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Palaeomagnetism and Palaeoclimates |
1 Department of Geological and Geophysical Sciences, Princeton University, Princeton, NJ 08544, USA
2 Institute of Geology, Chinese Academy of Geological Sciences, Baiwanzhuang Road, Beijing, PR China
The record of Palaeozoic oolitic ironstones reflects second-order Phanerozoic sea-level changes. Middle Cambrian- earliest Ordovician high stand: scattered ironstones developed on low-latitude Laurentia and locally on high southern-latitude NW Africa and Nova Scotia. Early-early Late Ordovician high stand: major and scattered minor ironstones were widespread on high southern-latitude N Africa and Peri-Gondwanan blocks. Minor ones on C Laurentia, NE and SW Baltica, SW Kazakhstan, and NW and SW Siberia, NW Malaysia, and C Australia accumulated in middle and low latitudes, as did all later Palaeozoic ironstones. Latest Ordovician-earliest Silurian low stand: during southern-latitude glaciation minor ironstones were limited to WC Algeria and low-latitude C and SE Laurentia. Early-early Late Silurian high stand: minor ironstones accumulated on NC, WC, and SE South America, N Africa, and Peri-Gondwanan blocks, while major ones developed on NW Africa and CE Laurentia. Latest Silurian-Early Devonian low stand: major ironstones developed on WC Algeria; minor ones on CE Laurentia, several Peri-Gondwanan blocks, N and W Africa, NC South America, and South China. Middle-early Late Devonian high stand: major ironstones accumulated on N Africa, SE Baltica, NW Iberia, and South China; minor ones on SW and CE Laurentia, and NW and SE Middle Europe. Latest Devonian-earliest Carboniferous low stand: well-developed latest Devonian ironstones were limited to N Africa and NW Middle Europe, minor ones to SE Middle Europe and CE Laurentia; minor earliest Carboniferous ones to NW Middle Europe and NC Africa.
