Glaukonit aus der Regensburger Oberkreideformation

Some of the upper cretaceous sedimentary rocks near Regensburg, Germany, are rich in glauconite pellets of 63–200µ diameter. The clay fractions < 2µ of the same rocks are rich in glauconite-mica too.X-ray analysis, chemical analysis and petrographical tests show that, the glauconite pellets must be excrements of marine animals which took up glauconite-mica from sea-bottom.The glauconite materials from these rocks are 1M-micapolymorphs. A comparison of this glauconite with 1M-glauconites cited in literature by other authors shows close aggreement in K₂O/MgO- and K₂O/Fe₂O₃ ratios. Within the range of analytical errors the structure formulae of all these 1M-glauconites differ from one another only by the oxidation ratio of iron and — corresponding to this ratio — by the aluminum contents of the octahedral lattice layer. The differences of the 1M-glauconites in octahedral layer populations may due to different redox potentials during glauconite formation or to oxidation during rock diagenesis or rock weathering later on.In a similar manner 1Md-polymorphs of glauconite-mica may have developed from 1M-glauconite by oxidation of iron and corresponding removement of K⁺ and (H₃O)⁺ ions from interlayer lattice positions.