KR-95(C)-1 (KIGAM Research Report) • i£ £ % W % Research on the Biostratigraphy RECEIVE-. AUG 0 6 1938 OSTI m % m Korea Institute of Geology, Mining & Materials IRTWUH Bf QMS B0CBHES! IS UBUIHIEI Bma wa mwna ^ KR-95(C)-1 (K1GAM Research Report) • * £ m W % Research on the Biostratigraphy ffi % PJr Korea Institute of Geology, Mining & Materials DISCLAIMER Portions of this document may be illegible in electronic image products, images are produced from the best available original document. ^7] m*\, ^4s Stratigraphy and Paleontology of the Cretaceous Sedimentary Strata in the Youngdong Basin Sung Ja Choi, Yoo Bong Kim, Bok Chul Kim Abstract The Yongdong Basin developed at the eastern margin of the Okcheon Orogenic Belt is in contact with the Yongnam Massif by the Yongdong Fault. This study deals with tectonic setting, sedimentological, paleontological study of the Yongdong Basin. Concerned with the formation of the basin, left lateral movement of the Ogdong and Youngdong faults gave a major role for the developement of the Youngdong Basin. The Yongdong Basin is tectonically subdivided into three parts (north, center, and south) on the basis of bedding form line and fracture patterns. Sedimentological study is concentrated in the southern part of the basin in order to establish stratigraphy in this area. The Mangyeri Formation is characterized by the deposit of debris flow and hyperconcentrated flow deposts developed at the steep gradient fan-delta slope and on alluvial fan along the southern basin margin. On the other hand, the formation in northern part of the basin is deposited in alluvial fan and braided rivers. The Gadongri Formation is mostly deposited by the process of turbidity current and density under current in lacustrine environment, and the Dongjongri Formation comprises alluvial fan and braided river sediments which mostly — 1 — deposited by debris flow, hyperconcentrated flood flow, sheetflood and stream flow. For paleontology, Ostracodes and charophytes are yielded from the Gadongri, Dongjeongri and Sonyoudong formations. On the basis of fossils, the Dongjongri formation is correlated with the Hjig Formation of the Euisung basin, the Sonyoudong formation is correlated with the Songnaedong and Geonchunri formations of the Milyang basin. Consequently, the Mangyeri and Gadongri formations are correlated with the Sindong Group, the Dongjongri and Sonyoudong formations are correlated with the Hayang Group. -2- 4 i 4- 4 y...................................................................................... s 41 2 # ..................................................................................... 7 2-1. 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PAEKMASAN SONYUOONG FM FM DONGJEONCRI FM MYONCNYUNDONG GADONGRI FM MANGYERI FM •Unconformity GRANITE METASEDIMENTARY ROCKS OKCHON GROUP LIMESTONE —Unknown — GNEISS Fig. 1. Geologic map of the Youngdong Basin. -8- #4 444 444 423 aolfe ####3 4# (Chun et al. 1993) 4# #4 4#, 2# $>#<9- #4 W# 442 2#44 $14. 4#4## 7)14# 44#4 4 ### 4 3500 m 4444. 4 #4 4#44# a##^4 #4# 444#4 4444- #3-4 #4 2-1. 444# 4 ## 4##$4 444 44#234, #4 #4 (1969)4 444 ^^4 $14. 4 #2# 424 2444 (1925)4 4 #4# 4#4 444# f^l, #4 n #42# (1/50.000H4# 4 #4# 23, 4#2iH4# 44 4 #4 4#2 4#4$14. #4 #4 (1969m mwm# (1925)4 4n4tf, #44 y#44#4 #24# 444 44-44 #44 #4#4 #5=4# 4444## #444. #44 44 4# 4#5- 44-4 #44# £443. 444a. 4# 44 4 #23, 4 44M# 4444#23 4#4a, 44# 4# 444 #3=4# 4-4 444 #44 44-4# 7}#4#23 44444 (Table 1 #&). a. 4 4##4 M4 (1986)# 4#4## 4#4 44-# 444a, 4# 444 4444-# £4-44 #44#-2.3. #4444. a44 #4 3 444# #4 44## 44 #34# #44 3 444 44*. 4#44* g 44-# £#4-2.3 3=#44, 4#4 444 ^ 44424-4- #44 444- 444 444 4471# a 44#4# a444 4## 2# 4: 4 4 #23 ###$14-.