The history of a continent from UPb ages of zircons from Orinoco River sand and SmNd isotopes in Orinoco basin river sediments

1997 ◽  
Vol 139 (1-4) ◽  
pp. 271-286 ◽  
Author(s):  
S.L. Goldstein ◽  
N.T. Arndt ◽  
R.F. Stallard
2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Adrian Gawedzki ◽  
K. Wayne Forsythe

Anthracene and arsenic contamination concentrations at various depths in the Buffalo River were analyzed in this study. Anthracene is known to cause damage to human skin and arsenic has been linked to lung and liver cancer. The Buffalo River is labelled as an Area of Concern defined by the Great Lakes Water Quality Agreement between Canada and the United States. It has a long history of industrial activity located in its near vicinity that has contributed to its pollution. An ordinary kriging spatial interpolation technique was used to calculate estimates between sample locations for anthracene and arsenic at various depths. The results show that both anthracene and arsenic surface sediment (0–30 cm) is less contaminated than all subsurface depths. There is variability of pollution within the different subsurface levels (30–60 cm, 60–90 cm, 90–120 cm, 120–150 cm) and along the river course, but major clusters are identified throughout all depths for both anthracene and arsenic.


2004 ◽  
Vol 41 (1) ◽  
pp. 103-125 ◽  
Author(s):  
Nathan T Petersen ◽  
Paul L Smith ◽  
James K Mortensen ◽  
Robert A Creaser ◽  
Howard W Tipper

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, Sm–Nd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic – Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and Sm–Nd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.


1986 ◽  
Vol 51 (3) ◽  
pp. 505-527 ◽  
Author(s):  
Julie K. Stein

The history of coring and augering at archaeological sites is traced to two periods in the twentieth century. In the first period, Period I (1935-1955), the technique was used primarily to correlate archaeological deposits with river sediments for dating purposes. Rarely were the deposits containing artifacts cored or augered; rather the stratigraphic relationship of cultural to non-cultural deposits was sought. Most of this work was done in the Lower Mississippi River Delta where geologists had calculated absolute dates for river deposits. This period seems to have ended with the availability of radiometric dating and was followed by Period II (1964-present). After 1964 there is a renewed interest in coring and augering, mostly following a shift in archaeological research interests from culture history toward ecological questions. This shift coincides with the availability of a new device: a mechanical corer. During Period II, coring is utilized in many different projects, including reconstructing the environment surrounding sites, collection of samples from subsurface deposits, and locating buried archaeological sites. Following the discussion of the history of coring and augering, a description of equipment, techniques, and data potential is presented.


2008 ◽  
Vol 8 (3) ◽  
pp. 165-176 ◽  
Author(s):  
Ondrej Bábek ◽  
Klára Hilscherová ◽  
Slavomír Nehyba ◽  
Josef Zeman ◽  
Martin Famera ◽  
...  

2020 ◽  
Author(s):  
Marco Giovanni Malusa' ◽  
Paul G. Fitzgerald

<p>Constraining spatial and temporal patterns of topography and exhumation along the Himalayan orogen is a starting point for studies aimed at understanding the development of Asian climate and tectonic evolution. Starting from the pioneering work of Cerveny et al. (1988), many scientists have applied a detrital thermochronologic approach to reveal the Cenozoic exhumation history of the Himalayas. Thermochronologic studies involve analyses of modern river sediments and sedimentary successions either accreted on the southern side of the orogen or accumulated in the Indus and Bengal fans. As datasets have grown and techniques evolved, the available interpretations are often contradictory.</p><p>In this contribution, we analyse previously published detrital-thermochronology datasets in the Himalayan region using the interpretive keys illustrated in Malusà and Fitzgerald (2020). These keys reinforce existing approaches and provide new perspectives for the application of detrital thermochronology to tectonic settings where the geologic evolution is often still debated. Different thermochronologic systems applied to proximal and distal sedimentary successions derived from Himalayan erosion yield a complex exhumation and tectonic history, but a relatively consistent picture for the Cenozoic evolution of India-Eurasia collision emerges. Detrital thermochronology data are supportive of a progressive southward thrust propagation towards the Himalayan foreland, progressively involving new eroding sources. The onset of fast exhumation in the Lesser Himalaya is constrained by different thermochronologic methods and datasets, indicative of onset at ~10 Ma, in line with independent geologic evidence. Coeval fast exhumation is also recorded in detritus derived from the Greater Himalaya. These findings are supportive of a major morphogenic phase of mountain building in the Himalayas at ~10 Ma, prior to the onset of fast exhumation in the Namche Barwa syntaxis.</p><p>Cerveny PF et al (1988). <em>History of uplift and relief of the Himalaya during the past 18 million years: Evidence from fission-track ages of detrital zircons from sandstones of the Siwalik Group</em>. In: New perspectives in basin analysis, Springer.</p><p>Malusà MG, Fitzgerald PG (2020). <em>The geologic interpretation of the detrital thermochronology record within a stratigraphic framework, with examples from the European Alps, Taiwan and the Himalayas.</em> Earth-Science Reviews, https://doi.org/10.1016/j.earscirev.2019.103074</p>


