• Title/Summary/Keyword: 2 poles

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Magnetic Characterization of the Cretaceous Rocks from the Buyeo and Hampyeong Basins (부여분지와 함평분지에 분포하는 백악기 암석에 대한 자기특성 연구)

  • Hong, Jun-Pyo;Suk, Dong-Woo;Doh, Seong-Jae
    • Economic and Environmental Geology
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    • v.40 no.2 s.183
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    • pp.191-207
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    • 2007
  • A paleomagnetic investigation for the Cretaceous rocks in the Buyeo and Hampyeong Basins, located out of the Gyeongsang Basin, was carried out in order to elucidate the paleomagnetic directions in conjunction with the formation of the basins. Typical stepwise thermal demagnetization and measurement methods were used to determine the directions of characteristic remanent magnetizations (ChRMs). The mean direction of the sedimentary rocks from the Buyeo Basin after bedding correction $(D/I=356.5^{\circ}/61.5^{\circ},\;k=39.3\;\alpha_{95}=7.4^{\circ})$, is more dispersed than that before bedding correction $(D/I=356.5^{\circ}/61.5^{\circ},\;k=39.3\;\alpha_{95}=7.4^{\circ})$, which suggests that the rocks in the Buyeo Basin were remagnetized. However, the statistics and dispersion of the ChRM directions after bedding correction are still acceptable and the paleomagnetic pole position after tilt correction $(Lat./Long.=69.3^{\circ}N/186.7^{\circ}E,\;K=11.6\;A_{95}=14.0^{\circ})$ is closer to that of the Late Cretaceous pole of the Korean Peninsula. More detailed study is needed to confirm the nature of the remagnetization in the Buyeo Basin. On the other hand, the paleomagnetic pole before bedding correction $(Lat./Long.=81.6^{\circ}N/106.9^{\circ}E,\;K=25.1\;A_{95}=9.3^{\circ})$ is positioned near the paleogene pole of the Eurasian APWP. The mean ChRM direction of the sedimentary rocks from the Hampyeong Basin after bedding correction is $D/I=32.5^{\circ}/55.4^{\circ},\;(k=35.6,\;\alpha_{95}=8.7^{\circ})$. It is more clustered than that before bedding correction $D/I=18.3^{\circ}/62.5^{\circ},\;k=14.1,\;\alpha_{95}=14.2^{\circ})$, indicating that the ChRM was acquired before tilting of the strata. The paleomagnetic pole position of the Cretaceous sedimentary rocks in the Hampyeong Basin, averaged out of site pole positions calculated from the tilt-corrected ChRMs, is $Lat./Long.=63.9^{\circ}N/202.7^{\circ}E,\;(K=21.3,\;A_{95}=7.6^{\circ})$, similar to the Late Cretaceous paleomagnetic pole of the Korean Peninsula $(Lat./Long.=70.9^{\circ}N/215.4^{\circ}E,\;A_{95}=5.3^{\circ})$, suggesting that the Hampyeong Basin has been stable since the Late Cretaceous period. One normal and two reversed ChRM directions are revealed through the measurements of the volcanic rocks from the Hampyeong Basin. Although these normal and reversed directions are not exactly antipodal, it is interpreted that the normal direction is the representative primary direction of the volcanic rocks of the Hampyeong Basin and the mixed polarity is the records of geomagnetic field at the time of the formation of the volcanic rocks. Paleomagnetic poles are at $Lat./Long.=70.2^{\circ}N/199.5^{\circ}E,\;(K=18.1,\;A_{95}=9.6^{\circ})$ for the normal direction, and $Lat./Long.=65.5^{\circ}S/251.3^{\circ}E,\;(K=7.1,\;A_{95}=20.7^{\circ})$ for the reversed direction. Compared with the representative pole positions of the Cretaceous period of the Korean Peninsula, it is concluded that the age of the volcanic rocks in the Hampyeong Basin is of the Late Cretaceous.

Paleomagnetic and Rock-Magnetic Studies of Cretaceous Sedimentary Rocks in the Poongam Basin (풍암분지에 분포하는 백악기 퇴적암류에 대한 고지자기 및 암석자기 연구)

  • Park, Yong-Hee;Doh, Seong-Jae
    • Economic and Environmental Geology
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    • v.37 no.2
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    • pp.195-206
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    • 2004
  • Paleomagnetic and rock-magnetic investigations have been carried out for the Cretaceous sedimentary rocks in the Poongam (also called Gapcheon) Basin in the eastern South Korea. A total of 128 independently oriented core samples were drilled from 13 sites for this study. The mean direction after bedding correction (D/I=353.1$^{\circ}$/55.6$^{\circ}$, k=21.5, =$$\alpha$_{95}$=10.1$^{\circ}$) is more dispersed than the mean direction before bedding correction (D/I=10.5$^{\circ}$/56.9$^{\circ}$, k=73.9, =$$\alpha$_{95}$=5.3$^{\circ}$), and the stepwise unfolding of the characteristic remanent magnetization (ChRM) reveals a maximum value of k at 20% unfolding. Secondary authigenic hematite accompanied by altered clays such as chlorite was identified by the electron microscope observations. These results collectively imply that the ChRM is remagnetized due to the formation of the secondary authigenic hematite after tilting of the strata. It is interpreted that the chemical remagnetization was connected to the introduction of mixed magmatic-meteoric fluids, which formed hydrothermal vein deposits near the study area. The paleomagnetic pole position (214.3$^{\circ}$E, 81.6$^{\circ}$N, =$A_{95}$=7.4$^{\circ}$) of the Cretaceous sedimentary rocks calculated from remagnetized directions is close to those of the Late Cretaceous and Tertiary poles of the Korean Peninsula. This Late Cretaceous to Tertiary remagnetization seems to be widespread over the Okcheon Belt because the chemical remagnetization is previously reported to be found in rocks from other Cretaceous small basins (e.g., Eumseong, Gongju and Youngdong basins) along the Okcheon Belt and some Paleozoic strata from the Okcheon unmetamorphosed zone.

