International Geologiical Congress - Oslo 2008

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SES-01 General contributions to sedimentology

 

Rhythmic deposits in the the upper Cretaceous lacustrine deposits at Yeosu area, Korea: Occurrences and origin

 

In Sung Paik, Pukyong National University (Republic of Korea)
Yoon Hwan So, Pukyong National University (Republic of Korea)
Hyun Joo Kim, Pukyong National University (Republic of Korea)
Ho Il Lee, Pukyong National University (Republic of Korea)
Ho Il Yoon, Korea Polar Research Institute (Republic of Korea)
Hyoun Soo Lim, Korea Polar Research Institute (Republic of Korea)
Min Huh, Chonnam National University (Republic of Korea)
 

 

Diverse modes of rhythmic deposits occur in the Upper Cretaceous lake margin deposits at Sado and Chudo islands at Yeosu Area in Korea. In this study their occurrences are described and the origins were interpreted. The main lithofacies at study area are composed of tuffaceous coarse- to fine-grained sandstone, planar- to cross-laminated fine-grained sandstone to siltstone, tuffaceous siltstone to mudstone, sandstone-dominated interlaminated fine-grained sandstone to siltstone and mudstone, and interlaminated fine-grained sandstone to siltstone and mudstone. These lithofacies are interpreted as sheetflood deposits on sandflat to mudflat, and numerous dinosaur tracks are associated with those deposits. Six types of rhythmic sedimentation are recognized at Sado island, viz., alternation of sandstone-dominated interlaminated fine-grained sandstone to siltstone and mudstone and interlaminated fine-grained sandstone to siltstone and mudstone in thin beds, alternation of tuffaceous sandstone and tuffaceous siltstone to mudstone in thin to medium beds, alternation of rippled and bioturbated layers within interlaminated fine-grained sandstone to siltstone and mudstone, alternation of planar-laminated and cross-laminated layers within planar-to cross-laminated fine-grained sandstone to siltstone in thin beds, alternation of tuffaceous sandstone and interlaminated fine-grained sandstone to siltstone and mudstone in thin beds, and alternation of tuffaceous beds and non-tuffaceous beds in a few meter scale. Two types of rhythmic sedimentation are recognized at Chudo, viz., alternation of planar-laminated and cross-laminated layers within planar-to cross-laminated tuffaceous fine-grained sandstone in thin beds, and alternation of planar- to cross-laminated fine-grained sandstone and bioturbated, interlaminated fine-grained sandstone to siltstone and mudstone in thin beds. The rhythmic sedimentation at Sado and Chudo is interpreted to have been attributed to the fluctuation of sheetflood energy and lake levels due to short-term to long-term climate changes and the non-periodic alternation of active and quiescent stages of volcanic activity. The rhythmic sedimentation records preserved at Sado and Chudo islands provide actual examples to understand a nature of paleoenvironmental changes in short-term to long-term scale.

 

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