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Because the instrumental record is short and does not extend to periods before the initiation of significant human impacts, full understanding of the processes and dynamics involved in the modern phase of very rapid global change depends on the interpretation of high resolution and precisely dated proxy archives. The identification of very long-lived species of bivalve mollusc in the extratropical marine environment has been a crucial recent advance. These molluscs form patterns of periodic (usually annual) banding in their shells that are synchronous within populations, so that long (centennial and millennial) stacked chronologies can be built by crossdating from live collected to fossil shells. The variable growth rates and precisely dated geochemical data from the shell material provide long term real world data that can in principle be used to constrain climate models and to define long baselines for environmental monitoring. However, the signals in these data usually result from the complex interaction of multiple influences, and the deconvolution and understanding of these influences is a major target of the scientific field of sclerochronology. This special issue presents some of the latest research into the sclerochronology of mollusc shells. It includes contributions to our understanding of shell growth, including the identification of endogenous (non-environmental) growth rhythms that persist throughout ontogeny, and analysis in two papers of variability through ontogeny in the season of growth and the implications of such variability for temperature reconstruction. One paper presents a new network of bivalve chronologies for UK waters, with a 200-year seawater temperature reconstruction. Three papers cover trace element geochemistry, including a novel approach to sampling for LA-ICP-MS that enables giant clam shells to be sampled at daily resolution, an attempt to identify an independent temperature proxy for coastal waters using limpet shells, and a detailed study of the drivers of variability in Sr/Ca and Ba/Ca ratios. One study looks at shell microstructure as a temperature proxy, finding a coherent temperature response in the shape of the prisms. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the Holocene record of extreme flood events in the upper Minjiang River valley of the eastern Tibetan Plateau, China. Slackwater deposits (SWDs), the fine-grained sediments of palaeofloods, were identified within debris flow deposits at a tributary mouth and in channel expansions along the bedrock gorge. Eight palaeoflood SWDs were dated to between 6.0 ± 0.9 ka and 4.6 ± 0.9 ka using optically-stimulated luminescence analysis in combination with the minimum age model and represent at least two phases of palaeoflood events. The palaeoflood history in the upper Minjiang River Valley is consistent with the record of the mid-Holocene flood events in the mainstream of the Yangtze River. These mid-Holocene extreme flood events were closely related to strong ENSO activity and variability of the monsoon climate in the eastern Tibetan Plateau. In our study area, minimum palaeoflood discharges were estimated as 6500–7800 m3/s by the step-backwater method. These estimated discharges are less than the values inferred for the outburst flood that occurred in the upper Minjiang River Valley in 1933. Flood-inundation maps show that palaeoflood SWDs were deposited in low-velocity backwater zones. Our palaeoflood reconstructions are important for improving regional records of maximum flood and help to develop risk analysis for rare flood events. • Sedimentary characteristics of palaeoflood records in complex environment were identified. • Palaeoflood discharges were estimated to be 6500–7800 m3/s at the three study sites. • Palaeoflood results redefine the envelope curve of the regional maximum floods. • Response of mid-Holocene (6.0–4.6 ka) extreme flood events to climate variability. • Palaeoflood reconstructions help to develop risk analysis for rare flood events. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we make an inventory of geomorphic remnants of past glaciations, especially glacial stages that occurred just after the Last Glacial Maximum (LGM). More than 35 terrestrial cosmogenic radionuclide (TCR) ages were obtained, providing new chronological benchmarks for defining the transition between the LGM and the Holocene, thus answering some remaining questions in the southern French Alps (upper Durance catchment). TCR ages fit very well with the scenario defined in other parts of the European Alps: two main generations of post-LGM moraines were identified, highlighting a synchronicity of glacial responses during the Younger Dryas and the Preboreal. Indeed, the first generation we identified corresponds to the Younger Dryas period, while the second generation was shaped during the Preboreal period. They suggest that a relatively thick glacier tongue (300m thick) occupied the upper catchment until the end of the Lateglacial period. The glacier tongue disappeared at the very beginning of the Holocene, before a short glacial re-advance during the Preboreal period. This scenario is linked to a very low equilibrium line altitude (ELA) during the Younger Dryas and the Preboreal: located respectively 340 and 150m below the Little Ice Age (LIA) ELA. Collectively, the results highlight a significant west–east gradient in ELA, probably in relation to westerly and northwesterly winds. Finally, the deglaciation pattern in this area is similar to that of the western and northern Alps, and appears significantly different from the patterns found in the inner and eastern Alps (such as the Ubaye and Maritime Alps patterns). [Copyright &y& Elsevier]

