Busan National Geopark Field Guidebook
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54th CCOP Annual Session & 71st Steering Committee Meeting October 28 ~ November 03, 2018 Busan, Republic of Korea BUSAN NATIONAL GEOPARK FIELD GUIDEBOOK November 01 2018 54th CCOP Annual Session & 71st Steering Committee Meeting CONTENTS Excursion Schedule 1 Location 2 01 Introduction 3 02 Geological background of Busan 5 2.1 Gyeongsang Basin 7 2.2 Yangsan Fault System 8 2.3 Geology of Busan 10 2.4 Dadaepo Basin located between 11 the Yangsan and Dongnae faults 03 Busan National Geopark 12 04 Geosites of the Busan National Geopark 15 4.1 Nakdonggang estuary 16 4.2 Morundae 17 4.3 Dusong peninsula 18 4.4 Songdo peninsula and Dudo island 18 4.5 Taejongdae 19 4.6 Oryukdo and Igidae 20 4.7 Jangsan 20 4.8 Geumjeongsan 21 4.9 Orbicular gabbro 22 4.10 Baekyangsan 22 05 Songdo Peninsula Geosite 24 06 Haedong Yonggungsa (Temple) 30 07 Reference 32 Busan National Geopark Field Guidebook Excursion Schedule Time Schedule 09:00~10:00 Hotel → Busan Air Cruse (Cable Car) 10:00~11:00 Cable Car Tour Songdo Peninsula Geosite 11:00~12:30 (Busan National Geopark) 12:30~13:00 Songdo → Restaurant Lunch 13:00~14:00 (Mokjangweon) 14:00~15:00 Restaurant → Yonggungsa 15:00~16:30 Haedong Yonggungsa (Temple) 16:30~17:00 Yonggungsa → Hotel 01 54th CCOP Annual Session & 71st Steering Committee Meeting Location Yonggungsa Grand Hotel Arrival Waypoint 1 SongdoSongdo Waypoint 2 RestaurantRestaurant 02 01INTRODUCTION 54th CCOP Annual Session & 71st Steering Committee Meeting 01 INTRODUCTION Welcome to Busan! Busan, a bustling city of approximately 3.6 million residents, is located on the southeastern tip of the Korean Peninsula (Fig. 1). The size of Busan is 768.408 km² which is 0.8% of the whole land of the Korean Peninsula. The natural environment of Busan is a perfect example of harmony among mountains, rivers, and sea. Its geography includes a coastline with superb beaches and scenic clis, mountains which provide excellent hiking and extraordinary views, and hot springs scattered throughout the city. You can enjoy four distinct and beautiful seasons in Busan. Many tourists visit Busan all year round because of the nice weather and beautiful scenery. Fig. 1. Location of Busan and photographs showing major tourist attractions. Busan is the second largest city in Korea. Its deep harbor and gentle tides have allowed it to grow into the largest container handling port in the country and the fth largest port in the world. As for its geopolitical location, the city comes at the southern tip of a strip that connects Asia, Siberia, and Europe. It also serves as a main gateway to the Pacic Ocean. This location places the city at the center of international sea transportation. The city's natural endowments and rich history have resulted in Busan's increasing reputation as a world class city of tourism and culture, and it is also becoming renowned as an international conventions (from http://english.busan.go.kr). A geopark is a unied area with geological heritages of international signicance. Busan became a national geopark of Korea in November 2013. Three Korean islands (Dok-do, Ulleung-do, Jeju-do) were also certied as national geoparks in December 2012. Busan is, however, the rst geopark located inland in Korea. The geopark initiative was launched by UNESCO in response to the perceived need for an international initiative that recognizes sites representing an earth science interest. In this eld excursion, we can review the geology of Busan and tour the Busan National Geopark. 04 02 GEOLOGICAL BACKGROUND OF BUSAN 54th CCOP Annual Session & 71st Steering Committee Meeting 02 GEOLOGICAL BACKGROUND OF BUSAN The Korean Peninsula, located on the eastern Eurasian continental margin, is an important tectonic link between eastern China and the Japanese Island Arc (Fig. 2A). Busan is located in the southeasternmost part of the Cretaceous Gyeongsang Basin wherein several NNE-trending major faults, such as Yangsan, Dongnae, and Ilgwang faults belonging to the Yangsan Fault System, are developed. Detailed explanations are as follows. Fig. 2. (A) Tectonic outline of the eastern Eurasian margin (modied after Xu et al., 1987; Ren et al., 2002; Itoh et al., 2006), (B) Distribution of Cretaceous sedimentary basins (greenish areas) in the Korean peninsula (after Chough and Sohn, 2000). (C) Simplied geological map (modied from Hwang et al., 1996; Kim et al., 1998; Choi et al., 2002) and key beds (modied from Jeong et al., 2005; Jeon and Sohn, 2008; Hwang and Woo, 2009) of the Gyeongsang Basin. 