Santa Marta Formation | |
---|---|
Stratigraphic range: Santonian-Campanian | |
Type | Geological formation |
Unit of | Marambio Group |
Sub-units | Alpha Member, Beta Member |
Underlies | Snow Hill Island Formation |
Overlies | Hidden Lake Formation |
Thickness | 1,000 m (3,300 ft) |
Lithology | |
Primary | Mudstone, sandstone |
Other | Siltstone, tuff |
Location | |
Coordinates | 63°00′S57°00′W / 63.0°S 57.0°W Coordinates: 63°00′S57°00′W / 63.0°S 57.0°W |
Approximate paleocoordinates | 60°54′S67°36′W / 60.9°S 67.6°W |
Region | James Ross Island |
Country | Antarctica |
The Santa Marta Formation is a geologic formation in Antarctica. It, along with the Hanson Formation and the Snow Hill Island Formation, are the only formations yet known on the continent where dinosaur fossils have been found. The formation outcrops on James Ross Island off the coast of the northern tip of the Antarctic Peninsula. In its entirety, the Santa Marta Formation is on average one kilometer thick.
The Santa Marta Formation was deposited during the Santonian and Campanian ages of the Late Cretaceous. It overlies the Gustav Group laid down during the Barremian and Santonian ages and is succeeded by the Snow Hill Island Formation of late Campanian age. Together, the Santa Marta Formation, Snow Hill Island Formation, the overlying López de Bertodano Formation (deposited from the late Campanian age of the Late Cretaceous to the early Paleocene epoch of the early Paleogene), and the Sobral Formation (deposited during the early Paleocene) form the Marambio Group. [1]
Originally, the formation was subdivided into three informal members termed the Alpha, Beta, and Gamma members. The names were later changed to the Lachman Crags, Herbert Sound, and Rabot members. [2] The Lachman Crags and Herbert Sound members, named after the areas in which they outcrop, are found in the northern part of James Ross Island. Both members are late Campanian in age. The Lachman Crags Member, the older of the two, is around 500 meters thick. The lower section of the member consists of tuffaceous mudstone while the upper section consists of tuffaceous turbidites formed by underwater avalanches. Bioturbation is evident in tuff beds throughout the member due to the disruption of sediments by benthic life during the time of deposition. The Herbert Sound member is also around 500 meters thick and also can be divided into two distinct sections. Channeled debris flows interbedded with turbides make up the lower portion of the member and are overlain by fine sandstones (followed by coarser sandstones and coquinas) that make up the upper portion of the member. [3]
The depositional environment is thought to have been a system of abyssal fans radiating out from a large river delta. The rapid aggradation of sediments from the delta produced a steep delta slope, [3] which may have resulted in occasional debris flows that formed the turbides. A high degree of tectonic activity in the region at the time may explain the intermittent tuff beds throughout the formation.
The Rabot Member of the Santa Marta Formation is confined to the southeastern part of James Ross Island and dates back to the early to late Campanian. Outcroppings of the member are separated from those of other members in the northern part of the island. Originally the member was regarded as its own formation, and now it is considered to be the lateral equivalent of both the Lachman Crags and Herbert Sound members. [4] Like the Lachman Crags and Herbert Sound members, the Rabot member consists of mudstones and beds of tuff that are often highly bioturbated, and also consists of rare conglomerates. Recently a fourth member has been assigned to the formation called the Hamilton Point Member. The beds of this member used to be considered part of the upper portion of the Rabot member, but now are considered to be their own distinct member. [1]
A wide variety of microorganisms inhabited the coastal waters at the time of the deposition of the Santa Marta Formation. Microfossils include ostracods [5] and dinoflagellates. [4]
Invertebrates were also common. Fossils of ammonites can be found in the formation, often embedded vertically in the bedding plane. Originally it was thought that dead ammonites could only be oriented this way in sediment if they were in shallow waters below a certain pressure, but there is evidence to support that due to specific conditions during burial, it was possible for these ammonites to be vertically oriented at greater depths. [6] Ammonite genera present in the formation include Anagaudryceras , Anapachydiscus , Eupachydiscus , Gaudryceras , Maorites , Natalites , Parasolenoceras , Yezoites , and the heteromorph ammonites Ainoceras , Eubostrychoceras , Ryugasella and Baculites . Many bivalve fossils have been found such as Cucullaea , Panopea , Pinna , and Pterotrigonia . Polychaete annelid worms such as Rotularia and gastropods such as the cerithiid sea snail Cerithium have also been discovered in beds within the formation.
