About This Item
Share This Item
Abstract
Journal of Sedimentary Research, Section
A: Sedimentary Petrology and Processes
Vol. 67 (1997)No.
3. (May), Pages 502-509
On Traction-Carpet Sedimentation
Y. K. Sohn
ABSTRACT
Traction carpets are highly concentrated bedload layers that are developed
beneath and driven by turbulent overlying flows. They have a "convex-up"
velocity profile and comprise a lower frictional and an upper collisional
region. The frictional region, having a particle concentration more than
80% of the packed bed, is characterized by nearly continuous grain contacts,
low strain rate, and hampered grain segregation. On the other hand, the
collisional region has a particle concentration between 15% and 80% of
the packed bed and is characterized by active grain collisions and higher
strain rate. Deposition from the traction carpets occurs via progressive
aggradation of the bed, rather than via en masse freezing, while
the downward grain flux from the overlying flow maintains the . The thickness
of a traction-carpet stratum is therefore determined by the cumulative
amount of sediment settled during the lifespan of a traction carpet and
can be much larger than the thickness of a moving traction carpet. Inverse
grading can be produced in the collisional region by the vertical gradient
of dispersive pressure, which is related to nonuniform distribution of
particles. When a thick frictional region develops, however, the inverse
size distribution in the collisional region is poorly recorded in the deposits.
Depositional features of traction-carpet strata are therefore determined
by the duration of a traction carpet and the thickness ratio of collisional
to frictional regions. The thickness ratio is further controlled by the
applied shear stress, sediment fallout rate, and grain size. Generally,
a collisional region is better developed beneath a highly competent and
coarse-grained (gravelly) flow, whereas a thick frictional region is developed
beneath a heavily sediment-laden fine-grained (sandy) flow. This explains
the more common occurrence of inverse grading in coarse-grained deposits.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
| Watermarked PDF Document: $14 |
Watermarked Document – A Watermarked Document is branded with the name of the original licensed customer to discourage unauthorized users from sharing the document outside the user's organization. The PDF is no longer restricted to one machine, but can be circulated to others in the same company or department. A Watermarked Document also can be printed for hard copy distribution internally but is not authorized for outside distribution nor posting on the internet. Users will not be able to cut-and-paste text or images from one document to another.
|
| Open PDF Document: $24 |
Open Document – An Open Document is a fully functional PDF that can be circulated (a digital copy or hard-copy printed documents) outside the purchasing organization. Purchase of an Open Document does NOT constitute license for republication in any form, nor does it allow web posting without prior written permission from AAPG/Datapages ([email protected]).
|
GIS Map Publishing Program
