DEFINITION OF FOLD ELEMENTS IN THE VICINITY OF LUTZOW-HOLM BAY AND PRINCE OLAV COAST, EAST ANTARCTICA

• Main Authors: イシカワ, マサヒロ, モトヨシ, ヨウイチ, ISHIKAWA, Masahiro, MOTOYOSHI, Yoichi
• Language: English
• Published: National Institute of Polar Research 1994
• Subjects: East Antarctica; Ongul; Ongul Island; Prince Olav Coast; East Ongul Island; Skarvsnes; Cape Hinode; Rundvagshetta; Kasumi Rock; Austhovde; Botnnuten; Berrodden; Skallen; Padda; Antarc*; Antarctica
• Online Access: https://nipr.repo.nii.ac.jp/record/2768/files/KJ00002368398.pdf; https://doi.org/10.15094/00002768; https://nipr.repo.nii.ac.jp/records/2768

P(論文) Granulite- to amphibolite-facies metamorphic terrain lies on the coastline of Luzow-Holm Bay (LHB) and Prince Olav Coast (POC). To examine as to whether there are distinct difference in the mode of deformation from place to place, we studied fold structures of the LHB and POC regions during JARE-33 and -34. Here we define five fold elements, F_<n-2>, F_<n-1>, F_n, F_<n+1> and F_<n+2>, in developing order. F_n folding : F_n folds are isoclinal and generally overturned (recumbent) folds with subhorizontal fold axes, and were dominantly developed in such area as Botnnuten, Rundvagshetta, Berrodden, Skallen, Austhovde, Padda, Skarvsnes, Breidvagnipa, the Ongul Islands, Akarui Point, Kasumi Rock and Cape Hinode. The plunge of F_n folds is generally parallel to those of the dominant mineral lineation (L_n) defined by sillimanite, orthopyroxene, hornblende, feldspar and quartz. Aligned biotite grains in garnet-biotite gneiss show axial plane foliation of the F_n fold except at the Rundvagshetta region where they crosscut the axial surfaces of F_n folds. The wavelength (up to hundreds of meters) depends on the layer thickness, implying that F_n folds were buckled folds. Thus asymmetry of smaller-scale folds indicates the larger regional enveloping surfaces. In Skarvsnes, the F_n folds partially exhibit sheath shapes. The F_n folds were clearly refolded by gentle folds. Post-F_n folding : Gentle folds commonly developed in the same areas where F_n folding are observed. These gentle folds have subvertical axial planes and subhorizontal fold axes and are characterized by buckling (up to 5km in wavelength). Two stages of gentle-folds are recognized in Botnnuten, East Ongul Island, Akarui Point and Kasumi Rock as well as Skarvsnes and Skallen (T. ISHIKAWA : Mem. Natl Inst. Polar Res., Ser. C, 9,1,1976; M. YOSHIDA : J. Geosci., Osaka City Univ., 21,65,1978). This suggests that development of gentle folds of two deformational stages (F_<n+1> and F_<n+2>) succeeded to the intense F_n ...