to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

Empirical parameterization of setup, swash, and runup

1. Introduction 2. Observation techniques 3. Description of ocean waves 4. Statistics 5. Linear wave theory (oceanic waters) 6. Waves in oceanic waters 7. Linear wave theory (coastal waters) 8. Waves in coastal waters 9. The SWAN wave model Appendices References Index.

/pdf/waves-in-oceanic-and-coastal-waters-6ofdu4icqi.pdf

Waves in Oceanic and Coastal Waters

This textbook outlines the physical, chemical, and biologic properties of the major sedimentary rocks, as revealed by petrographic microscopy, geochemical techniques, and field study It covers the mineralogy, chemistry, textures, and sedimentary structures that characterise sedimentary rocks, and relates these features to the depositional origin of the rocks and their subsequent alteration by diagenetic processes during burial In addition to detailed sections on siliciclastic and carbonate rocks, it also discusses evaporites, cherts, iron-rich sedimentary rocks, phosphorites, and carbonaceous sedimentary rocks such as oil shales This second edition maintains the comprehensive treatment of sedimentary petrography and petrology provided in the first edition, and has been updated with new concepts and cutting-edge techniques like cathodoluminescence imaging of sedimentary rocks and backscattered electron microscopy It is ideal for advanced undergraduate and graduate courses in sedimentary petrology, and is a key reference for researchers and professional petroleum geoscientists

Petrology of sedimentary rocks

Analyses of 3-D seismic data in predominantly basin-floor settings offshore Indonesia, Nigeria, and the Gulf of Mexico, reveal the extensive presence of gravity-flow depositional elements. Five key elements were observed: (1) turbidity-flow leveed channels, (2) channel-overbank sediment waves and levees, (3) frontal splays or distributary-channel complexes, (4) crevasse-splay complexes, and (5) debris-flow channels, lobes, and sheets. Each depositional element displays a unique morphology and seismic expression. The reservoir architecture of each of these depositional elements is a function of the interaction between sedimentary process, sea-floor morphology, and sediment grain-size distribution.

(1) Turbidity-flow leveed-channel widths range from greater than 3 km to less than 200 m. Sinuosity ranges from moderate to high, and channel meanders in most instances migrate down-system. The high-amplitude reflection character that commonly characterizes these features suggests the presence of sand within the channels. In some instances, high-sinuosity channels are associated with (2) channel-overbank sediment-wave development in proximal overbank levee settings, especially in association with outer channel bends. These sediment waves reach heights of 20 m and spacings of 2-3 km. The crests of these sediment waves are oriented normal to the inferred transport direction of turbidity flows, and the waves have migrated in an up-flow direction. Channel-margin levee thickness decreases systematically down-system. Where levee thickness can no longer be resolved seismically, high-sinuosity channels feed (3) frontal splays or low-sinuosity, distributary-channel complexes. Low-sinuosity distributary-channel complexes are expressed as lobate sheets up to 5-10 km wide and tens of kilometers long that extend to the distal edges of these systems. They likely comprise sheet-like sandstone units consisting of shallow channelized and associated sand-rich overbank deposits. Also observed are (4) crevasse-splay deposits, which form as a result of the breaching of levees, commonly at channel bends. Similar to frontal splays, but smaller in size, these deposits commonly are characterized by sheet-like turbidites. (5) Debris-flow deposits comprise low-sinuosity channel fills, narrow elongate lobes, and sheets and are characterized seismically by contorted, chaotic, low-amplitude reflection patterns. These deposits commonly overlie striated or grooved pavements that can be up to tens of kilometers long, 15 m deep, and 25 m wide. Where flows are unconfined, striation patterns suggest that divergent flow is common. Debris-flow deposits extend as far basinward as turbidites, and individual debris-flow units can reach 80 m in thickness and commonly are marked by steep edges. Transparent to chaotic seismic reflection character suggest that these deposits are mud-rich.

Stratigraphically, deep-water basin-floor successions commonly are characterized by mass-transport deposits at the base, overlain by turbidite frontal-splay deposits and subsequently by leveed-channel deposits. Capping this succession is another mass-transport unit ultimately overlain and draped by condensed-section deposits. This succession can be related to a cycle of relative sea-level change and associated events at the corresponding shelf edge. Commonly, deposition of a deep-water sequence is initiated with the onset of relative sea-level fall and ends with subsequent rapid relative sea-level rise.

http://www.zenzebra.net/posamentier/posamentier-deep-water-depositional-elements.pdf

Seismic Geomorphology and Stratigraphy of Depositional Elements in Deep-Water Settings

/pdf/beach-processes-and-sedimentation-1hp2lfbcte.pdf

Beach Processes and Sedimentation

A two-dimensional parametrization of a surf zone with a time-dependent breakpoint due to groupiness in the incident wave field is developed. The breakpoint is defined in terms of a mean position X plus a modulation Δa. Free wave solutions are obtained on a plane beach at the group frequency and its harmonics. Shoreward of the breakpoint, standing waves are found, while seaward an outgoing progressive wave exists. The amplitude of the standing wave is relatively insensitive to the incident wave field. The amplitude of the outgoing wave depends on X, the group frequency σ, and the beach slope tan β. For certain values of X = (σ2X/g tan β) the amplitude of the outgoing wave goes to zero. It appears that any ‘resonant’ response of the standing wave shoreward of the breakpoint is suppressed by seaward radiation of energy by the outgoing wave.