The Origin of Changseung and Ongjung Stone (장승의 기원과 옹중석)

  • Chung, Seung Mo
    • Korean Journal of Heritage: History & Science
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    • v.46 no.1
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    • pp.160-175
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    • 2013
  • There is the need to make a sharp distinction as regards JANGSEUNGs (Korean traditional totem poles) that are different in origin, history and function. This study is to identify the functions of the figures, as well as to trace stone JANGSEUNGs to their origins. In this regard, researched were conducted into the origins of JANGSEUNGs and their changes in history. There was a tradition in the GORYEO Dynasty (an ancient dynasty in the Korean Peninsula) that it erected JANGSAENGs (the archaic name of JANGSEUNGs) or allied stone figures within temples; especially, 'TONGDOSA GUKJANGSAENG SEOKPYO (a stone JANGSAENG that was erected by the royal command and is at the entrance of TONGDO Temple located in YANGSAN, South GYEONGSANG Province, South Korea)' functions as a stone monument rather than as a stone sign. In the engraved inscription, it is written that it should be erected in the form of PANA as before. 'PANA' refers to 'ZHONGKUI', a god in Chinese Taoism believed to exorcise devils that spread diseases. The inscription is to define the territory of TONGDO Temple. The article on HAN JUN GYEOM in a book 'WORAKGI (a travelogue on WORAK Mountain in North CHUNGCHEONG Province, South Korea)' written by HEO MOK makes it possible to guess the scale of GUKJANGSAENGs erected in DOGAP Temple. The stones, on which 'GUKJANGSAENG' or 'HWANGJANGSAENG' were engraved, are not JANGSAENGs but are demarcation posts. In the JOSEON Dynasty (the last dynasty in the Korean Peninsula) JANGSAENGs functioned as signposts. Unlike JANGSAENGs in temples, they were made of wood. At first, the word 'JANGSAENG' was written '長生' in Chinese characters, but in the JOSEON Dynasty another character '木 (wood)' was added to them, and thus the orthography was likely to change into 'JANGSEUNG.' In the JOSEON Dynasty, in addition, optative or geomantic figures were not called 'JANGSEUNG.' Historically, for instance, there has been no case where 'DOL HARBANGs (stone figures found only in JEJU ISLAND, South Korea)' are called 'JANGSEUNG.' In a book 'TAMRA GINYEON (a historical record on JEJU Island, South Korea)' it is written that KIM MONG GYU, JEJU governor, erected ONGJUNG Stones outside the fortress gate. ONGJUNG Stones usually refer to stone statues erected in front of ancient kings or dignitaries' mausoleums. Moreover, they were geomantic figures erected to suppress miasma. A magazine 'GWANGJUEUPJI (a journal on old GWANGJU, South Korea, 1899)' shows that two two ONGJUNG Stones were so erected that they might look at each other to suppress miasma from a pathway through which lucks lose. On the two stone figures located in BUAN-EUP, North JEOLLA Province, South Korea, inscriptions 'SANGWON JUJANGGUN' and 'HAWON DANGJANGGUN' were engraved. The words are to identify the figures' sexes. They are a kind of optative geomantic figures, and therefore there is no reason to call them 'JANGSAENG' or 'JANGSEUNG' or 'DANGSAN.' The words 'SANGWON' and 'HAWON' are closely associated with Taoism. Since then, the words have been widely used as inscriptions on stone figures in temples, and subsequently are used for JANGSEUNGs. A hatted ONGJUNG Stone, found in BUKANSAN Fortress, disappeared and other ones may be being buried somewhere. Meanwhile, ONGJUNG Stones in JEJU Island and stone figures in BUAN-EUP have hardly been displaced and thus have properly functioned. Stone figures, made in those days, seem to be most similar in function to JANGSAENGs made during the GORYEO Dynasty. Specifically, like earlier JANGSAENGs, stone figures made during the early to mid-18th century were likely to function not only as optative figures but as boundary stones. Most of stone figures in temples were made whenever the land use survey was conducted throughout the nation, but given that at the same period of time, the commonalty filed many lawsuits against grave sites, temples might erect many stone figures to mark their territories. Currently, wooden or stone figures are commonly called 'JANGSEUNG', but they were erected in different epochs and for different reasons. Their origins are to be sought in stone figures that functioned not only as optative figures in temples but as boundary stones during the GORYEO Dynasty.