Calibrating the middle and late Permian palynostratigraphy of Australia to the geologic time-scale via U–Pb zircon CA-IDTIMS dating

The advent of chemical abrasion-isotope dilution thermal ionisation mass spectrometry (CA-IDTIMS) has revolutionised U–Pb dating of zircon, and the enhanced precision of eruption ages determined on volcanic layers within basin successions permits an improved calibration of biostratigraphic schemes to the numerical time-scale. The Guadalupian and Lopingian (Permian) successions in the Sydney, Gunnedah, Bowen and Canning basins are mostly non-marine and include numerous airfall tuff units, many of which contain zircon. The eastern Australian palynostratigraphic scheme provides the basis for much of the local correlation, but the present calibration of this scheme against the numerical time-scale depends on a correlation to Western Australia, using rare ammonoids and conodonts in that succession to link to the standard global marine biostratigraphic scheme. High-precision U–Pb zircon dating of tuff layers via CA-IDTIMS allows this tenuous correlation to be circumvented—the resulting direct calibration of the palynostratigraphy to the numerical time-scale highlights significant inaccuracies in the previous indirect correlation. The new data show: the top of the Praecolpatites sinuosus Zone (APP3.2) lies in the early Roadian, not the middle Kungurian; the top of the Microbaculispora villosa Zone (APP3.3) lies in the middle Roadian, not the early Roadian; the top of the Dulhuntyispora granulata Zone (APP4.1) lies in the Wordian, not in the latest Roadian; the top of the Didecitriletes ericianus Zone (APP4.2) lies in the first half of the Wuchiapingian, not the latest Wordian; the Dulhuntyispora dulhuntyi Zone (APP4.3) is exceptionally short and lies within the Wuchiapingian, not the early Capitanian; and the top of the Dulhuntyispora parvithola Zone (APP5) lies at or near the Permo-Triassic boundary, not in the latest Wuchiapingian.     

Inter-population variability in the reproductive morphology of the shore crab (Carcinus maenas): evidence of endocrine disruption in a marine crustacean?

Environmental contaminants that are capable of causing endocrine disrupting effects are currently a major cause for concern. These chemicals are known to influence the reproductive development of vertebrates by mimicking or antagonising the actions of endogenous hormones. However, little is known regarding their potential effects on invertebrates. Here we examine variations in the reproductive morphology of the shore crab (Carcinus maenas) for evidence of endocrine disruption. Crabs were collected from a number of sites comprising a putative gradient of exposure to endocrine disrupting chemicals. Patterns of inter-population variability in the expression of sexually dimorphic traits were then examined for evidence of hormone disruption. Extensive variability was detected and patterns of chelal morphology were consistent with the gradient of endocrine disruption. However, overall, the patterns of morphological variability were not consistent with hormonally-mediated effects. This suggests that shore crabs are not susceptible to the same type of endocrine disrupting effects that have been detected in vertebrates, which are most commonly mediated via the oestrogen receptor. However, the potential for androgenic effects on crustacean morphology are discussed.     

36Cl, 26Al,and O isotopes in an Allende type B2 CAI: Implications for multiple secondary alteration events in the early solar system

Abstract— We measured ³⁶Cl‐³⁶S and ²⁶Al‐²⁶Mg systematics and O isotopes of secondary phases in a moderately altered type B2 CAI (CAI#2) from the Allende CV3 chondrite. CAI#2 has two distinct alteration domains: the anorthite‐grossular (An‐Grs) domain that mostly consists of anorthite and grossular, and the Na‐rich domain that mostly consists of sodalite, anorthite, and Fe‐bearing phases. Large ³⁶S excesses (up to ～400‰) corresponding to an initial ³⁶Cl/³⁵Cl ratio of (1.4 ± 0.3) × 10^?6 were observed in sodalite of the Na‐rich domain, but no resolvable 26Mg excesses were observed in anorthite and sodalite of the Na‐rich domain (the initial ²⁶Al/²⁷Al ratio < 4.4 × 10^?7). If we assume that the ³⁶Cl‐³⁶S and the ²⁶Al‐²⁶Mg systematics were closed simultaneously, the ³⁶Cl/³⁵Cl ratio would have to be on the order of ～10^?2 when CAIs were formed. In contrast to sodalite in Na‐rich domain, significant ²⁶Mg excesses (up to ～35‰) corresponding to an initial ²⁶Al/²⁷Al ratio of (1.2 ± 0.2) × 10^?5 were identified in anorthite of the An‐Grs domain. The ²⁶Al‐²⁶Mg systematics of secondary phases in CAI#2 suggest that CAIs experienced multiple alteration events. Some of the alteration processes occurred while ³⁶Cl (half‐life is 0.3 Myr) and ²⁶Al (half‐life is 0.72 Myr) were still alive, whereas others took place much later. Assuming that ²⁶Al was homogeneously distributed in the solar nebula, our study implies that alteration of CAIs occurred as early as within 1.5 Myr of CAI formation and as late as 5.7 Myr after.     

