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Silurian bentonites from Sweden and the eastern Baltic are correlated using XRD analysis of sanidine composition. Identifying the same bentonite in different sections has constrained correlations between the conodont, graptolite and chitinozoan zonations.

This paper describes vertical fine-scale geochemical heterogeneity of Estonian graptolite argillite (GA). GA samples from Pakri and Saka outcrop sections were collected at 20 cm intervals for chemical analysis of major and trace elements, including rare earth elements. The study indicates GA enrichment in U, V, Mo and Pb with respect to the average black shales and thus confirms the formerly reported data on GA geochemistry in general. However, the content of enriched elements and other trace metals was recorded to vary greatly across the sequences suggesting that trace metal distribution in GA is notably more heterogeneous than previously assumed. The origin of the observed complex distribution of trace elements was likely controlled by the interplay of different primary metal supply-sequestration factors/processes, such as synsedimentary redox-driven sequestration of redox sensitive elements, the provenance of clastic input, the postsedimentary redistribution, etc.

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The composition of altered volcanic ash of the Late Ordovician Kinnekulle bed was studied in geological sections of the Baltic Paleobasin. The composition of altered ash varies with paleosea depth from northern Estonia to Lithuania. The ash bed in shallow shelf limestones contains an association of illite-smectite (I-S) and K-feldspar, with the K2O content ranging from 7.5 to 15.3%. The limestone in the transition zone between shallow- and deep-shelf environments contains I-S-dominated ash with K2O content from 6.0 to 7.5%. In the deep-shelf marlstone and shale, the volcanic ash bed consists of I-S and kaolinite with a K2O content ranging from 4.1 to 6.0%. This shows that authigenic silicates from volcanic ash were formed during the early sedimentary-diagenetic processes. The composition of the altered volcanic ash can be used as a paleoenvironmental indicator showing the pH of the seawater or porewater in sediments as well as the sedimentation rate.