Abstract: Stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of Lake Bonneville. Based on key marker beds and geomorphic position, the deposits are interpreted to have accumulated during the period from the late transgressive phase, through the overflowing phase, into the regressive phase of the lake. Radiocarbon ages of sediments associated with the Provo shoreline indicate that Lake Bonneville dropped rapidly from the Provo shoreline at about 12,600 14C yr BP (15,000 cal yr B.P.). The presence of one or more sand beds in the upper part of the Provo-aged marl indicates rapid lowering of lake level or storm events at the end of the Provo episode. An accurate understanding of the timing and nature of Lake Bonneville''s climate-driven regression from the Provo shoreline is critical to correlations with records of regional and hemispheric climate change. The rapid descent of the lake from the Provo shoreline correlates with the decline of Lakes Lahontan and Estancia, and with the onset of the BØlling–AllerØd warming event. [Copyright &y& Elsevier]

Abstract: The ability of the ocean to absorb carbon dioxide is likely to be adversely affected by recent climate change. However, relatively little is known about the spatiotemporal variability in the oceanic carbon cycle due to the lack of long-term, high-resolution dissolved inorganic carbon isotope (δ 13CDIC) data, especially for the temperate North Atlantic, which is the major oceanic sink for anthropogenic CO2. Here, we report shell carbon isotope values (δ 13Cshell), a potential proxy for δ 13CDIC, of old-grown specimens of the long-lived bivalve mollusk, Arctica islandica. This paper presents the first absolutely dated, annually resolved δ 13Cshell record from surface waters of the North Atlantic (Iceland, Gulf of Maine) covering the time interval between 1753 and 2003. According to our results, the δ 13Cshell data were unaffected by trends related to ontogenetic age. However, the shell carbonate was precipitated with a constant offset from expected equilibrium by −1.54 to −2.7±0.2‰ corresponding to a 6.2 to 10.8±0.8% contribution of respiratory CO2 (−25‰). The offset did not appear to vary through the lifetime of individual specimens and among specimens. Therefore, the δ 13Cshell data of this species can very likely be used as a measure of δ 13CDIC. Furthermore, shell stable carbon isotope chronologies exhibited habitat-specific differences and a significant inter-annual and decadal variability related to the natural carbon cycle. In addition, a distinct negative δ 13Cshell shift was found reflecting the oceanic Suess effect, i.e. the admixture of anthropogenic CO2. However, this shift only occurred after the early 1920s when a major climate regime shift led to a northward movement of the oceanic Polar Front in the Nordic Seas and a large-scale reorganization of atmospheric and oceanic currents in the North Atlantic. This likely resulted in a reduced admixture of cold Polar water onto the North Icelandic shelf (through the East Iceland Current) and the Gulf of Maine (through the Labrador Current) with an increased volume of warmer, isotopically well-equilibrated Atlantic waters. Our shell-based δ 13CDIC proxy record provides the basis to quantitatively assess natural and anthropogenically induced patterns of carbon uptake in the North Atlantic. [Copyright &y& Elsevier]

Abstract: In the Miocene, the intra-montane basins of the Dinaric Mountain Chain harbored a series of long-lived lakes constituting the so-called Dinaride Lake System. The thick lacustrine sedimentary records of these lakes provide an excellent opportunity to study evolution and radiation of mollusks in an isolated environment. The 500m thick infill that accumulated in the Sinj Basin is one of the key records because of its excellent mollusk preservation. Recent studies on the depositional history, pollen assemblages and large mammals have enhanced the understanding not only of Lake Sinj, but also of the regional climatic developments and faunal migratory patterns. A reliable chronology of the development of Lake Sinj, which is crucial for global correlation of its endemic realm, was still lacking. In this paper we present a detailed time-frame for the Miocene Sinj basin based on palaeomagnetic and 40Ar/39Ar data. We conclude that deposition took place between 18.0 to 15.0Ma, a time span that correlates with the upper Burdigalian and lower Langhian Mediterranean stages and Ottnangian, Karpatian and lowermost Badenian Paratethys stages. Furthermore, we determined the timing of several events in mollusk evolution, important for correlation across the Dinarides. An age of 15.0Ma is attributed to the large mammals Conohyus and Gomphotherium, preserved in the upper part of the basin stratigraphy. [Copyright &y& Elsevier]

Abstract: A quantitative biochronological study by Cody et al. (2008) integrates comprehensive diatom biostratigraphy, magnetostratigraphy, and tephrostratigraphy from 32 Neogene sections around the Southern Ocean and Antarctic continental margin. A recent method, known as Constrained Optimization (CONOP), which can be viewed as a multidimensional version of graphic correlation, is applied to that very interesting database. The goal of the present paper is to discuss some theoretical aspects of quantitative biochronology and to compare the constrained optimization with the deterministic method called Unitary Associations (UAM), a graph theoretical model. We illustrate the fact that the UAM is an extremely powerful and unique theory allowing an in-depth analysis of the internal conflicting inter-taxon stratigraphic relationships, inherent to any complex biostratigraphical database. [Copyright &y& Elsevier]