Journal ArticleDOI
The Interpretation of Vertical Sequences in Turbidite Beds: The Influence of Longitudinal Flow Structure
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In this article, a turbidity current may deposit a structureless, poorly sorted bed where the capacity of the current is exceeded, i.e., where there is insufficient turbulent kinetic energy to maintain the entire suspended mass.Abstract:
Because turbidite beds aggrade progressively beneath a moving current, the vertical grain-size profile of a bed is generally an indication of the longitudinal velocity structure of the flow, and longitudinal gradients in suspended sediment concentration ("density"). A current is more likely to show a simple waning flow history farther from its source; this is because faster-moving parts of the flow overtake slower moving parts, and the flow organizes itself over time so that the fastest parts are at the front. Thus distal (e.g., basin plain) turbidites commonly show simple, normally graded profiles, whereas more proximal turbidites often show complex vertical sequences within a bed, related to unsteadiness. A turbidity current may deposit a structureless, poorly sorted bed where the capacity of the current is exceeded, i.e., where there is insufficient turbulent kinetic energy to maintain the entire suspended mass. Capacity-driven deposition may occur where the flow decelerates. Where flow nonuniformity is the cause of capacity-driven deposition, a massive interval will form the lowest part of the bed, and will have a flat base. Where flow unsteadiness is the cause, a normally graded massive interval may overlie erosional features or traction structures at the base of the bed. Based on the assumption of longitudinal gradients in velocity, density, and grain-size distribution, the longitudinal density structure of a current may induce a switch, at any given point, from capacity-driven deposition to either (1) bypass and resuspension, (2) bypass with traction, or (3) competence-driven deposition, each resulting in a characteristic upward change in deposit character. The temporal evolution of the flow at a point varies systematically in a streamwise sense. Taking account of these longitudinal variations permits predictions of complex vertical sequences within beds, and of their downstream relations.read more
Citations
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Journal ArticleDOI
Subaqueous sediment density flows: Depositional processes and deposit types
TL;DR: In this article, the authors summarized the processes by which density flows deposit sediment and proposed a new single classification for the resulting types of deposit, which is consistent with previous models of spatial decelerating (dissipative) dilute flow.
Journal ArticleDOI
Hybrid sediment gravity flow deposits – Classification, origin and significance
TL;DR: For example, hybrid event beds as mentioned in this paper contain up to five internal divisions: argillaceous and commonly mud clast-bearing sandstones overlie either banded sandstones (transitional flow deposits, H2) and/or structureless sandstone (high-density turbidity currents, H1), recording longitudinal and or lateral heterogeneity in flow structure and development of turbulent, transitional and laminar flow behaviour in different parts of the same flow.
Journal ArticleDOI
Deposit Structure and Processes of Sand Deposition from Decelerating Sediment Suspensions
TL;DR: In this paper, a series of experiments were conducted in an annular flume, in which fast (up to 3.5 m/s) and highly turbulent flows of sand and water were decelerated at different rates and processes of deposition and deposit character analyzed.
Journal ArticleDOI
Anatomy of turbidites and linked debrites based on long distance (120 x 30 km) bed correlation, Marnoso Arenacea Formation, Northern Apennines, Italy
Lawrence A. Amy,Peter J. Talling +1 more
TL;DR: In this paper, a study of the Miocene Marnoso Arenacea Formation (Italy) provides the most extensive correlation of individual turbidity current and submarine debris flow deposits yet achieved in any ancient sequence.
Journal ArticleDOI
Deep-Water Sediment Bypass
Christopher J. Stevenson,Christopher A.-L. Jackson,David M. Hodgson,Stephen M. Hubbard,Joris T. Eggenhuisen +4 more
TL;DR: In this paper, a suite of criteria are established to recognize bypass in the geological record from field data, each of which is associated with a set of diagnostic criteria: slope-channel bypass, slope-bypass from mass wasting events, base-of-slope bypass, and basin-floor bypass.
References
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Journal ArticleDOI
Sediment Gravity Flows: II Depositional Models with Special Reference to the Deposits of High-Density Turbidity Currents
TL;DR: In this article, sediment deposition from individual sediment flows commonly involves more than one of these mechanisms acting either serially as the flow evolves or simultaneously on different grain populations, and the effects of hindered settling, dispersive pressure, and matrix buoyant lift are con entration dependent.
Book
Gravity Currents: In the Environment and the Laboratory
J. E. Simpson,Michael Manga +1 more
TL;DR: In this article, Thorpe et al. discuss the nature of gravity currents and their role in industrial and industrial problems with gravity currents, including oceanography, oceanography and agriculture.
Journal ArticleDOI
Deep-Water Sandstone Facies and Ancient Submarine Fans: Models for Exploration for Stratigraphic Traps
TL;DR: In this article, five main facies of deep-water clastic rocks can be defined: classic turbidites, massive sandstones, pebbly sandstone, conglomerates, and debris flows (with slumps and slides).
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