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Monograph available for loan

Facies models : response to sea level change (1994)

Walker, Roger G. [Hrsg.] ; James, Noel P. [Hrsg.]

St. John's, Newfoundland : Geological Association of Canada

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Call number: M 96.0130

Type of Medium: Monograph available for loan

Pages: 454 S.

Edition: 2nd print.

ISBN: 0919216498

Classification:

Sedimentology

Language: English

Location: Upper compact magazine

Branch Library: GFZ Library

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Turbidites in the Upper Carboniferous Ross Formation, western Ireland: reconstruction of a channel and spillover system (2003)

Lien, Trond ; Walker, Roger G. ; Martinsen, Ole J.

Oxford, UK : Blackwell Science Ltd

Sedimentology 50 (2003), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The Upper Carboniferous deep-water rocks of the Shannon Group were deposited in the extensional Shannon Basin of County Clare in western Ireland and are superbly exposed in sea cliffs along the Shannon estuary. Carboniferous limestone floors the basin, and the basin-fill succession begins with the deep-water Clare Shales. These shales are overlain by various turbidite facies of the Ross Formation (460 m thick). The type of turbidite system, scale of turbidite sandstone bodies and the overall character of the stratigraphic succession make the Ross Formation well suited as an analogue for sand-rich turbidite plays in passive margin basins around the world. The lower 170 m of the Ross Formation contains tabular turbidites with no channels, with an overall tendency to become sandier upwards, although there are no small-scale thickening- or thinning-upward successions. The upper 290 m of the Ross Formation consists of turbidites, commonly arranged in thickening-upward packages, and amalgamated turbidites that form channel fills that are individually up to 10 m thick. A few of the upper Ross channels have an initial lateral accretion phase with interbedded sandstone and mudstone deposits and a subsequent vertical aggradation phase with thick-bedded amalgamated turbidites. This paper proposes that, as the channels filled, more and more turbidites spilled further and further overbank. Superb outcrops show that thickening-upward packages developed when channels initially spilled muds and thin-bedded turbidites up to 1 km overbank, followed by thick-bedded amalgamated turbidites that spilled close to the channel margins. The palaeocurrent directions associated with the amalgamated channel fills suggest a low channel sinuosity. Stacks of channels and spillover packages 25–40 m thick may show significant palaeocurrent variability at the same stratigraphic interval but at different locations. This suggests that individual channels and spillover packages were stacked into channel-spillover belts, and that the belts also followed a sinuous pattern. Reservoir elements of the Ross system include tabular turbidites, channel-fill deposits, thickening-upward packages that formed as spillover lobes and, on a larger scale, sinuous channel belts 2·5–5 km wide. The edges of the belts can be roughly defined where well-packaged spillover deposits pass laterally into muddier, poorly packaged tabular turbidites. The low-sinuosity channel belts are interpreted to pass downstream into unchannellized tabular turbidites, equivalent to lower Ross Formation facies.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-3091.2003.00541.x

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A storm and tidally-influenced prograding shoreline—Upper Cretaceous Milk River Formation of Southern Alberta, Canada (1986)

McCRORY, VERNON L. C. ; WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 33 (1986), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The Santonian-Campanian Milk River Formation of Southern Alberta represents the transition from an open shelf, through a storm-dominated shoreface into a non-marine sequence of shales and sandstones, with coal. The open shelf deposits consist of interbedded bioturbated mudstones with sharp-based hummocky cross-stratified sandstones. There are no indications of fairweather reworking of the sandstones, which are therefore interpreted as having been deposited below fairweather wavebase. The shoreface sequence consists of a 28 m thick sandstone. It has a very sharp, loaded base, and is dominated by swaley cross-stratification, a close relative of hummocky cross-stratification. Angle of repose cross-bedding is preserved in scattered patches only in the top 5 m of the sand body. Channels up to 180 m wide and 7 m deep are cut into this sand body, with channel margins characterized by lateral accretion surfaces. Regional dispersal trends, as well as local palaeocurrent readings suggest flow toward the NW. Within the channels there is some herringbone cross-bedding and at least two examples of neap-spring bundle cycles, suggesting that the channels are tidally-influenced. Above the channels there is a sequence of carbonaceous shales with in situ root casts and lignitic coal seams. No marine, brackish or lagoonal fauna was identified, and the sequence appears to represent a distal floodplain.The sequence from interbedded hummocky cross-stratified sandstones and bioturbated mudstones into a 10–20 m thick, sharp-based shoreface sandstone characterized by swaley cross-stratification is uncommon. The scarcity or absence of angle of repose cross-bedding in the shoreface, and the dominance of swaley cross-stratification suggests that the shoreface was so storm-dominated that almost no fairweather record was preserved. Other examples of swaley cross-stratified shorefaces are reviewed in the paper.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1986.tb00744.x

