Abstract

The Fe content of Ordovician limestones in northern Europe has been explained by land proximity. Non-calcareous deposition, including glauconite, averaged 0.1 mm/1,000 yrs. Signs of physical erosion wanting, this might be the true average rate, minus chemical dissolution of alkalis, Mg, and Ti. If so, then aeolian transport of terrigenics was below present rates in the mid-ocean, and the atmosphere's long-term suspension of volcanic dust might alone provide the non-calcareous material. SiO 2 : Al 2 O 3 : (Fe 2 O 3 + FeO) : MgO : TiO 2 ratios of roughly 3.0 : 1 : 0.66 : 0.17 : 0.035 would be explained by sedimentation of mainly basaltic ashes. Mn increased in the sediment.

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