Paleosecular variation during the Kiaman Superchron: a 1150 year record from glacial varves of the Seaham Formation, New South Wales

摘要: Glacial varves of the Seaham Formation at Abercrombie Quarry in eastern New South Wales, Australia, preserve a reverse-polarity characteristic remanence acquired high paleolatitude during early stages Kiaman Superchron, longest known interval constant geomagnetic polarity. Normal polarity overprinting, including pervasive Cretaceous overprint commonly observed on southeastern Australian seaboard, is present but does not obscure primary magnetisation. Ferrimagnetic grains are pseudo-single domain size range, confirming reliability as paleo-remanence recorders. Rip-up clasts maintain original direction chararacteristic despite their random orientation following redeposition, form conglomerate test that restricts timing acquisition to within most few years sedimentation. Characteristic directions from 11 sites spanning 1150 annual layers move through simple, systematic cy...