Results 301 to 310 of about 137,466 (363)

Permeability tensors for sedimentary structures

Mathematical Geology, 1994
Accurate modeling of fluid flow through sedimentary units is of great importance in assessing the performance of both hydrocarbon reservoirs and aquifers. Most sedimentary rocks display structure from the mm or cm scale upwards. Flow simulation should therefore begin with grid blocks of this size in order to calculate effective permeabilities for ...
G. E. Pickup, P. S. Ringrose, J. L. Jensen, K. S. Sorbie   +3 more
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Microbially Induced Sedimentary Structures: A New Category within the Classification of Primary Sedimentary Structures

Journal of Sedimentary Research, 2001
ABSTRACT Cyanobacterial films and mats syndepositonally influence erosion, deposition, and deformation of sediments. The biomass levels surface morphologies, and microbial mats stabilize depositional surfaces and shelter the sediment against erosion or degassing.
N. Noffke, G. Gerdes, Th. Klenke, W.E. Krumbein   +3 more
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Analysis of Sedimentary Structures

1994
Sedimentary structures are generally studied in the field, where sketches or photographs are taken to record characteristics and for later analysis, and where a compass and clinometer are utilized to quantitatively measure the three-dimensional attitude of the elements composing the structures (see Chapter 3 and PS Chapter 4).
Douglas W. Lewis, David McConchie
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Sedimentary Structures and Bedding

1972
Like texture and composition, sedimentary structures and bedding are inherent in sedimentation. Both are made visible by variations in grain size and to a lesser extent by mineralogy (Fig. 4-1). Because the great majority of structures can be seen with the naked eye, their study is as old as geology itself and, therefore, most of what we know has ...
F. J. Pettijohn, Paul Edwin Potter, Raymond Siever   +2 more
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Primary Sedimentary Structures

Annual Review of Earth and Planetary Sciences, 1979
While rivers flow, waves pound the shore, or winds shift sand and dust across the desert, particles moved and dropped by these processes build mounds, ridges, and corrugations or form layering that subtly records the history of events. We can see the most recent products of this action when we stroll across a now-dry river bed or tidal zone or over a ...
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Cyanobacteria: Architects of Sedimentary Structures

2000
Cyanobacteria, the oldest oxygenic phototrophs on the planet, once made the most significant impact on sediments and left an impressive fossil record of organo-sedimentary structures. Today, cyanobacteria dominate extreme environments where they participate in sediment production, construction and destruction, and leave characteristic, often species ...
Stjepko Golubic, Lee Seong-Joo, Kathleen M. Browne   +2 more
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Description of sedimentary structures

1987
Primary sedimentary structures are formed at the time of deposition or shortly thereafter. The character of these structures depends mainly on current velocity, water depth, grain size, and sedimentation rate. As such they are critical to the understanding of the processes and conditions of deposition and lead to an interpretation of the depositional ...
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Sedimentary deformational structures

1994
This chapter is concerned with those structures that develop as a result of deformation early in the burial history of a sediment. Historical aspects, including numerous literature references, are discussed by van Loon (1992). Some structures form very soon after or even during deposition and are sometimes referred to as penecontemporaneous structures.
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Flow Structures in Sedimentary Rocks

The Journal of Geology, 1960
A number of oriented sedimentary structures from graywacke sequences in North Lancashire and Devonshire, England, are described and their origin discussed. It is concluded that they originated by horizontal flow of sediment, induced either by the drag of the depositing current or by sliding down a slope.
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Analysis of sedimentary structures

1987
Directional properties of sedimentary structures are important in paleoenvironmental interpretation. Generally they indicate the current flow direction at the time of deposition and provide an important key for evaluating paleogeography. In fluvial, deltaic, and most turbidite deposits, paleocurrent patterns indicate paleoslope.
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