this important discovery "was tainted by connections to a widely discredited hypothesis and speculations that did not make it through peer review". A 2022 study using Argon–Argon dating of shocked zircon crystals in impact melt rocks found outwash less than 10 km downstream of the glacier pushed the estimate back to around 57.99 ± 0.54 million years ago, during the late Paleocene. Confirmation would require drilling almost through the ice sheet above the crater to obtain a sample of dateable, solidified impact melt from the crater. The age of the Bloody Creek crater is uncertain. As the trend in the Earth Impact Database for about 26 confirmed craters younger than a million years old shows that almost all are less than in diameter (except the Agoudal and Rio Cuarto), the suggestion that two large craters, Mahuika () and Burckle (), formed only within the last few millennia has been met with skepticism. However, the source of the young (less than a million years old) and enormous Australasian strewnfield (c. 790 ka) is suggested to be a crater about across somewhere in Indochina, with Hartung and Koeberl (1994) proposing the elongated Tonlé Sap lake in Cambodia (visible in the map at the side) as a suspect structure. The Decorah crater has been conjectured as being part of the Ordovician meteor event. Several twin impacts have been proposed, such as the Rubielos de la Cérida and Azuara (30–40 Ma), Cerro Jarau and Piratininga (c. 117 Ma), and Warburton East and West (300–360 Ma). However, adjacent craters may not necessarily have formed at the same time, as demonstrated by the case of the confirmed Clearwater East and West lakes. Some confirmed impacts like Sudbury or Chicxulub are also sources of magnetic anomalies and/or gravity anomalies. The magnetic anomalies Bangui and Jackpine Creek, the gravity anomalies Wilkes Land crater and Falkland Islands, and others have been considered as being of impact origin. Bangui apparently has been discredited, but appears again in a 2014 table of unconfirmed structures in Africa by Reimold and Koeberl. Several anomalies in Williston Basin were identified by Swatzky in the 1970s as astroblemes including Viewfield, Red Wing Creek, Eagle Butte, Dumas, and Hartney, of which only the last two are unconfirmed. The Eltanin impact has been confirmed (via an iridium anomaly and meteoritic material from ocean cores) but, as it fell into the Pacific Ocean, apparently no crater was formed.