Cyclostratigraphy of the Lower Ordovician Dumugol Formation, Korea: meter-scale cyclicity and sequence-stratigraphic interpretation

AbstractsThe Lower Ordovician Dumugol Formation in the southern part of the Baegunsan Syncline, Korea, comprises a succession of mixed siliciclastic and carbonate sediments. The depositional system of the Dumugol Formation is interpreted as a homoclinal ramp frequently influenced by storm activity,...

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Bibliographic Details
Published in:Geosciences journal (Seoul, Korea) Korea), 1998, Vol.2 (3), p.134-147
Main Authors: Kim, Jeong Chan, Lee, Yong Il
Format: Article
Language:English
Subjects:
Abstracts
Alternations
Carbonate sediments
Carbonates
Conglomerates
Cycles
Geology
Isotopes
Lithofacies
Lithology
Marl
Ordovician
Oscillations
Pebbles
Rocks
Sea level
Sedimentary facies
Sedimentary rocks
Sediments
Sequencing
Shale
Shoals
Storms
Stratigraphy
Synclines
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Summary:AbstractsThe Lower Ordovician Dumugol Formation in the southern part of the Baegunsan Syncline, Korea, comprises a succession of mixed siliciclastic and carbonate sediments. The depositional system of the Dumugol Formation is interpreted as a homoclinal ramp frequently influenced by storm activity, based on the lithological characteristics. Lithofacies associations are grouped into four depositional facies: shallow siliciclastic ramp, shallow carbonate ramp, deep carbonate ramp, and basin.The Dumugol Formation shows well-developed meter-scale cycles (0.5–5 m thick), especially in the basinal facies. The cycles consist of basal marl to shale, nodular- and/or planar-bedded ribbon rocks in the middle, and the capping flaser rocks and flat-pebble conglomerates and are characterized by a shallowing-upward character. The Dumugol cycles were formed in a subtidal setting, but did not shoal to intertidal levels. The average duration of these cycles is estimated to be 96 kyr, and matches well with that of high-frequency (fourth- to fifth-order) oscillations of sea level. The upward limit to subtidal carbonate accumulation seems to have been controlled by the intrinsic process of storm current/wave sweeping.The Dumugol Formation represents a third-order depositional sequence consisting of the lower transgressive systems tract and the upper highstand systems tract. The lower boundary of the Dumugol Formation represents a transgressive surface. The transgressive systems tract consists of siliciclastic-shallow-ramp facies, deep-ramp facies, and basinal facies in ascending order and records the deepening of basin. A maximum flooding surface is thought to be located within the upper part of the basinal facies. The highstand systems tract consists of alternations of deep- to shallow-ramp facies, and is characterized by an overall shallowing-upward trend. The predominance of aggradational stacking pattern and the subtidal lithofacies indicate that the highstand systems tract was developed during the early stage of sea-level highstand. The late stage of sea-level highstand and the upper sequence boundary could be found in the overlying Maggol Formation.
ISSN:1226-4806
1598-7477
DOI:10.1007/BF02910257