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In this paper, we describe porosity variations in Miocene to Holocene carbonates off the west coast of Australia and assess their compaction trends. The porosity values were measured using discrete samples of Sites U1459–U1464 obtained by the International Ocean Discovery Program Expedition 356. The carbonate deposits have been influenced by a range of textures and diagenetic conditions throughout a nearly continuous sequence of geological ages from the Miocene to Holocene and at core depths from 0 to 1100 m below the seafloor. The collected samples were mostly grainstone, packstone, wackestone and mudstone textures. Dolostones and dolomitic carbonates were described at the Miocene intervals. Compaction trends were estimated exponentially and linearly based on cored sites, carbonate textures and dominant mineralogies (dolomite, calcite/aragonite). At all six sites, porosity distribution and reduction were generally depth-dependent. The porosity converged to about 30% between 750 and 1100 m, which suggests that the carbonates were close to the densest packing by mechanical compaction at a burial depth of ∼750 m. The porosity deviations are associated with textures and dominant mineralogies. Increasing mud content from grainstone to mudstone is a controlling factor for initial porosity and porosity reduction rate. Dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains cause deviations from the depth-dependent compaction trends. Reflux-related cementation generally decreases porosity in Miocene dolomitic intervals. Higher porosity values of the Quaternary wackestone and mudstone at Site U1461 resulted from the presence of aragonite needle-rich mud hosting abundant micropores and from a high sedimentation rate. The occurrence of non-skeletal grains, such as ooids and peloids, as well as occasional meteoric exposure led to porosity inversion, occluding interparticle permeability and the creation of moldic pores.

Recently, the atomic ²³³U/²³⁶U ratio was proposed as a superior oceanographic tracer as the ²³³U/²³⁶U signature allows to distinguish environmental emissions of civil nuclear industry from weapons fallout [1] and uranium (U) behaves conservatively in sea water. In this previous work, the ratios detected in representative compartments of the environment affected either by releases of nuclear power production or by weapons fallout differ by one order of magnitude and varied between 0.1·10-²and 3.7·10-². Significant amounts of ²³³U were only released in nuclear weapons fallout, either produced by fast neutron capture on ²³⁵U or directly by ²³³U fuelled devices. For tracer applications, a careful characterization of the principal sources of ²³³U including the contribution from natural production is required. The ²³³U/²³⁶U ratios were analysed in samples from different locations, partly time-resolved or of well-known age to be able to narrow down the time span of the maximum ²³³U release. Samples comprised air filters from 1961-1965 collected in Austria, i.e. the period of maximum deposition of global fallout, two time-resolved sediment cores from the Baltic Sea and sediment from the urban layered archaeosphere in the underground of Vienna (Austria). In addition, a depth profile of ²³³U/²³⁶U in a water column located in the Northeast Pacific Ocean was also analysed. This sampling station is assumed to be less affected by tropospheric fallout from a suspected ²³³U fuelled device (Nevada Test Site, 1955). Whenever possible, the ²³³U/²³⁶U data were directly compared to other isotopic signatures and/or mono-isotopic makers, such as ²⁴⁰Pu/²³⁹Pu or ²⁴¹Am, respectively. The Baltic Sea sediment core confirms a maximum deposition of ²³³U around 1954/1955 [2]. This finding is supported by the rather low ²³³U/²³⁶U ratios (below 0.5·10-²) on the air filters from Vienna indicating a comparatively low ²³³U deposition during global fallout maximum. Values of around 0.1 were measured fo

Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore standard methods used in evaluation of round robin tests are not feasible. In our case the ‘true’ compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses f

© 2015This review provides a synopsis of ongoing research and our understanding of the fundamentals of sea-level change today and in the geologic record, especially as illustrated by conditions and processes during the Cretaceous greenhouse climate episode. We give an overview of the state of the art of our understanding on eustatic (global) versus relative (regional) sea level, as well as long-term versus short-term fluctuations and their drivers. In the context of the focus of UNESCO-IUGS/IGCP project 609 on Cretaceous eustatic, short-term sea-level and climate changes, we evaluate the possible evidence for glacio-eustasy versus alternative or additional mechanisms for continental water storage and release for the Cretaceous greenhouse and hothouse phases during which the presence of larger continental ice shields is considered unlikely. Increasing evidence in the literature suggests a correlation between long-period orbital cycles and depositional cycles that reflect sea-level fluctuations, implying a globally synchronized forcing of (eustatic) sea level. Fourth-order depositional sequences seem to be related to a ~ 405 ka periodicity, which most likely represents long-period orbital eccentricity control on sea level and depositional cycles. Third-order cyclicity, expressed as time-synchronous sea level falls of ~ 20 to 110 m on ~ 0.5 to 3.0 Ma timescales in the Cretaceous, are increasingly recognized as connected to climate cycles triggered by long-term astronomical cycles that have periodicity ranging from ~ 1.0 to 2.4 Ma. Future perspectives of research on greenhouse sea-level changes comprise a high-precision time-scale for sequence stratigraphy and eustatic sea-level changes and high-resolution marine to non-marine stratigraphic correlation.

© 2015. This review provides a synopsis of ongoing research and our understanding of the fundamentals of sea-level change today and in the geologic record, especially as illustrated by conditions and processes during the Cretaceous greenhouse climate episode. We give an overview of the state of the art of our understanding on eustatic (global) versus relative (regional) sea level, as well as long-term versus short-term fluctuations and their drivers. In the context of the focus of UNESCO-IUGS/IGCP project 609 on Cretaceous eustatic, short-term sea-level and climate changes, we evaluate the possible evidence for glacio-eustasy versus alternative or additional mechanisms for continental water storage and release for the Cretaceous greenhouse and hothouse phases during which the presence of larger continental ice shields is considered unlikely. Increasing evidence in the literature suggests a correlation between long-period orbital cycles and depositional cycles that reflect sea-level fluctuations, implying a globally synchronized forcing of (eustatic) sea level. Fourth-order depositional sequences seem to be related to a ~. 405. ka periodicity, which most likely represents long-period orbital eccentricity control on sea level and depositional cycles. Third-order cyclicity, expressed as time-synchronous sea level falls of ~. 20 to 110. m on ~. 0.5 to 3.0. Ma timescales in the Cretaceous, are increasingly recognized as connected to climate cycles triggered by long-term astronomical cycles that have periodicity ranging from ~. 1.0 to 2.4. Ma. Future perspectives of research on greenhouse sea-level changes comprise a high-precision time-scale for sequence stratigraphy and eustatic sea-level changes and high-resolution marine to non-marine stratigraphic correlation.