Distribution of phosphorus in the Middle and Upper Ordovician Baltoscandian carbonate palaeobasin

Baltoscandian Middle and Upper Ordovician carbonate rocks are relatively poor in phosphorus, with the P2O5 content of 0.05–0.5%, rarely exceeding 1%. Phosphorus distribution in the Ordovician carbonate succession shows spatial and temporal variations. In the Estonian Shelf P content is the highest in the Middle Ordovician, close to the Tremadocian P-rich siliciclastic sediments, decreasing towards younger carbonate rocks. In the basinal, i.e. deep shelf, sections two intervals of elevated P contents occur: the first is similar to the shallow shelf in the lowermost Darriwilian, the second is a moderate P increase in the upper Darriwilian–Sandbian interval. The Darriwilian–Sandbian interval of elevated P content in the deep shelf sections roughly corresponds to algal kukersite accumulations in the shallow shelf. Multiple processes determined phosphorus distribution in the studied sediments. Regional processes influencing P distribution include seawater circulation, e.g. P influx by coastal upwellings, and sedimentation rate. Global oceanic variation in bioproduction (δ13C trends) had no positive effect on P accumulation in the Baltoscandian epeiric sea

Data for: Hirnantian glaciation dynamics revealed in the Baltoscandian Basin

XRF, carbon isotopes, mean grain siz

Data for: Hirnantian glaciation dynamics revealed in the Baltoscandian Basin

XRF, carbon isotopes, mean grain sizeTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Internal stratification of two thick Ordovician bentonites of Estonia: deciphering primary magmatic, sedimentary, environmental and diagenetic signatures

Twenty-six samples from two major altered volcanic ash beds, Kinnekulle and BII Bentonite of the Kuressaare core section (K-3), Saaremaa Island, were explored to record the geochemical and mineralogical heterogeneity of beds. Signs of ash transport fractionation, redeposition of volcanic ash and diagenetic redistribution of material are described and interpreted. In authigenic mineralogy of the Kinnekulle Bentonite illite–smectite dominates with addition of K-feldspar at the margins. The BII Bentonite is composed of chlorite–smectite and illite–smectite. The stability of phenocryst compositions, including that of sanidine and biotite, indicates that both bentonites originate from a single eruption. The observed rather stable pyroclastic sanidine compositions in the cross section of bentonites confirm the reliability of sanidine-based fingerprinting of altered volcanic ash beds. Trace element distribution in bentonites and host rocks indicates that Zr, Ga, Rb, Nb, Ti and Th stayed largely immobile during volcanic ash alteration and reflect primary ash composition. However, some redistribution of Nb and Ti as well as Y has probably occurred near the contacts of bentonite with the host rock. More scattered grain size distribution and immobile element patterns of the Kinnekulle Bentonite support the idea that the primary ash bed had a heterogeneous composition and it was one of the biggest bentonites of the Phanerozoic and most likely records an extended volcanic event. Significant geochemical variations, including a high S content, near the upper and lower contacts of the Kinnekulle Bentonite and elevated Ca and P in host rocks of both bentonites suggest that the studied large ash-falls caused notable perturbations in shallow marine and early post-sedimentary environment

Correlation of Silurian bentonites from Gotland and the eastern Baltic using sanidine phenocryst composition, and biostratigraphical consequences

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. Three bentonites correlate the Cyrtograptus murchisoni Zone with the upper part of the Pterospathodus amorphognathoides Zone and both the Lower and the Upper Pseudooneotodus bicornis conodont biozones at their type locality. Thus the base of the Llandovery-Wenlock boundary stratotype can be correlated with a level in the upper part of the Cyrtograptus murchisoni graptolite Biozone. Identifying the Y Bentonite (Gotland, Sweden) in eastern Baltic drill-cores shows that the base of the Eisenackitina lagena chitinozoan Biozone is close to the base of the K patula conodont Biozone, which is coeval with an upper part of the C rigidus graptolite Zone. Sanidine data from the Grotlingbo Bentonite fit well with previous correlations. Some bentonites from Gotland with distinct sanidine compositions and bulk geochemistries have not yet been identified elsewhere