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The Early Toarcian, organic-rich, black shales of the Cleveland Basin, Yorkshire UK, are the type sediments for the supposed early Toarcian oceanic anoxic event. The sediments have values of Cd/Mo that are 0.4. These values are typical of sediment deposited in modern basins that are hydrographically restricted and show that the Cleveland Basin was hydrographically restricted when depositing organic-rich sediments. These palaeo-proxies confirm earlier interpretations, based on Mo/TOC values, that argued for hydrographic restriction. The term Toarcian oceanic anoxic event can now be discarded.

During the Early Toarcian, volcanic gases released by the Karoo-Ferrar large igneous province are widely believed to have caused severe environmental disturbances, including ocean acidification. Here we show records of δ44/40Ca and δ88/86Sr through the Early Toarcian, as recorded in three groups of biogenic calcite: Megateuthididae belemnites, Passaloteuthididae belemnites, and brachiopods of the species Soaresirhynchia bouchardi. We evaluate the data to eliminate the influence on isotopic composition of varying temperature, calcification rate, and salinity, through the section that may mask the environmental signals. Neither δ44/40Ca nor δ88/86Sr show negative isotope excursions across the suggested acidification interval as would be expected had acidification occurred. A profile of δ11B, re-interpreted from a published study, shows no variation through the interval. Taken together, these data provide little support for ocean acidification at this time. In our belemnites, values of δ88/86Sr are independent of temperature or Sr/Ca. For brachiopods, too few data are available to determine whether such dependences exist. Values of δ44/40Ca show a weak temperature control of magnitude +0.020 ± 0.004 ‰/°C (2 s.d.). In belemnites, δ44/40Ca also correlates positively with Mg/Ca and Sr/Ca.

The preparation of samples for strontium isotope stratigraphy (SIS) by whole rock dissolution results in contributions of Sr from contaminant phases as well as from the target carbonate phase. Here we highlight and quantify the errors in 87Sr/86Sr values that might result when calcium carbonate is dissolved using an inappropriate method. We report the variation in 87Sr/86Sr value of Sr released from four samples of differing calcite content and degrees of cementation, when subject to different methods of dissolution. We show that errors of up to ±0.000076 in 87Sr/86Sr, which correspond to errors of ±3.68 Ma in age, can be avoided by careful preleaching of the samples.

The concentrations of the major substitutents Na, Sr, CO 3 and SO 4 in the carbonate—fluorapatite phase of marine sedimentary phosphorites show large systematic variations between, and within, deposits now on land, whilst variations are minimal between, and within, present sea-floor deposits. These variations reflect the influence of weathering and suggest that all marine carbonate—fluorapatite originally has approximately the same chemical composition.

Phosphatic crusts and nodules recovered from the continental margin off Peru did not precipitate authigenically from anoxic pore water but were formed in post-Palaeogene times by phosphatisation of quartzitic and feldspathic carbonate-bearing sediments. The late Quaternary uranium-series and amino acid dates obtained for these phosphatic rocks are probably the result of secondary enrichment of organic matter and uranium and probably do not represent the times of phosphate mineralisation.

The abundance of rare-earth elements (REE's) in francolite increases with increasing age as a result of post-depositional enrichment. Abundances are higher in pelletal samples than in non-pelletal ones because the higher surface/mass ratio of pelletal francolite promotes enrichment during diagenesis. Onshore francolite has higher REE abundances than that found offshore. Distribution patterns in francolite may be similar to those reported for open-ocean water or shale, depending upon the dominant source of the REE's: different patterns result from weathering and deep-burial diagenetic modification of the original patterns and abundances. Negative Ce anomalies occur in francolites containing structural sulphur that is isotopically indistinguishable from seawater of the same age; zero or positive anomalies occur in francolites which contain sulphur that is isotopically lighter than seawater.