Author(s):  
Branimir Jovancicevic ◽  
Gordana Gajica ◽  
Gorica Veselinovic ◽  
Milica Kasanin-Grubin ◽  
Tatjana Solevic-Knudsen ◽  
...  

Biological markers (BMs) are organic compounds in oils in which a precursor is known, during the transformation of organic matter these compounds undergo certain structural and stereochemical changes. Based on the established precursors of BMs, the origin of the examined oils can be estimated, and based on the intensity and type of changes, geological history. It includes defining the deposition medium, the degree of maturation, the length of the oil migration path, the degree of biodegradation. The most studied and applied BMs are normal alkanes, isoprenoid aliphatic alkanes pristane and phytane, and polycyclic alkanes of the sterane and terapane type. On the other hand, in environmental chemistry, these compounds can significantly contribute to the identification of petroleum pollutants, as well as to the assessment of the migration mechanism and the intensity of biodegradation. This review paper first presents the results related to the application of BMs in organic geochemical correlations of oil in the southeastern part of the Pannonian Basin (I). The second part provides an overview of those researches in which the same BMs were used in the identification of oil pollutants and in monitoring its changes during migration and biodegradation in rivers and river sediments of Serbia (II).


2017 ◽  
Vol 89 (3) ◽  
pp. 769-785 ◽  
Author(s):  
Randall J. Schaetzl ◽  
Phillip H. Larson ◽  
Douglas J. Faulkner ◽  
Garry L. Running ◽  
Harry M. Jol ◽  
...  

AbstractOur study adds to the Quaternary history of eolian systems and deposits in western Wisconsin, USA, primarily within the lower Chippewa River valley. Thickness and textural patterns of loess deposits in the region indicate transport by west-northwesterly and westerly winds. Loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands, similar in some ways to shadow dunes. In many areas, sand was transported up and onto the western flanks of bedrock ridges as sand ramps, presumably as loess was deposited in their lee. Long, linear dunes, common on the sandy lowlands of the Chippewa valley, also trend to the east-southeast. Small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes. Finally, in areas where sediment was being exposed by erosion along cutbanks of the Chippewa River, sand appears to have been transported up and onto the terrace treads, forming cliff-top dunes. Luminescence data indicate that this activity has continued throughout the latest Pleistocene and into the mid-Holocene. Together, these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period.


Author(s):  
R.I. Spaggiari ◽  
M.C.J. de Wit

Abstract The Kasai alluvial field in southern Democratic Republic of Congo (DRC) is part of central Africa’s largest diamond placer that has produced more than 200 million carats, mainly derived from Quaternary deposits. A small part of these deposits, along and within the Longatshimo River, is the subject of this study providing a glimpse into the alluvial history of the Kasai diamond placer. This work documents their sedimentological and diamond mineralization attributes, as well as their emplacement processes, which can inform future exploration models. The key controls of this placer formation, notably Quaternary climatic variations, fluvial landscape evolution and bedrock conditions are also evaluated. A consequence of the interplay among these processes is that diamond supply (from Cretaceous alluvial sources), recycling and concentration were most pronounced and consistent, in the Late Quaternary. Alluvial diamond mineralization in this central African region thus evolved differently to those in southern Africa. Based on exploration results in the Longatshimo Valley, diamond concentration improves but diamond size diminishes with decreasing deposit age, and thus the modern river sediments contain the highest abundance but smallest diamonds. This is opposite to the grade and diamond size trend that characterises southern African fluvial diamond placers. The Longatshimo River study offers insight into the Kasai alluvial field, and its placer model is expected to be applicable to the exploration of other central African diamond placers.


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