Dating methods geochronology and landscape evolution observatory

dating methods geochronology and landscape evolution observatory

Dating and correlation of these data require high-resolution age constraints developed through a number of geochronological and chronostratigraphic methods. NJ, United States and Christopher J Lepre, Lamont -Doherty Earth Observatory, France; PP31B Landscape Evolution and Biogeographic Contexts in the. Dissertation: Reconstruction of landscape evolution and continental . Dating of Mono Lake Sediments - A complementary dating method to. Surface Exposure "Cosmogenic Noble Gases in Quaternary Geochronology - An Overview”. Dating methods geochronology and landscape evolution observatory. My broader interests in sedimentary geology and tectonics were stimulated by three years.

In addition, the history of landscapes strongly influences their present state and future evolution. Likewise, coastal erosion is still influenced by uplift and subsidence in response to shifts in ice loading over Holocene time. The fate of global deltas on which hundreds of millions of people depend in turn depends on the delicate interplay of subsidence and sedimentation developed over geologic time.

In upland regions, the general importance of tectonic history is obvious; more subtle are the possible effects of variations in uplift rate and climate in influencing the balance of sediment storage and release to downstream river systems. Soils are among the clearest examples of the influence of past time—the soils that support global agriculture represent the integrated effects of tens of thousands of years of biogeochemical processes. The evolutionary road from the prebiotic Earth and an atmosphere devoid of oxygen to the human-dominated conditions of today has been well documented in the popular Page 37 Share Cite Suggested Citation: Beyond the drama and fascination of Earth history, the record in landscapes and sediments gives us an archive of natural experiments, performed at full planetary length and time scales, from which to reconstruct planetary dynamics.

Practical reasons also exist for studying the record of surface evolution. Second, the subsurface heterogeneity that controls the availability of resources such as water, hydrocarbons, and minerals is in effect a three-dimensional tapestry of fossilized surface dynamics created via crustal subsidence and burial of paleo-landscapes in sedimentary basins. Lastly, the history of surface evolution in landscapes and sedimentary basins provides us with a rich archive from which to extract information on extreme events, natural variability in space and time, and how the surface responds to change.

The past as the context for the current environment. The further ahead we would like to forecast, the further back must we look to understand how the system arrived at its current state and how it is likely to evolve. For example, consider two contrasting scenarios for beach retreat, an issue that has consumed billions of dollars in the United States. One is a case of local erosion caused by interruption of longshore sediment flow by jetties.

In the other, the retreat is the result of long-term land sinking caused by adjustment from the last glaciation. Although the short-term responses to both cases might appear similar, their contexts and hence strategies for sustainable management may be entirely different. Page 38 Share Cite Suggested Citation: Centennial-scale or longer variations in seismicity and climate may control landslide frequency in steeplands, altering the supply of sediment to river systems, with a broad spectrum of environmental consequences.

Over much of the Northern Hemisphere the strong imprint of glacial history persists in the distribution of soils, surface biota, river courses, and groundwater. The extraordinary fertility of the breadbasket of the United States is related to soils developed on sediments deposited in the wake of glacial retreat; now human activities are changing the physical structure and geochemistry of these soils and locally stripping them rapidly from the landscape Box 1.

As long as we thought we could simply control the landscape for the convenience of humankind, temporal trends such as these were primarily of academic interest. This cannot be done unless we know what the natural tendencies are—a task that requires a new synthesis of process understanding with research to reconstruct past history quantitatively.

Buried surface features such as channels and beaches serve as conduits and reservoirs for water as well as for oil and natural gas Figure 2. In addition, the new field of carbon sequestration focuses on attempts to remove carbon dioxide CO2 from the atmosphere and store it indefinitely in subsurface reservoirs—often ones from which hydrocarbons have been extracted.

Again, this cannot be done safely and sustainably without detailed knowledge of the subsurface plumbing system.

The petroleum industry spends billions of dollars creating extremely detailed images of the subsurface architecture created as basin subsidence and sediment input build depositional sequences in three dimensions Figure 2.

These images are used to characterize hydrocarbon reservoirs, but as records of geomorphic evolution, their potential value for understanding surface dynamics is enormous and has hardly been tapped. Four billion years of natural experiments. Given the complexity of the surface environment, with its interwoven and highly nonlinear physical, geochemical, and biotic systems, it is not surprising that theoretical methods for predicting its evolution are only in their early stages.

Intentional scientific experiments in the field are common, but necessarily involve short length and time scales; reduced-scale laboratory experiments are proving to be useful, but they cannot capture all aspects of surface dynamics. Photo courtesy of Christopher Paola, University of Minnesota.

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Reflections from deeply buried surfaces were extracted from a three-dimensional seismic volume to produce these maps of ancient seascapes. Bertoni and Cartwright Reproduced with permission of Blackwell Publishing Ltd. Page 40 Share Cite Suggested Citation: We will learn from these experimental results even as we try to predict and perhaps influence them.

Yet the increasing influence of humans at global scales impels us to make better use of the roughly 4-billion-year record of natural experiments that have already occurred on Earth. The record of natural experiments includes extreme events such as meteor impacts and rapid climate changes, as well as states of the Earth—for example, one that is nearly ice-free—that are quite different from the one we know. Now as we put increasing pressure on environmental services, urbanize hazard-prone landscapes, and become predominant geologic agents ourselves, understanding the full range of planetary behavior has become crucial.

Numerous other examples of insights gained from studies of surface evolution on a range of time scales are included in other sections of this report. The archive of Earth history records a far richer range of states and behaviors of the landscape than we can observe directly in the tiny slice of time we occupy today.

dating methods geochronology and landscape evolution observatory

As such, sedimentary and other landscape records can provide critical information about how the landscape could change in the future. Quantitative Reconstruction Interpretation of landscape records by Earth surface scientists to this point has been mostly qualitative. The crucial next step is to accelerate the process of learning to read these often fragmentary records quantitatively, in order to understand long-term dynamics and reconstruct extreme events and variability and to provide the results in a form that can be used by decision makers.

