floating freely in open (salt) water. Smaller chunks of floating glacially-derived ice are called "growlers" or "bergy bits". The ...

, and he and his crew were forced to weather fourteen months on the neighboring

, surviving on penguins and seals. Ever since his voyage on the ''Jason'', the island has been the subject of paleontological study. The Cretaceous-Paleogene boundary (K-Pg) outcrops on Seymour Island in the upper levels of the López de Bertodano Formation. A small (but significant) iridium anomaly occurs at the boundary on Seymour Island, as at lower latitudes, thought to be fallout from the

Chicxulub impactor The Chicxulub crater () is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore near the community of Chicxulub, after which it is named. It was formed slightly over 66 million years ago when a large a ...

in the Gulf of Mexico. Directly above the boundary a layer of disarticulated fish fossils occurs, victims of a disturbed ecosystem immediately following the impact event. Multiple reports have described evidence for climatic changes in Antarctica prior to the mass extinction, but the extent to which these affected marine biodiversity is debated. Based on extensive marine

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 ...

collections from Seymour Island, recent work has confirmed that a single and severe

mass extinction An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. I ...

event occurred at this time in Antarctica just as at lower latitudes. Seymour Island has also been the site of much study of the

period of climatic cooling, a process that culminated in the initiation of Antarctic

glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate bet ...

. Studies of the fine fraction carbonate from sites in the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smal ...

suggest that, rather than a

monotonic In mathematics, a monotonic function (or monotone function) is a function between ordered sets that preserves or reverses the given order. This concept first arose in calculus, and was later generalized to the more abstract setting of ord ...

decrease in temperature over the Eocene period, the middle of the epoch was punctuated by a brief duration of warming (Bohaty and Zachos, 2003). Seymour Island has been a site of study of many fossils from this particular part of the Eocene period, during which there was a more flourishing

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

with diverse

biota Biota may refer to: * Biota (ecology), the plant and animal life of a region * Biota (plant), common name for a coniferous tree, ''Platycladus orientalis'' * Biota, Cinco Villas, a municipality in Aragon, Spain * Biota (band), a band from Color ...

as a result of the warmer climate. A diverse array of

fossilize 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 i ...

d species has been studied on the island, including extinct

penguin Penguins ( order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adapt ...

species (such as '' Palaeeudyptes klekowskii'' and ''

Archaeospheniscus wimani ''Archaeospheniscus wimani'' is an extinct species of penguin. It was the smallest species of the genus ''Archaeospheniscus'', being approximately high, or about the size of a gentoo penguin. It is also the oldest known species of its genus, as ...

''), various species in the

bivalvia Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

class and various types of

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

and

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''biota''. Zoo ...

, including a frog. A fossil

marsupial Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...

of the extinct family Polydolopidae was found on Seymour Island in 1982. This was the first evidence of land mammals having lived in Antarctica. Further fossils have subsequently been found, including members of the marsupial orders Didelphimorphia (opossum) and Microbiotheria, as well as

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraff ...

s and a member of the enigmatic extinct order

Gondwanatheria Gondwanatheria is an extinct group of mammaliaforms that lived in parts of Gondwana, including Madagascar, India, South America, Africa and Antarctica during the Upper Cretaceous through the Paleogene (and possibly much earlier, if '' Allostaff ...

, possibly ''

Sudamerica ameghinoi ''Sudamerica'', literally "South America" in Spanish language, Spanish, is a genus of mammal from the extinct suborder Gondwanatheria that lived in Patagonia, Argentina (Salamanca Formation) and Antarctica (La Meseta Formation) from the Paleocen ...

''.Mills, William James. ''Exploring Polar Frontiers: A Historical Encyclopedia'', ABC-CLIO, 2003. ,

IUGS geological heritage site

In respect of the site being the 'most representative high latitude K-Pg boundary location and one of the most significant and best exposed globally' the 'Cretaceous-Paleogene Transition at Seymour (Marambio) Island' was included by the International Union of Geological Sciences (IUGS) in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an 'IUGS Geological Heritage Site' as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'

Features

* Bertodano Bay *

Cross Valley Seymour Island or Marambio Island, is an island in the chain of 16 major islands around the tip of the Graham Land on the Antarctic Peninsula. Graham Land is the closest part of Antarctica to South America. It lies within the section of the isla ...

Fossil Bight Seymour Island or Marambio Island, is an island in the chain of 16 major islands around the tip of the Graham Land on the Antarctic Peninsula. Graham Land is the closest part of Antarctica to South America. It lies within the section of the isla ...

* Larga Valley *

Penguin Bight Penguin Bight () is a bight on the southeast coast of Seymour Island Seymour Island or Marambio Island, is an island in the chain of 16 major islands around the tip of the Graham Land on the Antarctic Peninsula. Graham Land is the closest part o ...

References

{{Authority control Islands of the James Ross Island group Argentine Antarctica British Antarctic Territory Chilean Antarctic Territory Cenozoic Antarctica First 100 IUGS Geological Heritage Sites Historic Sites and Monuments of Antarctica Paleontological sites of Antarctica