06 Busan National Geopark Field Guidebook 02.1GYEONGSANG BASIN In the Cretaceous, the Korean Peninsula was located behind the volcanic arc, induced by oblique subduction of the proto-Pacic (Izanagi/Kula) plate (Chough et al., 2000; Chough and Sohn, 2010). A large nonmarine sedimentary basin named the Gyeongsang Basin formed in the southeastern part of the peninsula, whereas a number of small basins formed in the southwestern part (Fig. 2B). These small basins are interpreted to have formed by sinistral, brittle shearing at the releasing fault bends and stepovers along several strike–slip faults and then terminated in the Late Cretaceous when the Izanagi plate changed in the direction of motion, resulting in orthogonal subduction against the Asian continent (Chun and Chough, 1992; Ryang and Chough, 1997; Lee, 1999; Lee and Chough, 1999; Chough et al., 2000; Kim et al., 2003, 2009; Chough and Sohn, 2010). The extension mode of the Gyeongsang Basin, however, is still uncertain, although it is interpret- ed as a backarc basin produced by oblique subduction of the proto-Pacic plate underneath the Eurasia plate (Chough et al., 2000; Chough and Sohn, 2010). The Gyeongsang Basin comprises three subbasins: Yeongyang, Uiseong, and Miryang subbasins from north to south (Chang, 1975; Fig. 2C). The Yeongyang subbasin is demarcated from the Uiseong subbasin by the Andong Fault System (Won et al., 1978) or Cheongsong Ridge (Chang, 1975; Kang and Lee, 2008), and Uiseong and Miryang subbasins are bounded by the Palgongsan Fault (Chang, 1977; Chang and Park, 1997; Fig. 2C). The basin was lled by alluvial, uvial, and lacustrine deposits with subduction-re- lated magmatic rocks. They are subdivided into (1) the non-volcanic sedimentary strata of the Sindong Group, (2) the partly volcanic strata of the Hayang Group, (3) dominantly volcanic strata of the Yucheon Group, and (4) the Bulguksa intrusive rocks in ascending order, according to their occurrence and the amounts of volcanic materials (Chang, 1975; Choi, 1986; Chang et al., 2003; Fig. 2C). Recently, Chough and Sohn (2010) suggested that the volcanic and plutonic rocks constitut- ed a volcanic arc platform (Gyeongsang Volcanic Arc) and that sedimentary rocks located in the west of the arc are backarc strata (Gyeongsang Backarc Basin). 07 54th CCOP Annual Session & 71st Steering Committee Meeting Fig. 3. Geologic map of Busan area, with the Yangsan Fault System. 02.2 YANGSAN FAULT SYSTEM NNE or NE-trending tectonic lines distributed in the eastern part of the Eurasia plate, such as the Tan-Lu Fault in China and Median Tectonic Line in Japan, can give important clues to understand tectonic regime and to reveal the volcanic activities and crustal deformations in the East Asia during the Cretaceous to Neogene. Especially, the NNE-trending Yangsan Fault System (abbreviated as YFS), located in the eastern part of the Gyeongsang Basin, appears to have played a signicant role in crustal deformation and sedimentation in the Gyeongsang Basin during the late Cretaceous and Paleogene. The YFS is composed of the Jain, Miryang, Moryang, Yangsan, Dongnae, and Ilgwang faults, from west to east (Fig. 2C). Among them, the Yangsan Fault is the most conspicuous strand of the YFS and is traced for more 200 km with a few km-thick fractured zone. Many studies, such as structural, geophysical, petrological, and magnetic anisotro- py researches, reported that the YFS underwent the multiple deformations in the Cretaceous to Quaternary (Chang et al., 1990; Kim, 1992; Chang, 2002; Chang and Chang, 1998; Hwang et al., 2004, 2007a,b, 2008a,b, 2012; Cho et al., 2007, Choi et al., 2009; Kang and Ryoo, 2009; etc.) due to the change of the movement directions 08 Busan National Geopark Field Guidebook and subduction angles of the proto-Pacic plate (Xu et al., 1987; Maruyama et al., 1997; Zhang et al., 2003; Chough and Sohn, 2010). The magnetic fabric study of the granite rocks adjacent to the Yangsan Fault documented that the granitic rocks were emplaced within the NW-trending extensional ssures produced secondarily by the sinistral movement of the Yangsan Fault during 70 to 60 Ma (Cho et al., 2007). Meanwhile, the dextral movement of the Yangsan Fault, showing ca. 21 km horizontal oset, was produced by a NE-SW compressional stress according to fault slip data (Chang and Chang, 1998) after ca. 48 Ma based on the laterally separated granitic body (Hwang et al., 2004, 2007a). In addition, K-Ar ages of the Dongnae Fault gouges are 57.5 to 40.4 Ma (Choo and Chang, 2000). Several studies also reported that some segments of the YFS recently reacted as reverse faults under the current E-W compressional stress regime (Kyung et al., 1999; Kim and Jin, 2006; etc.). Fig. 4. Geological map of the Dadaepo Basin (modied after Chang et al., 1983). 09 54th CCOP Annual Session & 71st Steering Committee Meeting Fig. 5. (A) Schematic representation of the extensional features and stress-eld associated with the sinistral movement of the NNE trending strike-slip faults. (B) A pull-apart basin model originat- ed by NNE-trending sinistral simple shear. (C) Movement of structural lines and plate tectonic setting of the eastern Eurasian margin in the late Cretaceous (after Kim, 1992).