Numerous ichnofossils provide evidence of benthic activity, along with previously mentioned bioturbated sediments. Vertical spreite trace fossils have been found as part of fodinichnia dominated ichnocoenosis and were assigned to ichnogenre such as Paradictyodora . [3] Trackways thought to belong to decapods have also been found. [7]
Fish were present, including one of the first frilled sharks, Chlamydoselachus thomsoni . [8] Other marine vertebrates included the small mosasaur Taniwhasaurus antarcticus , previously known as Lakumasaurus antarcticus . [9] The close relation of T. antarcticus to other species of Taniwhasaurus found in New Zealand and Patagonia provides evidence for a Gondwanan endemism. [10]
Antarctopelta oliveroi , an ankylosaur, was discovered in 1986 on the northern part of James Ross Island about 2 kilometers south of Santa Marta Cove in beds that were part of the Santa Marta Formation. [11] It was the first dinosaur found in Antarctica. It may be a possible nodosaur but there has been no formal phylogenic analysis to prove its relationship with other ankylosaurs. Although the formation is made up of only marine deposits, the bodies of these animals along with other debris may have frequently been washed out to sea to later sink to the bottom and be buried by sediment.
Leaves and fragments of plants are commonly found as fossils throughout the formation as well as large tree trunks in the lower members. This is evidence of the forested environment that covered Antarctica during the Late Cretaceous due to the overall warmer global temperature and milder climate. At that time the river delta had much vegetation, and was able to support large herbivores such as Antarctopelta .
The Chalk Group is the lithostratigraphic unit which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur across the wider northwest European chalk 'province'. It is characterised by thick deposits of chalk, a soft porous white limestone, deposited in a marine environment.
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 1,630 metres (5,350 ft), it is irregularly shaped and extends 64 km in a north–south direction. It was charted in October 1903 by the Swedish Antarctic Expedition under Otto Nordenskiöld, who named it for Sir James Clark Ross, the leader of a British expedition to this area in 1842 that discovered and roughly charted a number of points along the eastern side of the island. The style, "James" Ross Island is used to avoid confusion with the more widely known Ross Island in McMurdo Sound.
The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian spans the time from 83.6 to 72.1 million years ago. It is preceded by the Santonian and it is followed by the Maastrichtian.
The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period. It overlies the older Lohan Cura Formation and is itself overlain by the younger Allen Formation of the Malargüe Group, separated from both by unconformities, dated to 98 and 79 Ma respectively.
Antarctopelta was a genus of ankylosaurian dinosaur with one known species, A. oliveroi, which lived in Antarctica during the Late Cretaceous Period. It was a medium-sized ankylosaur, reaching 4 meters in length or more, and showed characteristics of two different families, making more precise classification difficult. The single known fossil specimen was discovered on James Ross Island in 1986, constituting the first dinosaur remains ever discovered on Antarctica, although it is the second dinosaur from the continent to be formally named behind Cryolophosaurus.
The Fruitland Formation is a geologic formation found in the San Juan Basin in the states of New Mexico and Colorado, in the United States of America. It contains fossils dating it to the Campanian age of the late Cretaceous.
The Bearpaw Formation, also called the Bearpaw Shale, is a geologic formation of Late Cretaceous (Campanian) age. It outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear Paw Mountains in Montana. It includes a wide range of marine fossils, as well as the remains of a few dinosaurs. It is known for its fossil ammonites, some of which are mined in Alberta to produce the organic gemstone ammolite.
