page_title: Adare Basin
section_title: Adare extension
hierarchical_section_title: Adare Basin / Antarctic extension / Adare extension
caption_attribution_description: English: Arial view
context_page_description: The Adare Basin is a geologic structural basin located north-east of Cape Adare of Antarctica, for which its named, and north of the western Ross Sea. The Adare Basin is an extensional rift basin located along a seafloor spreading center that forms the failed arm of the Tertiary spreading ridge separating East and West Antarctica, known as the West Antarctic Rift System and similar in structure to the East Africa Rift System. Centrally located in the Adare Basin is the Adare Trough. The extension of this rift system is recorded in a series of magnetic anomalies which run along the seafloor at the extinct, north-south trending, Adare spreading axis. The Adare spreading system continues unbroken into the Northern Basin underlying the adjacent Ross Sea continental shelf.
context_section_description: Since the Middle Cretaceous Era 100 million years ago, paleomagnetic measurements suggest that there have been between 500 and 1000 km transtentional motions between East and West Antarctica. Offset magnetic lineations can be used to establish spreading history of the Adare Basin specifically. These resolvable marine magnetic anomalies run along the spreading axis of the Adare basin and reveal a rate of extension between the plates. Extension took place for 17 million years during the middle Cenozoic Era, from between 43-26 million years ago. Seafloor spreading in the basin took place at a constant rate in opposite directions, the seafloor spread faster in an eastward direction at a rate of 7.5 mm/year, while it spread to the west at a rate of 5 mm/year. This spreading has accounted for about 170 km of plate separation. The formation of the Adare Trough, an uplift feature, formed as a result of fault reactivation within the first 5 million years after spreading stopped. No significant extension takes place in the Adare Basin after the Adare trough in the Neogene Era from 23-3 million years ago. The set of magnetic lineations defining the Adare Basin continue unbroken under the adjacent continental shelf of north western Ross Sea. These anomaly lineations coincide with the Northern Basin, implying that Northern Basin is floored by oceanic crust that was subsequently infilled by younger sediments to form the morphological continental shelf. In addition, rupture of the continental crust in this region must have occurred at the onset of Adare Basin formation
caption: Geologic map of the Adare Basin off coast of Antarctica. Adare Trough prominent in center of image.
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