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The Cambro-Ordovician Cap Enragé Formation, Queébec, Canada: conglomeratic deposits of a braided submarine channel with terraces (1982)

HEIN, FRANCES J. ; WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 29 (1982), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The Cambro-Ordovician Cap Enragé Formation is interpreted as a deep submarine channel complex of conglomerates, pebbly sandstones and massive sandstones. The formation is up to 270 m thick, and crops out in a coastal belt 50 km long. In general terms, it has previously been interpreted as a deep sea channel deposit, with the channel about 300 m deep, at least 10 km wide and trending south-westward, parallel to the coastal outcrops. Eight facies have been defined in this study and they have been grouped into three major facies associations. In the Coarse Channelled Association, conglomerates with carbonate boulders up to about 4 m are associated with graded-stratified finer grained conglomerates. Facies of this association make up about 25% of all the beds in the formation. The association is also characterized by abundant major channels 1–10 m deep and up to 250 m wide. Excellent outcrop allows the reconstruction of topographic highs (bars) within the channels and the association is interpreted as a braided channel and bar system.The second association, Multiple-Scoured Coarse Sandstones, contains some graded-stratified fine conglomerates, along with massive to structureless coarse and pebbly sandstones, and rare cross-bedded pebbly sandstones. Deep channels are absent, but multiple channelling on the scale of 0.5–1 m is characteristic. In the absence of the very coarse conglomerates and deeper channelling, this association is interpreted as being deposited on topographically higher terrace areas adjacent to the main braid plain.The third facies association, Unchannelled Sandstones, is characterized by massive sandstones with abundant fluid-escape structures, classical turbidites and thin shales. In the absence of any scouring deeper than a few tens of centimetres, this association is interpreted as being deposited on an even higher and smoother terrace, farther from the braid plain.Palaeoflow directions for conglomerate facies indicate fairly consistent south-westward transport, apparently parallel to the base of the Cambro-Ordovician continental slope. Flow directions in the finer-grained facies are rather variable, suggesting complex bar development and overbank spills.Thinning-and fining-upward sequences are present on two scales. The smaller, 1–10 m sequence, is related to channel filling and abandonment. Thicker sequences (10–100 m), with facies of the Multiple Scoured, and Unchannelled Sandstone Associations, may indicate switching of a main channel away from the area and its subsequent burial by marginal terrace and higher terrace deposits.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1982.tb01798.x

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Facies relationships in Pleistocene outwash gravels, southern Ontario: a model for bar growth in braided rivers (1974)

EYNON, GEORGE ; WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 21 (1974), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: Facies relationships in Pleistocene braided outwash deposits in southern Ontario demonstrate the presence of a large braid bar with adjacent side channel. The core of the bar is up to 6 m high, and consists of crudely horizontally stratified gravels. Downstream from the core is the bar front facies, consisting of large gravelly foresets up to 4 m high, rounded off in many places by reactivation surfaces. Upstream from the core is the bar stoss side facies consisting of several sets (individually up to 35 cm thick) of tabular cross-bedding, arranged in coarsening-upward sequences. The stoss side—core—bar front relationships are continuously exposed in one 400 m long quarry face which is cut almost parallel to the palaeoflow direction. A transverse quarry face shows the side channel facies, which consists of trough cross-bedded sands. Gravel layers can be seen to finger from the main gravelly bar into the sandy side channel, but they do not reach the base of the channel. This surprising relationship indicates that gravel moved only in the topographically higher parts of the system. After deposition in the side channel, and growth upstream and downstream from the bar core, the entire system aggraded. Crudely horizontally stratified, and imbricated gravel sheets were laid down as a bar top facies.Grain size analyses indicate strongly bimodal distributions, implying that much of the sand in the spaces between pebbles and boulders filtered in after the gravel had been deposited. This interpretation is strengthened by velocity calculations—mean velocities in excess of 300 cm/s would be needed to roll the gravel as bed load, but at such a velocity, a large amount of sand would be transported entirely in suspension.In a final section of the paper, our results are combined with other work on braided systems in an attempt to formulate a more general facies model.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1974.tb01781.x

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Internal architecture and sedimentary evolution of coarse-grained, turbidite channel-levee complexes, Early Eocene Regência Canyon, Espírito Santo Basin, Brazil (1997)