Recent examples of reconstruction include the spectacular findings from ice-core analysis showing that climate can change dramatically see also Section 2. These inspiring results represent a first step to unlocking the surface and sedimentary archive. Initiatives to study the Paleocene-Eocene Thermal Maximum approximately 55 million years agoan ancient warm interval potentially analogous to an anthropogenically warmed Earth, provide a good example of this approach.

Dating Methods Geochronology And Landscape Evolution Observatory

The Calamitous 14th Century. Page 41 Share Cite Suggested Citation: Equally importantly, new radiometric and other surface-dating methods Box 1. These tools are precisely those needed to quantify landscape evolution and to reconstruct the path that has led to the present state.

In tectonically active areas, analysis that includes data from these tools can, for instance, extend seismic records to time spans beyond those of human records see also Section 2. In any area, reading geomorphic history quantitatively will allow us to measure fluctuations in key environmental quantities, such as fluxes of sediment and nutrients through Holocene time the last 11, years of Earth historyand to constrain the magnitudes of extreme events see also Section 2.

These essential data provide the natural context for the observed acceleration of anthropogenic changes to the surface environment. Documenting Topography at the Scale of Transport and Erosion Processes Airborne laser mapping began only in the mid s, and the technology has improved rapidly since then.

In the National Science Foundation NSF supported the founding of the National Center for Airborne Laser Mapping NCALM to provide research-grade airborne laser swath data to the national research community, to advance the technology, and to provide education and training for students.

By Januarymore than 60 projects covering some 13, km2 had been flown.

Dating methods geochronology and landscape evolution observatory

NCALM makes available the data for all its surveys through its web page http: By the end of its first 10 years, NCALM will have flown about 80 seed projects in support of graduate research, providing key data and contributing to a new generation of researchers advancing the field of Earth surface processes through use of high-resolution topography.

InNSF supported an international workshop on High-Resolution Topographic Data and Earth Surface Processes to explore how high-resolution topographic data can advance understanding of Earth surface processes Merritts et al.

dating methods geochronology and landscape evolution observatory

Nearly half of the more than 60 participants were graduate students or postdoctoral researchers who had received a doctorate within the past three years. Page 42 Share Cite Suggested Citation: The confluence of the need to understand and predict the evolution of the surface environment and the availability of large volumes of high-resolution information on the subsurface archive—much of it from the oil and gas industry—provides a new level of motivation to bring these two fields together both to improve prediction in the subsurface and to use the archive to understand how the surface system works.

Another key element is to develop observations and methods that link processes across the range of time scales from the present day to deep time. Laboratory experiments that, in effect, speed up time are one way of approaching this. These experiments are being investigated intensively for their value in understanding climate dynamics and testing numerical climate models.

A glance out an airplane window on a clear day is enough to remind us of the remarkable capacity of landscape processes to create spatial patterns. These geopatterns comprise a diversity of scales and forms, and most show a fascinating mix of order and disorder.

Familiar examples include the treelike, branching patterns of stream networks that create erosional and depositional landscapes; river channels, with their ornate meanders and braids; sand dunes; glacial valleys and landforms; deltas; barrier islands; and the zones and fabrics of soils Figures 2.

Physical landscape patterns are often closely associated with biotic ones, ranging from the variation in forest type with upland elevation to riparian ecosystems tied to stream channels to the exquisite control of marsh vegetation by small changes in land elevation and wetting frequency.

These include cultivated areas with simple geometric boundaries quite unlike the intricate patterns of natural landscapes, as well as cities and towns that may exhibit locally regular spatial structures. New kinds of surface geopatterns appear as we explore landscapes that are new or are on unfamiliar scales. For example, advances in sonar and other underwater imaging techniques have enabled us to visualize underwater landscapes as if from an airplane, revealing spatial patterns on the seafloor that often appear to be scaled-up cousins to their terrestrial counterparts Figure 2.

Page 43 Share Cite Suggested Citation: These and many other geopatterns arise through local interactions and structure the landscape. What do they tell us? The image on the left shows patterns in a mountain and valley landscape on the border of China and Myanmar, while the image on the right shows the sinuous and branching patterns present at the mouth of the Kayan River, Indonesia.

Different isotopes will have unique half-life decay periods, so an isotope that decays slowly can be used to analyze samples hundreds of millions of years old and an isotope such as carbon which can be applied to samples younger than 60, years.

dating methods geochronology and landscape evolution observatory

The age of the coronadite, together with fluid inclusion studies that indicate temperatures of formation in the range degrees C, clearly support a hypogene origin Groves et al.

This recharge can be measured and compared to the latent luminescent signal. Luminescence datingand cosmogenic nuclides indicate that dune systems and stony deserts gibbers are significantly olderthan previously thought.

A study using combined thermochronology, geochronology and provenance analysis. A single job interview, with Consolidated Goldfields towards the end ofand during my final year at Cambridge, went badly.

Relative dating methods Biostratigraphy Biostratigraphy is a relative dating method that relies on the comparison of fossil assemblages of sedimentary rocks and assigning them to an interval of time when the fossils are known to have existed. The project is being spearheaded by Michael J.

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This method of dating is especially useful in explaining the thermal history of a deposit or mineral grain. The isotopic signatures can be found within sediment of any lithology or sediment age. If you wish to use this item outside this site in ways that exceed fair use see http: It can be used for rock that has been exposed between 10 and 30 million years. Sean Fox, Carleton College Reuse: