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Exuberant Life
The terrestrial organisms of the Galápagos Islands live under conditions unlike those anywhere else. At the edge of a uniquely rich mid-ocean upwelling, their world is also free of mammalian predators and competitors, allowing them to live unbothered, exuberant lives. With its giant tortoises, marine iguanas, flightless cormorants, and forests of giant daisies, there's no question that this is a magnificent place. Long before people traversed the Earth, evolution endowed native species with adaptations to these special conditions and to perturbations like El Niño events and periodic droughts. As the islands have grown ever-more connected with humanity, those same adaptations now make its s...
Molybdenum as a Paleoredox Proxy
Molybdenum (Mo) is a widely used trace metal for investigating redox conditions. However, unanswered questions remain that concentration and bulk isotopic analysis cannot specially answer. Improvements can be made by combining new geochemical techniques to traditional methods of Mo analysis. In this Element, we propose a refinement of Mo geochemistry within aquatic systems, ancient rocks, and modern sediments through molecular geochemistry (systematically combining concentration, isotope ratio, elemental mapping, and speciation analyses). Specifically, to intermediate sulfide concentrations governing Mo behavior below the 'switch-point' and dominant sequestration pathways in low oxygen conditions. The aim of this work is to 1) aid and improve the breadth of Mo paleoproxy interpretations by considering Mo speciation and 2) address outstanding research gaps concerning Mo systematics (cycling, partitioning, sequestration, etc.). The Mo paleoproxy has potential to solve ever complex research questions. By using molecular geochemical recommendations, improved Mo paleoproxy interpretations and reconstruction can be achieved.
Environmental AnalysisThe NEPA Experience
Environmental Analysis reviews information gathered during NEPA assessments, summarizes the state of the art in methods and approaches, and defines future opportunities and new approaches required to link high-quality science to the decision-making process. Individual chapters address the process itself, present examples of recent experience with ecological impact assessment, evaluate social impact assessment and the important role the public must play, discuss the difficult challenge of assessing cumulative effects of multiple impacts, consider the regional and global implications of NEPA, and examine the important role of follow-up studies in the process. The authors of the 59 individual papers comprising this book represent the major sectors that have been key participants in the decision-making process from the beginning. These sectors include academia, national laboratories, federal agencies, state agencies, private industry, and foreign nations. Environmental Analysis will be interesting reading for environmental scientists, engineers, policy makers, and lawyers in government and academia; private consultants; and non-government environmental organizations.
Iron Formations as Palaeoenvironmental Archives
Ancient iron formations - iron and silica-rich chemical sedimentary rocks that formed throughout the Precambrian eons - provide a significant part of the evidence for the modern scientific understanding of palaeoenvironmental conditions in Archaean (4.0–2.5 billion years ago) and Proterozoic (2.5–0.539 billion years ago) times. Despite controversies regarding their formation mechanisms, iron formations are a testament to the influence of the Precambrian biosphere on early ocean chemistry. As many iron formations are pure chemical sediments that reflect the composition of the waters from which they precipitated, they can also serve as nuanced geochemical archives for the study of ancient marine temperatures, redox states, and elemental cycling, if proper care is taken to understand their sedimentological context.
Sr Isotopes in Seawater
Studies of Sr isotopic composition of thousands of samples of marine sediments and fossils have yielded a curve of 87Sr/86Sr versus age for seawater Sr that extends back to 1 billion years. The ratio has fluctuated with large amplitude during this time period, and because the ratio is always uniform in the oceans globally at any one time, it is useful as a stratigraphic correlation and age-dating tool. The ratio also appears to reflect major tectonic and climatic events in Earth history and hence provides clues as to the causes, timing, and consequences of those events. The seawater 87Sr/86Sr ratio is generally high during periods marked by continent-continent collisions, and lower when continental topography is subdued, and seafloor generation rates are high. There is evidence that major shifts in the seawater ratio can be ascribed to specific orogenic events and correlate with large shifts in global climate.
Magnesium Isotopes
Magnesium is a major constituent in silicate and carbonate minerals, the hydrosphere and the biosphere. Magnesium is constantly cycled between these reservoirs. Since each of the major planetary reservoirs of magnesium have different magnesium isotope ratios, there is scope to use magnesium isotope ratios to trace 1) the processes that cycle Magnesium at a spatial scales from the entire planet to microscopic and 2) the relative fluxes between these reservoirs. This review summarises some of the key motivations, successes and challenges facing the use of magnesium isotopes to construct a budget of seawater magnesium, present and past.
Local and Global Controls on Carbon Isotope Chemostratigraphy
Over million-year timescales, the geologic cycling of carbon controls long-term climate and the oxidation of Earth's surface. Inferences about the carbon cycle can be made from time series of carbon isotopic ratios measured from sedimentary rocks. The foundational assumption for carbon isotope chemostratigraphy is that carbon isotope values reflect dissolved inorganic carbon in a well-mixed ocean in equilibrium with the atmosphere. However, when applied to shallow-water platform environments, where most ancient carbonates preserved in the geological record formed, recent research has documented the importance of considering both local variability in surface water chemistry and diagenesis. These findings demonstrate that carbon isotope chemostratigraphy of platform carbonate rarely represent the average carbonate sink or directly records changes in the composition of global seawater. Understanding what causes local variability in shallow-water settings, and what this variability might reveal about global boundary conditions, are vital questions for the next generation of carbon isotope chemostratigraphers.
The Iron Speciation Paleoredox Proxy
In one form or another, iron speciation has had a long history as a paleoredox proxy. The technique has been refined considerably over the years, and the most recent scheme is unique in its potential to distinguish three major oceanic redox states - oxygenated, ferruginous and euxinic. This Element covers the theory behind the proxy, methods involved in applying the technique, and potential complications in interpreting Fe speciation data. A series of case studies are also provided, which highlight how more advanced consideration of the data, often in concert with other techniques, can provide unprecedented insight into the redox state of ancient oceans.
Vulnerability and Adaptation Assessments
The possible impacts of global climate change on different countries has led to the development and ratification of the Framework Convention on Climate Change (FCCC) and has a strong bearing on the future sustainable development of developing countries and countries with economies in transition. The preparation of analytical methodologies and tools for carrying out assessments of vulnerability and adaptation to climate change is therefore of prime importance to these countries. Such assessments are needed to both fulfill the reporting requirements of the countries under the FCCC as well as to prepare their own climate change adaptation and mitigation plans. The vulnerability and adaptation a...
