Characteristics and depositional processes of large-scale gravelly Gilbert-type foresets in the Miocene Doumsan fan delta, Pohang Basin, SE Korea SCIE SCOPUS

Cited 84 time in WEB OF SCIENCE Cited 0 time in Scopus
Title
Characteristics and depositional processes of large-scale gravelly Gilbert-type foresets in the Miocene Doumsan fan delta, Pohang Basin, SE Korea
Author(s)
Sohn, YK; Kim, SB; Hwang, IG; Bahk, JJ; Choe, MY; Chough, SK
Publication Year
1997-01
Abstract
The Doumsan fan delta in the Miocene Pohang Basin (SE Korea) includes large-scale gravelly Gilbert type foresets that are more than 150 m high and dip at about 20 degrees. The foresets consist of sis sedimentary facies: medium- to thick-bedded sandy gravel deposits with variable grading patterns and bed geometries (Facies A), thin- to medium-bedded, commonly inversely graded sandy gravel deposits (Facies B), sheet-like layers, a few grains thick, of pebble gravel (gravel sheets; Facies C), lensoidal layers, a few grains thick, of cobble to boulder gravel (gravel lenses; Facies D), thin-bedded sand with outsized clasts (Facies E), and very thick-bedded (> 10 m thick) disorganized gravel deposits in the toeset area (Facies F). These facies are indicative of deposition from cohesionless debris hows (Facies A and B), debris falls (Facies C and D), turbulent hows (Facies E), and very thick debris hows that are related to large-scale foreset failure (Facies Fl. These facies are in close association with one another, except for Facies F, and are either vertically superposed or laterally juxtaposed within single sedimentation units. This suggests that these facies originated from a series of evolving sediment gravity hows. A cohesionless debris flow generated at the topset-foreset boundary or on the middle of the foreset slope segregated its sediments into a pebble-rich lower division and a sandy upper division with sparse cobble-to-boulder clasts by preferential upward drift of large clasts and surface transformation of fine-grained material. The pebbly lower division was emplaced by frictional freezing, forming Facies A beds, On the other hand, the sediments in the upper division continued to move as a sandy turbulent flow and bouldery debris fall, resulting in Facies E and D deposits downslope. The cohesionless debris flow occasionally transformed into a series of thinner hows by development of roll waves along the top of the how, producing Facies B layers on the margin of a Facies A bed, Otherwise, the cohesionless debris how transformed into grain-assemblage debris fall and single-grain debris fall consecutively by removal of interstitial sand via downward percolation and stripping into ambient water. The debris falls produced gravel sheets (Facies C) and gravel lenses (Facies D), During this dow transformation, cobble- to boulder-size clasts and sandy material were selectively transported farther downslope, resulting in prominent textural bimodality of the prodelta deposits, which comprise isolated large clasts and lensoidal deposits of cobble-to-boulder gravel set in sandy background material.
ISSN
1073-130X
URI
https://sciwatch.kiost.ac.kr/handle/2020.kiost/6381
Bibliographic Citation
JOURNAL OF SEDIMENTARY RESEARCH, v.67, no.1, pp.130 - 141, 1997
Publisher
SEPM-SOC SEDIMENTARY GEOLOGY
Subject
SEDIMENT GRAVITY FLOWS; TURBIDITY CURRENTS; DEBRIS FLOWS; STRESS TENSOR; CROSS STRATA; GRAIN FLOW; EVOLUTION; MARGIN; SLOPE
Type
Article
Language
English
Document Type
Article
Publisher
SEPM-SOC SEDIMENTARY GEOLOGY
Files in This Item:
There are no files associated with this item.

qrcode

Items in ScienceWatch@KIOST are protected by copyright, with all rights reserved, unless otherwise indicated.

Browse