Taniwhasaurus is an extinct genus of mosasaurs who lived during the Late Cretaceous in what is now New Zealand and Antarctica, possibly even in other continents. The genus belongs to the subfamily Tylosaurinae, a lineage of mosasaurs characterized by a long toothless conical rostrum.
Polyptychoceras is an extinct genus of ammonites from the Late Cretaceous of Asia, Europe, and North and South America. It was first named by Hisakatsu Yabe in 1927.
The Milk River Formation is a sandstone-dominated stratigraphic unit of the Western Canada Sedimentary Basin in southern Alberta, Canada. It was deposited in near-shore to coastal environments during Late Cretaceous time. Based on uranium-lead dating, palynology and stratigraphic relationships, deposition occurred between ~84.1 and 83.6 Ma.
The Gosau Group is a geological stratigraphic group in Austria, Germany and western Slovakia whose strata date back to the Late Cretaceous to Eocene. It is exposed in numerous sporadic isolated basins within the Northern Calcareous Alps. It is divided into two subgroups, the Lower Gosau Subgroup which dates from the Turonian to Campanian, approximately 90 to 75 Ma and the Upper Gosau Subgroup which dates to the Santonian to Eocene, about 83.5 to 50 Ma. The formations within each subunit vary significantly between basins. The sequence is largely marine, but the Grünbach Formation represents a terrestrial deposit. Many of the units of the group are fossiliferous, typically providing marine fossils such as ammonites, though terrestrial remains including those of dinosaurs are known from the Grünbach Formation and Schönleiten Formation.
The Yezo Group is a stratigraphic group in Hokkaido, Japan and Sakhalin, Russia which is primarily Late Cretaceous in age. It is exposed as roughly north–south trending belt extending 1,500 kilometres through central Hokkaido from Urakawa to Cape Sōya and Sakhalin from the south coast to Alexandrovsk-Sakhalinsky District. It consists of marine forearc basin sediments, typically turbiditic and bioturbated mudstones and sandstones with subordinate conglomerate primarily deposited on the continental shelf and slope of the ancient Yezo subduction margin. It forms a continuous depositional sequence with the Sorachi Group, which overlies the Horokanai Ophiolite. The sequence gradually shallows upwards with the terminal Hakobuchi Formation representing a fluvial-inner shelf environment.
The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.
The Menefee Formation is a lower Campanian geologic formation found in Colorado and New Mexico, United States.
The Snow Hill Island Formation is an Early Maastrichtian geologic formation found on James Ross Island, James Ross Island group, Antarctica. Remains of a paravian theropod Imperobator antarcticus have been recovered from it, as well as the elasmarian ornithopods Trinisaura santamartaensis, Biscoveosaurus and Morrosaurus antarcticus, the ankylosaurian Antarctopelta oliveroi, and the shark Notidanodon sp. Alongside these described genera are also the remains of indeterminate elasmosaurids, lithostrotian titanosaurs and an indeterminate pterosaur.
Agathoxylon is a form genus of fossil wood, including massive tree trunks. Although identified from the late Palaeozoic to the end of the Mesozoic, Agathoxylon is common from the Carboniferous to Triassic. Agathoxylon represents the wood of multiple conifer groups, including both Araucariaceae and Cheirolepidiaceae.
Kaikaifilu is a genus of mosasaur from the Late Cretaceous part of the Lopez de Bertodano Formation of Antarctica, just before the Cretaceous–Paleogene extinction event. It is thought to be among the largest members of the tylosaurines, a group of marine lizards that lived during the Cretaceous, and the largest Antarctic mosasaur. However, some researchers disagree with this classification.
Condonella is an extinct genus of land snail in the family Urocoptidae known from the fossil species Condonella suciensis of Western North America.
The Köpinge Sandstone is a highly calcareous and glauconitic sandstone geologic formation of the Vomb Trough in Skåne, southernmost Sweden. The formation dates to the latest early to middle late Campanian stage of the Late Cretaceous and has provided fossils of ammonites, belemnites, the shark Cretalamna borealis and the mosasaurid Hainosaurus. Ex situ occurrences in Pleistocene deposits have provided a dorsal vertebra of a possible elasmosaurid.