BRUHN, CARLOS H. L. ; WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 44 (1997), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: Successions of Early Eocene coarse-grained turbidites up to 400 m thick fill fault-controlled canyons along the eastern Brazilian continental margin. They form part of a Late Albian to Early Eocene transgressive succession characterized by onlapping, deepening-upward sedimentation. In the Lagoa Parda oil field (Regência Canyon, Espírito Santo Basin) the turbidite facies consist mostly of unstratified conglomerate and sandstone, with interbedded bioturbated mudstone and thin-bedded, stratified sandstone. Within the main Regência Canyon, the coarser grained facies occur within 38 deeply incised channels. The fills are 9 to 〉50 m thick, 210 to 〉1050 m wide and 〉1 km long. The finer grained facies build asymmetrical levees that are higher and thicker on the left side (looking downstream) of their channels, probably as an effect of the Coriolis force (to the left in the Southern Hemisphere). Nine levee successions up to 50 m thick are associated with the 20 youngest channels. The deposits filling the low-sinuosity Lagoa Parda channels record successive channel abandonment through relatively rapid avulsions. Avulsions of unleveed channels took place randomly, but channels with well-developed levees show preferential avulsion to the right (looking downstream), opposite to the direction of preferential levee growth.Lagoa Parda channels can be grouped into three complexes 20–100 m thick. These complexes have an estimated duration of about 140 000 years. It is suggested that control of the development of individual channel complexes was related to variation in sediment supply, in turn probably related to climatic changes. The deposition of each channel complex would have followed an increase in sediment supply into the Regência Canyon through delta/fan-delta and littoral drift systems, which in turn would have responded to phases of higher denudation rates in the high-relief, ancestral coastal ranges of south-eastern Brazil.Overall, the three Lagoa Parda channel complexes form a turbidite succession characterized by channel fills that become narrower, thinner and finer grained upward. These trends were induced mostly by a longer term (〉400 000 years) decrease in sediment supply, which in turn resulted from the combined effects of a long-term (second-order) trend of sea-level rise, and the decreasing fault activity at the basin margin and source area.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1997.tb00422.x

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Fluvial processes and facies sequences in the sandy braided South Saskatchewan River, Canada (1978)

CANT, DOUGLAS J. ; WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 25 (1978), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: The South Saskatchewan River has a long term average discharge of 275 m3/sec, with flood peaks in the range of 1500 to 3800 m3/sec. South of Saskatoon, the four major types of geomorphological elements recognised are channels, slipface-bounded bars, sand flats and vegetated islands and floodplains. Major channels are 3-5 m deep, up to 200 m wide, and flow around sand flats which are 50-2000 m long, and around vegetated islands up to 1 km long. At areas of flow expansion, long straight-crested cross-channel bars form. During falling stage, a small part of the crest of the cross-channel bar may become emergent, and act as a nucleus for downstream and lateral growth of a new sand flat.The dominant channel bedforms are dunes, which deposit trough cross bedding. Cross-channel bars deposit large sets of planar tabular cross bedding. Sand flats that grow from a nucleus on a cross-channel bar are mostly composed of smaller planar tabular sets, with some parallel lamination, trough cross-bedding, and ripple cross-lamination. A typical facies sequence related to sand flat growth would consist of in-channel trough cross-bedding, overlain by a large (1-2 m) planar tabular set (cross-channel bar), overlain in turn by a complex association mostly of small planar tabular cross-beds, trough cross-beds and ripple cross-lamination.By contrast, a second stratigraphic sequence can be proposed, related only to channel aggradation. It would consist dominantly of trough cross-beds, decreasing in scale upward, and possible interrupted by isolated sets of planar tabular cross-bedding if a cross-channel bar formed, but failed to grow into a sand flat. During final filling of the channel, ripple cross-lamination and thin clay layers may be deposited. In the S. Saskatchewan, these sequences are a minimum of 5 m thick, and are overlain by 0.5-1 m of silty and muddy vertical accretion deposits.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1978.tb00323.x

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DISTINCTIVE TYPES OF RIPPLE-DRIFT CROSS-LAMINATION (1963)

WALKER, ROGER G.

Oxford, UK : Blackwell Publishing Ltd

Sedimentology 2 (1963), S. 0

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ISSN: 1365-3091

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Geosciences

Notes: From work on two Upper Carboniferous formations in southwest England, three morphologically distinct types of ripple-drift cross-lamination have been recognised. Type 1 is characterised by strong erosion of laminae on the stoss (or up-current) side of the ripples, and absence of grading. Type 3 is characterised by an absence of erosion on the stoss sides, concentration of mud in the ripple troughs and an upward gradual decrease in grain size and amplitude of rippling. Type 2 is an intermediate form with some characteristics in common with types 1 and 3. An examination of the illustrated literature has shown that types 1 and 3 occur frequently, and that type 2 has not pre- viously been recorded.It is suggested that type 1 is formed in fluvial and shallow water environments at times of net deposition of sediment, and that type 3 is formed by deposition from a tur- bidity current. Type 2 suggests hydrodynamic conditions intermediate between fluvial or shallow water traction currents, and turbidity currents.Since all current ripples move forwards, or “drift”, it is suggested that the term “ripple-drift” should be used to describe ripple cross-lamination where the ripples can be seen to climb onto the stoss slope of the ripple immediately downstream, there having been a net deposition, and not merely a forward drift of sediment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-3091.1963.tb01212.x

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