Spatial correlation of shear-wave velocity in the San Francisco Bay Area sediments

Ground motions recorded within sedimentary basins are variable over short distances. One important cause of the variability is that local soil properties are variable at all scales. Regional hazard maps developed for predicting site effects are generally derived from maps of surficial geology; however, recent studies have shown that mapped geologic units do not correlate well with the average shear-wave velocity of the upper 30 m, V_s(30). We model the horizontal variability of near-surface soil shear-wave velocity in the San Francisco Bay Area to estimate values in unsampled locations in order to account for site effects in a continuous manner. Previous geostatistical studies of soil properties have shown horizontal correlations at the scale of meters to tens of meters while the vertical correlations are on the order of centimeters. In this paper we analyze shear-wave velocity data over regional distances and find that surface shear-wave velocity is correlated at horizontal distances up to 4 km based on data from seismic cone penetration tests and the spectral analysis of surface waves. We propose a method to map site effects by using geostatistical methods based on the shear-wave velocity correlation structure within a sedimentary basin. If used in conjunction with densely spaced shear-wave velocity profiles in regions of high seismic risk, geostatistical methods can produce reliable continuous maps of site effects.     

The oxidation state of manganese in marine sediments and ferromanganese nodules

Marine sediments and ferromanganese nodules from the Pacific Ocean have been analyzed for the $\text{O}\text{Mn}$ ratio of solid manganese. We tested six chemical methods and concluded that the iodometric and oxalate methods were equivalent and were the best choice in terms of accuracy and precision on natural samples. We choose the iodometric method for most of our analyses because the oxalate procedure is a method of differences.The ferromanganese nodules that we analyzed were all from MANOP site H and had $\text{Mn}\text{Fe}$ ratios that ranged from 5.6 to 70. These nodules were invariably highly oxidized with $\text{O}\text{Mn}$ values ranging from 1.90 to 2.00. Our most precise analyses suggest that less than 1% of the total manganese is present as Mn(II).We also analyzed red clay and hemipelagic sediments from the eastern tropical Pacific (Baja borderland and MANOP site H) and carbonate ooze samples from the equatorial Pacific. These sediments are also highly oxidized ($\text{O}\text{Mn}\text{= 1.90 to 2.00}$) except when Mn(II) appears in the interstitial water. As dissolved Mn(II) increases the value of the $\text{O}\text{Mn}$ ratio in the solid phase decreases. The $\text{O}\text{Mn}$ ratio decreases to values as low as 1.40. This decrease appears to be due to a decrease in oxidized manganese by reduction, however, an increase in reduced manganese in the solid sediments by adsorption or MnCO₃ formation can not be ruled out in all cases.     

