This study reports the results of interdisciplinary investigations of Tournaisian deposits from the German Rheinisches Schiefergebirge and provides a genetic and sequence stratigraphic interpretation. Microfacies and geochemical data confirm normal marine outer shelf to slope environments for the Lower Tournaisian Hangenberg Formation. In contrast, data from the condensed, phosphatic "Liegender Alaunschiefer" black shale indicate low current energy and anoxic conditions in the sediment and the water column. We suggest that anoxia was caused by eutrophication and high organic productivity due to factors such as upwelling, a climaterelated improvement of oceanic ventilation, and volcanic nutrient input. The Hangenberg Formation represents the lowstand through the early transgressive systems tract of a third-order depositional sequence, while the "Liegender Alaunschiefer" is a late transgressive systems tract and maximum flooding deposit. The Richrath Limestone was deposited during the highstand systems tract. Thus, quickly rising sea level and eutrophication may account for the peculiar and uniform facies of the "Liegender Alaunschiefer".

The Meishucun Section (Yunnan Province, South China) is considered to be an important Precambrian–Cambrian boundary section, primarily because of its rich small shelly fossil record. In this article, we report the results of a sulphur isotope study of phosphate-bound sulphate from the Meishucun Section and several correlative sections in South China. Forty clastic, granular phosphorites from Meishucun yield tightly grouped δ 34 S values averaging 33‰ (CDT), which agree well with published evaporite data for the lower Cambrian of Siberia and elsewhere. We argue that these strongly positive values reflect the sulphur isotopic composition of ambient seawater, confirming further the existence of uniquely high δ 34 S values in the earliest Cambrian oceans. This novel use of trace-sulphate in phosphate to constrain seawater δ 34 S represents the first time that sulphate δ 34 S data for this period have been given precise biostratigraphic assignments. Superimposed on the overall trend are short-term, stratigraphic variations, which might reflect local variations in the sedimentary and early diagenetic environment. Our data, together with other published data, indicate that seawater sulphate δ 34 S rose from low values (15–20‰) during the pre-750 Ma Proterozoic to possibly all-time high values (>32‰) by the earliest Cambrian. We argue that this rise may, in part, relate to increases in the amount of sulphur isotopic discrimination during microbially mediated sulphate reduction as a result of increased sulphide reoxi-dation. On the other hand, the Neoproterozoic trend to high δ 34 S values appears to mirror a trend to decreasing seawater δ 13 C towards the Proterozoic–Phanerozoic transition, implying progressive increases in the efficiency of organic carbon recycling, which would normally be coupled with real increases in sulphate reduction on the global scale. We consider that both these changes in biogeochemical cycling derive ultimately from the introduction of macrofauna around this time and, in particular, from the influence of bioturbation on early diagenesis. Precise constraints on S-isotopic evolution during the Neoproterozoic require additional trace sulphate studies.

Lower Cambrian phosphorite samples from Maotianshan, Yunnan Province, South China, yielded a variety of small shelly fossils. Sclerites of the second pre‐trilobite faunal assemblage of Meishucun, the Paragbborilus‐Siphogonuchites–Lapworthella association of Nemakit–Daldynian to Tommotían age, were dominant. They comprise previously unknown spine‐bearing specimens of Ocruranus finial Liu, 1979, and new morphotypes of Eohalobia diandongensis Jiang, 1982. Well‐preserved sclerites reveal a laminated, composite fine structure with marginal, incremental growth. Each lamella consists of radial series of minute growth elements. The shells are phosphatically preserved, but micropetrographic evidence from drill‐core samples indicates calcium carbonate as primary shell material. In the light of this new evidence, Ocruranus–Eohalobia group fossils are interpreted as parts of coeloscleritophoran scleritomes.

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