Ellsworth Land Volcanic Group
The Ellsworth Land Volcanic Group is a geological formation in the Latady Basin, Ellsworth Land, Antarctic Peninsula, with a calculated maximum depositional age of 183.4 ± 1.4 Ma, and a younger age around 177.5 ± 2.2 Ma, covering the Toarcian stage of the Jurassic Period in the Mesozoic Era. This group is made up of volcanoclastic material, with the Mount Poster Formation, composed of silicic ignimbrites, and the Sweeney Formation, consisting of a mix of basaltic and sedimentary facies.
| Ellsworth Land Volcanic Group | |
|---|---|
| Stratigraphic range: Toarcian ~ | |
| Type | Geological formation |
| Sub-units |
|
| Underlies | Anderson Formation (In part) |
| Thickness | 600–2000 m |
| Lithology | |
| Primary | Silicic ignimbrites |
| Other | Mudstone, Sandstone |
| Location | |
| Coordinates | 74°S 65°E |
| Region | Antarctic Peninsula |
| Country | Antarctica |
| Extent | Ellsworth Land |
| Type section | |
| Named for | Ellsworth Land |
| Named by | Hunter & Cantrill |
Ellsworth Land Volcanic Group (Antarctica) | |
The Mount Poster Formation was the first described in 1985, found on the locality of the same name, with exposures across northwestern areas of the southern Black Coast, Orville Coast, and eastern Ellsworth Land. It was found to be made of pyroclastic rocks along lava flows, all from intracaldera origin, interbedded with few sedimentary rocks. Originally, dating analyses indicated ages 189 ± 3 Ma-188 ± 3 Ma for the lowermost sections (Lower Pliensbachian), and 167 ± 3 Ma (Bathonian) for different locations within the formation, yet was latter constrained to the Toarcian-only, between 183 and 177 Ma. Due to this datations it was allocated in the lowermost section of the Jurassic Latady Basin layers, overlied by what was defined back then as "Latady Formation" (now Latady Group), now proven to be the Sweeney Formation. The Sweeney Fm rocks outcrop on W Potter Peak, Mount Jenkins, Mount Edward, Mount Ballard and Mount Wasilewski. Local vulcanism is know to have continued in the Middle-Late Jurassic, as evidenced in the Latady Group deposition. The Ellsworth Land Volcanic Group belongs to the Patagonia-Antarctic Peninsula sequence, along the Brennecke Formation, form part of the wider first-stage event (V1) of the Chon Aike Province, proving connection with both areas in the Early Jurassic, with the closest unit being the Marifil Formation. The sedimentary layers are correlated with the Cañadón Asfalto Formation along with the Lonco Trapial Formation, Bajo Pobre Formation, Cañadón Huemules Formation and Roca Blanca Formation in Argentina.