扬子克拉通东北缘岩石圈地幔的Re-Os同位素地球化学:大陆岩石圈地幔的形成和演化的制约

苏皖地区新生代碱性玄武岩中有丰富的地幔橄榄岩捕虏体 ,测定了 2 0多个样品的Re Os元素丰度和锇同位素组成 ,结果 :Re =0 .0 2 7× 10 - 9～ 0 .375×10 - 9,Os=0 .112×10 - 9～ 3.35× 10 - 9,1 87Os 1 88Os=0 .117～ 0 .134。由代理等时线法1 87Os 1 88Os Yb获得该区岩石圈地幔早期熔体亏损事件的年龄为 1.7Ga(中元古代 )。苏皖地区岩石圈地幔的古老性表明它是元古代后岩石圈拆沉 减薄作用的残余地幔部分。岩石圈地幔经过了亏损 富集多阶段演化。     

Disaster Management and Community Planning, and Public Participation: How to Achieve Sustainable Hazard Mitigation

The paper offers first a brief historical overview of disaster management planning. Second, it reviews Australian and American research findings and show that they urge the field of disaster management to shift its focus from response and recovery to sustainable hazard mitigation. It is argued that in order for this shift to occur, it is necessary to integrate disaster management and community planning. Current practice seldom reflects such a synthesis, and this is one of the reasons why hazard awareness is absent from local decision-making processes. Third, it is asserted that if mitigative strategies are to be successfully implemented, then the disaster management process must incorporate public participation at the local decision-making level. The paper concludes with a case study of California's Portola Valley, which demonstrates that when public participation is integrated into disaster management planning and community planning, the result is sustainable hazard mitigation.     

A method to dynamically subdivide parcels in land use change models

Spatial simulation models have become a popular tool in studying land use/land cover (LULC) change. An important, yet largely overlooked process in such models is the land subdivision, which is known to govern LULC change and landscape restructuring to a large extent. To fill this gap, we propose an efficient and straightforward method to simulate dynamic land subdivision in LULC change models. Key features in the proposed method are implementing a hierarchical landscape where adjacent cells of the same LULC type form patches, patches form properties, and properties form the landscape and incorporating real subdivision layouts. Furthermore, we use a queue-based modified flood-fill algorithm to dynamically reset LULC patches following a subdivision. The proposed subdivision method is demonstrated in action using a prototype agent-based LULC model developed for an amenity landscape in Australia. Results show that it is computationally feasible to run the subdivision method even as spatial resolution is increased, thus providing a proven means for spatial simulation models to dynamically split parcel land.     

The Kuroshio Extension and its recirculation gyres

This paper reports on the strength and structure of the Kuroshio Extension and its recirculation gyres. In the time average, quasi-permanent recirculation gyres are found to the north and south of the Kuroshio Extension jet. The characteristics of these recirculations gyres are determined from the combined observations from the Kuroshio Extension System Study (KESS) field program (June 2004–June 2006) and include current meters, pressure and current recording inverted echo sounders, and subsurface floats. The position and strength of the recirculation gyres simulated by a high-resolution numerical model are found to be consistent with the observations. The circulation pattern that is revealed is of a complex system of multiple recirculation gyres that are embedded in the crests and troughs of the quasi-permanent meanders of the Kuroshio Extension. At the location of the KESS array, the Kuroshio Extension jet and its recirculation gyres transport of about 114 Sv. This represents a 2.7-fold increase in the transport of the current compared to the Kuroshio's transport at Cape Ashizuri before it separates from the coast and flows eastward into the open ocean. This enhancement in the current's transport comes from the development of the flanking recirculation gyres. Estimates from an array of inverted echo sounders and a high-resolution ocean general circulation model are of similar magnitude.     

Hydrologic parameters of salt marsh peat

Because of their profound influence on water movement and nutrient cycling in salt marshes, the two key physical properties of hydraulic conductivity and compressibility were studied in the Great Sippewissett Marsh and in the Ebben Creek Marsh in Massachusetts. Hydraulic conductivity was the most variable property: most frequently observed conductivities were of the order of 10^?3 cm s^?1 in both marshes, but extremes ranged from about 10^?1 to 10^?5 cm s^?1. Compressibility was much less variable, and contributed of the order of 10^?3 cm^?1 to the specific storativity of marsh sediment, making compression a major mechanism for changes in water storage in the sediment. Surface sediments frequently exhibited below-average conductivity, in contrast to freshwater bog peats which are usually most conductive at the surface. These measured properties may be applied to estimate the importance of many critical processes, such as the extent of infiltration occurring on the marsh surface, the hydrologic influence of the tidally varying creeks, and the hydrologic response to spring-neap tidal cycles.