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The Guaritas sequence is the uppermost stratigraphical level of the Camaqua Basin (southern Brazil) and comprises an alluvial, deltaic and aeolian continental facies association up to 800 m thick. Facies mapping of this unit has revealed a lateral association of tributary fans and trunk braided rivers developed under semi-arid conditions.
We substantially revised the first and second editions of this book while retaining our original objectives: to help you better understand (1) the processes that erode, transport, and deposit sediments (sedimentology); (2) the characteristics and origins of sedimentary rocks (sedimentary petrology); and (3) the complex distribution of the sedimentary rock record in space and time (stratigraphy). The first two areas are the subjects of Chapters 1 through 14. The field of stratigraphy is covered in Chapters 15 through 19.
Some 75% of the rocks at the Earth’s surface are sedimentary in origin, and these include the familiar sandstones, limestones and shales, and the less common but equally well-known salt deposits, ironstones, coal and chert. Sedimentary rocks of the geological record were deposited in the whole range of natural environments that exist today. The study of these modern environments and their sediments and processes contributes much to the understanding of their ancient equivalents. There are some sedimentary rock types; however, for which there are no known modern analogues, or their inferred depositional environments are only poorly represented at the present time.
LISP-UK studies BLACK, K. S. & PATERSON, D. M. LISP-UK Littoral Investigation of Sediment Properties: an introduction DYER, K. R. The typology of intertidal mudflats AMOS, C. L., BRYLINSKY, M., SUTHERLAND, T. F., O'BRIEN, D., LEE, S. & CRAMP, A. The stability of a mudflat in the Humber estuary, South Yorkshire, UK CHRISTIE, M. C. & DYER, K. R. Measurements of the turbid tidal edge over the Skeffling mudflats
LAW, D. J. & BALE, A. J. In situ characterization of suspended particles using focused-beam, laser reflectance particle sizing BROWN, S. L. Sedimentation on a Humber saltmarsh WIDDOWS, J., BRINSLEY, M. & ELLIOTT, M. Use of in situ flume to quantify particle flux (biodeposition rates and sediment erosion) for an intertidal mudflat in relation to changes in current velocity and benthic macrofauna
formations or indeed on any other process in which time played an integral and fundamental role. The advent of radionuclide dating, with the attendant absolute measure of age, changed the views of geology and processes that can occur in ways that have been of major significance. In addition, the radionuclides allow a direct comparison of absolute age to the prior proxies. Accordingly, not only had one available a true age dating but also a proxy scale that could be tie <...>
Sedimentary rock-hosted disseminated gold ores lithologically and chemically similar to those of Carlin-type deposits of the western United States are present in the Yauricocha district, central Peru. The Purisima Concepcion deposit is located in the core of a steeply plunging anticline several hundred meters beyond large pipe-shaped Cu-Zn-Pb-Ag-Au replacement orebodies in limestone bordering a late Miocene granodiorite stock. The central part of the stock is potassium-silicate altered and contains high-salinity fluid inclusions.
The study of sedimentary rocks has come a long way in the past 200 years. In the nineteenth century, they were regarded as the matrix in which fossils occurred and their study, as far as it went, was mainly tied up with the understanding of stratigraphy. Sedimentary rocks had clearly been deposited through time in some way, but little attention was paid to asking exactly how. There was a general appreciation of the idea that ancient processes and conditions of deposition were probably similar to those prevailing at the present day (actualism and uniformitarianism), but, with a few notable exceptions, detailed study concentrated on description of the rocks as materials, rather than as products of dynamic processes and environments. This attitude prevailed until the middle of the twentieth century, although pioneering studies had, by then, used sedimentary structures as indicators of top and bottom (way-up) in deformed successions and as a means of deducing palaeocurrent directions. <...>
The intensive studies in the I 960's and I 970's of modern hallow marine carbonate environments in the Persian Gulf (e.g., Shearman, 1963, 1966; Kinsman, 1966; Butler, I 970; Kendall and Skipwith, 1969; Purser, 1973), Florida and the Bahamas (e.g., Shinn and others, 1969; Hardie, 1977a; Enos and Perkins, 1979), and Western Australia (e.g., Logan and others, 1970, 1974b), led to spectacular advances in our understanding of the deposition and early diagenesis of carbonate rocks. These stud1es were part of a major revolution in edimentology that saw a radical change from an approach based heavily on grain textures to one based on sedimentary structures and early diagenetic features. In this new approach, paleo-environments of serumentary deposits are ruagnosed from the vertical and lateral rustribution of elemental rock uruts (subfacies and faCJes), characterized principally by their assemblages of sedimentary structures and early diagenetic features in combinallon With other properties such as sedimentary textures and biota, using analogs established from observations of processes and their sedimentary records 10 modem depositional environments (the "comparative sedimentology" method of Ginsburg, I 974) <...>
Sedimentary structures that show up in outcrops and cores tell us about physical, biological and sometimes also chemical conditions at the time they were formed. Varying hydraulic or aerodynamic conditions result in assemblages of structures that often bear diagnostic features of sedimentary environments. Therefore an understanding of the origin of sedimentary structures and their assemblages is a prerequisite for sedimentologists and petroleum geologists involved in core description and interpretation.
Sedimentary structures arise in immediate or close association with the transport of sedimentary materials. Some form where erosion predominates, others as net deposition prevails, and yet further kinds in the brief interval of time between sediment deposition and significant lithification. Many sedimentary structures are ordered features visible on sedimentation (bedding) surfaces, whereas others, often related to surface forms, are expressed as compositional and/or textural patterns (stratification) within Sedimentary deposits. Sedimentary structures can be created by chemical and biological as well as by physical agencies, but this book is about those structures wholly or predominantly shaped by physical mechanisms. The latter are much the most important and have continued to attract attention since the earliest days of the earth sciences in their modern form. <...>