Two-dimensional surf beat: Long wave generation by a time-varying breakpoint

‘Set-down’ and set-up, the negative and positive changes in mean water level due to the presence of a train of surface waves, was measured in a wave channel. Well outside the break point the experimental results are in good agreement with the theoretical relationship determined by Longuet-Higgins and Stewart. Near the break point, where the wave height is greater than predicted by first-order wave theory, the measured ‘set-down’ was consistently less than theory would predict from the deep water wave height. Inside the break point the bore height was found to be a linear function of the mean water depth. In this region, the gradient of the set-up, , was related to the beach slope tan β and the mean ratio of wave height to water depth by the equation .

Wave ‘set-down’ and set-Up

A two-dimensional parametrization of a surf zone with a time-dependent breakpoint due to groupiness in the incident wave field is developed. The breakpoint is defined in terms of a mean position X plus a modulation Aa. Free wave solutions are obtained on a plane beach at the group frequency and its har- monics. Shoreward of the breakpoint, standing waves are found, while seaward an outgoing progressive wave exists. The amplitude of the standing wave is relatively insensitive to the incident wave field. The amplitude of the outgoing wave depends on X, the group frequency o, and the beach slope tan . For certain values of X -- (o2X?g tan ) the amplitude of the outgoing wave goes to zero. It appears that any 'resonant' response of the standing wave shoreward of the breakpoint is suppressed by seaward radiation of energy by the outgoing wave. As waves propagate onshore and through the surf zone, en- ergy is transferred away from the primary incident wave fre- quencies. Within the surf zone, a mean pressure gradient is es- tablished resulting in wave setup (Longuet-Higgins and Stewart, 1964) and obliquely incident waves drive longshore currents (Bowen, 1969; Longuet-Higgins, 1970a, b). The first reports of low frequency motions in the nearshore zone were made by Munk (1949) and Tucker (1950). Since then, rela- tively high levels of low frequency energy in the nearshore have been widely reported in the literature. The resonant excitation of free edge waves can account for a significant part of this low frequency energy (Huntley, 1976; Holman et al., 1978; Holman, 1979). Theoretically, obliquely incident wave groups may transfer energy to free waves satis- fying the edge wave dispersion relation (Gallagher, 1971; Bowen and Cruza, 1978), and this resonant process can result in large amplitude waves trapped to the shoreline. There is, however, evidence that other motion not associ- ated with free edge waves also contributes significantly to the low frequency energy (Tucker, 1950; Huntley et al., 1981). Tucker observed a correlation between a long wave and the envelope of the incoming swell, with a lag approximately equal to the time required for the swell to propagate into the surf zone and for the associated long wave to be reflected back as a free wave. Longuet-Higgins and Stewart (1964), using the concept of radiation stress, were able to show the existence of a long period forced wave associated with incident wave groups. This forced wave is 180 o out of phase with the in- cident wave group and travels at the group velocity. In view of Tucker's observations, Longuet-Higgins and Stewart suggest that this forced wave is released at the breakpoint and travels seaward as a free wave; but the mechanism by which this oc- curs is not discussed. Huntley et al. (1981) describe data from an extensive array of two component electromagnetic current meters that consistently show energy levels in the onshore- offshore component of flows to be substantially larger than predicted from measured longshore flows by using edge wave theory. Forced wave motion is a possible source of energy that, for near-normally incident waves, may be predominantly in the onshore-offshore direction. None of the published models of long wave forcing account

Long Wave Generation by a Time-Varying Breakpoint

Turbidite muds in cores from the outer Scotian continental margin, off eastern Canada, contain abundant thin silt laminae. Graded laminated units are recognized in parts of this sequence. These represent single depositional events, and show a regular decrease in modal grain size and thickness of the silt laminae through the unit. A similar fining trend is shown by both silt and mud layers over hundreds of kilometres downslope. Textural analysis of individual laminae allows the construction of a dynamically consistent physical model for transport and sorting in muddy turbidity currents. Hydraulic sorting aggregates finer material to the top and tail regions of a large turbidity flow which then overspills its channel banks. Downslope lateral sorting occurs with preferential deposition of coarser silt grains and larger mud flocs. Depositional sorting by increased shear in the boundary layer separates clay flocs from silt grains and results in a regular mud/silt lamination. Estimates can be made of the physical parameters of the turbidity flows involved. They are a minimum of several hundreds of metres thick, have low concentrations (of the order of 10−3 or 2500 mg 1−1), and move downslope at velocities of 10-20 cm s−1. A 5 mm thick, coarse silt lamina takes about 10 h to deposit, and the subsequent mud layer ‘blankets’ very rapidly over this. A complete unit is deposited in 2-6 days which is the time it takes for the turbidity flow to pass a particular point. These thick, dilute, low-velocity flows are significantly different from the ‘classical’ turbidity current. However, there is mounting evidence in support of the new concept from laboratory observations and direct field measurements.

A physical model for the transport and sorting of fine‐grained sediment by turbidity currents

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